CGRO Cycle 5 Viewing Program: Abstracts

THE SEARCH FOR ABSORPTION LINES IN GAMMA RAY BURST SPECTRA

   BATSE has not detected the absorption lines reported
by previous detectors. We propose to continue our spectral line
research by participating in the computerized search for these
lines. In addition, we plan to evaluate the consistency between
BATSE and previous instruments and calculate the frequency with
which lines occur based on all the available observations. Finally,
using our statistical techniques and the results of the
computerized search we will study the rate of false positives
 which affects both the line detection criteria and the line
statistics calculations.                                          
                                                                  

PHOTON SPLITTING AND SCATTERING IN SOFT GAMMA REPEATERS AND PULSARS

   This proposal requests funding for the theoretical
modelling of radiation attenuation and scattering in neutron star
magnetospheres with high surface magnetic fields. The role of
photon splitting in magnetar models of soft gamma repeaters (SGRs)
and pulsars having fields above $10^{13}$ Gauss will be
investigated. This will include the construction of numerical
models of photon splitting cascades in the curved field geometry of
neutron star magnetospheres, and radiation generation by reso
nant Compton scattering and attenuation by single photon pair
production. Emergent spectra of photons and pairs for different
locations in such magnetospheres will be determined and compared to
the observed spectra of SGRs and strongly magnetized pulsars such
as PSR1509-58.                              

DISTRIBUTION OF GRB COORDINATES IN REAL TIME FOR MULTI-BAND FOLLOW-UP OBSERVATIONS

   We propose (1) to continue to operate the BATSE
Coordinates Distribution Network (BACODINE), (2) to improve the GRB
location accuracy of BACODINE, & (3) increase the number of methods
by which the locations are distributed. BACODINE is a system of
computers & programs that calculates GRB locations from the BATSE
telemetry data in real time & distributes those positions to
instruments to make multi-band follow-up observations of GRBs in
real time -- less than 6 seconds. Our approach allows
 the making of multi-band observations of the GRBs while they are
still in progress. This is providing a new tool for GRB research.
At the least, coordinated observations will set new, more stringent
upper limits to GRB models, & at the most, will make a positive
identification of a GRB source object.  

OSSE OBSERVATIONS OF NGC 2110 AND NGC 526 A

   The goal of this investigation is to correlate BATSE
solar hard X-ray (HXR) emission with soft X-ray (SXR) emitting
plasma flows observed by the Yohkoh Bragg Crystal Spectrometers.
The investigation will test the hypothesis that localized electron
beam heating is the operative energy transort mechanism in
impulsive solar flares. For suitably impulsive HXR emission, an
analysis of the hydrodynamic equations predicts a relationship
between the HXR intensity and the second time derivative of
 the SXR plasma's momentum. To quantify the flows and momentum of
SXR emitting plasma, we utilize a novel technique involving the
velocity differential emission measure (VDEM) which has not yet
been applied to this problem.                                     
                                           

BATSE OBSERVATIONS OF THE PICCINOTTI SAMPLE OF ACTIVE GALACTIC NUCLEI

   We propose archival analysis and real time
observations of a number of sources thought to be powered by
accretion onto black holes, in order to test the validity of a
novel model for the emission of radiation from this type of
sources. The main region of interest in the hard X-ray band
accessible to BATSE and OSSE, but in general, observations spanning
the entire electromagnetic spectrum can provide useful constraints
to our model. For Cyg X-1, we propose new OSSE observations of in
addit
ion to requesting rights to the BATSE continuous data. We propose
additionally to use archival data for Cyg X-1 as well as, GX339-4,
the Seyfert galaxy NGC 4151 and the transient sources GRO J0422+32
and GRO J1655-40 which have been extensively by CGRO as well as at
other                                

MODELING THE HIGH ENERGY SPECTRA OF BLAZARS AND SEYFERTS

   We propose to conduct theoretical research on high
energy processes in AGN in light of recent observations by CGRO.
This will be a 2-pronged research program, for both blazars and
Seyfert galaxies. For the former, we will further develop the
``external-radiation Compton" model, in which the GeV emission is
produced via Comptonization of the external radiation by
relativistic particles in the jet. For the latter, we will focus on
models in which the keV - MeV spectra are produced by therma
l pair plasma in active regions of an accretion disk corona, using
our recently published Non-Linear Monte Carlo code, which can
self-consistently simulate radiative transfer and high-energy
processes in inhomogeneous sources in 3-D geometries.             
                                              

FURTHER STUDY OF GAMMA RAY PULSARS AT MEV ENERGIES

   Only two radio pulsars are easily detectable by
COMPTEL: PSR0833 and PSR0531. PSR1509-58 has also been detected but
at a low significance level as have hints from PSR1951+32, PSR
0740-28, PSR 1823-13. We propose to further investigate those
pulsars which COMPTEL has detected only marginally in order to
confirm these pulsations, and if so better define their MeV pulse
characteristics. We do not propose specific dedicated observations,
but request that if any observations take place with th
ese objects in the FOV that we be granted the right to analyse the
data and that consideration be given to putting the object within
10deg of the Comptel optical axis.                                

INVESTIGATION OF ENERGETIC GAMMA RAYS IN SOLAR FLARES OBSERVED BY EGRET

: The EGRET observations of the June 1991 series of solar
flares provided spectral and temporal measurements of high energy
gamma ray emissions up to 1 GeV, lasting hours after the impulsive
phase of the flare. The spark chamber and energy calorimeter
observations provided information on the spectrum of accelerated
particles at the Sun, and on their interactions and confinement. We
propose to continue these studies by analyzing all CGRO phase 5
data in the calorimeter, and in the spark cham
ber when the Sun flares and when it is in the field of view. A
target of opportunity is requested to point to the Sun under
specific and extraordinary conditions that are specified in this
proposal.                                                         
                                                

SEARCH FOR ULTRA HIGH ENERGY GAMMA RAYS FROM BURST SOURCES

   We propose to develop a method for the analysis of
data from BATSE, OSSE, and COMPTEL on CGRO as if they were a single
``super-instrument''. We show how to combine the data in a way
equivalent to solving directly the huge least-squares system
obtained by concatenating the equations from all the instruments,
but far more efficient. We will apply the method to mapping the
Virgo region with resolution (angular and spectral) and sensitivity
unreachable by any separated analyses. During the se
cond year of this Type-1 investigation, the method will be extended
to diffuse sources and used to map the galactic center. The
investigators have experience with all three instruments and bring
to bear a powerful set of new and effective mapping and analysis
techniques.                                 

MORPHOLOGICAL STUDY OF SHORT GAMMA RAY BURST

   We propose to use BATSE Earth-Occultation data from
JPL, in conjunction with corresponding data from MSFC, to perform
a comprehensive analysis of the types of temporal variability which
occur in 30, and possibly as many as 55, long-lived gamma-ray
sources whose intensities and spectra are now in production. The
objectives include the identification of the general properties of
variability over an interval of at least one year; the search for
possible groupings of sources by these properti
es; a first look for correlations of these properties with other
observed parameters such as spectral characteristics; and the
comparison of any such identified properties with a corresponding
behavior of the same sources in other databases under study by the
principal investigator.                     

COMPLETION DEEP COMPTEL EXPOSURE OF ORION/MONOCEROS

   The evidence for 4.4 and 6.1 MeV gamma rays from the
deexcitation of 12C and 16O, seen by COMPTEL in the direction of
the Orion complex, has opened a new chapter in astrophysical
gamma-ray spectroscopy. The available/scheduled exposure of the
Orion/Monoceros region is currently very asymmetric, as
demonstrated here. We propose two observations with stringent
pointing directions about 15-20 degrees away from Orion/Mon, which
will complete a deep exposure in combination with existing observ
ations. Our key goals are to distinguish narrow line emission from
broad line emission, which has major astrophysical implications, to
search for accompanying lines in the 1-3 MeV range, which set
important constraints on composition and particle spectra, and to
study the diffuse bremsstrahlung emission.

MEV BLAZARS AND THE MEV BUMP IN THE COSMIC BACKGROUND RADIATION

   COMPTEL has recently detected blazar-type AGNs that
are exceptionally bright at MeV energies. The apparent MeV bumps in
the spectra of these sources (named MeV blazars) seem to put strong
constraints on the proposed gamma-ray emission models. The enhanced
MeV emission coincides with the well-known MeV bump in the diffuse
cosmic gamma-ray background radiation. The possibility of a
transient nature of the MeV blazar behaviour suggests that
essentially all gamma-ray blazars might contribute 
to the MeV bump in the diffuse background. We propose COMPTEL and
EGRET observations of GRO J0516-609 and PKS 0208-512 (the most
prominent MeV blazars). In addition, a multiwavelength campaign
will be initiated in the radio, optical, and X-ray regimes.       
                                            

REFINING A SPIRAL STRUCTURE MODEL FOR THE GALACTIC 26AL SOURCE DISTRIBUTION

   Ever since COMPTEL obtained the first high quality sky
maps ofthe 1.8 MeV line emission of 26Al, searching for a
physically sound and coherent explanation for the mysteriously
clumpped map features has become a major thrust in the field. Our
recent work suggests that these features originate from the curving
spiral arms and star formation enhancement at the Galactic center.
We propose to test this hypothesis by a quantitative comparison
between the model and the COMPTEL data using maximum-likelihood
model fitting techniques. Our results will provide the best picture
of the Galactic nucleosynthesis sites in the past million years and
may improve our understanding of the galactic spiral structure and
chemical evolution.                                               

MULTIWAVELENGTH STUDIES OF OCTOBER 91 X-CLASS SOLAR FLARES OBSERVED BY EGRET

   The EGRET total absorption spectrometer (TASC)
recorded significant spectra above 1 MeV from at least four X-class
flares during October 1991. We propose to carry out a
multiwavelength analysis of all the data available for the solar
flares. Preliminary analysis by the EGRET team (private
communication) shows an especially strong 2.2 MeV line from the
X6.1 flare at 0539 UT on October 27 which lasts over 5 minutes with
a very hard spectrum above 10 MeV, Working with the EGRET team we
will 
do a detailed analysis of the TASC flare data for all events. We
will then use existing correlated optical and radio data from NOAA
and other ground based observatories and X-ray images from the
Yohkoh satellite for a full characterization of the flares.       
                                          

HIGH ENERGY OBSERVATIONS OF THE BRIGHT  LOW MASS X-RAY BINARY  X1755-33

   The bright galactic source X1755-33 is a dipping, Low
Mass X-Ray Binary, and has been seen as a possible black hole
candidate. It was detected by HEAO A4 up to a 80-180 keV band. We
have made detailed studies of the X-ray spectrum revealing a
blackbody component and also Comptonised emission from an Accretion
Disk Corona. Understanding this source and binary sources in
general will depend on obtaining the parameters of this Comptonised
component and thus of the Comptonising region, which 
can only be done with high energy observations in the OSSE range.
We clearly demonstrate the feasibility of observing X1755-33: the
Galactic latitude of -5 deg means that source-confusion is not a
problem; good background subtraction can be made with offsets of 11
deg.                                   

MULTIWAVEBAND OBSERVATIONS OF OUTBURSTS FROM A0535+26

   This proposal requests any BATSE data recorded during
an outburst from the Be/X-ray binary system A0535+26. This system
is being monitored by us at IR and optical wavelengths. A major
outburst in February 1994 is currently being analysed in
collaboration with the BATSE team and a paper will be submitted for
publication very soon. We plan to use any new X-ray data to help
answer some of the questions raised by the Feb '94 super-outburst. 
                                                   
                                                                  

ISO/CGRO SIMULTANEOUS TOO OBSERVATIONS OF UP TO 8 HIGH MASS X-RAY BINARIES

   This proposal requests any BATSE data recorded during
outbursts from eight Be/X-ray binary systems. Observing time on the
Infrared Space Observatory has been approved as Target of
Opportunity observations should any of these systems go into
outburst. Since all these systems are both IR bright and X-ray
bright during these outbursts we seek matching data from BATSE. All
these systems are also being monitored by us at near-IR and optical
wavelengths.                                         
                                                                  

MULTIWAVEBAND TOO OBSERVATIONS OF 4 BE/X-RAY BINARIES

   This proposal requests any BATSE data recorded during
an outburst from four Be/X-ray binary systems. These systems are
V0332+53, GRO J1008-57 A1118-616 and EXO 2030+375. All these
systems are being monitored by us at IR and optical wavelengths. We
plan to use the X-ray data to further our understanding of the
accretion processes in these systems.                             
                                                                  
                                                

COMPTEL OBSERVATIONS OF SELECTED AGN AT MEV ENERGIES

   It is proposed to continue COMPTEL observations
(0.75-30 MeV) of 5 sources (one source has two potential
counterparts) from which definite MeV-emission has been detected.
4 of the sources are bright blazar-type AGN which have been
discovered originally in Gamma-rays by EGRET. The other source is
an unidentified object, presumably an AGN as well. It is only seen
by COMPTEL, not by EGRET. We want 1) to measure the spectral shape,
especially the spectral breaks, 2) to determine possible corr
elations between source intensity and spectra, 3) to determine the
duty cycles of high intensity states, 4) to search for further,
previously undetected MeV-sources, 5) to estimate the contributions
of unresolved AGN to the diffuse background radiation, and 6) to
participate in multiwavelength campaigns.

OSSE OBSERVATIONS OF PSR 1259-63 NEAR APASTRON

   We propose OSSE observations of the unique radio
pulsar Be-binary PSR 1259-63 near apastron. Hard X-ray emission was
detected from this system during a 3 week OSSE observation near
periastron in January, 1994. Since the stellar wind environment at
apastron differs greatly from that at periastron in this highly
eccentric, wide binary, OSSE measurements of the luminosity and
spectrum near apastron will greatly constrain the proposed shock
emission models, and will increase our understanding
 of the pulsar-wind interaction mechanism which produces the high
energy radiation.                                                 

OSSE & EGRET OBSERVATIONS OF KNOWN AND NEW PULSARS

   The proposed work includes new OSSE and EGRET
observations of pulsars that we predict to be detectable if they
are beamed toward us. Some of these are recently discovered
pulsars; two are objects whose distances are much smaller than
cataloged and so have been ignored in EGRET analyses to date;
others are objects for which we will have better timing models. We
also propose refolding of OSSE data on several pulsars, and
searching OSSE data for periodicities in the directions of SN1987a
and
 the galactic center using a method that can counteract phase
smearing from orbital motion in short period binaries. We will also
interpret our results using models for the radio and gamma-ray
beams developed at Cornell and Stanford.                          
                                            

MULTIWAVELENGTH OBSERVATIONS OF THE BRIGHT QUASAR 3C 273

   We propose two observations of the bright quasar 3C
273. Each observation should be 2 weeks long. The observations can
be made simultaneously with observations of 3C 279. We will study
the high energy emission of 3C 273 and its variability in time. We
will also relate these data with those obtained in coordinated
programs at other energies. This is a powerful approach to
understand the physics of AGN.                                    

