CGRO Status Report for April 1996 (5'th Anniversary Edition)

[SHRADER@grossc.gsfc.nasa.gov]

 Compton Gamma Ray Observatory Status Report #191
              Thursday, April 4 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
GRO-SSC WWW Site: http://cossc.gsfc.nasa.gov/cossc/cossc.html



Guest Investigator News:

Proposals are due, in case you'd forgotten, two weeks from tomorrow!!
Tomorrow, by the way, is the 5'th anniversary of the launch of CGRO!!

To clarify any confusion, the page limit for Cycle-6 proposal technical sections
(including text, figures and references) is 6 pages = 3 double sided sheets.
Cover forms, statement of past CGRO work and work in progress do NOT
count against the 6-page limit. "Appendices" to the technical section are no
longer permitted. Do not submit a budget at this time.

Remember, electronic submission of proposal forms, in addition to paper
submission of the forms with the main body of the proposal is a requirement.
The paper forms will be generated for you automatically by the Remote
Proposal Submission (RPS) software. Send a blank e-mail message to
rps@legacy.gsfc.nasa.gov detailed instructions; or visit our WWW site. Please
read the instructions - the software is really not too difficult to use; I've
done it myself! Report insolvable problems to the GRO-SSC staff: (Paul Barrett,
barrett@compass.gsfc.nasa.gov). Electronic submission DOES NOT mean e-mailing 
us an edited LaTeX form or a PostScript file; the RPS software has a "submit" 
option which will register your proposal and import the coverform information 
into our database. 

If you have questions about the NRA, or on general policy issues contact us: 
(Chris Shrader, shrader@grossc.gsfc.nasa.gov, 301-286-8434).  

The electronic versions of Appendix A-D and G have been modified so that
they should now work properly with PostScript screen previewers. Also, the
Figures for these appendices are now available as well. All materials are
available via FTP (grossc.gsfc.nasa.gov, nra/cycle6) and will appear on the
WWW imminently (http://cossc.gsfc.nasa.gov/cossc/cossc.html). 

There are  now approximately 1000 days of BATSE  data at the GRO-SSC
for use with the JPL Enhanced Batse earth Occultation Package (EBOP). This
covers most of the first three phases of the mission. Anyone interested in its
use should contact our staff; additional consultation with JPL (Jim Ling, 
jling@jplsp.jpl.nasa.gov) is also advisable. 


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.

Bob Hartman reports that not only was 3C 279 in a high state during the
recent target of opportunity, but also there was a flare.

During the first three weeks of April, EGRET will be pointed in the direction
of 0716+714.  Following that pointing, EGRET will be observing the region
around 3C 345.

At the five year point of the Compton Gamma Ray Observatory, a mission
designed for a two year lifetime, it seem appropriate to summarize some of
the highlights of what has been achieved thus far.  Therefore, here are
some for EGRET.


* THE DISCOVERY OF A NEW CLASS OF OBJECTS --
  HIGH-ENERGY GAMMA-RAY EMITTING BLAZARS

* THE OBSERVATION OF HIGH ENERGY GAMMA-RAYS FROM A
  GAMMA-RAY BURST FOR OVER AN HOUR, WITH SOME
  GAMMA RAYS HAVING ENERGIES OVER A GEV AND TWO
  OVER 10 GEV

* THE LONG ACCELERATION AND TRAPPING TIME OF SOLAR
  PARTICLES FOLLOWING A SOLAR FLARE

* THE OBSERVED INCREASED EFFICIENCY OF GAMMA-RAY
  EMISSION FROM PULSARS WITH AGE

* THE ABSENCE OF MICROSECOND BURSTS AND ITS
  IMPLICATIONS OR CERTAIN UNIFICATION THEORIES

* THE DETERMINATION WITH HIGH CERTAINTY THAT COSMIC
  RAYS ARE GALACTIC

* THE DETAILED MAPPING OF THE GALACTIC DIFFUSE
  RADIATION AND THE OBSERVATION OF THE PION BUMP

* THE MEASUREMENT OF THE SPECTRUM OF THE DIFFUSE,
  PRESUMABLY EXTRAGALACTIC, GAMMA RADIATION AND
  THE APPARENT CONSISTENCY OF THE HIGH ENERGY
  SPECTRAL REGION WITH A BLAZAR ORIGIN


COMPTEL 

The COMPTEL instrument is performing well and continues routine
observations.

