Compton Observatory Science Report #165, Friday, September 2, 1994 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 Spacecraft Status The Observatory, scientific instruments and all spacecraft subsystems continue to function nearly flawlessly. Science Support Center Activities Many CGRO Guest Investigators outside of the United States have noted that they have not yet received their notification letters for the Cycle-4 program. We apologize for this inconvenience, but note that THE LETTERS WERE ALL BEEN MAILED THREE OR MORE WEEKS AGO at this time. Members of the CGRO-SSC, in collaboration with the EGRET team announced the serindipitous discovery of a new gamma-ray blazar QSO; a copy of an IAU telegram is appended: GAMMA-RAY FLARE FROM DIRECTION OF NRAO 190 T. A. McGlynn and J. R. Mattox, Compton Observatory Science Support Center, Goddard Space Flight Center, NASA; W. T. Vestrand, University of New Hampshire; and the Compton Observatory EGRET Team (B. L. Dingus, D. L. Bertsch, J. A. Esposito, C. E. Fichtel, R. C. Hartman, S. D. Hunter, C. von Montigny, R. Mukherjee, P. Sreekumar, and D. J. Thompson, Goddard Space Flight Center, NASA; D. A. Kniffen, Hampden-Sydney College; Y. C. Lin, P. F. Michelson, and P. L. Nolan, Stanford University; E. Schneid, Grumman Aerospace Corporation; and G. Kanbach and H. A. Mayer-Hasselwander, Max- Planck-Institut fur Extraterrestrische Physik) communicate: "We report the detection of a gamma-ray source, having a position consistent with the quasar NRAO 190 (Pauliny-Toth et al. 1966, Ap.J. Supp. 13), in the energy range above 100 MeV during Aug. 9- 20. The maximum-likelihood position from the EGRET quicklook data is l = 197o.0, b = -29o.5 (R.A. = 4h38m.7, Decl. = -0o41', equinox 2000.0), with a 95-percent error cone having a radius of at least 1 deg. The proposed identification is 1o from the gamma-ray position and is the only strong radio-loud active galactic nucleus within the 95-percent confidence contour. EGRET will continue to view this region of the sky until Aug. 29. The identification is consistent with the typical EGRET detection of strong, flat-spectrum, optically-violently variable QSOs. The outburst has a flux at least four times the 95-percent upper limit of 8 x 10E-8 count cmE-2 sE-1 (E > 100 MeV) obtained during the EGRET all-sky survey. We urge observations at other wavelengths to attempt to determine the characteristics of the outburst." Instrument Reports EGRET EGRET operations were normal this biweekly period. Delivery of data to the CGRO-SSC remains on schedule. Interaction with guest investigators remains at a good level. A "glitch" occurred in the Vela Pulsar just before the observation began yesterday. We are very anxious to see if there is any change in the gamma-ray emission beyond the expected change in period. We are now in the process of making preparations for Cycle 4 and should be finished shortly. OSSE We have disabled the newly implemented gamma-ray burst observing strategy for the time being. The duration of the burst trigger signal from BATSE to OSSE is used to encode OSSE's scan angle to the burst; however there appears to be some occasional confusion in either the generation or readout of this signal. The cause is under investigation. Approximately 15 hours of data were lost on day 94/235 (1994 Aug 23) when OSSE slewed to the wrong location for two separate triggers. In viewing period 338.0 (29-31 Aug), the Z-axis target was the recent X-ray nova GRO J1655-40 (PI team), and the X-axis target was Cen A (PI team). In viewing period 338.5 (31 Aug - 20 Sep), the Z-axis target is the Vela pulsar region (Guest Investigator A. Harding), and the X-axis target is 3C273 (PI team). Data from viewing periods 221 and 222 were delivered to the Compton GRO Science Support Center archive this week. The targets during period 221 the Crab pulsar, GT 0236+610, PSR 1951+32, and Cyg X-1. The targets during period 222 were NGC 4151 and MCG+8-11-11. COMPTEL The COMPTEL instrument is performing well and continues routine observations. A first circular announcing the Third Compton Symposium, to be held next summer (12-14 June 1995) in Munich, Germany, has recently been distributed. An expression of interest from potential attendees is requested by October 31. Further information can be obtained from the organizers via anonymous ftp to cgro95.mpe-garching.mpg.de. Interest is already running high for two other conferences being organized in part by members of the collaboration: The Second Waterville Valley Workshop on High-Energy Solar Phenomena (6-10 March 1995) in Waterville Valley, New Hampshire, and the 29th ESLAB Symposium, "Towards the Source of Gamma-Ray Bursts," scheduled for 25-27 April 1995 at ESA/ESTEC in The Netherlands. Further details can be found on the GRONEWS on-line bulletin board (or see below). Ever on the forefront, the Astrophysics Division of ESA/ESTEC announces that it has established its own home page on the World Wide Web, which can be accessed at the following URL: "http://astro.estec.esa.nl/". Among other items of interest can be found: contact information for members of the COMPTEL group within the Space Science Department of ESA/ESTEC, an image of the latest gamma-ray burst detected by COMPTEL, further details on the upcoming ESLAB symposium on gamma-ray bursts, easy routings to data-bases and analysis tools inside and outside ESA and the "patron saint" of (at least one member of) the Astrophysics Division. BATSE BATSE continues to operate normally. During the last week the BATSE pulsed source monitor has detected pulsed emission from the x-ray binary pulsars Her X-1, Cen X-3, 4U 1626-67, OAO 1657-415, Vela X-1, and GX 301-2. BATSE folded on board data is currently being collected for the Crab Pulsar, the Vela Pulsar, and Her X-1. Single sweep data (31 ms resolution) is also being collected for pulsar searches. As of September 1st, BATSE has detected 1103 cosmic gamma-ray bursts out of a total of 3043 on-board triggers in 1103 days of operation. There have been 737 triggers due to solar flares with emission above 60 keV.