STUDY OF GAMMA-RAY EMISSION FROM THE UNIDENTIFIED EGRET SOURCES GRO J0617+22 AND GRO J2019+40

   We propose to analyze archival COMPTEL and EGRET data
from the unidentified EGRET sources GRO J0617+22 and GRO J2019+40
in order to test the hypothesis that these sources are associated
with the nearby supernova remnants IC 443 and gamma Cygni,
respectively. We also propose OSSE observations of the supernova
remnant IC 443. The goal of this work is to establish the nature of
these gamma-ray sources and to identify the gamma-ray production
mechanisms at work. We plan to do this by studying
 whether the emission is consistent with a point source or an
extended source and through detailed spectral fitting of models
with the data. In support of this research, we will develop a pion
production code and will further develop theoretical models for
pulsar emission.                               

OSSE OBSERVATIONS OF THE EXTREMELY LUMINOUS FAR-INFRARED GALAXIES ARP 220 AND NGC 6240

   We propose to search for nuclear activity in the
nearby infrared luminous mergers Arp 220 and NGC 6240. These
objects are examples of a class of extremely luminous (greater than
1e11 Lo) far-infrared galaxies (ELF) that emit the bulk of their
radiation at far-infrared wavelengths. Because ELF systems are
obscured by gas and dust, the detection of buried active nuclei may
only be possible with gamma-ray detectors. New stellar dynamical
studies of Arp 220 show that its nuclear gas content i
s less than was derived from studies of 12CO(J=1-0) line emission,
so that OSSE detection is likely. Recent ASCA observations show
variable X-ray activity in NGC 6240; thus its nuclear origin could
be confirmed with OSSE observations.                              
                                       

44TI FROM SUPERNOVA REMNANT GAS A

   As first noted by the COS-B group, the SAS-2 and COS-B
observations of the Crab pulsar show a long-term variation of the
intensity of the 1st peak to the 2nd peak of the gamma-ray light
curve. This apparent sinusoidal variation might be due to the
nutation of the neutron star with a period of about 14 yrs. While
EGRET observations are consistent with this variation, for the
combined SAS-2, COS-B and EGRET data, the null hypothesis cannot be
ruled out with a high degree of confidence. A 3 
week EGRET observation of Crab, during a time when the intensity
ratio should be increasing, is proposed. The observation, combined
with previous observations, can establish whether the periodicity
is real or not. This will be the last opportunity for a decade or
more to address this question.          

CONSOLIDATING THE VELA REGION 1809 MEV DATA

ANALYSIS OF EGRET DATA FOR GAMMA-RAY BURSTS

   EGRET detects less than two gamma-ray bursts per year;
however, the results from these few bursts have been astounding.
Thirty MeV to greater than a GeV emission has been observed to last
as long or longer than the emission observed by BATSE. In
GRB940217, high energy emission is observed in the next orbit --
over an hour after the BATSE detection, and the highest energy
gamma ray was 18 GeV. Also, EGRET has collected spectra in the
energy range of 1 MeV to 100 MeV that have been combined
 with observations from other instruments to yield spectra spanning
up to four orders of magnitude in energy. We propose to continue
analyzing the EGRET data from the gamma ray bursts in Cycle 5.    

INTENSIVE SEARCH FOR HIGH ENERGY DISCRETE SOURCES IN THE GALACTIC CENTER REGION

   Recent low-statistics but high-angular-resolution
observations have suggested that discrete sources could make a
significant contribution to the narrow (2 deg. FWHM) component of
the galactic plane emission. We propose to preform a deeper
analysis of EGRET data from the galactic plane within 20 degrees of
the center region to better determine discrete source contributions
to the observed diffuse emission. We will improve on current
analyses of this region by using a new image reconstructi
on concept, the pixon, which will allow separation of point and
diffuse constributions. Optimum use of the EGRET's angle/energy
resolution capabilities could greatly improve our understanding of
the galactic center region.                                       

LONG TERM MONITORING OF THE GAMMA-RAY AND RADIO EMISSION FROM THREE COMPACT OBJECTS WITH BATSE

   We propose to use EGRET to obtain a deep exposure of
3C345, with two objectives: first, to detect the quiescent
component of the $\gamma$-ray emission from four blazars in this
field to test the hypothesis that blazars are responsible for the
diffuse $\gamma$-ray background (DGRB); and second, to gain
information regarding the duty cycle and magnitude of $\gamma$-ray
flares in blazars. To date only three objects have been detected in
possibly quiescent states. Also, little information is 
available regarding the duty cycle and typical magnitude of
$\gamma$-ray flare emission. Such information would constrain
models for the production of $\gamma$-rays in blazars. If quiescent
emission from one or more blazars is found, we will determine to
what extent blazars can account for the DGRB.    

GAMMA-RAY SPECTROSCOPY OF NEARBY OB ASSOCIATIONS

   Recent COMPTEL measurements of C-12 (4.4 MeV) and O-16
(6.13 MeV) de-excitation lines from the Orion Complex have renewed
interest in hot, massive stars as sources of galactic cosmic-rays.
If particle acceleration by OB supergiants, Of stars and Wolf-Rayet
(WR) stars is common in our galaxy it would have importnat
implications for galactic cosmic-ray abundances and for the
production of the light elements lithium, beryllium and boron. We
propose using archival COMPTEL and EGRET data to st
udy the gamma-ray emission from other nearby (less than 2.5 kpc) OB
associations to look for evidence of enhanced cosmic-ray densities.
Based on measurements of distance and stellar wind power of OB
associations we select five nearby OB associations to search for
Orion-like emission.                    

ANALYSIS OF GAMMA-RAY BURST CHARACTERISTICS USING INTEGRAL MOMENTS

   We propose to analyze the distributions of duration
and spectral peak energy in gamma-ray bursts observed by BATSE. The
technique of integral moments self-consistency analysis, hitherto
applied to the brightness distribution of GRBs, and capable of
placing significant constraints on the characteristics of the
source population, will be used. Cosmological effects affect the
duration and peak energy distributions in similar ways;
consequently, comparison of the results from these two compon
ents of our study will reinforce each other in yielding constraints
on cosmological parameters.                                       

THE ORIGIN OF SOFT GAMMA REPEATERS

   We propose to investigate questions concerning the
physical nature of Soft Gamma Repeaters (SGR) that are raised by
the CGRO observations of SGR recurrences and counterparts. Our work
will focus on four issues: (1) Are SGR events powered by an energy
source internal to the neutron star or by accretion of objects onto
the star? (2) What are plausible internal energy sources, and how
do they differ in the observed occurrence rate and size and
structure of the SGR events they produce? (3) Ho
w can these explosive events produce gamma radiation? (4) Is there
any physical relationship between SGR and gamma ray bursts, and how
could this be tested observationally?                             

UNIDENTIFIED GAMMA-RAY SOURCES NEAR THE GALACTIC PLANE

   One hundred twenty-nine gamma-ray emitting sources
have been detected in the data from EGRET aboard GRO (Thompson et
al., 1995). Thirty-eight of these sources lie in or near the
Galactic plane. Only six of the Galactic plane sources are
identified, the remaining 32 are unidentified. We have studied the
unidentified sources near the Galactic plane in terms of
variability and spectral features. Further observations will be
useful to monitor source variability, determine better positions
and
 to increase the high energy statistics for spectral analysis. We
request non-exclusive data rights to the 32 unidentified gamma-ray
sources near the Galactic plane as defined in the target list. No
specific pointing of the instrument and no funds are requested.   
                                      

EGRET OSERVATIONS OF GAMMA-RAY PRODUCTION IN ULTRALUMINOUS INFRARED GALAXIES

   A complete catalog of 324 bright galaxies 60 micron
flux densities greater than 5 Jy has been selected from the IRAS
catalogs by Soifer et al., 1988, ApJ, 320, 257. The median distance
of the galaxies in the sample is about 30 Mpc and median
far-infrared luminosity is about 2x10$^12$ Lo, where Lo is the
solar luminosity. Much attention has been focused on the relation
of these objects to quasi stellar objects (QSOs). Observations of
nearby starburst galaxies can answer questions pertainin
g to the power source of these objects and their relation. We
request non-exclusive data rights to the twelve ultraluminous
infrared galaxies listed tabulated in our target list and in Table
1. No specific pointing of the instrument and no funds are
requested.                                            

ENERGY CORRECTIONS TO TIME DILATION

   The detection of time dilation in gamma-ray bursts
(GRBs) is strong evidence that GRBs are cosmological. The time
dilation, when coupled with the observed spectral shapes and
intensities, directly gives the distance to the sources. The
detected time dilation implies distance scales to the events that
are larger than from the Log N- Log P distribution. A crucial
component of the relationship between the time dilation and
distance is the correction for the tendency for time structures in
GR
BS to be narrower at higher energies. In the past this has been
crudely approximated. We propose to use the 16 channel MER data to
determine accurately the energy correction and therefore the
distance to GRBs.                                                 
                                             

A SEARCH FOR MARCH 5TH EVENTS IN BATSE

   We have recently shown that the initial peak of the
March 5th, 1979 gamma-ray transient had all the characteristics of
a classic gamma-ray burst. Bursts like March 5th can be detected
with BATSE out to 5.5 Mpc. We propose to study the short (1 s)
GRBs. If we do find a statistically significant correlation with
nearby galaxies then we have identified one component of GRBs. If
we find that BATSE could not detect pulsations or rapid rises from
short events because of poor statistics, then we
 have removed the argument that March 5th has unique features,
bolstering the galactic interpretation of GRBs. If we find that
BATSE could detect pulsations and fast rise times but did not, then
this would bolster the comologist argument that March 5th events
only look like GRBs.                        

STUDY OF ACCRETION PROCESSES IN A0535+262

   During 1994 the x-ray binary pulsar A0535+262
underwent a major outburst which was observed by GRO. The BATSE
observations revealed a QPO. Our analysis of the BATSE data has
shown that the observed relationships between the QPO frequency,
flux, and spin-up rate are consistent with the QPO occurring at the
beat between the rotation rate of the inner edge of an accretion
disk and the rotation rate of the neutron star. The GRO
observations therefore provide powerful contraints on accretion m
odels. We propose both an archival analysis to probe the nature of
the QPO, and analysis of cycle 5 BATSE observations to improve our
knowledge of the binary orbit, and monitor the torque behavior of
the system . To study the QPO at low flux levels we are proposing
a correlative study with XTE.         

RADIO MONITORING OF HIGH ENERGY TRANSIENTS

   We argue that the solution to the gamma ray burster
mystery lies with the detection of counterparts at other
wavelengths. The radio band is particularly promising in that radio
emission is an excellent tracer of high energy phenomena and radio
imaging routinely offers arcsecond localization. This argument is
best illustrated by the breakthrough that has been achieved by
multi-wavelength observations of soft gamma ray repeaters. The
radio observations both pinned down the associated supern
ova remnants and the arc-second localization of the associated
stellar counterpart to SGR 1806-20. We have designed three
experiments with demonstrated high sensitivity to detect and
localize the radio counterparts of both classical gamma ray bursts
and soft gamma ray repeaters.                         

THE ORIGIN OF THE CONTINUUM EMISSION IN SEYFERTS

   Recent evidence from the X-ray spectra of AGN suggests
that a large fraction of the X-rays are absorbed by optically thick
material. This radiation re-emerges in the IR, optical & UV.
Variability and energetic arguments suggest that this reprocessing
can account for the entire luminosity of the nuclear region,
implying that the primary energy source is that which produces the
X-rays. We intend to test this hypothesis by determining the
spectral energy distributions of two Seyfert-1 galaxi
es from optical to gamma-rays simultanously. The proposed CGRO/OSSE
data will provide an extremely important constraint, as the high
energy extent of the primary power law is crucial to our knowledge
of the luminosity available for reprocessing.                     

OSSE OBSERVATIONS OF THE CARINA REGION OF THE GALAXY

   We propose two OSSE observations in the Carina region
of the Galaxy capable of distinguishing between the arm and
inter-arm regions in low-energy gamma-rays. Simulated observations
of the 50 -- 150 keV continuum suggest that observations at l=285
deg and l=277 deg with a collimator position angle of 45 deg (with
respect to the Galactic plane) could differentiate these two
regions at up to the 9 sigma level in this band. These measurements
will help confirm important COMPTEL results sugges
ting the connection between large-scale Galactic structure and
diffuse low-energy gamma-ray emission in this region. In addition,
they will serve as an important proof-of-concept study for future
OSSE mapping observations in Carina, and for OSSE mapping methods
in general.                               

STUDIES OF BATSE TRANSIENTS AND BLACK HOLE BINARIES

   We propose to continue our successful Cycle 4 study of
black hole transients with BATSE to study both known historical
transients, searching for low level outbursts and spectral
features, and to search for new faint transients in the same
fields. We propose 7 new fields, with minimal source confusion, in
addition to the 7 from Cycle 4 that will allow coverage of more
than half the galactic disk. Using both archival and Cycle 5 data,
we expect to discover several new faint transients and t
o constrain models for black hole sources. We shall carry out
correlative optical and x-ray studies of both historical and newly
discovered faint transients and compare black hole vs. neutron star
transients to derive constraints on the total populations of each
in the Galaxy.                           

WHERE DOES THE POWER LAW BREAK IN X-RAY BURSTERS?

   We propose to observe the low-luminosity X-ray burster
4U0614+091. This source has always been observed with a hard
power-law like spectrum in X-rays (E less than 20 keV).
Furthermore, there is indication o f weak hard X-ray emission in
both the HEAO 1 A-4 and BATSE data. Given the OSSE sensitivity, we
will obtain for the first time a high-quality spectrum of a neu
tron star system. In particular, we will search for any possible
energy break or cutoff. Our observation will enable us to ma
ke a detailed comparison between bl ack hole and neutron star hard
X-ray spectra.                                                    

SCIENCE AND ENGINEERING OBSERVATION OF THE CRAB

   We propose a standard two-week observation of the Crab
nebula to address the following scientific and engineering issues:
(1) Time variability in the total Crab emission below 100 keV and
above 1 MeV; (2) Hardening of the spectrum of the total Crab above
1 MeV; (3) Time variability of the pulse profile; (4) Transient
narrow lines near 75 keV from the pulsar; and (5) Calibration of
OSSE's pulse-shape discrimination efficiency. Furthermore, we
request that this observation b                

CONTINUED MONITORING OF THE SOFT GAMMA-RAY EMISSION OF THE SEYFERT GALAXIES IC 4329A AND NGC 4388

   We propose standard two-week OSSE observations of the
bright Seyfert 1 galaxy IC 4329A and Seyfert 2 galaxy NGC 4388,
both of which have been strongly detected by OSSE repeatedly
through the GRO mission. Because of their brightness, these objects
are the best candidates for the study of spectral and temporal
variability of the Seyfert class of active galactic nuclei (AGN) in
the low-energy gamma-ray range covered by OSSE. The intent of these
proposed observations is to accumulate the high
est possible quality spectra above 50 keV to help distinguish
whether the two types of Seyferts are indeed the same object viewed
at different angles---as the simple unified models of AGNs
propose---or sources with distinct instrinsic characteristics.    

