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CGRO bi-Weekly Report for January 7, 1994

Compton Observatory Science Report #148 Friday, January 7, 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 Spacecraft and all subsystems continue to perform nominally.
The current Z-axis target is PSR 1259-63 which is a 47-ms pulsar
in an eccentric binary orbit about a Be star primary. The neutron
star is currently undergoing perisaton passage - its orbital
period is 3.4 years.  

                   Science Support Center News

The Science Support Center staff are planning a series of
demonstrations for the forthcoming AAS meeting. An approximate
schedule of the planned demonstrations follows:

Wednesday:     1:45 PM   SSC Data Archive
Thursday:      9:30 AM   EGRET Analysis Tools
Thursday:      1:45 PM   Gamma Core, SSC Quick Look Tools
Friday:        1:45 PM   OSSE Analysis Tools (IGORE)

The CGRO Cycle 4 NRA will be issued shortly. The due date for
proposals will be April 10, 1994, with Cycle 4 observations
commencing on 4 October 1994. Copies of the NRA and appendices
will be available electronically on GRONEWS. 

                       Instrument Reports


OSSE operations are normal.

In viewing period 313, the Z-axis target was the Virgo sky survey
(Key project) near galactic coordinates (l,b) = (289,+79), and
the X-axis target was the galactic center region (PI team).  The
Sun was accessible along the scan plane, and OSSE slewed to the
Sun in response to BATSE triggers at the following times (TJD): 
9348.7858, 9351.2427, 9352.0345, 9352.3463, 9352.9219, and

In viewing period 314, the Z-axis target is the binary pulsar PSR
1259-63 (Guest Investigator M. Tavani), and the X-axis target is
the nova N Her 1991 (Guest Investigator S. Starrfield).  The Sun
is not accessible along the scan plane, and the slewing response
is disabled.

Data from viewing periods 25, 27, and 31 will be delivered to the
Compton GRO Science Support Center Archive today.  The targets
during vp 25 were the galactic center region, Mrk 841, and NGC
7582.  During vp 27, the targets were 4U 1543-57 and NGC 7314. 
During vp 31, the targets were MCG+8-11-11, PKS 0548-322, and SN


EGRET observations were normal this week. It was a relatively
quiet period in terms of interactions with the outside community
because of the holidays. However, there was substantial work here
in preparation for the forthcoming American Astronomical Society
Meeting wher many results summarizing the all-sky survey will be
presente for the first time.


The COMPTEL instrument is performing well and continues routine

Final preparations are underway for team presentations at next
week's meeting of the AAS in Washington, D.C. The collaboration
will be presenting its latest results on the topics of gamma-ray
line spectroscopy (Bloemen et al.), x-ray binaries (McConnell et
al.), and active galaxies (Bennett et al.). 


The following report was published in IAU circular No. 5915:

     GX 339-4
     B. A. Harmon, W. S. Paciesas, S. N. Zhang, G. J. Fishman,
     and M. H. Finger, Marshall Space Flight Center, NASA, report
     for the  Compton Observatory's Burst and Transient Source
     Experiment (BATSE) Team: ``The black-hole candidate GX 339-4
     has again entered its hard (low) emission state, being
     detected by earth occultation beginning in late December
     1993. Its intensity has increased gradually and is currently
     at about 0.2 Crab (Dec. 30-1994 Jan. 1) in the band 20-100
     keV with a hard spectrum. Outbursts of GX 339-4 beginning in
     late June 1991 (IAUC 5327) and early September 1992  (IAUC
     5647), and now in December 1993, indicate an interval
     between hard x-ray outbursts of about 440 +/- 30 days. This
     is a strong indication of long-term periodicity in this
     suspected-but-unproven binary system. If the periodicity is
     associated with the binary orbit, GX 339-4 does not fit
     conveniently into the canonical model of a low-mass, x-ray
On January 5th an anomaly occurred in BATSE detector module 3
that caused the loss of its 16 and 128 channel LAD data types.
The problem is thought to have been due to a latch-up in the
monolithic charge to time conversion (MQT) electronics. The power
to the module was cycled on January 6th which restored normal
behavior. Three simular events have occurred since launch, all
with module 3.

BATSE folded-on-board pulsar data is currently being collected
from the Crab pulsar, PSR 0950+08, PSR 0818-13, and PSR 1259-63.
The pulsar hardware is also being used to collect 31 ms single
sweep data for pulsar searches.