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CGRO Monthly Status Report for August 1995

  Compton Observatory Science Report #184, Wednesday, August 9 1995
      Chris Shrader, Compton Observatory Science Support Center

         Questions or comments can be sent to the CGRO SSC.
          Phone:    301/286-8434
          e-mail:   NSI_DECnet: GROSSC::SHRADER 
          Internet: shrader@grossc.gsfc.nasa.gov

                       Guest Investigator News

Notification letters for all Cycle-5 Guest Investigator proposals
were mailed out during July. A list of accepted programs (titles and
abstracts) as well as the Cycle-5 Viewing Plan and a list of all
scheduled targets are available on GRONEWS. You can access GRONEWS by
telnet'ing to grossc.gsfc.nasa.gov (login as GRONEWS) or via the WWW
GRO-SSC home page on the World Wide Web:

The long-awaited BATSE 3B Gamma-Ray Burst Catalog has been delivered
to the SSC by the BATSE Team!!! (see the BATSE instrument report
below). It is available for browsing and/or downloads on GRONEWS.

Portions of the JPL Enhanced Earth Occultation analysis Package
(EBOP) are now available for general GI use at the SSC. About 250
days of data (from phase 1 and 2) for use with EBOP are online.
Anyone interested in using this data and software should contact the
SSC. Consultation with JPL is also strongly recommended, particularly
in interpretation of results (JPL contact is Jim Ling,
jling@jplsp.jpl.nasa.gov). Work to make the software more user-
friendly is ongoing as a collaborative effort between JPL and the

OSSE high-level data products (currently for the first 16 viewing
periods) are now available at the SSC. See the "OSSE" item on our WWW
home page. These include PostScript plots, summed background
subtracted spectra in IGORE and XSPEC compatible formats, as well as
simple ascii text files containing approximate photon fluxes vs
energy - and much more! For more information contact Tom Bridgman

A second announcement for the 3'rd Huntsville Gamma-Ray Burst
Workshop (October 1995) is appended to this report.

                         Instrument Reports


EGRET operations were normal this monthly period.  Delivery of the
final phase 3 data to the GRO SSC remains on schedule and delivery of
the phase 4 preliminary data to the GRO SSC is now running ahead of 
schedule. Interaction with guest investigators continues at a good

The viewing plan for phase 5 has been received.  For most of the
viewing periods, EGRET will be in the narrow field viewing mode to
conserve the remaining spark chamber gas.  For  four weeks, it will
be in the fan mode, and for thirteen weeks it will be turned off. 
The approved targets for each viewing period have been received and
are being loaded into the EGRET computer so that guest investigators
may be informed when results exist, as in previous cycles.

On August 8, 1995, the pointing direction changes to the anticenter
and, on August 22, 1995, the pointing direction moves to Galactic
coordinates (l=154o, b=-10o).


OSSE operations are normal.  The slewing response to BATSE burst
triggers has been enabled since 30 June.

Recent observations are listed in the following table.

View period    Dates          Target         (owner)
    424        10-25 Jul      Cen A          (GI H. Steinle)
                              PSR J0631+10   (GI J. Cordes)
    425        25 Jul - 8 Aug 4C 15.05       (PI team)
                              3C 109         (GI L. Bassani)
    426        8-22 Aug       Crab pulsar    (PI team)
                              NGC 4388       (GI L. Piro)

Data up to viewing period 324 have been delivered to the Compton GRO
Science Support Center archive.

OSSE papers on the Crab pulsar (Ulmer et al.), PSR B1259-63 (Grove et
al.), and Cen A (Kinzer et al.) have recently appeared in ApJ.  A few
members of the OSSE team will present recent results at the 24th
International Cosmic Ray Conference at the end of the month.