INVESTIGATION OF ACCRETION POWERED PULSARS WITH BATSE

   BATSE on the CGRO has a unique capability for long
term monitoring of accretion powered pulsars, due to its all-sky
sensitivity to hard X-rays. We propose in Cycle 5 to use Phase 1-4
BATSE LAD data to search for previously unknown binary pulsars, to
continue our study of 4U1626-6, GX1+4, OAO1657-415, the Be/X
transient pulsars, and monitor and search for previously detected
X-ray binary pulsars, and continue to develop new techniques and
search tools. The specfic goal of this Cycle 5 prop
osal is to use the background subtracted continuous data to perform
systematic studies of pulse period variations, pulse shape, and
spectra for these X-ray binary pulsars. This research will be
carried out continuing the collaboration with the BATSE team at the
Marshall Space Flight Center, and Caltech.

GAMMA-RAY BURST MODEL CONSTRAINTS IMPOSED BY BATSE OBSERVATIONS

   Models of Galactic and cosmological gamma-ray burst
spatial distributions and luminosity functions will be generated,
analyzed, and compared to BATSE angular and intensity distributions
as part of an ongoing investigation. Research plans proposed for
Cycle 5 include incorporation of the updated BATSE sky exposure map
in the analysis, continued study of geometric constraints on
Galactic models (including effects of repetition), and a detailed
attempt to identify constraints imposed on cosm
ological models by broad luminosity functions. Improvements to the
existing analysis techniques are relevant to the controversies
surrounding burst origins. This project requires high-level
processed data pertaining to burst peak fluxes, locations,
subclassification parameters, and BATSE skymaps.       

BATSE/COMPTEL SPECTRAL CHARACTERISATION OF GAMMA--RAY BURSTS

   The primary objective of this research proposal is to
carry out joint spectral analysis on a sample of gamma--ray bursts
observed by both the COMPTEL and BATSE instruments. By
characterising the time averaged and time resolved spectra over
this broad energy range (20 keV to 10 MeV) it is possible to
constrain the parameter space of inter-burst and intra-burst
spectral variability in an unbiased manner. Furthermore, the errors
on derived spectral parameters are significantly reduced compar
ed to those obtained from fitting spectra from either instrument
individually. We will pay particular attention in our study to the
implications of our results for cosmological models, which predict
a correlation between burst hardness and intensity, due to the
cosmological redshift effect.             

OSSE OBSERVATIONS OF THE VELA SUPERNOVA REMNANT

   Our Phase 3 OSSE observation of the Vela pulsar region
resulted in the first detection of the Vela SNR above 80 keV. The
-(1.7 +- 0.23) photon spectrum is consistent with an extrapolation
of the -1.7 power law spectrum of the compact (2') nebula. However,
the OSSE index is also marginally consistent with the -2.7 index
derived from HEAO A-4 observations (13 - 80 keV) of the extended 1
degree Vela X synchrotron nebula. A three week OSSE observation of
the Vela pulsar is requested for an im
provement in the measurement of the OSSE spectrum. Better
statistics would allow a two-component fit if the extended nebula
dominates at low energies and the compact nebula dominates at high
energies.                                                         
                                              

MAPPING OF THE COSMIC-RAY INDUCED GAMMA-RAY LINE EMISSION FROM ORION WITH OSSE

   We propose to follow up the detection by COMPTEL of
gamma-ray lines at 4.44 and 6.13 MeV in the Orion molecular cloud,
by using OSSE to map the distribution of this emission. We propose
two 14-day observations of the Orion region for this purpose.     

"THE BEHAVIOR OF GAMMA-RAY BURSTS IN THE 7-14KEV BANDPASS: FLUENCES, STRUCTURE, DURATIONS, AND DELAYS"

   We propose to extract 4X gain (7-14 keV) Spectroscopy
Detector (SD) DISCSP data on 100 gamma-ray bursts (GRBs) to
determine thier photometric and temporal behavior in this bandpass.
The limited, currently available observational data set has shown
that the fluences of GRBs at soft x-ray energies (below 15 keV) are
a few percent of their high-energy fluences. This observation has
been used to constrain popular models for GRBs. With our
statistically significant data set, we will be able to
 examine this constraint more throughly. We will combine the
extracted SD data with published LAD data to examine the temporal
and spectral behavior of bursts over a very wide range in energy.
In an investigation of Sco X-1, we developed techniques for
flux-calibrating the SD data.                      

A MULTIWAVELENGTH SEARCH FOR CORRELATED TIME VARIATIONS IN THE BRIGHTEST EGRET BLAZARS

   In order to better understand the processes by which
high energy gamma rays are produced in blazars, we propose to
search for correlated multiwavelength time variations in 6 of the
7 blazars which have shown the highest fluxes in previous EGRET
observations. The emphasis here is on short timescale (1-3 day)
variations, which can be detected by EGRET only during bright
flares. This is a 2-part proposal: (1) For each of the 6 objects
proposed, we request 2 EGRET observations in narrow-FOV m
ode, each 2 weeks in duration, spaced 4-6 months apart; (2) In the
event one of the targeted objects is seen to be in a flare state,
we request a Target of Opportunity (ToO) extension of the
observation for a minimum of 2 weeks.                             

GAMMA-RAY BURST DISTRIBUTIONS WITH BATSE

   The arguably most stimulating scientific return from
the COMPTON Observatory continues to be the fact that BATSE
observations indicate a cosmological origin of GRBs. Burst
recurrence is thus not expected. Analysis of the 1B catalog led to
the opposite conclusion, while our cycle 4 study suggests that 2B
data are consistent with the null hypothesis of no recurrences. We
propose to study the angular distribution properties of GRBs.
Methods include angular correlation analysis and nearest ne
ighbor analysis. We also propose to carry out spherical harmonic
expansion analysis, and to combine brightness and angular
constraints. This is crucial for testing extend galactic halo (EGH)
models.                                                           

ENHANCED SEARCH METHODS FOR GAMMA-RAY PULSARS

   We propose to further develop statistical tools for
the detection of high energy photon emission from pulsars. To
improve the detection sensitivity for pulsed gamma-ray signals we
developed a technique that also utilizes photon arrival directions
through photon weighting with a point spread function (PSF). We
propose to complete the development of the PSF method and to
demonstrate it with EGRET data of known gamma-ray pulsars.
Implementation of this method in the search program for new ga
mma-pulsars could increase the sample while reducing the required
amount of dedicated EGRET pointings.                              

THE GAMMA-RAY LUMINOSITY FUNCTION OF RADIO PULSARS

   Only six rotation-powered neutron stars have been
detected at energies above 100 MeV and many questions concerning
the efficiencies, beaming factors, and evolution of these gamma-ray
pulsars remain unanswered. As a consequence, their contribution to
the gamma-ray luminosity of the Galaxy remains uncertain by a
factor of 30. We have developed a formalism which uses the
detection and non-detection of radio pulsars in gamma-ray surveys
in order to constrain these parameters. We propose here 
to conduct a deep survey of the region of the Galactic plane which
is maximally effective for the purpose of determining the gamma-ray
luminosity function of pulsars.                                   

REVISITING THE VELA AND GEMINGA GAMMA-RAY PULSARS

   Very important for discriminating between different
pulsar models are accurate studies of pulsar characteristics such
as phase-resolved energy spectra, beaming properties and time
variability for a few well-studied pulsars. The Vela and Geminga
pulsars have been studied in depth above 100 MeV by EGRET and
earlier by COS-B. However, the extrapolation to lower energies is
still uncertain; a combination of spectral breaks and possibly time
variability as seen in the COS-B data cause these so
urces to show up near the COMPTEL detection threshold. We ask for
additional deep observations by COMPTEL and EGRET to allow a better
estimate of the time-averaged source properties in the poorly
covered energy range below 100 MeV, and to search for long-term
time variability.                           

ANALYSIS OF BATSE GAMMA-RAY BURST SELECTION EFFECTS

   In order to understand the nature of gamma ray bursts
detected by BATSE and their sources, and apply meaningful
constraints on burst models, it is essential that we consider all
of the burst selection effects which bias the observed properties
of gamma ray bursts. Some of these selection biases have been
discussed in conjuction with the BATSE measurements, but the
effects of other very important biases have not yet been
investigated. Thus, we propose to make a thorough analysis of the
imp
act of the various competing selection effects on the BATSE data,
and we will show how these effects can be treated quantitatively in
generating unbiases data samples and in comparing the data with
model predictions.                                                
                                       

CONTRIBUTION OF GIANT HII REGIONS TO DIFFUSE 1.809 MEV EMISSION

   COMPTEL has imaged (Diehl et al. 1995) recent sites of
galactic nucleosynthesis using 1.809 Mev line emission, created in
the decay of unstable Al. This emission is concentrated in an
irregular, clumpy ridge in the inner Galaxy. Diehl et al. found
that no known galactic population reproduces their observations.
Consequently, I propose investigate the contribution of correlated
type II supernova explosions to the interstellar budget of unstable
Al. To identify sites of the last generation 
of massive stars, which died in type II supernovae generating the
observed interstellar Al, I intend to employ published tabulations
of giant HII regions, since sites of massive star formation should
be visible (Blaauw 1991) for approximately 20 million yr.         

ANALYSIS OF SIMULTANEOUS SOLAR FLARE X-RAY AND MICROWAVE SPECTRA IN TERMS OF ELECTRIC FIELD HEATING AND ACCELERATION

   We propose to analyze and interpret simultaneous,
high-resolution solar flare x-ray spectra from BATSE/SHERB and
microwave spectra from the Owens Valley Radio Observatory (OVRO) in
terms of the direct electric current heating and acceleration of
electrons. This is the continuation of a study begun in 1994. The
study will (1) test the applicability of the model and, therefore,
the direct electric field particle acceleration mechanism to a
variety of flares, (2) provide a better understandi
ng of the relationship between the energetic electrons responsible
for the x-ray and microwave emissions, and (3) provide quantitative
information about the physical properties of the acceleration
region and their evolution, as required by the model.             
                                        

SPECTRUM DETERMINATION OF THE HIGH-LATITUDE UNIDENTIFIED GAMMA-RAY SOURCE FOUND WITH COMPTEL

   Only two radio pulsars are easily detectable by
COMPTEL: PSR0833 and PSR0531. PSR1509-58 has also been detected but
at a low significance level as have hints from PSR1951+32, PSR
0740-28, PSR 1823-13. We propose to further investigate those
pulsars which COMPTEL has detected only marginally in order to
confirm these pulsations, and if so better define their MeV pulse
characteristics. We do not propose specific dedicated observations,
but request that if any observations take place with th
ese objects in the FOV that we be granted the right to analyse the
data and that consideration be given to putting the object within
10deg of the Comptel optical axis.                                

THE MYSTERY OF THE X-RAY/GAMMA-RAY SPECTRA OF SEYFERTS

   We propose analysis of archival observations of
Seyfert galaxies performed by OSSE and EXOSAT to obtain the average
X-ray/gamma-ray spectrum. The spectra for type 1 and 2 Seyferts and
radio-quiet and radio loud Seyferts will be obtained. The results
should resolve the long standing discrepancies between different
estimates of the average amplitude and spectral form of Seyfert
galaxies. The results will enable us to infer what physical
processes are responsible for the spectra and what fra
ction of the cosmic X-ray background is attributable to Seyferts. 

OSSE AND COMPTEL OBSERVATIONS OF BLAZARS

   We propose coordinated OSSE and COMPTEL observations
of four blazars, and Target of Opportunity pointings for the
blazars 3C 273 and 3C 279 in association with EGRET target of
opportunities. The four blazars we choose for scheduled pointings
are the BL Lac object PKS 0235+164, the quasars 1741-038 and PKS
0528+134, and the COMPTEL blazar 0506-612.                        
                                    

OSSE OBSERVATIONS OF THE GALACTIC CENTER REGION

   We propose OSSE observations of the Galactic Center
Region. See printed copy.                                         

TRANSIENT HARD X-RAY EMISSION FROM GLOBULAR CLUSTERS

   Binary star systems containing compact objects produce
transient emission extending into the hard x-ray regime. We propose
to monitor hard x-ray emission from globular clusters, which are
known to contain a high density of binary systems, using BATSE. The
search should provide information important for understanding the
mechanisms of hard x-ray emission and the dynamics of mass transfer
in x-ray binaries. We have begun a preliminary search of 25
globular clusters. Our search has already l
ed to the identification of a new transient source, GRO J1849-03,
exhibiting 241 day periodic outbursts. Continuation of the search
will constrain the frequency and distribution of hard x-ray
transients in clusters and should identify a number of new hard
x-ray transient sources.                        

A SEARCH FOR BE/X-RAY BINARIES IN HARD X-RAYS

   We propose to use BATSE to monitor several active star
forming regions along the galactic plane for hard x-ray transient
events. Star forming regions contain significant populations of
young massive stars. Binary systems containing massive stars and a
compact object, Be/x-ray binaries (Be/XRBs), exhibit large
variability, periodic recurring outbursts, and pulsed emission in
the hard x-ray band. A number of Be/XRBs have been detected with
BATSE in the hard x-ray band, and a new one, GRO J1
849-30, was recently discovered. We target star forming regions for
which we calculate a large number of expected Be/XRBs. We expect
our search to add to the number of known Be/XRBs and to yield
information on the evolution of massive binary systems.           

