Compton Gamma Ray Observatory Status Report #192
                 Friday May 10, 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:
We received 231 Guest Investigator Proposals in response to the Cycle-6 NRA!
This essentially identical to the number (228) received last cycle. Thanks
for your continuued interest! The oversubscription rates for observing time
on the pointed instruments are about 2-3X. The proposals will be
"peer-reviewed" in late June, a time line developed in mid-July, after which
final announcements of awards and budget solicitations wil be made. Budget
request will be peer-revied by a subset of the scientific peer-review
committee.
Recent additions to the CGRO Data archive at the SSC make various data types
easier obtain and easier to use than ever! Give it a try. Refer to the
intrument team reports for details, notably OSSE (high-level product archive)
and BATSE (thereare now over two years of occultation histories for 25 sources
in a simple, FITS table format).
Please keep us* on your preprint mailing lists. The CGRO Users Committee is
preparing a proposal in response to the NASA Headquarters Missions and Data
Analysis (MO&DA) Senior Review - its very important for us to keep up with
any new science results. We're also extremely interested in hearing about any
CGRO related public outreach or educational initiatives you or your
collaborators may be involved with.
* send to the CGRO Science Support Center, c/o Chris Shrader, Code 660.1,
 NASA/GSFC, Greenbelt MD 20771 (or just tell me how to retreive
 electronically).
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.
Information on EGRET is now available on the World Wide Web.  You may
access it through:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/EGRET/egret.html
The material includes a discussion of the EGRET instrument and the
scientific goals, the institutions involved, a list of some major EGRET
discoveries, guest invesitgator information in relation to the GRO Science
Support Center, a list of EGRET papers in refereed journals, and some EGRET
preprints that have been accepted by journals, but have not yet appeared in
print, as well as other material such as a picture of the instrument and
the high-energy gamma-ray all-sky map.
At the forthcoming AAS meeting in Madison, Wisconsin, Bob Hartman and his
co-authors will be reporting on the large increase seen in 3C 279 reported
here last month, on the related multi-wavelength coverage, and on the
scientific implications.  These results seem to represent an important
addition to our understanding of this remarkable object.  Carl Fichtel and
his  co-authors at the same meeting will describe the BL Lac blazars that
have been seen in high-energy gamma radiation.
A paper by Joe Esposito et al. on supernova remants appeared in the April
20, 1996 issue of the Astophysical Journal.  Papers recently accepted by
the Astophysica Journal for publication include one by Sreekumar et al. on
the  gamma-ray sky north of b=40o, one by Nel et al. on a pulsar survey,
and one by Rshmi Mukherjee et al. on 0528+134.  Most of the papers
presented at the Third Compton Symposium have been accepted by now for
publication in the A & A.
COMPTEL
The COMPTEL operations group reports the resolution of a recent
problem in sending commands to the instrument.  In the course of a
test in early April it was noted that realtime serial commands sent as
blocks to COMPTEL from either UNH or the command console at the POCC
at GSFC failed to execute properly.  The source of the problem was
traced and identified as a flipped bit in a RAM patch of the COMPTEL
instrument's on-board software.  Commands were sent to reset this bit,
and realtime commanding capabilities have since been fully restored.
The routine operation of the instrument, and the acquisition of
scientific data, were not affected during this period.  The
collaboration acknowledges the great assistance of the Flight
Operations Team at the GSFC in analysing and correcting this problem,
while maintaining normal instrument operations.
A recent gamma-ray burst (GRB 960409) occurring inside the COMPTEL
field of view was localized by BATSE and found to lie in the direction
of Comet Hyakutake on that date (see IAUC 6384).  Analysis of the
COMPTEL data from GRB 960409 indicates a marginal detection, whose
location is consistent with the BATSE result.  Further details related
to this event can be found on the COMPTEL gamma-ray burst page on the
WWW.
A number of COMPTEL-related reports were presented by team members and
guest investigators at the recent AAS HEAD meeting in San Diego.  New
results on the gamma-ray emission observed with COMPTEL from the Orion
complex were presented by Bloemen et al.  In brief, a combination of
all data currently available shows that the excess in 3-7 MeV emission
reported previously extends essentially over the entire Orion cloud
complex.  Further, it is now apparent that the observed emission is
not due to *narrow* C and O lines at 4.44 and 6.13 MeV (from energetic
protons and alpha particles exciting ambient C and O).  These data can
be modeled as line-splitting of the Doppler-broadened emission from
the deexcitation of C and O cosmic-ray nuclei, although other
interpretations may be consistent with the measured spectrum.  A more
detailed description of this line-splitting phenomenon has been
presented in a recent Letter by Bykov, Bozhokin, and Bloemen (1996,
A&A 307, L37).  Also reported at the meeting was a new detection (by
Blom et al.)  of an extended excess of MeV gamma-ray emission at high
Galactic latitudes which may be associated with high-velocity clouds
(HVCs), and possibly related to the diffuse soft X-rays from HVCs seen
by ROSAT.  Updates were also presented on the observations of
gamma-ray bursts with COMPTEL (Kippen et al), measurements of Galactic
gamma-ray lines due to diffuse 26Al and 44Ti (Diehl et al.), limits on
2.2 MeV line emission from X-ray binaries (McConnell et al.), Bayesian
analysis techniques applied to pulsars (Connors et al.), as well as
multiwavelength observations of selected gamma-ray AGN (Collmar et
al., Stacy et al.).
