CGRO Status Report for March, 1996

[SHRADER@grossc.gsfc.nasa.gov]

   Compton Gamma Ray Observatory Status Report #190
                 Friday March 11, 1996

      Questions or comments can be sent to
          Chris Shrader at the CGRO-SSC.
          Phone:  301/286-8434
          e-mail: shrader@grossc.gsfc.nasa.gov


Guest Investigator News:

A new proposal season is rapidly bearing down upon us - don't forget, due 
date is April 19, 1996. For information on (mandatory) electronic form 
submission, send a blank e-mail message to "rps@legacy.gsfc.nasa.gov", 
or on the WWW under "http://cossc.gsfc.nasa.gov/cossc/cossc.html  under 
the item "The Cycle 6 remote proposal Submission Form ..." The procedure
is similar to last years (minus some bugs), and similar to that of the 
other NASA High-Energy Missions. Report problems to Paul Barrett 
(barrett@compass.gsfc.nasa.gov, 301-286-1108), 

If you need hard copy of the NRA and appendices please let us know ASAP:
send requests to Sandy Barnes at barnes@grossc.gsfc.nasa.gov (301-286-7780).
You can download the various documents, minus the figures, from our WWW
site, or by ftp: open grossc.gsfc.nasa.gov, cd nra, cd cycle6, ...  At the 
very minimum, even if you've proposed many times in the past, PLEASE READ
THE BULLETED LIST OF IMPORTANT CHANGES the beginning of the NRA (and 
replicated at the beginning of Appendix A). 

If all else fails, give me a call!

The proposals will be evaluated by a peer-review committee, (under the
supervision of NASA HQ) on June 24-26, 1996. If you are interested in 
volunteering to serve on a review committee, please contact Chris Shrader
(shrader@grossc.gsfc.nasa.gov, 301-286-8434). The meeting will be in the 
Washington DC area. Its great fun!

A change to the current viewing plan has been implemented by the project 
scientist to support Target-of-opportunity observations of GRO J1655-40; 
the effected Viewing Periods are 516 and 517; details will be posted on 
GRONEWS and the WWW imminently.

A new piece of user-contributed software is available from CGRO-SSC; an
alternate version of the EGRET maximum-likelihood point-source detection 
routine "LIKE", incorporating a number of improvements, has been contributed 
by Dr. John Mattox (Universty of Maryland). For details,and a copy of the
software, retrieve the files in cossc.gsfc.nasa.gov, /pub/usr_contrib.

CGRO will be 5 years old next month! (recall that launch was on April 5, 
1991). Also, the CGRO exhibit at the National Air and Space Museum has 
opened last month! Both of these events both of these events will be 
celebrated in an event sponsered by TRW and the Air and Space Museum
later this month! Congratulations to all who have contributed!

Finally, we note that a CGRO (BATSE) image of GRO J1744-28 was pictured on the
front page of USA Today (February 29 Issue). I have not thoroughly researched
this, but will go out on a limb and venture that this is the first ever
radon-transform image to adorn the cover of that particular publication!



Instrument Team Reports

EGRET

EGRET operations were normal this monthly period.  Delivery of the final
phase 4 data to the GRO SSC is on schedule, and delivery of the phase 5
preliminary data to the GRO SSC is also on schedule.  Interaction with
guest investigators continues at a good level.

A paper on PSR B1706 by D. J. Thompson et al. has recently been accepted by
the Astrophysical Journal.  In this paper, observations from 1991 to 1995
are summarized.  An energy spectrum exists up to 30 GeV.  It has a marked
change in spectral slope at about 1 GeV.  A detailed figure of the emission
as a function of phase is also presented.

In a paper by Fichtel et al. to appear in the proceedings of the Third
Compton Gamma-Ray Burst meeting, there is an improved upper limit to
microsecond bursts derived from the EGRET instrument which is capable of
measuring them directly should they be present.  Since the bursts that
would have been seen would have been from our Galaxy within 100 pc, this
limit is especially significant in terms of the prediction of such bursts
by the Hawking model which attempts to make general relativity compatible
with quantum mechanics.

During March, EGRET will be viewing PKS 0208-512 and MRK 501.


COMPTEL 

The COMPTEL instrument is performing well and continues routine
observations.

Quick-look analysis of data associated with the recent
target-of-opportunity observation of the gamma-ray blazar 3C 279 shows
no evidence to date for this source in the MeV range observable by
COMPTEL; 3C 273 is seen, however. A further, more detailed analysis of
these data is currently in progress.

Several more gamma-ray bursts have occurred within the field of view
of COMPTEL since the last report (GRBs 960207, 960208, 960214, and
960220).  Once again, none of these was detected at MeV energies by
COMPTEL, further extending the longest period (nine months and
counting) without a field-of-view burst detection by COMPTEL.  On a
more positive note, a reanalysis of earlier COMPTEL data has uncovered
a burst missed in the original processing, GRB 920627; further details
on this event will soon appear on the new COMPTEL Burst Page on the
WWW (at URL, http://wwwgro.unh.edu/bursts/cgrbpage.html).

A new release of COMPTEL data to the CGRO public archive at the COSSC
is imminent.  These data will include all remaining low-level and
first high-level data products covering the balance of Phase 3 of the
CGRO mission (VP 326 through VP 339).

A general team meeting of the collaboration was held during the week
of 27 February to 1 March at SRON-Utrecht in The Netherlands.


OSSE

The OSSE status report will be circulated separately as an addendum
to this report.


BATSE

The following was reported in IAU Circular 6335:

   GRO J1744-28                                                              
        B. A. Harmon, Marshall Space Flight Center, NASA; J. van             
   Paradijs and W. S. Paciesas, University of Alabama, Huntsville; and       
   S. N. Zhang and C. Kouveliotou, Universities Space Research               
   Association, report for the BATSE Team:  "The 20- to 100-keV flux         
   of GRO J1744-28, as measured with BATSE using earth occultations,         
   has steadily decreased from 0.9 photon cmE-2 sE-1 on Feb. 19 to 0.5       
   photon cmE-2 sE-1 on Mar. 2.  This may signal the upcoming end of         
   the outburst of this unique source.  No convincing optical/infrared       
   counterpart of the source has so far been found, likely due to its        
   high interstellar extinction (Augusteijn et al., IAUC 6326).  The         
   non-detection of a V-band counterpart implies that the interstellar       
   column density, NH, is at least 2 x 10E22 cmE-2.  At a source             
   distance of 7 kpc, the unabsorbed apparent K magnitude is expected        
   to be about 13.  Since the K-band extinction, A(K), increases with        
   column density by A(K)/NH about 7.5 x 10E-23 mag cm^2, the only way       
   to identify a counterpart would appear to be deep K-band imaging          
   centered on the variable radio source (IAUC 6323) down to at least        
   mag 19.  In view of the possible upcoming termination of the              
   outburst, we urge observers that such images be made as soon as           
   possible."                                                                

During the past 30 days (TJD 10119 - 10149) the following pulsed sources 
have been detected by the BATSE pulsed source monitor: GRO J1744-28, Her X-1,
Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, GRO J2058+42, Vela X-1, and 
GX 301-2.
                                                                               
The burst trigger is currently using count rates from 20-300 keV energy range.
As of 8 March BATSE has detected 1472 gamma-ray bursts out of a total of 5062
on-board triggers in 1781 days of operation. There have been 766 triggers due
to solar flares, 10 due to SGR events, and 54 due to terrestrial gamma-ray
flashes.  There have been 1138 triggers due to bursts from GRO J1744-28.