A LOCALIZED EXCESS OF GAMMA RADIATION

   Using archival EGRET gamma-ray data and atomic
hydrogen (H I) column densities derived from 21 cm radio
observations, we have found a large irregular region in the
northern galactic hemisphere with a significant enhancement in the
gamma-ray emissivity compared to the surrounding sky. The
enhancement may be due to a local site of cosmic-ray acceleration,
inverse-Compton scattering associated with the local spiral arm, or
the presence of a significant column density of matter other than
H I
 We request an EGRET/Comptel observation of the region to obtain a
more accurate energy spectrum and to determine whether the emission
arises from a localized enhancement in cosmic-ray density or from
the presence of matter other than H I.                            
                                   

A SEARCH FOR EGRET/RADIO PULSARS IN THE ETA CARINA REGION

   Although gamma-ray emission is key to neutron star
energetics, the paucity of observed gamma-ray pulsars and their
properties' surprising inhomogeneity has left models poorly
constrained. Only by discovering new gamma-ray pulsars and studying
those known can progress be made. We request EGRET time to observe
the Eta Carina region, a prime target area containing four compact
sources above 100 MeV: two coincident with the energetic radio
pulsars PSR B1046-58 and PSR J1104-61; 2CG 284-01, on
e of the brightest unidentified sources in the gamma-ray sky; and
the known gamma-ray pulsar PSR B1055-52. We propose to search for
and study periodic gamma-ray emission from PSRs B1046-58 and
J1104-61, possibly resolve the nature of 2CG 284-01, and, in the
process, improve statistics for PSR B1055-52. 

HYDRODYNAMICS OF COMOLOGICAL GAMMA-RAY BURSTS

   We propose a one year study of hydrodynamic flow
underlying the leading models of cosmological gamma-ray bursts. An
efficient smooth particle hydro (SPH) code will be used to model
the disruption and coalescence of neutron stars in neutron-star
black-hole binary systems and in double neutron-star systems.
Simulations of expanding fireballs and of shock formation in
interstellar medium will also be performed.                       

INVESTIGATION OF THE HIGH ENERGY DIFFUSE GAMMA-RAY EMISSION

   The proposed investigation is a continuation of work
which formed a major part of the original EGRET proposal. Previous
studies have shown that the high galactic latitude diffuse emission
is likely extragalactic. EGRET offers the last opportunity for a
decade or more to study this radiation. However, this is one of the
most difficult of the EGRET undertakings. Intensities are weak, the
galactic background is high and background point sources are
variable. We seek access to all data on at 
all latitudes to go with data from previous phases of the mission
in order to have the most information possible. We do not request
exclusive rights, but for access during the protected period of
Phase 5. We request source data data only to allow removal for
diffuse studies.                             

STUDY OF SOFT GAMMA REPEATERS WITH BATSE

   During the first 4 years of its operation, BATSE
detected recurrent emission from two of the three known SGR
sources, SGR 1900+14 and SGR 1806--20. The reactivation of the
latter prompted an immediate, international campaign resulting in
the identification of the X-ray counterpart of the source, which
also coincides with a compact radio source and a rare type of a
very luminous and massive blue star. So far, this is the only
identification of the source of a transient high--energy ($>$ 30
 keV) phenomenon. We propose to monitor and analyze (temporally and
spectrally) SGR emissions for at least 3 years, periodically
reconfiguring BATSE to obtain better sensitivity to SGRs. Our
analysis will enable multiple source identifications and lead to a
better understanding of the phenomenon.       

STUDY OF CORRELATED TEMPORAL AND SPECTRAL VARIABILITY GAMMA-RAY BURSTS

   We propose to make a unified study of GRB temporal and
spectral characteristics to identify GRB subclasses, guided by the
success of this approach in the study of low-mass X-ray binaries.
We will use FFT based techniques, but intend to develop other
timing analysis techniques as well to quantify GRB variability. In
the FFT approach we will use as a measure of temporal variability
(TV) the ``fractional rms'' of the power density spectrum of each
event; we have performed Monte Carlo simulat
ions to understand the Poissonian noise in highly non-stationary
events, such as GRBs. We propose to study the distribution of TVs
in different energy channels, to compute and study the time lags
between different energy channels, and study the TVs in combination
with the GRB Color-Color Diagrams (CCDs).

STUDY OF THE TEMPORAL AND SPECTRAL VARIABILITY OF BLACK-HOLE CANDIDATES WITH BATSE

   BATSE has produced a unique database on the bright
black--hole candidates Cyg X--1, GX 339--4, GRO J1719--24, GRO
J0422+32, and GRO J1655--40; new transient black-hole candidates
are discovered at a rate of at least one per year. We propose to
continue our study of the temporal (fast variability) and spectral
(color-color diagrams) behavior of all these sources over a wide
range of luminocities and spectral states. Motivated by the fact
that the latter three sources are transients, we als
o propose to expand this study to include temporal analysis of
transient sources detected with BATSE in the future. With BATSE we
cover a frequency domain from ~ 4 mHz to 30 Hz. Our study will
cover ~ 20-300 keV, a range only barely explored, and an
unprecedented time span of months to years.           

   We propose to observe bright transient sources with
temporal and spectral characteristics similar to those typical of
potential black hole candidates during cycle V of the Compton Gamma
Ray Observatory (GRO) mission. These objects would be observed as
Targets of Opportunity (ToO) following outburst. Detection of the
outburst and monitoring of the light curve will be provided by the
Burst and Transient Source Experiment (BATSE), while spectral
measurements will be provided                 

OSSE SKY SURVEY OBSERVATIONS FOR CYCLE 5

   We propose to continue OSSE sky survey observations in
Cycle 5 of the COMPTON Observatory Mission. During Phases 3 and 4,
OSSE sky survey investigations were initiated with observations of
the Virgo region and the South Galactic Pole region. We have
demonstrated the capability to use OSSE for survey work in a
mapping mode and have obtained results on broad band spectra and
temporal variability of a number of AGN. In Cycle 5 we propose an
OSSE survey in the region of the North Ecliptic Pol
e. This is a region rich in AGN and which has been extensively
observed by several X-ray missions. This program continues work
toward a first sensitive low-energy gamma-ray sky survey which
could be uniquely accomplished by OSSE on an extended COMPTON
mission.                                            

CORRELATED OBSERVATIONS OF MARKARIAN 421 AND A POSSIBLE TARGET OF OPPORTUNITY

   Markarian 421 remains the only EGRET-detected AGN yet
detected at TeV photon energies. Thus it is a unique laboratory for
the study of AGN phenomena and the relativistic particle beams and
gamma-rays which they sometimes create. This proposal seeks
continuing support for multiwavelength observations of this object
during cycle 5. Observations will be conducted at radio, sub-mm,
near ir, optical, uv, and X-ray wavelengths as well as with the
Whipple Observatory's sensitive gamma-ray telesc
ope operating above 250 GeV. Our previous 1994 campaign discovered
a curious lack of correlation between a strong TeV/X-ray flare and
the intensity profile of the source as determined by EGRET. In the
event of another strong TeV flare, a 7-14 day EGRET ToO is
requested                                   

OBSERVATION OF RADIO-LOUD BL LACERTAEI OBJECTS AND SUPERLUMINAL AGN

   The proposal seeks support for observations above 200
GeV of a selected list of 9 radio-loud, BL Lacertae objects
augmented by 3 superluminal AGN's which are also radio-loud and
core dominant. These sources are chosen to be similar to Markarian
421, a nearby BL Lacertae object, and the only AGN yet detected at
very high photon energies. More than 1/2 of these objects are
nearer than redshift, z$=$0.2, and thus absorption effects should
not prevent their detection if they have intrinsic em
ission to more than $\sim$1 TeV. These observations should provide
a sensitive test of the hypothesis (Dermer and Schlickeiser 1994)
that the reason Mkn 421 is visible to TeV energies is that the
source photons are not absorbed by the thick emission line clouds
which surround many AGN, since in Mkn 421,

ANALYSIS AND MODELING OF THE CYCLOTRON LINE IN HERCULES X-1

   The cyclotron line at about 35 keV in the spectrum of
Her X-1 affords an opportunity to calibrate the BATSE Spectroscopy
Detectors (SDs), and to study the shape and strength of the line as
a function of pulse phase. This we propose to do. First, we will
obtain additional SD observations of Her X-1 during the high state
of its 35-day cycle. Second, we will carry out a joint fit to these
and earlier observations of Her X-1. Extensive simulations show
that such a joint fit should detect the 
cyclotron line with high significance (Q-value of order 10^{-20})
and thereby calibrate the sensitivity of the SD to lines like those
seen by Ginga in a few gamma-ray bursts. Third, we will compare
radiation transfer calculations of the Her X-1 line spectrum with
the SD data, once the line is detected. 

ANALYSIS AND MODELING OF CYCLOTRON LINES IN THE SPECTRA OF GAMMA-RAY BURSTS

   The harmonically-spaced lines seen in the spectra of
some gamma-ray bursts is the strongest evidence that some bursts
are Galactic, rather than cosmological, in origin. Given the
importance of this implication, it is imperative to test the
cyclotron line hypothesis further. This we propose do. First, we
will continue to develop rigorous statistical methods based on
Bayesian inference that address the key problems of establishing
the existence of spectral lines and of determining the best-
fit values and credible regions for the physical parameters
describing them. Second, we will continue to search for lines in
the BATSE Spectroscopy Detector (SD) data, using these methods.
Third, we will exploit our experience in analyzing Ginga data to
compare models with SD data, if lines are found.  

TESTING THE VIABILITY OF GALACTIC HALO MODELS OF GAMMA-RAY BURSTS

   We will test the viability of Galactic halo models of
gamma-ray bursts by calculating the spatial distribution of neutron
stars born with high velociities in the Galactic disk, and
rigorously comparing the resulting brightness and angular
distributions with the BATSE 3B data. Assuming that M31 has a halo
of high velocity neutron stars like that of the Galaxy, we will
determine the constraint M31 imposes on BATSE's sampling depth. In
both studies we will use a powerful maximum likelihood m
ethod to compare the predicted burst probability density
p(F_{pk}^{1024},l,b), where F_{pk}^{1024} is the peak flux in 1024
ms and l and b are Galactic longitude and latitude, with the
observed BATSE distribution of bursts in this 3-dimensional space. 

ANALYSIS OF CLUSTERING AND REPEATING OF GAMMA-RAY BURSTS

   Earlier we found evidence that gamma-ray burst sources
repeat on a time scale of months. If true, this significantly
constrains the range of allowed models. The BATSE post-2B data is
expected to provide a fair test of the repeating hypothesis. We
will analyze this data using the nearest neighbour statistic that
we used earlier. We will also analyze the data using two powerful
maximum likelihood methods that we have developed and already
applied to the BATSE 2B data. These maximum likeliho
od methods, which are based on counts-in-cells and on partitioning
the bursts into clusters, allow us to evaluate the odds favoring
repeating over non-repeating, and find the maximum likelihood
values of the number of repetitions per repeating source and the
repeating fraction of bursts.                

POLARISATION STUDY OF THE CRAB PULSAR WITH COMPTEL

   Various models have been proposed to explain the
featureless power law emission spectrum of the Crab pulsar, almost
all involve the strong magnetic field associated with neutron
stars, and most are very successful in reproducing the observed
spectrum. A study of the polarisation behaviour of the gamma rays
will be an important indicator of the mechanism leading to their
emission. COMPTEL when used as a gamma ray polarimeter can detect
the Crab pulsar in a two weeks observation, if 100% po
larised. We propose 1) to carry out polarisation analysis of the
archived data in which 24.4 weeks exposure of the Crab pulsar has
been accumulated; 2) to perform polarisation analysis of data
obtained in cycle-5, in particular data from the proposed
observation of Crab by COMPTEL team.                 

SEARCH FOR GALACTIC GAMMA-RAY LINE EMISSION USING BATSE

   We propose to continue our search for gamma-ray line
emission in the Galaxy with BATSE, particularly the 511 keV
positron-annihilation radiation and the 26Al line at 1809 keV. To
date, we have derived important limits on bursts of annihilation
radiation from compact objects reported by other authors, made the
first detection of the Galactic 511 keV line with BATSE, and
completed a scan of the Galactic Plane for hidden supernovae by
looking for the lines of 56Co. In Cycle 5, we plan to pro
duce a model-independent map of the Galaxy in the 511 keV line,
extend the sensitivity of the supernova search to see type Ia
supernovae in nearby galaxies, and monitor variations in the MeV
emission of Cyg X-1.                                              

GAMMA RAYS FROM GALACTIC BLACK HOLES

   This a Compton Cycle 5 Guest Investigator Proposal for
the renewal of Cycle 4 grant NAG5-1547. It deals with the
observation and monitoring of selected Galactic Black Hole (GBH)
Candidates with COMPTEL, OSSE and BATSE, modeling and analysis of
GBH spectral and correlative data in collaboration with COMPTEL,
OSSE and BATSE P.I. teams, and theory developments. We will combine
CGRO data with other multiwavelength data (ASCA, SIGMA, ROSAT, XTE
and VLA) to systematically test and refine a prop
osed unified framework for GBH emissions and activities.          

STUDY OF THE SOFT GAMMA-RAY REPEATERS

   This is a Compton Cycle 5 Guest Investigator proposal
for the renewal of Cycle 4 Grant NAG5-1547-01. We propose an
in-depth investigation of the Soft Gamma-Ray Repeaters through a
combination of spectral data modeling, multiwavelength correlative
study, and theoretical interpretations. We will use data from
BATSE, ASCA, ICE, KONUS and ground based telescopes, in
collaboration with BATSE and ASCA team members and with groups at
LANL, Berkeley, and an international team of multiwavelength o
bservers.                                                         

MODELING BATSE GAMMA RAY BURST CONTINUUM SPECTRA AND SPECTRAL EVOLUTION

   This a Compton Cycle 5 Proposal for the renewal of
Cycle 4 grant NAG5-1515. It concerns the modeling, analysis and
interpretation of gamma ray burst continuum spectral evolution data
obtained by CGRO. This project is an on-going collaboration between
Rice University and BATSE PI teams. Using WINGSPAN to model
time-resolved spectral data we extract minimal sets of spectral
parameters and study their time evolution and correlations between
spectral hardness with flux, fluence and other para
meters. These are used to classify spectral evolution patterns and
constrain emission models. Data from OSSE and COMPTEL will also be
used when necessary.                                              

OBSERVATIONS OF CLOSE BL LACERTAE OBJECTS WITH THE EGRET TELESCOPE

   Out of the 90 BL Lacertae objects in the recent QSO
catalog of Hewitt and Burbidge, 11 have redshifts less than 0.1 out
of which EGRET has detected 3, and another 12 with redshifts
between 0.1 and 0.2 out of which EGRET has detected 3 more. There
appears to be a duty cycle of about 25\% for any of these 23 close
BL Lac objects to be detected by EGRET at any time. We propose to
continue this study of the duty cycle of detecting close BL Lac
objects with the EGRET telescope in Cycle 5. We f
urther request observation time of 2 weeks in narrow-field mode to
observe 1219+285 for its steady appearance in previous EGRET data
and for its more significant detection at higher energies.        

