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CGRO BiWeekly Status Report

Compton Observatory Science Report #157, Monday, May 16, 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

A CGRO-SSC Users Guide has been prepared by the SSC staff. It will
be distributed at the Minneapolis AAS Meeting, and will be made
available electronically shortly. This document will continue to be
revised and expanded as additional data and software are added to
the SSC.

                        Instrument Reports


EGRET operations were normal this biweekly period. The average
percentage of possible data that is being recovered remains at or
above 80%. Interactions with guest investigators remains at a good

The first EGRET catalog will appear in the October issue of the
Astrophysical Journal Supplement. A paper entitled"EGRET
High-Energy Gamma-Ray Pulsar Studies. I. Young Spin-Powered
Pulsars", by David Thompson et al. has been accepted by the
Astrophysical Journal and preprints will be available shortly.
Preprints will also be available shortly of a paper entitled
"Search of the Energetic Gamma Ray Experiment Telescope (EGRET)
Data for High Energy Gamma Ray Microsecond Bursts", by Carl Fichtel
et al.


OSSE operations are normal.

In viewing period 326 (10-17 May), the Z-axis target is QSO
1028+313 (Guest Investigator M. Maisack), and the X-axis target is
NRAO 140 (Guest Investigator M. Maisack). The Sun is not available
on the scan plane.

In viewing period 327 (17-24 May), the Z-axis target is NGC 7469 
(Guest Investigator R. Cameron), and the X-axis target is NRAO 140
(Guest Investigator M. Maisack). When neither target is above the
horizon, the target for detectors 1 and 2 is MRK 509, while
detectors 3 and 4 slew to the position of the occulted X-axis
target and stare. The Sun is not available on the scan plane.

Data from viewing period 208 were delivered to the Compton GRO
Science Support Center archive last week. The targets during this
period were NGC 4507 and NGC 6814.


The outburst from the newly discovered 18.7 s x-ray pulsar GRO
J1948+32 has ended. The outburst lasted from April 6 to May 12. The
pulse timing delays indicate a binary orbit with a period of
approximately 40 days. Orbital analyses are underway.

An outburst from the x-ray binary 4U 0115+63 is currently being
observed. The source was first detected on May 8. Folded-on-board
data for this source is being collected using both the large area
and spectroscopy detectors.

As of May 8, BATSE has detected 979 cosmic gamma-ray bursts out of
a total of 2861 on-board triggers in 1111 days of operation. There
have been 731 triggers due to solar flares with emission above 60


The COMPTEL instrument is performing well and continues routine

Recent COMPTEL results related to solar flares and cosmic gamma-ray
bursts will be presented at the upcoming meetings of the Solar
Physics Division of the American Astronomical Society in Baltimore,
and the general meeting of the AAS in Minneapolis.

By general consensus, the annular solar eclipse of May 10 was a
spectacular event. Viewing conditions at UNH were excellent, and
all those present enjoyed the rare phenomenon. Preparations are
already underway to mark with suitable fanfare the next total solar
eclipse viewable from New England (on April 20, 2024).