Compton Observatory Science Report #149 Friday, January 21, 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 Spacecraft Status The CGRO remains a healthy spacecraft, with all subsystems are operating nominally. As of January 14, 1994 the Compton GRO orbit had a mean orbital altitude of 450.9 km. The throughput efficiency of real-time telemetry is increasing as a result of the TDRSS reconfiguration and bringing online of the Australian Ground station. Based on the number of packets of data delivered to instrument teams from the Packet Processing Facility, the percentage of full time coverage achieved with 32- kbps real-time data between January 6 and January 9 was 79%, including 10% from the new ground station. An additional 8% coverage was achieved with the BATSE 1-kbps data during this time. Science Support Center News The SSC staff manned a CGRO display booth at last weeks AAS meeting in Crystal City. Demonstrations on archive search and retrieval, as well as various instrument specific software were given. Development on the Cycle 4 proposal submission software is continuing. Additionally, the NRA Appendices A-H will be posted on GRONEWS within the next several working days. The BATSE GRB Spectroscopy catalog has been delivered to the SSC by Brad Schaefer. It will shortly be made available through online access. Stay tuned to GRONEWS for details. The SSC staff, along with the Project Scientist, are developing plans for a CGRO exhibit, which if approved by the museum board, will be on display in the main lobby of the National Air and Space Museum. The display will feature a 10 minute video on the CGRO mission tentatively entitled "Our Violent Universe" (the video is being produced by Jim Lynch with consultation from the CGRO project). Guest Investigator News An ongoing Guest investigation by Drs. Jay Norris and Robert Nemiroff on detailed temporal analysis of GRBs was the subject of an AAS press release last Saturday. Norris and Nemiroff presented mounting evidence for a cosmological interpretation of GRBs by showing that, statistically, fainter bursts are longer in duration and show greater time structure than brighter bursts. Additionally, the fainter bursts appear to be have softer spectra. Both effects are qualitatively consistent with a cosmological origin (but alternatively, they can be a result of intrinsic GRB population properties). A copy of the text of their press release is available on GRONEWS under sub-menu 1, "Recent Scientific Results." Dr. Malcolm Coe, who is the Principal Investigator on several ongoing CGRO Guest Investigations involving multi-wavelength studies of high-mass X-ray binaries, has identified an optical counterpart to the transient GRO J1008-57 (IAUC 5836,5838). A transcript of his report follows: Malcolm Coe (Southampton University), Juan Fabregat (Valencia University) and Dave Buckley (SAAO) announce that they have found the optical counterpart to the CGRO transient source J1008-57. This object was discovered by CGRO last year (IAUC 5836 and 5838) and subsequently observed by ASCA and ROSAT (IAUC 5851 and 5877, respectively). A deep red image taken at the UK Schmidt telescope on 28 July 1993 (just a few days after BATSE detected the start of the outburst) revealed just 2 objects within the ROSAT error circle and a further 3-4 close by. Observations carried out at the South African Astronomical Observatory in December 1993 revealed that the brightest source in the error circle is a strong H alpha emitter. This then confirms this system as another Be/X-ray binary system, as was suspected from the X-ray characteristics. Instrument Reports OSSE OSSE operations are essentially normal, with only minor interruptions from power outages in the DC area. In viewing period 315, the Z-axis target is the binary pulsar PSR 1259-63 (Guest Investigator M. Tavani), and the X-axis target is the galactic center region (Key project). The Sun is not accessible along the scan plane, and the slewing response to BATSE solar flare triggers is therefore disabled. A number of OSSE team members attended the 183rd Meeting of the American Astronomical Society in Crystal City, VA. Many new or improved scientific results from OSSE data were presented on such topics as the galactic positronium continuum, the diffuse galactic continuum, hard X-rays from SN1993J, the Virgo sky survey, the average Seyfert spectrum, and the X-ray novae GRS 1009-45 and GRS 1716-249. EGRET EGRET operation was normal this week. Beginning in mid-December, there has been a gradual increase in the percentage of possible data that is being recovered by EGRET as a result of the new TDRS placement and the Australian ground station. It had averaged about 65% for some time, and it has gradually increased to about 82%. There are, of course, daily and weekly fluctuations due to pointing direction and the relative location of the South Atlantic Anomaly. A large number of EGRET papers were presented at the January American Astronomical Society meeting. They included details of the galactic plane, results on the variation of quasars, and an upper limit on the high-energy microsecond bursts that is considerably more severe than previous ones. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The COMPTEL operations group reports that in spite of the the current wave of cold-weather-related problems at Goddard and elsewhere the health and safe operation of the instrument continues to be monitored with only occasional interruption; the routine production processing of incoming flight data should not be affected. BATSE No report was submitted this week.