EFFECTS OF COMPTON SCATTERING ON BATSE GAMMA-RAY BURST SPECTRA

   There is general uncertainty about the existence of
absorption lines in gamma-ray burst spectra. Lines were reported in
KONUS, HEAO-1 and GINGA data, but BATSE searches find features in
data from one detector but not from another also viewing the burst.
However, Compton scattering of burst emission by the surrounding
spacecraft and the Earth's atmosphere can reduce the significance
of such features in BATSE spectra. Thus, we propose a systematic
analysis of the effects of Compton scatteri
ng from the spacecraft and the Earth on burst spectra measured by
BATSE. We will provide an independent test of BATSE spectral
analysis and generate new detector response matrices that include
azimuthal angle dependences, not considered in current BATSE
analysis programs.                                

ANALYSIS OF ORION GAMMA-RAY LINE AND CONTINUUM DATA

   We propose to analyze high-level processed COMPTEL
Phase 1--4 and OSSE Phase 4 data on nuclear line emission from
accelerated particles in Orion. We will determine by this analysis
the accelerated particle composition from: (i) the C and O line
shapes; (ii) the ratio the 1--2 MeV line flux to that at 4--7 MeV;
and (iii) the ratio of the alpha-alpha complex flux at 0.4--0.5 MeV
to that at 4--7 MeV. We will also determine the accelerated
particle energy spectrum from the C and O line width 
and from the ratio of the pion decay flux to nuclear line flux,
utilizing EGRET continuum data. Our results are essential for
constraining the possible origins of the accelerated particles in
Orion, as well as their acceleration mechanism.                   

SIMULTANEOUS EGRET - ASCA STUDY OF GEV BRIGHT BLAZAR CTA102

   The detection of gamma-ray emission from 3C279, and
subsequently from some 30 OVV quasars, was one of the great
discoveries of the Compton GRO. While Comptonization is the most
likely mechanism for the gamma-rays, the source of the soft photons
is still a mystery: are they Comptonized synchrotron photons,
produced in the same jet as the gamma-rays (as in
Synchrotron-self-Compton models), or is it Comptonized external,
diffuse ultraviolet radiation? The simultaneous X-ray/gamma-ray
observa
tions provide such a crucial test, specifically as to the nature of
the break between the X-ray and gamma-ray regimes. We propose an
EGRET GRO observations of an object CTA 102 (where this break is
extreme), to be coordinated with an approved Asca observation, to
test the theoretical models.            

DEEP SEARCH FOR UNTRIGGERED BATSE GAMMA-RAY BURSTS

   We propose to continue our deep search of BATSE data
for bursts which did not cause an on-board trigger. Our approach
involves searching residual counts above a sophisticated background
model that has already been developed and is undergoing continual
improvement at JPL under a separate BATSE Guest Investigation. By
using net residual counts, the major orbital variations in the
background are eliminated which allows deeper searches and improves
measurements for weak bursts, whether trigge
red or not. During Cycle 5 we propose to improve the automatic
burst search algorithms and to extend the analysis to a total of 2
years of BATSE observations. We will also address the
characterization of the observed peak flux distribution, with
emphasis on depth-dependent sky exposure.                 

MEV EMISSION FROM SEYFERT GALAXIES

   We propose the study of gamma-ray emission of Seyfert
galaxies in the energy range 3-30~MeV with Comptel. Complementary
to a survey at energies 0.75-3~MeV, this study will address the
question of whether Seyfert galaxies contribute significantly to
the extragalactic background at MeV energies, and the issue of
whether Seyfert galaxies have nuclear outflows which are
substantially decelerated close to the central engine.            
                                    

  We propose a two-week OSSE observation of the radio
quiet quasar III~Zw~2. The goal of this proposal is to study the
hard X-ray spectrum of a bright radio quiet quasar, to check

AN OSSE OBSERVATION OF III ZW 2

 We propose a two-week OSSE observation of the radio
quiet quasar III~Zw~2. The goal of this proposal is to study the
hard X-ray spectrum of a bright radio quiet quasar, to check
whether this type of object behaves more like Seyfert galaxies or
more like blazars in this energy range. The object was chosen by
virtue of its previously known X-ray characteristics, and by
similarity to another radio quiet quasar already detected by OSSE,
PG~1416-129.                                            

MULTIFREQUENCY OBSERVATION OF W COMAE

   We propose a two-week observation of the nearby blazar
1219+285 (ON 231, W Comae) preferably during March 1996 in the
framework of a multifrequency campaign covering optical, X-ray,
COMPTEL, EGRET and TeV energy ranges. Due to its proximity and hard
gamma ray spectrum (Gamma=1.4+-0.4) this source could be discovered
as the second extragalactic TeV source after Mrk421. In order to
assess the effect of absorption on the cosmic infrared background
in the TeV range, EGRET observations are mos
t important narrowing down the possible theoretical models for the
gamma ray emission.                                               

A CUMULATIVE COMPTEL FLUX FOR SEYFERTS IN VIRGO

   We propose to search for a cumulative gamma ray flux
in the 3-30 MeV range from Seyfert galaxies in the Virgo region. A
thorough analysis of archival data of the Virgo region, which has
received the deepest exposure at high galactic latitudes, should
improve the flux limit obtained for the all-sky Seyfert 1 sample
studied by Maisack et al. (1995). Thereby we plan to attack the
problem of whether Seyfert galaxies contribute to the extragalactic
gamma ray background in the MeV regime, and w
hether the radiation process responsible for the X-ray emission of
Seyferts involves anisotropic nonthermal pair cascades.           

GAMMA-RAY BURSTS AND RELATIVISTIC MHD AROUND COALESCING NEUTRON STARS

   We propose to do relativistic hydrodynamic simulations
of the coalescence of neutron-star binary systems supplemented with
magnetohydrodynamic simulations of the magnetic reconnection as the
stars merge. The aim of this calculation will be to develop a
theoretical model for the temporal and spectral evolution of
cosmological gamma-ray bursts produced during the magnetic
reconnection. The results will be combined with radiation transport
calculations with the aim of comparing the resultant
 gamma-ray burst simulations directly with BATSE observations. We
will also search for new observable signatures which might be
detectable in future missions.                                    

TIMING THE GEMINGA PULSAR WITH HIGH-ENERGY GAMMA RAYS

   In continuation of our cycle 4 program, we propose a
deep exposure of Geminga in cycle 5. With this data, we expect to
be able to produce an ephemeris which has sufficient precision to
count cycles well into the 21st century (assuming no glitch
occurs), and to compare phase between EGRET, COS-B, and SAS-2. We
expect to either find evidence for a glitch, or to obtain coherence
over this 24 year baseline. We will also refine new results which
we obtained with data from cycles 1, 2, 3, and 4
: 1) The proper motion is detected in the gamma-ray timing,
consistent with the optical measurement of Bignami et al. (1993).
2) Two additional peaks, as expected in the outer gap model, are
tentatively detected in the off-pulse region.                     
                                              

A PROGRAM TO STUDY GALACTIC CENTER HIGH-ENERGY GAMMA RAYS

   EGRET data show an intense excess which is associated
with the center of the Galaxy. We propose a comprehensive study of
this excess. We will attempt to determine if the source is compact
(if so, it is probably Sgr A*), or diffuse. First, we will
investigate the evidence for variability. Also, we will carefully
test the extent of the emission. If we can show it to be broader
than the PSF, a diffuse origin is established. In parallel, we will
develop models of diffuse emission near the Gal
actic center, and for the gamma-ray emission of Sgr A*. Further
EGRET observation is not warrented because previous and scheduled
observations already comprise the equivalent of approximately 4
months of on-axis exposure.                                       
                                           

PROMPT OSSE OBSERVATION OF BATSE BURST POSITIONS

   The BATSE and OSSE teams have implemented a system
allowing prompt (2 min or less) slewing of the OSSE detectors to
burst positions determined on-board by BATSE. This allows us to
make the most sensitive ever tests for post-burst emission from 50
keV to 10 MeV. OSSE can respond rapidly enough to detect the tails
of long duration events, giving good spectra and improved
positioning. We can also observe positions provided by other
instruments within 1-2 hr. Our event rate is expected to be 
1-2 per month, based on our field of view and the BATSE event rate.
The 12 hr observations will not significantly reduce the
sensitivity of any scheduled pointings. We propose to continue
these observations in Cycle 5 and beyond. We will also study
archival serendipitous observations of burst positions.

MULTIWAVELENGTH OBSERVATIONS OF CYGNUS X-3

   OSSE has shown, for the first time, that Cyg X-3 is
highly variable in the hard X-rays (above 50 keV). The variability
includes strong orbital modulation and a new low-intensity hard
X-ray state of Cyg X-3 which may be associated with an intense
radio flare. Rapid flux changes also occur in radio, IR, and soft
X-rays. Simultaneous multiwavelength observations are required to
understand the crucial relationship between the variations at
different frequencies. We propose a target of opportu
nity observation of Cyg X-3 in the event of a large radio flare, or
flare precursors, to look for the X-ray low state and the recovery
to the high state. We also request scheduled pointings for which
coincident radio monitoring will be available and IR observations
will be requested.                    

EGRET IN-FLIGHT CALIBRATION

SURVEY OF HARD X-/GAMMA-RAY EMISSION FROM SUPERNOVA REMNANTS

   Using the BATSE data we propose to do a survey of the
hard x-ray/gamma-ray emission originating in supernova remnants
(SNRs). Hard x-ray/gamma-ray emission would appear likely from some
of the many high energy processes that are believed to associated
with SNRs. We intend to use the BATSE occultation software to
examine several different SNRs. Preliminary work has indicated that
at least five SNRs indicate some emission. One of the best
candidates for emission MSH15-52, if confirmed, will
 be the weakest source detected using the occultation technique.
This study will attempt to push the limits of BATSE's sensitivity
to the lowest possible level and allow us to take full advantage of
BATSE's long timescale of measurements.                           

COMPTEL OBSERVATIONS OF CYGNUS X-1

   Above 1 MeV, there have been several reports of
emission from Cyg X-1, but the various measurements are not all
consistent. COMPTEL has now collected several weeks exposure to Cyg
X-1, which show no significant variability near 1 MeV. The spectrum
indicates detectable emission out to at least 5 MeV, with a
significant hardening of the spectrum between 2 and 5 MeV. This
hardening is at a flux level more than 2 orders of magnitude below
that reported by some previous experiments. Given the 
intriguing nature of these results, coupled with the lack of
COMPTEL observations during cycle 4, we propose to collect
additional COMPTEL data during cycle 5. These data will not only
improve the statistics of the MeV spectrum, but will add to the
search for variability at MeV energies.                

SEARCH FOR NUCLEAR LINE EMISSION FROM ACCRETING BINARIES

   COMPTEL is ideally suited to search for nuclear line
emissions (1-30 MeV) due to its superior sensitivity and its large
FoV. We propose to collect additional data which will be used to
search for various types of line emissions: nuclear de-excitation,
neutron capture, and neutral pion decay. This is part of an
on-going COMPTEL study of X-ray binaries. For cycle 5, we propose
dedicated observations of some sources, selected on the basis of
both the relative COMPTEL exposure to date and the
 potential for interesting results. Data rights for several other
sources are requested should those sources lie within the COMPTEL
FoV. We also request the declaration of a COMPTEL ToO (and the
associated data rights) for those X-ray novae which exceed 2 Crab
in the 20-300 keV range.                   

BATSE ALBEDO POLARIMETRY OF GAMMA-RAY BURSTS AND SOLAR FLARES

   We propose to continue our effort to use BATSE data to
measure linear polarization in both gamma-ray bursts and solar
flares. This is to be achieved by measuring the asymmetries
inherent in the radiation which is reflected from the Earth's
atmosphere, a technique which we call albedo polarimetry. Using
Monte Carlo studies, we have estimated the efficiency of BATSE for
measuring polarization. For bursts, we find that BATSE has
sufficient sensitivity to constrain polarization parameters for
 events with fluence greater than 10**-5 ergs cm**-2 (about 40
events in the 2B catalog). For flares, we expect that many events
will have sufficient statistics for a meaningful analysis. Here we
propose to continue our Monte Carlo studies and to begin a detailed
analysis of individual events.          

A LONG-TERM BATSE SD STUDY OF SCO X-1

   Sco X-1 is the proto-type low-mass x-ray binary. It is
the brightest, continuous, non-solar x-ray source in the sky and is
detectable by the BATSE Spectroscopy Detectors (SDs) when it is
above the Earth's limb as seen from CGRO. Work under this proposal
will focus on three areas, 1) the study of the long-term,
high-energy variations which exist within the Sco X-1 system, 2)
the study of its long-term correlated optical and x-ray emission,
and 3) the study of flares using simultaneous opti
cal and BATSE SD data. This work will be accomplished without
interference to other CGRO programs by using the all-sky monitoring
capabilities of the BATSE SDs.                                    

COSMOLOGICAL GAMMA RAY BURST MODELS: SIGNATURES AND CONSTRAINTS

   Building upon our previous encouraging results on a
generic GRB scenario, we intend to develop specific models
addressing several major current issues. Among these are the
reported bimodal time distribution and the related apparent
hardness-duration correlation and hardness-brightness correlations.
We will investigate astrophysical scenarios for the initial energy
source and baryon loading capable of producing the high Lorentz
factors implied by the observations, and will explore their co
nsequences for the temporal and spectral correlations in both
cosmological and galactic halo models, and will calculate predicted
observational signatures and correlations that will be contrasted
between the models and the data.                                  

TESTING GALACTIC GAMMA-RAY BURST MODELS

   Strong constraints can be placed on the allowed
fraction of Galactic spiral arm sources in arm plus halo models.
The 3B BATSE catalog will give even stronger constraints, and we
propose to use it to effectively rule out the spiral arm geometry:
a large fraction of the bursters can still be local neutron stars,
but they must either have a disk geometry, or be essentially
homogeneous. Another possible class of gamma-ray burst models uses
high velocity neutron stars in an extended Galactic h
alo. We show that the assumed distribution of neutron star
velocities strongly affects the simulated distributions of isolated
radio pulsars. We propose to test the high velocity neutron star
models in both pulsar and gamma-ray burst simulations to determine
which ones are allowed.                      

"IS THERE A LONG-TERM, PERIODIC MODULATION OF THE HIGH-ENERGY GAMMA-RAY LIGHT CURVE OF THE CRAB PULSAR?"

