CGRO biWeekly Status Report

[SHRADER@GROSSC.GSFC.NASA.GOV]

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   Compton Observatory Science Report #158, Friday, May 27, 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
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                         Spacecraft Status

The Observatory, scientific instruments and all spacecraft
subsystems continue to function nearly flawlessly.

                    Science Support Center News

Several new Xmosaic services are available from the SSC:

Batse Burst table: The Batse burst table, also available on GRONEWS
(see the BATSE Instrument Report below) has now been placed on our
BATSE Services page. In addition to the burst table itself one can
"click" on a trigger number to obtain a simple light curve and
summary information about each burst. For those of you who want to
add it to your hotlist the reference is:

     http://cossc.gsfc.nasa.gov/batse/BATSE_Ctlg/index.html

Enjoy! The CGRO-SSC Users Guide is also available on Xmosaic from
the CGRO-SSC home page.

A CD Rom containing the Phase-1 EGRET Sky Survey data, and software
for reading it and performing basic analysis, has been produced by
the SSC staff. It will be distributed at the Minneapolis AAS
meeting next week.

A model of the high-energy diffuse emission has been provided to
the SSC by the EGRET team (see the EGRET report below). It has been
installed in our software for use by guest investigators or is
available for use with other software.

The Second Compton Symposium Proceedings have been printed and are
now being mailed out to all meeting participants.


                        Instrument Reports


EGRET

EGRET operations were normal during this biweekly period. The data
reduction and analysis is progressing as planned. Interaction with
guest investigators remains at a good level. Delivery of data to
the CGRO-SSC is on schedule.

Several papers on EGRET results will be presented at the American
Astronomical Society Meetings next week. One of these will be on
the remarkable high-energy gamma ray results related to the
February 17, 1994 burst mentioned in this report four weeks ago.

The high-energy gamma-ray diffuse emission model of Bertsch, Dame,
Fichtel, Hunter, Sreekumar, Stacy, and Thaddeus with recent
improvements by the same group has been transferred to the CGRO-SSC
in FITS format for anyone who wishes to use it. Additional
refinements with the relevant references will be transferred to the
SSC in the near future. Scientists are, of course, still free to
use any model they choose.

OSSE

OSSE operations are normal.

In viewing period 328 (24-31 May), 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 this viewing period, we directed two
detectors to monitor Cyg X-1.  Preliminary analysis of these data
indicate that the source has returned to a flux level and
temperature characteristic of most OSSE observations of Cyg X-1, in
contrast to the low-flux, low-temperature spectrum we reported in
February (IAU Circ 5930).

Data from viewing periods 209 and 210 were delivered to the Compton
GRO Science Support Center archive this week.  The targets during
period 209 were 2CG010-31, Cyg X-1, and 3C390.3, and during period
210 were 1E1740.7-2942 and MCG-2-58-22.

BATSE

The second BATSE catalogue of gamma-ray bursts is now available
through the Gamma-Ray Observatory Science  Support Center.  The
catalogue comprises 585 bursts observed through  1993 Mar. 9 and
includes the previously released 1B catalogue.  To  access the
catalogue, INTERNET users should type 'telnet 
grossc.gsfc.nasa.gov'; DECNET users should type 'set host grossc'. 
The login name is 'gronews', and no password is required.

The following was included in IAU Circular 5990:

     4U 0115+634                                                    
  
     D. M. Scott, M. H. Finger, R. B. Wilson, and T. A. Prince
     report for the Compton Gamma Ray Observatory BATSE pulsar
     team: "Pulsed hard x-ray flux in the energy range 20-70 keV is
     currently being detected from the x-ray binary 4U 0115+634.
     This is the second outburst of this source observed by BATSE,
     the first occurring in April 1991. In the current outburst,
     pulsed flux was first detected on 1994 May 8. An intrinsic
     pulse period of 3.6145107 +/- 0.0000010 s and a period
     derivative of (5.9 +/- 1.9) x 10E-11 were determined for epoch
     May 13.0 UT. The phase-averaged pulsed flux, averaged over
     20-40 keV, was about 45 mCrab (total) on May 15. The spectrum
     is well fit by an optically thin thermal bremsstrahlung model
     A/E exp(-kT), with kT = 16 +/- 4 keV, and a flux at 35 keV of
     (2.0 +/- 0.2) x 10E-4 photon cmE-2 sE-1 keVE-1." 

The source is still being observed. The pulsed flux has gradually
been increasing since May 15, with the total increase approximately
25%.

As of May 22, BATSE has detected 993 cosmic gamma-ray bursts out of
a total of 2883 on-board triggers in 1125 days of operation. There
have been 732 triggers due to solar flares with emission above 60
keV.


COMPTEL

The COMPTEL instrument is performing well and continues routine
observations.

The latest cosmic gamma-ray burst to occur within the field of view
of COMPTEL was recorded on May 20, 1994 (name TBD).  The first
determination of burst location, based on approximately 55 COMPTEL
telescope events, was distributed through the BATSE/COMPTEL Rapid
Response Network within 3 hours of burst occurrence.

The most recent burst location determined from the COMPTEL data,
which agrees well with the preliminary IPN location annulus, is
given below, along with the coordinates of the one-sigma error box:

*****************************************************
BURST_DATE :  9492 TJD; 20-MAY-1994
BURST_TIME :  1298.00 SEC;  0:21:38 UT
BURST_SCZEN:  23.5 Deg.
BURST_SCAZI: 219.8 Deg.
BURST_CLASS: Medium  (Approx  55 events)
*****************************************************
COORD_J2000: [RAsc     Decl]   [RAsc            Decl]
============ ===============   ======================
MAXLIK_POS : [324.6d   7.8d] = [21h38m14s   7d45m48s]
-----------------------------------------------------
ERRBOX1_POS: [325.7d   8.9d] = [21h42m42s   8d56m13s]
ERRBOX2_POS: [325.5d   6.2d] = [21h41m52s   6d12m56s]
ERRBOX3_POS: [323.5d   6.4d] = [21h33m54s   6d21m36s]
ERRBOX4_POS: [323.7d   9.1d] = [21h34m40s   9d 4m57s]
*****************************************************
COORD_B1950: [RAsc     Decl]   [RAsc            Decl]
============ ===============   ======================
MAXLIK_POS : [324.0d   7.5d] = [21h35m54s   7d31m39s]
-----------------------------------------------------
ERRBOX1_POS: [325.1d   8.7d] = [21h40m22s   8d41m53s]
ERRBOX2_POS: [324.9d   6.0d] = [21h39m31s   5d58m38s]
ERRBOX3_POS: [322.9d   6.1d] = [21h31m32s   6d 7m39s]
ERRBOX4_POS: [323.1d   8.8d] = [21h32m21s   8d50m58s]
*****************************************************
 
Investigators who do not routinely receive such reports through the
BATSE/COMPTEL Rapid Response Network, and who wish to be added to
the distribution list for future notices, should contact either Dr.
Bernie McNamara at NMSU (bmcnamar@nmsu.edu) or Dr. Jim Ryan at UNH
(jryan@unh.edu) for further details.