Several more gamma-ray bursts have occurred within the field of view of
COMPTEL since the last report (GRBs 960312, 960316, and two on
960403).  Once again, in a sad refrain, none of these was detected at MeV
energies by COMPTEL, further extending the longest period (ten months and
counting) without a field-of-view burst detection by COMPTEL.  Since
activated in September 1995, the automated BATSE/COMPTEL/NMSU
rapid-burst-response network has responded to 25 BACODINE triggers
within an average time of ~15 minutes from burst
occurrence.

A new delivery of COMPTEL data to the CGRO public archive at the COSSC
has recently taken place; these data include the balance of all low-level and
first high-level data products covering Phase 3 of the CGRO mission.

With the CGRO proposal season well underway, proposers are reminded that
the COMPTEL exposure calculator, recently updated, is available on the
WWW.  Further, the COMPTEL electronic publications archive has also been
extensively updated to include 60+ team publications, as well as a complete
bibliography of all COMPTEL publications since the launch of the CGRO.
Access is available via anonymous ftp to unhgro.unh.edu, or via the
COMPTEL pages on the WWW.


OSSE

OSSE operations are normal.  The instrument is working as designed, with all
subsystems in complete and full operation.  The slewing response to BATSE
burst triggers remains disabled because of the bursting pulsar, GRO J1744-28.

Regarding this fascinating source, our letter (Strickman et al.) has been 
accepted for publication in ApJ.  It summarizes OSSE pulse profiles, the 
distribution of times between bursts, the average burst profile, burst and 
pulsar spectroscopy, and our discovery that pulses within bursts lag those at 
times away from bursts.  The accepted preprint will be available at our Web 
page almost immediately (see URL http://osse-www.nrl.navy.mil/osselib.htm).

OSSE also just completed an observation of Cyg X-1 coordinated with ASCA
and RXTE.  The combined dataset will provide the best test to date of
high-energy emission models for galactic black holes.

Data through viewing period 407 have been delivered to the Compton GRO
Science Support Center archive.

BATSE

The X-ray nova, and Galactic superluminal jet source, GRO J1655-40,
discovered by BATSE in 1994, was the subject of an intense worldwide
observing campaign ending on April 1, 1996 involving CGRO, ASCA,
ROSAT, XTE, 2 radio telescopes (VLA and MOST) and 10 optical
telescopes at 6 observatories (CTIO, ESO, SAAO, MSSSO, Brazil and
Tasmania).  The campaign was planned and coordinated by Craig Robinson
and Nan Zhang of the BATSE Team.  Analysis of the data has started and will
be managed by members of the BATSE Team at NASA/MSFC.

A preliminary investigation of the BATSE occultation data supports the
existence of the new transient GRS1739-278 in the galactic center region.  
Initial occultation images indicate a shift in the image centroid of the  bursting
pulsar GROJ1744-28 toward the reported TTM location (IAUC 6350) of 
GRS1739-278, particularly in the higher energy bands.  A light curve for 
GRS1739-278 created with channels corresponding to the energy range of  75
- 230 keV indicates a sudden rise beginning at around tjd 10119, reaching a 
peak at tjd 10124, followed by a gradual decline to pre-outburst level around 
tjd 10145.  Work is in progress to derive more information by fitting out the
contribution of GROJ1744-28 to the light curve of GRS1739-278.

The outburst from the bursting pulsar GRO J1744-28 is still in progress.
Triggered data has been collected for 1341 bursts to date. Initial processing of
these data (creation of IBDB's) has been completed for 516 of these bursts.
Folded-on-board data is being collected to monitor the pulse profile and
pulsed flux. The pulsed flux has been decreasing since the third week of
January. If the pulsed flux continues its current trend, the pulsations will fall
below our detection threshold in one to two weeks.

During the last month 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 2 April BATSE has detected 1487 gamma-ray bursts out
of a total of 5292 on-board triggers in 1806 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.