   As first noted by the COS-B group, the SAS-2 and COS-B
observations of the Crab pulsar show a long-term variation of the
intensity of the 1st peak to the 2nd peak of the gamma-ray light
curve. This apparent sinusoidal variation might be due to the
nutation of the neutron star with a period of about 14 yrs. While
EGRET observations are consistent with this variation, for the
combined SAS-2, COS-B and EGRET data, the null hypothesis cannot be
ruled out with a high degree of confidence. A 3 
week EGRET observation of Crab, during a time when the intensity
ratio should be increasing, is proposed. The observation, combined
with previous observations, can establish whether the periodicity
is real or not. This will be the last opportunity for a decade or
more to address this question.          

LIGHTNING GENERATED GAMMA RAY BURSTS

   Objective of this proposal is to advance state of
understanding of correlation between lightning flashes and
gamma-ray bursts. It will be accomplished by collecting the CGRO
observations, correlate them with lightning data available from
NLDN and than run various models to compare them with the
observations.                                                     

MONITORING OF THE CRAB NEBULA AND PULSAR

   The Crab is the strongest permanent source in the
COMPTEL energy range. Pulsar theories can describe the Crab pulsar
phase average spectrum, but it is a challenge to test theories on
phase resolved spectra of the pulsed emission. Although the COMPTEL
data analysed yet cannot be used to determine the spectral slope of
the phase resolved spectra in the most cases, they can be used with
the EGRET data to constrain the spectral behaviour. Adding data of
further observations will yield a signi
ficant signal of the phase resolved spectra in more energy
intervals than so far achieved. COMPTEL and EGRET data have shown
a time variability of the Crab unpulsed emission on a time scale of
16 months. In order to obtain a basis for modelling it is necessary
to monitor the Crab unpulsed emission.     

DATA RIGHTS FOR QUASARS NOT SEEN IN HIGH ENERGY GAMMA RAYS BY EGRET

   High energy gamma-rays have been detected by EGRET
from more than 33 active galactic nuclei (AGNs), all of which are
radio-loud sources with flat radio spectra. Many of the AGNs
detected by EGRET are known or suspected superluminal sources.
However, a large number of strong flat-spectrum radio sources and
superluminal quasars have not been seen by EGRET. Here we propose
for data rights for some of these sources not seen in high energy
gamma-rays, if they fall within EGRET's FOV. In additi
on, a target of opportunity (ToO) is requested for the first
flaring quasar from the requested list of sources.                
                                                                  
                                          

SEARCHING FOR GRAVITATIONAL LENSING EFFECTS IN GRB DATA

   A gravitational lens echo could give the strongest
evidence yet that gamma-ray bursts (GRBs) lie at cosmological
distances. Previously, the PI has led several efforts to find
gravitational lensing artifacts in BATSE data. Here we propose to
continue these methods and implement another method involving
correlation between satellites which is together capable of
detecting or limiting a significant cosmological density of compact
dark matter over some 15 orders of magnitude in mass.         

HOW DO GRB PULSES CHANGE WITH ENERGY?

   GRB light curves do not imply random emission - clear
``pulse" structures occur. Fluent pulses occur in relative
isolation only rarely - then providing opportunities to study these
building blocks of gamma-ray bursts. Preliminary investigation by
the PI has uncovered, so far, simple rules that appear to operate
in GRB pulses between energies. These relations promise to greatly
help in the quantification, decomposition, and modeling of GRB
attributes. We propose to study fluent, isolated p
ulses to better understand these relations.                       

ENERGETICS OF IMPULSIVE SOLAR FLARES: CORRELATING BATSE HARD X-RAY BURSTS AND THE SOLAR ATMOSPHERE'S SOFT X-RAY RESPONSE

   The goal of this investigation is to correlate BATSE
solar hard X-ray (HXR) emission with soft X-ray (SXR) emitting
plasma flows observed by the Yohkoh Bragg Crystal Spectrometers
(BCS). The investigation will test the hypothesis that localized
electron beam heating is the operative energy transport mechanism
in impulsive solar flares. For suitably impulsive HXR emission, an
analysis of the hydrodynamic equations predicts a relationship
between the HXR intensity and the second time deriva
tive of the SXR plasma's momentum. To quantify the flows and
momentum of SXR emitting plasma, we utilize a novel technique
involving the velocity differential emission measure (VDEM) which
has not yet been applied to this problem.                         

IDENTIFICATION OF HIGH-LATITUDE EGRET SOURCES

   There are seven high-latitude, unidentified EGRET
gamma-ray sources for which additional data might prove useful in
establishing an identification. One of the might be the radio
galaxy Centaurus A, an identification which needs to be confirmed.
Two of them are bright and fairly steady, which does not clearly
identify them either as blazars or pulsars. The remaining four
flared once or twice, so they are likely to be unidentified
blazars. We request data rights for these objects, but no de
dicated observations.                                             

PRECISE MEASUREMENTS OF NUMBER-INTENSITY RELATION AND TIME-DILATION EFFECTS IN SHORT GAMMA-RAY BURSTS

   Pulses in short (less than 2 s) GRBs are much shorter
than the integration time (64 ms) used to measure their peak
intensities; thus the short burst number-intensity relation is
ill-defined. Searches for time dilation have not yet been performed
for short bursts. We will apply a completely automated
burst-fitting algorithm based on Bayesian statistics, designed to
operate in the low signal-to-noise regime, to BATSE and PVO high
time resolution data on short bursts. Statistical errors and 
systematic biases are straightforwardly conputed via a bootstrap
approach. Much more precise measurements of peak intensities and
pulse widths will result for short bursts, and meaningful fits of
their number-intensity relation, incorporating any time-dilation
effects, will be performed.                

A SEARCH FOR OPTICAL COUNTERPARTS OF GAMMA-RAY BURSTS

   The ETC is a fully-automated, optical transient
detection facility dedicated to the search for optical flashes
spatially and temporally coincidnent with GRBs. Operational since
1991, the ETC currently observes ~3 BATSE-localized GRBs/yr
coincident withBATSE. Any coincident flashes are localized to ~10"
accuracy, ~10^5 times finer than with BATSE alone. To date, 6
ETC/BATSE coincidences have been detected, none of which have
associated ETC optical flashes. With improvements currently under
way, the number of ETC/BATSE coincidences will rise to ~1/month in
mid-1995. A close collaboration with the BATSE and BACODINE teams,
proposed here, will establish and rapidly disseminate small (~10")
error boxes from positive ETC detections for multiwavelength
astronomical studies.                     

CONTINUOUS MONITORING OF THE HARD X-RAY SPECTRUM AND FLUX OF NGC 4151

   We propose to continue using BATSE occultation data to
continuously monitor the nearby Seyfert galaxy NGC 4151. This AGN
is variable on time scales of a few days, but long-term daily
monitoring has never been possible in X-rays or gamma-rays prior to
BATSE. Of prime interest are spectral studies to determine the
nature and duty-cycle of the recently discovered break or
exponential cutoff at ~100 keV. We intend to use the standard
occultation analysis which will allow detection on few-day 
time scales and spectral measurements on week time scales. We will
improve the occultation software by studying the systematic effects
of lengthening the occultation interval; NGC 4151 is well-suited
for this study because it is fairly isolated in the X-ray sky and
is often observed by OSSE.            

A BROAD-BAND OBSERVATION OF CYGNUS X-1 WITH THE COMPTON OBSERVATORY AND XTE

   We propose spectral and timing observations of the
black hole candidate Cygnus X-1 with OSSE. The observation would be
contemporaneous with an XTE observation. While various models have
been succcessful matching the X-ray spectrum or the gamma ray
spectrum of galactic black hole candidates independently, the
extrapolation from one energy band into the other is not
successful.Since the source is highly time variable, a
contemporaneous measurement of the X-ray and gamma ray spectra is
requi
red. The proposed OSSE observation would be two weeks long, with a
matching $10^5$ second HEXTE observation and short daily PCA
snapshots to complement the low end of the energy spectrum. A
contemporaneous ASCA observation is also planned.                 
                                               

A SEARCH FOR RADIO QUIET GAMMA-RAY PULSARS

   We propose long on-axis observations of strong EGRET
point sources such as GRO J1837+59 to undertake a sensitive search
for radio-quiet gamma-ray pulsars. This investigation will utilize
the significant computational resources of the Center for Advanced
Computing Research at Caltech to compute Gigapoint power spectra to
search for periodicity over a wide range of periods and period
derivatives, We have demonstrated the ability to detect Vela-like
pulsars with signal-to-noise similar to th
ose expected from the proposed deep observations of individual
sources. We will also continue our archival analysis of data from
Phases 1-3.                                                       

OSSE MAPPING OF DIFFUSE GALACTIC GAMMA-RAY EMISSION

   We propose to continue our multi-year investigation to
map the galactic plane using OSSE. During the past year, we have
developed a promising analysis technique for generating maps using
OSSE data. In this proposal we request: 1) support to continue
refining this mapping technique, and 2) a systematic set of OSSE
observations of the galactic plane. Maps generated from these data
will allow the galactic diffuse emission to be studied with good
sensitivity and spatial resolution. This study
 will also aid in the analysis of weak point sources of emission
located near the plane of the galaxy by reducing the uncertainty in
the contribution from the diffuse emission.                       

OSSE OBSERVATIONS OF GALACTIC POSITRON ANNIHILATION RADIATION

   Positron annihilation provides a unique and powerful
mechanism for increasing our understanding of the astrophysics of
our Galaxy and its chemical evolution. OSSE observations show that
both the 511 keV line and positronium continuum have similar
longitude distributions, which can be described by a nuclear bulge
component (FWHM ~ 12 degrees) plus a relatively constant galactic
disk component. Deeper observations of the plane are required to
better constrain the disk and bulge components. 
New analysis techniques are also being developed to generate maps
using OSSE data. In this proposal we request: 1) deep observations
of the galactic plane to better measure the disk component, and 2)
support to continue developing the OSSE mapping technique.        
                                     

A DETAILED INVESTIGATION OF THE LONG TERM BEHAVIOR OF ACCELERATED PARTICLES IN THE 11 JUNE 1991 FLARE

   We shall analyze the time evolution of the accelerated
particles in the 11 June 1991 flare. We are assembling a wide range
of high energy CGRO data and we plan to analyze archival BATSE data
for both lines and continuum. We shall also utilize 17, 35 and 80
GHz microwave data and neutron monitor GLE data. We shall follow
the temporal evolution of the ion spectrum from 10 MeV to a few GeV
for 8 hours and of the electron spectrum from an MeV to 100 MeV for
3 hours. Our results will have clea
r implication on the issue of trapping vs. acceleration in long
duration high energy events; they will also put strong constraints
on acceleration mechanisms capable of operating over long periods
of time. Long duration solar flare gamma ray emission is a new
feature of solar activity discovered by CGRO.  

A CYCLE 5 SEARCH FOR THE COUNTERPARTS OF GAMMA-RAY BURSTS USING THE BATSE/COMPTEL/NMSU RAPID RESPONSE NETWORK

   This is a COMPTEL Type 3 proposal to search on
real-time notice for optical and radio counterparts to cosmic
gamma-ray bursts. Using a procedure developed and improved over the
last four years of Compton Observatory operations, we will produce
sub-degree size error boxes of large gamma-ray bursts that occur in
the COMPTEL field-of-view in less than 5 minutes. These error boxes
will be quickly imaged by a global network of optical and radio
observatories to faint flux limits. Searches of t
his magnitude and speed open up a whole new time and flux domain in
the gamma-ray burst counterpart search problem. We believe these
capabilities are unique and provide our best hope of identifying a
GRB counterpart.                                                  

STUDIES OF SOLAR FLARE AND EARTH-ALBEDO NEUTRONS WITH COMPTEL

   We propose to investigate neutron emission from solar
flares and the flux of neutrons from cosmic ray interactions with
the Earth's atmosphere. The Earth-albedo neutron flux has not yet
been studied with the instruments on the Compton Observatory. To
make a significant improvement in the study of solar neutrons we
must utilize the full capabilities of the COMPTEL instrument rather
than using the severely reduced data set as has been done to date.
In order to accomplish these studies, we w
ill develop a comprehensive treatment of the COMPTEL neutron
response and data inversion techniques. This treatment consists of
two parts: a comprehensive Monte Carlo simulation of neutron events
in the instrument; and statistical regularization procedures to
infer the incident neutron distribution.    

CONTINUED STUDIES OF SOLAR MICROFLARES WITH BATSE

   We propose to continue our studies and automated
cataloging of solar microflares using the continuous 1 s/4 channel
BATSE data. To date we have searched and processed almost all
available data. We have established that microflares cannot heat
the corona and that flare-rate tracks that as measured in soft
X-rays. Although at solar minimum, we wish to continue searching
data as they become available, to cover all phases of the solar
cycle. Using experience and new computers we also wish to 
reprocess old data to (1) improve the rejection of non-solar events
and (2) include more flare parameters, e.g. duration and spectral
fits. The resulting enhanced dataset (available pubicly) will
facilitate multiwavelength studies of global flare activity and of
individual flares or sets of flares.     

"A SEARCH FOR HIGH ENERGY COMPONENT OF COSMIC GAMMA RAY BURSTS BY AVERAGING BATSE, COMPTEL, AND EGRET DATA."

   The high-energy time histories of GRBs observed by
COMPTEL and EGRET will be averaged together after being aligned at
the times of peak intensity as observed by BATSE. This will reveal
the general time-history of high-energy photons and enable
comparison of the high-energy time profile to the time histories
seen by BATSE. For GRBs which occurred in the fields-of-view of
COMPTEL and EGRET, we will form maps of the detected photons binned
versus time from BATSE peaks and angular distance fr
om the BATSE position. Using these maps we will search for the
presence of hard-components not detectable in individual bursts.
This will reveal whether a hard-component is typical of all GRBs or
is a special property of the brightest. Important constraints on
the physical nature of GRBs will be derived.

THE GAMMA-RAY BURST PULSE PARADIGM AND THE BIMODAL DURATION DISTRIBUTION

   Long duration Gamma-Ray Bursts often consist of
multiple PULSES -- with shapes characterized by ASYMMETRY,
NARROWING at high energy, and SOFTENING of the spectrum with time.
We will use a novel algorithm to decompose bursts into pulses,
quantify their shapes, and compare pulse attributes in short and
long bursts. It uses maximum Poisson likelihood, concurrent fitting
of energy bands, a Bayesian criterion for counting pulses, and
bootstrap estimation of error and bias. Results will be mode
led with relativistic beaming (to explain correlations of pulse
widths with burst duration, and with viewing geometry (to explain
pulse asymmetry and hardness).                                    

