Compton Observatory Science Report #174, Friday January 6, 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. Several papers on active galaxies have been accepted by the Astrophysical Journal. Work on the long, complex analysis of the all sky data to determine the diffuse radiation as a function of position is nearing completion; preliminary reports have been presented at scientific meetings, and papers on the galactic and presumably extragalactic components should be submitted to scientific journals in the near future. The deep exposure to the Virgo region will be completed next Tuesday. The results of this study when it is finished should add significantly to our understanding of active galactic nuclei. OSSE In the past two weeks, OSSE detector #1 has failed to step twice, on 94/358 (24 Dec) and 95/002 (2 Jan). There have now been three such occurrences since launch; the first was 16 Dec 1994. 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. The circumstances of all three failures suggest that it is not a mechanical problem with the drive or drive motor, and we are investigating possible electronic or software causes. OSSE is currently in normal operations on all four detectors. In viewing period 408 (3-10 Jan), the Z-axis targets are 3C 273 and 3C 279 (PI team), and the X-axis target is H1822-37.1 (Guest Investigator E. Liang). When neither scheduled target is visible, the targets are NGC 3227 and PKS 2155-304. Three very interesting OSSE papers have been accepted for publication recently, summarizing the long-term (spanning 18 months) spectral behavior of 3C 273 (Johnson et al.), observations of the starburst galaxies NGC 253 and M82 (Bhattacharya et al.), and the absence of a red-shifted annihilation feature in the spectrum of 1E 1740.7-2942 (Jung et al.) on 20 Sep 1992. With OSSE substantially greater sensitivity, this last result is in direct conflict with the report by SIGMA of transient emission on that day. Data from viewing periods 303.2 and 303.4 were delivered to the Compton GRO Science Support Center archive this week. The targets during these viewing periods were N Cyg 1992, NGC 5548, Cyg X-1, and 3C273. COMPTEL The COMPTEL instrument is performing well and continues routine observations (and sends New Year's greetings to all its friends and colleagues). There will be several presentations by members of the COMPTEL collaboration, and Guest Investigators, at next week's meeting of the AAS in Tuscon. Topics include recent spectral results for Cygnus X-1, the current state of the BATSE/COMPTEL/NMSU burst rapid-response network, and the latest results on searches for gamma-ray lines, and signs of radiative neutrino decay, from supernovae. We remind colleagues that abstract deadlines are approaching for contributions to several conferences sponsored in part by the collaboration: the 29th ESLAB Symposium, "Toward the Source of Gamma-Ray Bursts" (meeting dates 25-27 April 1995; abstracts due January 13); the Second Waterville Valley Workshop on High-Energy Solar Phenomena (meeting dates 6-10 March 1995; abstracts due February 1); and the Third Compton Syposium, in Munich (meeting dates 12-14 June 1995; abstracts due March 31). Refer to the GRONEWS on-line bulletin board for further details. BATSE At upcoming AAS Meeting in Phoenix BATSE team scientists will be presenting results from BATSE observations of the transient x-ray / radio jet sources GRO J1655-40 and GRS 1915+105. The following sources were detected by the BATSE pulsed source monitor in the past two weeks: 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. The x-ray binary GX 1+4 is still spinning up. The outburst that began in October continues, with typical pulsed fluxes of 80 mCrab (20-100 keV). As of January 4th, BATSE has detected 1199 cosmic gamma-ray bursts out of a total of 3239 on-board triggers in 1352 days of operation. There have been 741 triggers due to solar flares with emission above 60 keV. Since the BATSE burst trigger criteria were changed on September 19th 1994, there have been 15 triggers due to terrestrial gamma-ray flashes.