Lastly, a paper on the "COMPTEL detection of the high-energy gamma-ray
source 2CG 135+01" by van Dijk et al. has recently been accepted for
publication in Astronomy and Astrophysics. A postscript verson is
available in the collaboration's electronic publications archive,
accessible from 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.  With the demise of the bursting pulsar,
GRO J1744-28, it will likely be re-enabled soon.
Several members of the OSSE team attended the HEAD meeting in San Diego last
week.  They summarized OSSE observations of GRO J1744-28, two classes of
galactic black hole spectra, an AGN catalog, limits on nuclear lines from the
Orion region, maps of galactic Al26, models of diffuse galactic continuum
emission, a clear detection of a hard tail from Sco X-1, gamma ray emission
from radio pulsars and X-ray pulsars, and the contribution of Type Ia SNe to
galactic positrons.
OSSE results from GRO J1744-28 have been accepted for publication in
ApJ Letters (Strickman et al.).  The letter summarizes 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.
Data through viewing period 409 have been delivered to the Compton GRO
Science Support Center archive.
Also, the OSSE High Level Products Archive has been updated at the CGRO-SSC:
High-Level OSSE Data products are now available from VPs 1.0 through 208.0
(excluding VP 203.0).  VPs 223.0, 303.4, 318.1, 328.0 and 331.0 have been
added via Guest Investigator request. Refer to the CGRO-SSC page on the
WWW (http://cossc.gsfc.nasa.gov), or contact Tom Bridgman
(bridgman@grossc.gsfc.nasa.gov) for more information.
BATSE
Follows is the BATSE contribution to the monthly report:
The following was reported in IAU circular 6395:
     GRO J1744-28
          C. Kouveliotou, Universities Space Research Association (USRA);
     K. Deal, P. Woods, M. Briggs, University of Alabama in Huntsville
     (UAH); B. A. Harmon, G. J. Fishman, Marshall Space Flight Center,
     NASA; J. van Paradijs, UAH and University of Amsterdam; M. H.
     Finger, USRA; and J. Kommers and W. H. G. Lewin, Massachusetts
     Institute of Technology, report:  "BATSE is no longer detecting
     bursts or persistent emission from the bursting pulsar GRO J1744-28.
     A total of 3080 bursts were detected from this source (not
     corrected for earth occultation or other deadtime effects) between
     its onset on 1995 Dec. 2 until its cessation on 1996 May 3.  During
     most of this 152-day interval, the burst rate was fairly constant
     at an average of about 20 bursts/day, but after Apr. 27 the rate
     declined rapidly.  The last detected event had a fluence of 1.2 x
     10E-7 erg cmE-2.  The pulsing signal in the persistent emission was
     last detected on Apr. 26; after this date, the pulsed flux was
     below 7 x 10E-10 erg cmE-2 sE-1 (r.m.s., between 20 and 40 keV).
     Between Apr. 30 and May 6, earth-occultation measurement yields a
     3-sigma upper limit on the total flux above 20 keV of 2.7 x 10E-9
     erg cmE-2 sE-1, or about 150 mCrab."
During the last month the following pulsed sources have been detected by the
BATSE pulsed source monitor: Her X-1, GRO J1744-28, Cen X-3, 4U 1626-67,
OAO 1657-415, GRO J1008-57, GX 1+4, GRO J2058+42, Vela X-1, and GX 301-2.
The burst trigger is currently using count rates from 50-300 keV energy range.
As of May 1 BATSE has detected 1518 gamma-ray bursts out of a total of 5347
on-board triggers in 1835 days of operation. There have been 766 triggers due
to solar flares, 10 due to SGR events, 54 due to terrestrial gamma-ray flashes,
and 1477 due to the bursting pulsar GRO J1744-28.
Approximately 830 days (Truncated Julian Dates 8369-9200) of BATSE Earth
occultation data for 25 sources have been delivered to the COSSC.  These are
in the form of source count rate histories  for single occultation steps and
photon fluxes in one day averages. The single step light curves have been
partially  evaluated for data quality, and allow the user to impose additional
criteria on data selection.  We anticipate future deliveries at a rate of about
150 days per month. The histories are available for: the Crab, Her X-1,
Cen X-3, Cyg X-1, GX 301-2, NGC 4151, 3C 273, Sco X-1, GX 339-4, 4U 1700-377,
Cyg X-3, Vela X-1, Cen A, OAO 1657-415, Nova Muscae, GRS 0834-43, 4U 1543-45,
GRO J0422+32, GRS 1915+105, GRS 1009-45, GRO J1719-24, GRO J1655-40,
4U 1608-522, GRO J1008-57, and 2S 1417-624.
In addition, occultation fit datasets (an intermediate level Earth occultation
data product) have also been delivered for 7 sources which offer a more
detailed look at the results of the Earth occultation measurements with fitting
coefficients, errors, and segments of raw data from which the occultation
measurements are made. These are available for: the Crab, Cyg X-1, Sco X-1, Cyg
X-3, Vela X-1, GRO J0422+32, and GRO J1655-40.
These Earth occultation data products are produced by the BATSE Earth
occultation team, and should not be confused with the EBOP Earth occultation
dataset produced by JPL.