THREE EXTREME RED EGRET BLAZARS

   We will study the 1-30 MeV properties of 3 red EGRET
blazars optimized for a strong COMPTEL signal, using a combination
of new and archival COMPTEL and EGRET data. A simultaneous
determination of the 1--30 MeV and $>$ 100 MeV spectral indices in
these 3 Bright sources (PKS 1508$-$089, 1606+106, and PKS
1741$-$038) will allow us to distinguish between inverse Compton
and proton-meson cascade jet models. Of our sources, the most
extreme case for these models is PKS 1741$-$038 with $\Gamma_\
gamma = 3$ (predicted to be nearly as bright as PKS 0528+134 at 3
MeV).                                                             

LARGE-SCALE MAPPING OF THE LOW-ENERGY GAMMA-RAY SKY WITH COMPTEL

   A principal objective of the COMPTEL instrument is to
study the large- scale Galactic emission, both diffuse and from
discrete sources, and in both continuum and lines. Full sky images
based on Phase 1, 2 and 3 have already shown that the Galactic
plane is detected with high significance. The presence of other
components not related to the gas is however likely, and it is a
principal goal to identify correctly the astrophysical origins of
the emission. Full sky mapping of the 26Al 1.8 MeV
 line and the search for nuclear interaction lines are other major
goals. The combined exposure and quality of the data from phases
1-4 is extremely non-uniform; we therefore propose a 3-year plan of
pointings designed to yield a far more homogeneous coverage of the
entire sky.                          

BATSE SOLAR FLARE SPECTROSCOPY

   This proposal supports the spectral and temporal
analysis of solar flare hard X-ray events observed with BATSE on
CGROSSC by the proposer and many other members of the United States
and international solar physics community. Specifically this
proposal supports the enhancement of spectral analysis routines
both for usability and accuracy. Scientifically this proposal
supports detailed spectral analysis below 100 keV, the study of
time-of-flight delays, and the study of the high energy even
ts of June 1991.                                                  

OSSE/BATSE COMBINED SPECTRAL ANALYSES OF GAMMA-RAY LINE FLARES

   We propose to utilize spectral data from both the OSSE
and BATSE spectrometers to obtain a more complete picture of the
hard X-ray and gamma-ray spectra of the intense 1991 June flares.
OSSE has derived good line spectra of these flares at energies >1
MeV; analyses of these spectra are providing information on the
elemental abundances of the flare plasma, accelerated ion spectra,
and the ion to electron ratio during the flares. Although the 511
keV annihilation line and alpha-alpha lines 
are visible in the OSSE spectra, their absolute intensities cannot
be determined due to saturation effects. We propose to use BATSE
spectra to normalize the OSSE data in order to obtain 0.1 to 9 MeV
spectra, including all lines and continua.                        
                                      

MULTIWAVELENGHT STUDY OF X-RAY NOVAE

   We propose to continue a program of mutltiwavelength
study of X-Ray nova detected by BATSE. Our objectives include
carrying out coordinated programs of radio, infrared, optical an
ultraviolet observations utilizing major facilities, covering
critical outburst stages and tracking the source into quiescence.
This will be facilitated by frequent communications with the BATSE
experiment team and prompt analysis of the hard X-ray data in
support of critical real-time decisions on observing str
ategies. Specific scientific issues we hope to address include
determining the nature of the compact object, constraining models
of outburst mechanisms, clarifying the empirical picture regarding
the early- outburst synchrotron bubble events seen at radio.      

BLAZAR AGN AS TARGETS OF OPPORTUNITY

   We propose to continue an EGRET target-of-opportunity
program, initiated during Phase 3, to observe of blazar AGN during
periods of exceptional activity. Our programs of supporting
observations include long-baseline photometric monitoring,
densely-sampled follow-up monitoring, optical and ultraviolet
spectroscopy and ground-based high-energy gamma-ray coverage. This
has led to the discovery of numerous episodes of high-amplitude
variability among our target objects: events involving energ
y releases of 10**54 ergs have been documented. There is as yet
very little knowledge of how blazar high-energy emission is
correlated with other wavelengths, the observation strategy we
propose can provide crucial insight into the empirical blazar
variability picture.                                   

OSSE OBSERVATIONS OF THE DIFFUSE GALACTIC LOW-ENERGY GAMMA-RAY CONTINUUM

   OSSE observations have revealed that the diffuse
gamma-ray emission from the inner Galaxy is more intense than
anticipated and that its spectrum turns up below about several
hundred keV. If this emission is bremsstrahlung then there exists
a population of low-energy cosmic-ray electrons which requires a
power of 10^41 erg/s, exceeding that of the nuclear cosmic-rays by
about an order of magnitude. We request observations at Galactic
longitudes 95 deg. and 250 deg. to supplement previous O
SSE and COMPTEL observations and constrain models for the
distribution of the diffuse Galactic low-energy gamma-ray
continuum.                                                        

COSMIC RAY STUDIES IN THE LARGE MAGELLANIC CLOUD USING HIGH ENERGY GAMMA RAYS

   Gamma ray observations provide a direct way to study
cosmic rays in external galaxies. EGRET has reported the only
detection of an external normal galaxy, the Large Magellanic Cloud
at MeV energies. The gamma ray emission is consistent with that
expected from the H1 distribution and the non-thermal electron
distribution. Due to its proximity the LMC offers an ideal site to
study the density and energy spectra of cosmic ray electrons and
protons. Of the 6 weeks of EGRET observations awarde
d to us in phase IV, only 4 weeks will be completed in phase IV. We
request scheduling of the missing two weeks in phase V. We also
request rights to data on the LMC from other scheduled observations
in phase V.                                                       

MONITORING THE SPECTRAL VARIABILITY OF CENTAURUS A IN THE ENERGY RANGE COVERED BY COMPTON GRO

   The active radio galaxy Centaurus A has repeatedly
been observed with CGRO. The analysis of the data obtained during
Phases I-III shows variable emission up to energies and probably
even above 100 MeV. The spectral analysis of the OSSE and COMPTEL
data shows large changes between observations. OSSE detected
spectral variations even on short time scales during single
observations. Data from the 4 simultaneous OSSE/COMPTEL
observations indicate a possible correlation/anticorrelation of the
emission below 1 MeV and above. In this joint proposal of the
COMPTEL and OSSE teams, 2 observation periods and a ToO condition
for simultaneous observations in Cycle 5 with all 4 CGRO
instruments are proposed to continue the monitoring of Cen A in the
whole energy range of CGRO.                        

MONITORING THE GAMMA-RAY/RADIO-STAR 2CG 135+1/LSI 61 303

   We propose to continue a CGRO multi-instrument series
of observations of the gamma-ray source 2CG 135+1. The Cycle 5
observations will be supported by continuous monitoring at Green
Bank of the radio emission of its possible massive star/radio
counterpart GT 0236+610/LSI + 61 303. The main aim of our
investigation is to study the time variability of 2CG 135+1 and
possibly confirm its association with LSI +61 303. 2CG 135+1 can be
a binary containing a massive star orbiting around an energ
etic pulsar enshrouded in nebular material and producing gamma-rays
by shock emission. A clarification of the nature of 2CG 135+1 is of
great importance for the interpretation of unidentified and
time-variable galactic gamma-ray sources.                         
                                         

THEORY OF HIGH ENERGY EMISSION FROM X-RAY BURSTERS

   Recent BATSE observations of X-ray bursters containing
accreting neutron stars led to the remarkable discovery of
transient hard X-ray emission from Aquila X-1 and 4U 1608-52. We
propose to carry out a theoretical study of thermal and non-thermal
processes in accretion disks surrounding neutron stars able to
produce a significant flux of hard X-ray emission. In particular,
we will study magnetic field reconnection and time variable
particle acceleration near the disk-magnetosphere boundar
y surrounding weakly magnetized neutron stars. Our investigation is
relevant for the understanding of different acceleration and
radiation mechanisms affecting accretion disks surrounding black
hole and neutron star systems.                                    
                                           

PULSAR TIMING PARAMETERS IN SUPPORT OF GRO

   This document supplements a "Type 2 Proposal" in
response to NRA 95-OSS-01, entitled Gamma-Ray Observations of PSR
B1055-52 and Other Selected Pulsars, submitted separately to NASA
from the EGRET office. The proposed observations of pulsars with
CGRO depend on accurate and contemporaneous timing observations
made at radio frequencies. Princeton U.'s contribution to the
project will be in providing the necessary pulsar timing
parameters. We present here a few additional details related to 
this correlative radio frequency work.                            

DIFFUSE GAMMA-RAY EMISSION FROM THE TANGE NTS OF SPIRAL ARMS

   We propose studies of the diffuse gamma-ray emi ssion
toward the tangents of spiral arms in the inner Galaxy using
archival EGRET data. By studying tangents at a range of
Galactocentric distances we would determine the variation of
cosmic-ray densities and of CO as a molecular mass tracer across
the inner Galaxy. The lines of sight we propose to examine are
well-suited for such studies, having the majority of their
interstellar gas on two or three well-defined distance ranges. In
addition
, we should be able to test whether cosmic rays are coupled to the
interstellar gas on the scale of spiral arms, and determine whether
unresolved point sources significantly affected previous analyses
of COS-B data for the inner Galaxy.                               
                                    

DIFFUSE GAMMA-RAY EMISSION IN MONOCEROS A ND THE OUTER GALAXY

   We propose an EGRET observation of the diffuse
gamma-ray emission in Monoceros to study the cosmic rays and
interstellar gas across the outer Milky Way. The study would
complement our recent analysis of the diffuse emission in Cepheus,
on the other side of the anticenter. We plan to determine the
generality of our findings in Cepheus on the gradients of
cosmic-ray density and the calibration of CO as a molecular mass
tracer. Monoceros shares many of the advantages of Cepheus for such
a st
udy, although the existing exposure is particularly poor. We are
aware that EGRET has limited spark chamber gas remaining and under
this circumstance this observation of Monoceros is the only new
observation of Galactic emission that we feel merits proposing.   
                                         

GAMMA-RAY OBSERVATIONS OF PSR B1055-52 AND OTHER SELECTED PULSARS

   Of the known X-ray and gamma-ray pulsars, PSR B1055-52
has the highest apparent conversion efficiency of spin-down
luminosity into high-energy radiation. The flat gamma-ray energy
spectrum may be related to one component of the X-ray emission seen
with ROSAT. The EGRET observations of this pulsar are
statistics-limited. This proposal, which is coordinated with an XTE
proposal, seeks additional observing time to clarify the gamma-ray
light curve and energy spectrum in order to test pulsar 
models.                                                           

INTEGRATED INVESTIGATION OF CORPUSCULAR AND ELECTROMAGNETIC EMISSIONS OF THE JUNE 1991 SOLAR FLARES

   Integrated investigation of different types of
emission gives a chance to decrease uncertainties of interpretation
of observational data in each band. We propose to use our
experience for the systematic analysis of solar flare produced
neutron and gamma-ray emission as detected by COMPTON GRO and
energetic protons as detected by GOES and IMP satellites and
neutron monitor network. Developed earlier our theoretical models
and software enable us to recalculate observed values of secondary
e
mission into parameters of accelerated particles at the Sun. The
main objective of the investigation is determination of
characteristics of energetic particles and plasma at the flare
site.                                                             
                                                     

GAMMA RAYS FROM CLASSICAL NOVAE

   Classical novae provide environments in which
hydrogen-burning reactions proceed on CNO and heavier nuclei at
high temperatures. For such conditions, there exist several
possible mechanisms by which astrophysically significant fluxes of
gamma rays can be produced, that may be detectable with the Compton
Observaotry. These include: (1) the positron decays of the short
lived unstable isotopes of CNO nuclei ($^{13}$N, $^{14}$O,
$^{15}$O, $^{17}$F, and $^{18}$F) can drive a phase of gamma ray
 emission during the earliest stages of the outbursts; (2) the
decay of $^{22}$Na can produce a detectable flux of 1.275 MeV gamma
rays on a timescale of order two years after the outburst,
particularly in novae enriched in the elements neon-to-aluminum;
and (3) the production of $^{26}$Al.             

HIGH RESOLUTION OSSE SCANNING OBSERVATIONS OF THE GALACTIC CENTER 511 KEV SOURCE

   The distribution of positron annihilation line
emission from the Galactic Center (GC) is arguably the most
important gamma-ray line measurement that OSSE can make. After
nearly 20 years of observations, the source of the positrons is
still unknown. Although OSSE has scanned the GC many times, there
are only two scans with the collimator perpendicular to the plane.
They show a significant offset from the Galactic Center
(-1.36+/-0.33 degrees; ~4 sigma). The centroid is consistent with
the 
black hole source 1E1740.7-2942. Our phase 4 proposal was accepted
(scheduled June '95) and a test observation shows good performance
for our new technique. This observation will confirm the offset
from the GC, but more observations are needed to distinguish a
point source from an extended source.      

OSSE SEARCH FOR LINE FEATURES FROM THE CRAB PULSAR IN THE 500-600 KEV ENERGY RANGE

   We propose to extend the energy range of our cycle 4
proposal to the 500-600 kev range. This will allow us to extend our
cycle 4 search for lines in the Crab pulsar spectrum from the
400-500 keV range to the 500-600 range where unshifted or blue
shifted electron/positron annihilation flux could be present.
Copious amounts of electron/positrons may very well be produced in
the atmosphere of the Crab pulsar, and there has been at least one
report of a blue shifted line at 545 keV (Gilnafov 
et al.). This is an observation for which OSSE is ideally suited
with its high sensitivity (about 7E-5 photons/sq-cm-sec over an
about 1/10 fraction of the light curve) and good (0.1 FWHM) energy
resolution.                                                       
                                         

"CGRO MAPS OF 26AL USING NEW, IMPROVED TECHNIQUES"

   The goal of this project is to produce an improved and
more reliable map of 26Al emission in the Galactic plane so that we
can associate the emission with known objects, e.g SNRs, Wolf-Rayet
stars, etc. With this information in hand, we will be much closer
to understanding the origin of recent nucleo-synthesis in the
Galaxy. In order to do this, we will develop and apply new
background subtraction technique to the OSSE data, and we will use
the OSSE data to constrain the maps derived from
 the COMPTEL 26Al data. We will also use a new better mapping
technique that can be applied both for the COMPTEL and OSSE data
(if the improved background subtraction technique is successful)
and our approach will provide an improved map of 26Al galactic
diffuse emission.                                

