Compton Gamma Ray Observatory Status Report #201 Tuesday February 11, 1997 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 Reminder: Abstracts for the Fourth Compton Symposium are due by this weekend week! (Febrary 15). The conference is on April 27-30, and it will be preceded by a public workshop on April 25 and 26. For more information refer to the 4th Compton Symposium hompage: http://osse-www.nrl.navy.mil/cgrosymp.htm Relase of the Cycle-7 NRA has been further delayed. It is now likely that the release will be early next month, and the propsal due date will most likely be in June. All of us in the CGRO project are pleased to extend our congratulations to Volker Schoenfelder, the COMPTEL Principal Investigator, who has been awarded the Philip-Morris Research Prize for 1997, in recognition of his many contributions to the successful development of the double-Compton telescope technique, and for the exciting discoveries made by the COMPTEL instrument aboard NASA's Compton Observatory. This is one of the most prestigous science awards issued in Germany, and the ceremony, this June, will be attended by the by the German Minister of Science. Instrument Team Reports EGRET EGRET has been turned off since the Target of Opportunity to view Cygnus was added. This cut short the 8 week multiwavelength campange to study 3C-279 by one week. Operations have been normal, and the instrument performance has remained nearly constant since the last gas fill. Data analysis is essentially current. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The COMPTEL operations group has nearly completed the definition of COMPTEL-related reboost procedures in preparation for the reboost maneuvers of the CGRO spacecraft scheduled for the near future. An accelarated processing of data is expected in the coming weeks for the recent target-of-opportunity observation of Cygnus X-1. A flurry of abstracts is making the rounds between the various COMPTEL sites, in view of the impending (and coincident) submission deadlines for both the 4th Compton Symposium and the 25th ICRC. OSSE OSSE operations are currently normal. The instrument is working as designed, with all subsystems in complete and full operation. The slewing response to BATSE burst triggers was reenabled on 28 January, having been disabled on 6 January 1997 to protect against slews to the bursting pulsar GRO J1744-28. Recent bursts are available on the WWW at . Recent observations are listed in the following table. We have completed target of opportunity pointings at GRO J1744-28 and Cyg X-1. Analysis of both of these targets is currently in progress. View period Dates Target (owner) 610 7-14 Jan 3C 279 (W.N. Johnson) GPLANE 16 (W.R. Purcell) 610.5 14-21 Jan 3C 279 (W.N. Johnson) 3C 273 (public) GRO J1744-28 (J.E. Grove) 611.1 21-28 Jan 3C 279 (W.N. Johnson) GPLANE 20 (W.R. Purcell) 612.5 28 Jan - 4 Feb Cyg X-1 (B.F. Phlips) PKS 2155-304 (public) NGC 7172 (public) 624.1 4-11 Feb GPLANE 16 (R.L. Kinzer) PKS 2155-304 (public) Low-level OSSE data products through viewing period 506 are awaiting delivery to the Compton GRO Science Support Center archive. High-level data products through viewing period 220 have been delivered. In addition, by special request all subsequent public Cyg X-1 data sets, both low and high level, have been delivered. 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 GRO J1744-28 is still in outburst. The flux peaked at the end of January and is now declining. So far from this outburst 1373 bursts have been detected, with 273 triggering the BATSE burst mode. During the last month the following pulsed sources have been detected by the BATSE pulsed source monitor: GRO J1744-28, Her X-1, Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1,and GX 301-2. Quick-look results from the BATSE occultation and pulsar monitoring programs are now available over the world-wide-web. Tabular reports are currently being posted twice weekly. They can found at the BATSE Web site : http://www.batse.msfc.nasa.gov/ under the links "earth occulted sources" and "pulsed sources". A list of monitored sources can be found under "cosmic gamma-ray sources". Future plans for the web site include plots of the recent occultation flux history of bright sources, and pulsed flux and frequency history of accretion-powered pulsars. The burst trigger continues to use rates from channels 1+2 (20 - 100 keV), with thresholds of 5.5 sigma for 64ms and 256ms timescales and 7.0 sigma for the 1.024s timescale. As of February 6 BATSE has detected 1732 gamma-ray bursts out of a total of 5932 on-board triggers in 2116 days of operation. There have been 779 triggers due to solar flares, 39 due to SGR events, 64 due to terrestrial gamma-ray flashes, and 1750 due to the bursting pulsar GRO J1744-28.