Compton Observatory Science Report #177, Friday February 17, 1995 Chris Shrader, Compton Observatory Science Support Center Questions or comments can be sent to the CGRO SSC. Phone: 301/286-8434 e-mail: NSI_DECnet: GROSSC::SHRADER Internet: shrader@grossc.gsfc.nasa.gov Instrument Reports EGRET EGRET operations were normal this biweekly period. Delivery of data to the GRO SSC remains on schedule. Interaction with guest investigators continues at a good level. Work is nearing completion on the Second EGRET Catalog, and it should be submitted to a journal shortly. Several abstracts have been submitted for presentation at the American Physical Society Meeting in April and at the International Cosmic Ray Conference. Careful studies are in progress on the whole high energy gamma ray sky as observed by EGRET including all the refinements that currently exist, and they will be submitted as a series of papers over the next several weeks. At the moment, EGRET has just begun to view a region centered at RA=98.5 and DEC=69.8, that includes QSO 0716+714. OSSE OSSE detector #1 failed to step last night (16 Feb), the fourth such event since launch and the first since 2 Jan. The motor drive positioning process, which in normal operation moves the detectors every 2 minutes, takes the detector off line when it detects a positioning error. We restored the detector to normal operation without any difficulty. How the drive knows to cause problems only in the middle of the night remains a mystery. OSSE is currently in normal operations on all four detectors. The slewing response to BATSE burst triggers remains disabled while the BATSE trigger is in its current low energy setting. We will re-enable the slewing when the test period ends. In viewing period 411.1 (14-21 Feb), the Z-axis target is Mrk 3 (Guest Investigator P. Nandra), and the X-axis target is Cas A (PI team). Data from viewing periods 306 and 307 were delivered to the Compton GRO Science Support Center archive this week. The targets during these viewing periods were the Virgo region sky survey, the galactic center region, and PSR 1800-21. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The collaboration forwarded to the SSC this week a major delivery of archival data, encompassing all low-level and first high-level data products for Phase 2 of the CGRO mission. It has come to our attention that there is a page missing (page number 8) from the COMPTEL preprint recently distributed on "COMPTEL Observations of Galactic 26-Al Emission" by Diehl et al. A corrected version of this preprint is currently being prepared for redistribution. In the interim, postscript versions of the missing page, or of the complete document, are available from either R. Diehl at MPE (rod@mpe-garching.mpg.de) or via anonymous ftp to unhgro.unh.edu (a user should "cd" to the /pub/papers directory). (Note: This anonymous ftp facility is currently under construction; it will eventually contain electronic postscript versions of all COMPTEL team publications.) BATSE The x-ray transient GRO J1719-24 = GRS 1716-249 remains visible at a flux of 200-300 mCrab in the 20-100 keV energy range. The LMXB pulsar GX 1+4 has been markedly brighter in Earth occultation (about 300 mCrab 20-100 keV) since it began to spin up. The following sources were detected by the BATSE pulsed source monitor in the past two weeks: Her X-1, Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. As of February 16, BATSE has detected 1228 cosmic gamma-ray bursts out of a total of 3326 on-board triggers in 1395 days of operation. There have been 748 triggers due to solar flares with emission above 60 keV.