CGRO biWeekly Status Report

[SHRADER@GROSSC.GSFC.NASA.GOV]

   Compton Observatory Science Report #159, Friday June 10, 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 Observatory, scientific instruments and all spacecraft
subsystems continue to function nearly flawlessly.

                    Science Support Center News

Several typographical errors to the Gamma-Ray Burst Basic
Information Table on GRONEWS were noted by the BATSE Instrument
Team. They have been corrected and a revised version installed (see
the BATSE Instrument Report below).

The Burst Catalog has been an extremely popular item -
approximately 150 downloads per week have occurred since it was
first announced.

The 236 Cycle 4 Guest Investigator Proposals have all been 
distributed to panels of anonymous referees. A peer-review meeting
later this month, followed by the detailed timeline devlopment 
during early July will determine what subset of these proposals
will be approved for Cycle 4.


                        Instrument Reports

EGRET

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

Several papers were presented at the AAS meeting, including the
results on the February 17, 1994 gamma-ray burst event described
here two weeks ago. Dr. Joe Espositio described the statistically
quite significant correlation between unidentified sources in the
plane and supernova remnants. Because the size of the emission
region cannot be distinguished from a point source, pulsars not
seen in the radio wavelength range are a possible origin of the
radiation as well as diffuse emission. Other talks on pulsars and
the galactic diffuse radiation were also presented. A paper by Dr.
Stan Hunter and others on rho Ophiucus was accepted by the
Astrophysical Journal; in this paper, they show that the emission
is consistent with cosmic rays at the local intensity level
interacting with the material and photons in the region.


OSSE

OSSE operations are normal.

In viewing period 329 (31 May - 7 June), the Z-axis target was PSR
J0437-47 (Guest Investigator M. Bailes) and the X-axis target was
the Crab Nebula and Pulsar (Guest Investigator J. Cordes). The Sun
was not available on the OSSE scan plane. During the Crab
observations, the housekeeping telemetry was modified to retrieve a
limited amount of calibration data to monitor the pulse-shape
discrimination efficiency in detector 1.

In viewing period 331.0 (7-10 June), the Z-axis target is Cyg X-3
(PI team), and the X-axis targets are PSR 0611+22 (Guest
Investigator J. Cordes) and 4U 0115+63 in its current outburst. 
The Sun is not available on the scan plane, so the slewing response
to BATSE solar flare triggers is disabled. For the first 24 hours
of vp 331.0, we used two detectors to monitor the spectral state of
Cyg X-1.

OSSE reports on SN1993J (M.D. Leising et al., ApJL), on NGC 1275
(C.Y. Osaka et al., ApJ), and on NGC 253 and M82 (D. Bhattacharya
et al., ApJ) have recently been accepted for publication. 
Preprints will be distributed shortly.

Data from viewing period 211 were delivered to the Compton GRO
Science Support Center archive this week.  The targets during
period 211 were 4U0115+63, NGC 253, 47 Tuc, and SMC X-1.


BATSE

BATSE's 1000th gamma-ray burst (trigger # 2996) occurred on May
27th. 

The BATSE Science Team wishes to express their extreme gratitude to
all of the wonderful people associated with the Compton Observatory
who have helped us to achieve this important milestone. 

We are especially grateful to the outstanding GRO project office at
GSFC, the TRW personnel who designed, assembled, and tested one of
the finest (and largest) spacecraft in the history of NASA, and the
dedicated and conscientious GSFC/TRW/Allied-Signal operations team
who continue to provide us with high quality data in a timely
manner.

At Marshall SFC a contest to guess the date of the 1000th burst was
held. This was won by Georgia Richardson. Zamir Sariff won an award
for doing the burst processing for the day the burst occurred. A 
party was held in the burst's honor at the residence of P.I. Jerry
Fishman.

The following was included in IAU Circular 5999:

     4U 0115+634

     R. B. Wilson, M. H. Finger, and D. M. Scott report for the 
     Compton Gamma Ray Observatory BATSE pulsar team: "The outburst
     from the x-ray binary pulsar 4U 0115+634 previously reported
     on IAUC 5990 continues as of May 30. The flux in the energy
     band 20-50 keV rose at a constant rate from the onset of
     detection on May 8 to about 65 mCrab on May 18, increased at a
     lesser rate to about 75 mCrab on May 28, then increased more
     rapidly, reaching about 180 mCrab on May 30."

The source is still currently being detected.

As of June 8th, BATSE has detected 1009 cosmic gamma-ray bursts out
of a total of 2915 on-board triggers in 1125 days of operation.
There have been 733 triggers due to solar flares with emission
above 60 keV.

An error in the names of 16 bursts (col 2) in the BASIC table of
the 2nd burst catalog was found. This problem is now corrected in
the table available from the GROSSC.


COMPTEL

The COMPTEL instrument is performing well and continues routine
observations.

The collaboration forwarded this week to the CGRO public archive at
the Science Support Center low-level and first high-level COMPTEL
data products for Viewing Periods 29-44 of Phase 1.  With the
exception of a few files of processed burst spectra, currently
being prepared, these data complete the delivery by COMPTEL of
initial Sky Survey datasets to the CGRO archive.