CGRO bi-Weekly Status Report - 01/21/94

[SHRADER@GROSSC.GSFC.NASA.GOV]

Compton Observatory Science Report #149 Friday, January 21, 1994 
Chris Shrader, Compton Observatory Science Support Center

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


                        Spacecraft Status
  
The CGRO remains a healthy spacecraft, with all subsystems are
operating nominally. As of January 14, 1994 the Compton GRO orbit
had a mean orbital altitude of 450.9 km. 

The throughput efficiency of real-time telemetry is increasing as
a result of the TDRSS reconfiguration and bringing online of the
Australian Ground station. Based on the number of packets of data
delivered to instrument teams from the Packet Processing
Facility, the percentage of full time coverage achieved with 32-
kbps real-time data between January 6 and January 9 was 79%,
including 10% from the new ground station. An additional 8%
coverage was achieved with the BATSE 1-kbps data during this
time.                    

                   Science Support Center News

The SSC staff manned a CGRO display booth at last weeks AAS
meeting in Crystal City. Demonstrations on archive search and
retrieval, as well as various instrument specific software were
given.

Development on the Cycle 4 proposal submission software is
continuing. Additionally, the NRA Appendices A-H will be posted
on GRONEWS within the next several working days.

The BATSE GRB Spectroscopy catalog has been delivered to the SSC
by Brad Schaefer. It will shortly be made available through
online access. Stay tuned to GRONEWS for details.

The SSC staff, along with the Project Scientist, are developing
plans for a CGRO exhibit, which if approved by the museum board,
will be on display in the main lobby of the National Air and
Space Museum. The display will feature a 10 minute video on the
CGRO mission tentatively entitled "Our Violent Universe" (the
video is being produced by Jim Lynch with consultation from the
CGRO project).


                     Guest Investigator News

An ongoing Guest investigation by Drs. Jay Norris and Robert
Nemiroff on detailed temporal analysis of GRBs was the subject of
an AAS press release last Saturday. Norris and Nemiroff presented
mounting evidence for a cosmological interpretation of GRBs by
showing that, statistically, fainter bursts are longer in
duration and show greater time structure than brighter bursts.
Additionally, the fainter bursts appear to be have softer
spectra. Both effects are qualitatively consistent with a
cosmological origin (but alternatively, they can be a result of
intrinsic GRB population properties). A copy of the text of their
press release is available on GRONEWS under sub-menu 1, "Recent
Scientific Results."

Dr. Malcolm Coe, who is the Principal Investigator on several
ongoing CGRO Guest Investigations involving multi-wavelength
studies of high-mass X-ray binaries, has identified an optical
counterpart to the transient GRO J1008-57 (IAUC 5836,5838). A
transcript of his report follows:

Malcolm Coe (Southampton University), Juan Fabregat (Valencia
University) and Dave Buckley (SAAO) announce that they have found
the optical counterpart to the CGRO transient source J1008-57. 
This object was discovered by CGRO last year (IAUC 5836 and 5838)
and subsequently observed by ASCA and ROSAT (IAUC 5851 and 5877,
respectively).  A deep red image taken at the UK Schmidt
telescope on 28 July 1993 (just a few days after BATSE detected
the start of the outburst) revealed just 2 objects within the
ROSAT error circle and a further 3-4 close by. Observations
carried out at the South African Astronomical Observatory in
December 1993 revealed that the brightest source in the error
circle is a strong H alpha emitter.  This then confirms this
system as another Be/X-ray binary system, as was suspected from
the X-ray characteristics. 


                       Instrument Reports


OSSE

OSSE operations are essentially normal, with only minor
interruptions from power outages in the DC area.

In viewing period 315, the Z-axis target is the binary pulsar PSR
1259-63 (Guest Investigator M. Tavani), and the X-axis target is
the galactic center region (Key project).  The Sun is not
accessible along the scan plane, and the slewing response to
BATSE solar flare triggers is therefore disabled.

A number of OSSE team members attended the 183rd Meeting of the
American Astronomical Society in Crystal City, VA.  Many new or
improved scientific results from OSSE data were presented on such
topics as the galactic positronium continuum, the diffuse
galactic continuum, hard X-rays from SN1993J, the Virgo sky
survey, the average Seyfert spectrum, and the X-ray novae GRS
1009-45 and GRS 1716-249.


EGRET

EGRET operation was normal this week. Beginning in mid-December,
there has been a gradual increase in the percentage of possible
data that is being recovered by EGRET as a result of the new TDRS
placement and the Australian ground station. It had averaged
about 65% for some time, and it has gradually increased to about
82%. There are, of course, daily and weekly fluctuations due to
pointing direction and the relative location of the South
Atlantic Anomaly.

A large number of EGRET papers were presented at the January
American Astronomical Society meeting. They included details of
the galactic plane, results on the variation of quasars, and an
upper limit on the high-energy microsecond bursts that is
considerably more severe than previous ones.

COMPTEL

The COMPTEL instrument is performing well and continues routine
observations.

The COMPTEL operations group reports that in spite of the the
current wave of cold-weather-related problems at Goddard and
elsewhere the health and safe operation of the instrument
continues to be monitored with only occasional interruption; the
routine production processing of incoming flight data should not
be affected.

BATSE 

No report was submitted this week.