TARGET-OF-OPPORTUNITY OBSERVATIONS OF RADIO-FLARING AGN

   Comparison of the EGRET Phase 1 catalog with radio
monitoring shows that gamma-rays are detected mainly in quasars
with high optical polarization, and when their millimeter flux is
rising. If these two requirements are fulfilled, the detection rate
is in excess of 70-80%. Detections of other kinds of AGN are rare,
as are detections when the millimeter flare is decreasing or at low
levels. The strength and the rapidity of the radio flare also
correlate positively with the gamma flux. On th
e basis of these new results, we propose to monitor a sample of 35
AGN at 22 - 230 GHz and trigger a ToO observation when a suitable
radio flare is detected. The primary aim is to detect strong gamma
flares to follow short-timescale variations, the secondary to
detect new gamma-ray sources.             

PULSE TIMING OF VELA X-1 AND CEN X-3

   We propose to continue timing the pulses of Vela X-1
and Cen X-3 with BATSE. Our main aims are to (i) determine the
apsidal motion of Vela X-1, (ii) study the accretion torques and
the neutron star's response to them. We now have more than 16000
pulse profiles of Vela X-1 and more than 9000 of Cen X-3; the final
BATSE data set will be unique in size (10**2 times larger than
previous), span and homogeneity. Using new techniques which make
optimal use of the unique characteristics of the da
ta set, we have measured the pulse phase fluctuation spectra of
both sources (they are very different) and detected a new feature
in that of Vela X-1. Preliminary orbital parameter determinations
show that the precision that we require for (i) is being reached. 

SEARCH FOR UNTRIGGERED EVENTS IN THE BATSE DATABASE.

   We propose to continue our search of the BATSE data
base for events which have not led to a burst trigger. In our work
so far we have developed a new search algorithm which is more
sensitive than the one which simply mimicks the on-board trigger
mechanism. Results from the analysis of 56 days of data yield 21
solar flares, 15 gamma-ray burst candidates, 32 fluctuations from
Cyg X-1, and 60 unclassified events. The anisotropy of the
unclassified events suggests activity of just a few sourc
es in the northern galactic hemisphere. We suspect Sco X-1 is one
of them.                                                          

CONTINUED OBSERVATIONS OF HIGH ENERGY EMISSION FROM X-RAY BINARY SYSTEMS

   We propose to use the COMPTON observatory to continue
our studies of high-energy emission from X-Ray Binary(XRB) systems.
Our Cycle 4 discovery of 30 MeV-10 GeV gamma rays from Centaurus
X-3 indicates that XRB system has entered a state of enhanced
high-energy emission and raises the question of how this variable
gamma-ray emission is related to phenomena at lower energies. For
Cycle 5 we request simutaneous EGRET and OSSE observations of Cen
X-3 which can provide important clues about pa
rticle acceleration and gamma-ray production in XRB systems. We
also propose to continue our survey of high-energy emission from
XRBs with EGRET which complements the on-going COMPTEL team studies
of XRB's at energies below 30 MeV.                                

CONTINUED OBSERVATIONS OF PKS 0208-512 AND 2155-304: TESTING THE PARADIGMS FOR TWO PROTOTYPES OF GAMMA-RAY AGNS

   We propose to continue our successful Cycle 4
observing program to study the high-energy properties of blazars at
high southern galactic latitudes. In particular, we propose
follow-up observations of two primary targets, each a prototypical
member of its class: the bright, variable gamma-ray quasar PKS
0208-512, and the nearby x-ray-selected BL Lac PKS 2155-304,
newly-discovered as a gamma-ray source during our Cycle 4 survey.
The CGRO observations will be carried out in conjunction with 
a campaign that will make simultaneous measurements from GHz radio,
including VLBI mapping, to GeV gamma-ray energies (TeV for
2155-304); these will provide ``snap-shots'' of the spectral energy
distribution in the sources and, for a strong flare, can serve to
``map out'' the structure of the blazar jet.

THE ONLY TWO SUPERLUMINAL QUASARS WITH STRAIGHT JETS NOT SEEN BY EGRET

   Although superluminal radio sources should be the most
promising candidate sources for being high energy gamma-ray
emitters a significant number of the known superluminal sources
have not yet been detected by EGRET. One possible explanation could
be that the precise orientation and geometry of the jet plays an
important role. Looking at the distribution of the misalignment
angles between the VLBI and VLA jets one finds that EGRET has
detected all but two of the superluminal sources with m
isalignment angles $\le$~$15^\circ$. We therefore propose to look
at these two sources (3C~120 and 3C~179) with EGRET for 3 weeks
each. The narrow field of view mode would be sufficient for these
observations.                                                     
                                         

GAMMA-RAY MONITORING OF THE BL LAC OBJECT 0716+714

   We propose to monitor the BL Lac object 0716+714 for
a three week period during cycle 5. This source had always been
detected whenever it was observed by EGRET and is therefore likely
to be visible again. It has displayed low amplitude variations
within previous viewing campaigns. These variations show trends
similar to those in simultaneously recorded optical light curves.
Due to the poor photon statistics, this correlation is not
conclusive, however. We suggest a further observation to 
investigate whether the similarities of optical and gamma-ray
changes seen in a previous campaigns are unique and to determine
the broad-band energy distribution simultaneously with EGRET, XTE,
ISO and ground-based telescopes.                                  
                                           

THERMAL AND NON-THERMAL ELECTRON POPULATIONS IN SOLAR BURSTS DEDUCED FROM HARD X-RAY AND MICROWAVE OBSERVATIONS

   A total of 553 bursts observed by BATSE have been
identified in data from OVRO. For some of the events, observations
from BBSO and Yohkoh are available. Our primary scientific goal is
to exploit the unique capabilities of the BATSE for solar bursts to
learn about the energy release process by studying the electron
energy distribution: (1) We will compare the X-ray flux measured by
LAD with the total power microwave flux. (2) From the subset of
events with flare triggering (82 events), we 
will select the best observed events for more detailed study. We
will compare the BATSE/SD spectra with the brightness temperature
spectra derived from the microwave spectral imaging. These will
enable us to identify thermal and non-thermal sources and locate
them spatially.                             

THRESHOLD-DEPENDENT PEAK DURATION DISTRIBUTION OF CLASSCICAL GAMMA-RAY BURSTS

   The bimodality in burst duration observed by BATSE and
the apparent anti-correlation between duration and hardness ratio
indicate there are two distinct classes of gamma-ray burst, placing
serious constraints on the models. However, the traditional
duration measurement is a mixture of the time scales of individual
burst peaks and peak separations. I suggest the bimodality is
caused by the superposition of these two time scales and duration
$-$ hardness ratio correlation is the result of s
pectral evolution. Therefore, I propose to study the distribution
of all burst peaks in 2B catalog. Various threshold levels should
be applied to remove instrumental effect.                         

STATISTICS OF GAMMA RAY BURSTS

   We propose to study two problems in gamma ray burst
phenomenology: (1) What fraction of gamma ray bursts may be in the
galaxy? (2) Is there evidence that classical gamma ray bursts
repeat? We address the first question by comparing the
probabilities of obtaining the observed properties of the BATSE
catalog for models in which a fraction $f$ of all bursts are
galactic, and the remaining $1-f$ extragalactic. We address the
second in a similar fashion by comparing models in which there are
$
N_1$ sites at which only one burst occurs, $N_2$ sites of pairs of
bursts, $N_3$ sites of triplets, and so on.                       
                                                                  

A SEARCH FOR TEV EMISSION FROM BURSTS DETECTED BY BATSE

   The recent technical advanes represented by the
atmospheric Cherenkov imaging technique have raised the
possiblility that these techniques can be used in exploring the
gamma-ray burst phenomenon at energies of 250 GeV and above. Only
as few as three gamma-rays are needed to define a burst and to give
its location in an error box of radius 0.15 deg. Because of the
large collection area of the Cherenkov telescope the fluence is
very small (6$\times 10^{-9}$ erg cm$^{-2}$). In this proposal 
we seek to continue our on-going search for TeV gamma-ray bursts as
well as to make some improvements to our observing capability to
permit the detection of the delayed component of BATSE-type bursts. 

TARGET OF OPPORTUNITY OBSERVATIONS OF BLAZARS WITH INFRARED FLARES (ISO)

   We propose to obtain target-of-opportunity
observations of flaring gamma-ray blazars with EGRET and COMPTEL.
The observations would be triggered if the Infrared Space
Observatory detected an infrared flare in an EGRET blazar. We
expect that there will be 1-3 such flares during the 18-month
lifetime of ISO. The infrared emission in blazars is dominated by
highly beamed synchrotron radiation from a relativistic jet.
Photons from the peak of the synchrotron energy output, in the
infrared for
 most blazars, or from the external radiation field, are
inverse-Compton scattered to gamma-ray energies by the
synchrotron-emitting electrons. The time interval between infrared
and gamma-ray flares should elucidate the relative location of
their production.                                             

SPECTRAL AND TEMPORAL PROPERTIES OF GALACTIC BLACK HOLES

   BATSE, OSSE, and Ginga spectral and temporal power
spectra data on Galactic Black Hole Candidates (GHBC) will be
compared to models. Constraints will be placed on thermal versus
non-thermal mechanisms for the high energy power law that
characterizes the hard X-ray/soft gamma ray spectrum. Special
attention will be paid to epochs of rapid spectral evolution. The
differences between emission in static coronae and dynamic pair
winds will also be evaluated. Phase lag information from power sp
ectra will be used in an attempt to discriminate thermal from
non-thermal mechanisms and static from dynamic structures for the
high energy emission. This will result in a significant advance in
our understanding of the inner disk region of stellar mass black
holes.                                      

SPECTRAL PROPERTIES OF BLACK HOLE CANDIDATES

   We propose archival analysis and real time
observations of a number of sources thought to be powered by
accretion onto black holes, in order to test the validity of a
novel model for the emission of radiation from this type of
sources. The main region of interest in the hard X-ray band
accessible to BATSE and OSSE, but in general, observations spanning
the entire electromagnetic spectrum can provide useful constraints
to our model. For Cyg X-1, we propose new OSSE observations of in
addit
ion to requesting rights to the BATSE continuous data. We propose
additionally to use archival data for Cyg X-1 as well as, GX339-4,
the Seyfert galaxy NGC 4151 and the transient sources GRO J0422+32
and GRO J1655-40 which have been extensively by CGRO as well as at
other                                

"COMPTEL SPECTRAL, TEMPORAL AND SPATIAL ANALYSIS OF GAMMA-RAY BURSTS"

   We propose to analyse and interpret gamma-ray burst
(GRB) data using both, ``single burst detector'' data (0.1 to 1.6
MeV and 0.3 to 10.6 MeV) and double-scatter telescope events (0.75
MeV to 30 MeV), from COMPTEL on the Compton Gamma-ray Observatory
CGRO. The main theme of our proposal is to continue our on-going
analysis (following accepted Phase III and Cycle IV proposals) of
a sample of gamma-ray bursts -- as complete as possible -- observed
by COMPTEL in the MeV energy region. In par
ticular, we propose to study spectral continua, investigate
evidence of time variability, derive precise burst locations,
analyse time histories in order to search for possible periodic
effects, and examine spectral evolutions (e.g. hard - to - soft
ratio as a function of time).                         

CORRELATIVE ANALYSIS OF HARD AND SOFT X-RAY EMISSIONS IN SOLAR FLARES

   We propose to continue a study that we have commenced
under the Cycle 3 and 4 GI programs. Our broad aim is to test flare
models by comparing their predictions with simultaneous BATSE hard
X-ray and Yohkoh soft X-ray observations. For Cycle 5, we will
focus on the hydrodynamic consequences of current heating and
runaway acceleration. We will use BATSE spectra in the 20-300 keV
range from the Large Area detectors to deduce the nonthermal hard
X-ray component that is related to the electron
 heating rate. We will use Yohkoh soft X-ray data to deduce the
thermal heating rate and the plasma cooling rates of the
evaporating chromospheric component. By comparing these rates, we
will place tighter constraints on the physical parameters that
control heating and acceleration in solar flares.     

SEYFERTS WITH HARD VARIABLE X-RAY SLOPE -- A GAMMA-RAY STUDY OF NGC 4151 AND MCG --5-23-16

   We propose a campaign of simultaneous observations of
NGC 4151 and MGC --5-23-16 by OSSE, XTE, ASCA, and IUE. The two
objects appear to belong to a new class of Seyferts characterized
by variable and hard X-ray spectra and no Compton reflection
component, distinctly different from classical Seyfert 1's. The
proposed observations will test the hypothesis of the existence of
such a class. Furthermore, they will help to determine the form of
the high-energy cutoff in the object, and the vari
ability of gamma-rays and the 511 keV flux in NGC 4151. The results
can be then used to determine the physical processes responsible
for the emission and the contribution of such objects to the cosmic
X-ray/gamma-ray background.                                       

LONG TERM HARD X-RAY MONITORING OF X-RAY BURSTERS

   Hard X-ray emission episodes from several X-ray
bursters (XRBs) have been recently discovered. We propose to carry
out a search for hard X-ray emission from the complete sample of
Galactic XRBs with the use of the BATSE Earth occultation and
mapping techniques. Recent technical developments of the BATSE data
analysis software make possible an extensive search for a large
number of potential sources. For the first time, our investigation
will provide comprehensive information on the hard X
-ray emission characteristics of XRBs (durations, luminosities,
spectra). An important goal of our study is the clarification of
the high energy emission properties of neutron star systems vs.
black hole candidate systems.                                     

PERIODIC HARD X-RAY EMISSION FROM GRO J1849-03

   We have recently discovered periodic transient hard
x-ray emission from a source, GRO J1849-03, possibly located in the
5 kpc arm of the galaxy using archival BATSE data. The source
produces hard x-ray transients at regular 241 day intervals. Each
transient lasts roughly 13 days, reaches a peak luminosity of 75
mCrab, and has a photon power law index of -2.8 extending out to
100 keV. We have interpreted the emission as due to close
encounters between a compact object and a companion star 
in a binary system. We propose to continue monitoring this source
with BATSE and to observe the source with OSSE during an outburst.
We also propose correlative observations to be made with the ASM on
XTE to monitor the standard x-ray emission from GRO J1849-03.     

SPECTRAL DEFINITION AND VARIABILITY OF COMPTEL AGN SOURCES

   We propose to perform high sensitivity imaging and,
simultaneously, spectral analysis of AGN sources using the full
information contained in each CGRO COMPTEL event. The main focus
will be the analysis of archival data for the quasars 3C273 and
3C279. A "grand deconvolution" approach will be applied which
produces a three-dimensional image, for which two of the dimensions
are spatial and one energy. Our proposed "grand deconvolution"
merges the constrained linear algebraic deconvolution i
maging technique (CLAD), recently developed at UCR, with the
"pixon" technique of Puetter (1994). This new method will permit
the full COMPTEL data set to be deconvolved with image and energy
pixels that are statistically justified by the data.