The COMPTEL instrument is performing well and continues routine

Members of the COMPTEL team have carried out an accelerated
processing of the data associated with the recent
target-of-opportunity observations of the gamma-ray-bright quasar PKS
1622-297. There is NO strong evidence for this source in the COMPTEL
band at MeV energies in either the quick-look or standard processing
for Viewing Periods 423 and 423.5.  Nor is there any evidence at
present of the other prominent source reported by the EGRET team, GRO
J1629-49.  A more refined analysis of these data is currently in

An article by Morris et al. on "Neutron measurements in near-Earth
orbit with COMPTEL" has recently appeared in JGR, Vol. 100, No. A7,
pp. 12,243-12,249 (1995).  Also, a review article on "High-Energy
Particles in Solar Flares" (Hudson and Ryan) will soon appear in the
1995 volume of the Annual Reviews of Astronomy and Astrophysics. A
COMPTEL preprint has also recently been distributed containing
contributed papers by team members and collaborators presented at the
29th ESLAB Symposium "Towards the Source of Gamma-Ray Bursts."

Attendees of the The 3rd Compton Symposium recently held in Munich
should note that contributions to the proceedings volume for the
symposium are now due by October 1.

The electronic version of the 3B burst catalog was delivered to the
GROSSC on August 8. This catalog comprises 1122 bursts and extends
from launch until 19 September 1994. The locations of all bursts have
been recomputed using an improved algorithm. The systematic error in
the 3B locations is estimated to be 1.6 degrees.

The outbursts of GX 339-4 and GRO J1719-24 continue to be detectable
using BATSE occultation monitoring, and new active episodes have been
observed during July in GRS 1915+105 and GRO J1655-40. The latter
activity was reported in IAU Circular No. 6196 as follows:


     B. A. Harmon, M. L. McCollough, S. N. Zhang, W. S. Paciesas and
     C. A. Wilson report, for the Compton Observatory/BATSE Team:
     "The x-ray/radio transient GRO J1655-40 is undergoing a bright
     outburst in hard x-rays above 20 keV. The source became
     detectable around July 22; its intensity exceeded 300 mCrab on
     July 27 and increased to 400 mCrab (+/- 10 percent) on July
     29-30. This is the brightest outburst in hard x-rays since that
     of February-April (IAUC 6143, 6147). The spectrum on July 29-30
     extends to at least 200 keV and is well fitted by a power law
     with spectral index -2.4 +/- 0.1."

The following sources have been detected by the BATSE pulsed source
monitor in the last month : Her X-1, Cen X-3, 4U 1626-67, OAO
1657-415, GX 1+4, Vela X-1, and GX 301-2. 

BATSE monitoring of Cygnus X-1 shows that the source is currently in
a state of high flickering, as evidenced by visual inspection of the
raw data as well as an increased number of false burst triggers
attributable to fluctuations from Cyg X-1.
The energy range for the BATSE burst trigger was changed on July 24
from 25-100 keV to E > 25 keV. During the final four days using the
25-100 keV interval, single-detector triggers were accepted in order
to collect data on phosphorescent events for studies of systematics.
As of August 6, BATSE has detected 1331 gamma-ray bursts out of a
total of 3644 on-board triggers in 1566 days of operation. There have
been 757 triggers due to solar flares, 9 due to SGR events, and 48
due to terrestrial gamma-ray flashes.  

            3'rd Huntsville Symposium on Gamma-Ray Bursts

         Third Huntsville Symposium on Gamma-Ray Bursts
                    October 25-27, 1995
                     Invited Speakers

Opening Remarks

   G. Fishman

Closing Remarks  

   C. Kouveliotou

Spatial & Intensity Properties and Implications

   E. Fenimore
   D. Hartmann
   D. Lamb
   C. Meegan

Temporal Properties

   I. Mitrofanov
   J. Norris

Spectral Properties

   D. Band
   M. Briggs


   K. Hurley
   F. Vrba


   C. Thompson
   S. Woosley

For further information:
Email your address to workshop@batse.msfc.nasa.gov,
or consult the WWW page 
The deadline for abstracts is September 7th.