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CGRO Biweekly Status Report

  Compton Observatory Science Report #172, Monday December 12, 1994
      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

                     Science Support Center News

The schedule for the release of the Cycle-5 NRA and the due date for
proposals is being modified  resolve conflicts with the scheduled
releases of the XTE and ROSAT NRAs. If we followed our original plan
of an April 3, 1995 due date, proposals for all three missions would
be due at the same time - not a pleasant prospect for proposal
writers or review organizers! The exact due date for CGRO Cycle-5
proposals has not been finalized, but March 22, 1995 is most likely.
Once the dates are finalized, the NRA and Appendices will be made
available electronically at the CGRO-SSC.

The BATSE CD rom, which contains data for gamma-ray bursts in the 2B
catalog is being pressed at Goddard this week. It will be distributed
at the forthcoming 185'th meeting of the American Astronomical

FYI, several CGRO-SSC computers have undergone name changes:
 old name    new name
 enemy   --> cossc
 fiend   --> grjuke
 villain --> cosmic

(in all cases the internet extensions are ".gsfc.nasa.gov"). Please
update your files/software to reflect this change. The original names
are currently still supported but this will no the case after January

                         Instrument Reports

EGRET operations were normal this biweekly period. Delivery of data
to the GRO SSC remains on schedule. Interaction with guest
investigators continues at a good level.

The deep survey of the Virgo region began on November 29, 1994; the
results of this survey should add significantly to our knowledge of
AGN's, including their time histories and luminosity distribution.

There will be a series of talks at the Relativistic Astrophysics
meeting in Munich next week, including a talk on EGRET highlights in
a session of Highlights from the Compton Gamma Ray Observatory, a
talk on pulsars, a paper on AGN's, and a talk on gamma-ray bursts.


OSSE operations are normal.

In viewing period 405.0 (29 Nov - 7 Dec), the Z-axis target was 3C
279 (PI team) and the X-axis target was the galactic center region,
including GX1+4 in its current active state (PI team). In the Target
of Opportunity viewing period 405.5 (7-13 Dec), the Z-axis target
remains 3C 279 (PI team), while the X-axis target is the X-ray nova
GRO J1655-40 (PI team) during an outburst.

In data from the first 7 hours of this Target of Opportunity, the
X-ray nova is clearly detected to at least 300 keV. The spectrum is,
so far, consistent with a simple power law.

Data from viewing periods 232 and 232.5 were delivered to the Compton
GRO Science Support Center archive this week. The targets during
these viewing periods were the galactic plane near (l,b) = (347,0), a
portion of the Virgo Sky Survey region, Mrk 421, NGC 4388, and M87.
The delivery of data products is now complete through the end of
Phase 2 of the mission.


The COMPTEL instrument is performing well and continues routine

An extensive report on "COMPTEL Observations of Galactic 26-Aluminum
Emission" by R. Diehl et al. has recently been accepted for
publication and will appear in Astronomy & Astrophysics. Preprints
are currently being prepared for distribution. 

Also, a paper entitled "Diffuse Continuum Gamma Rays from the Galaxy
observed by COMPTEL" by Strong et al. has appeared in A&A (1994) Vol
292 pp 82-91 (Dec 1 issue). It contains the full details of the
analysis of the Galactic diffuse emission for Phase 1 data.
postscript version is available from the author
(aws@mpe-garching.mpg.de). The collaboration is investigating ways to
make postscript versions of team publications available to interested

The COMPTEL Burst Rapid Response team continues to refine its
processing procedures, to alert outside investigators of the
positions of GRBs detected by COMPTEL. With the new automated
data-processing procedures now in place, a GRB within the field of
view of COMPTEL can routinely be located within approximately 16
minutes of burst occurrence (this includes the accumulation of 6
minutes of post-trigger COMPTEL data, plus 10 minutes of rapid
data-processing, to produce a skymap of the burst field).


The x-ray transient GRO J1655-40 is currently in outburst with
variable intensity. Since Dec 3 the 20-100 keV flux has averaged 1.3
Crab. On Nov 28, the source reached nearly 2 Crab. The current
outburst which has lasted nearly a month, is longer and more intense
than the two other episodes detected in August and September.

The following sources were detected by the BATSE pulsed source
monitor in the past two weeks: Her X-1, Cen X-3, 4U 1626-67, 2S
1417-624, GX 1+4, Vela X-1, and GX 301-2. The outburst of 2S 1417-624
has now lasted 104 days. The x-ray binary GX 1+4 is still spinning

Three BATSE Scientists, Drs. Fishman, Kouveliotou, and Paciesas, are
currently attending IAU Colloquium 151,"Flares and Flashes: Views
from the Ground & Space" in Sonneberg, Germany, where they will
present papers.

As of December 6th, BATSE has detected 1181 cosmic gamma-ray bursts
out of a total of 3207 on-board triggers in 1323 days of operation.
There have been 740 triggers due to solar flares with emission above
60 keV. Since the BATSE burst trigger criteria were changed on
September 19th, there have been 11 triggers due to terrestrial
gamma-ray flashes.