Compton Observatory Science Report #146 Friday, December 10, 1993 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 Note: The frequency of CGRO Science Reports will be reduced to bi-weekly subsequent to this report. Thus there will be no report for December 16, then next report being 23 December, then January 6, and so on. In the event of important new results or other mission related "newsworthy" occurrences, special releases of the science reports may be made. Also, up-to-date mission related information is posted on the GRONEWS electronic bulletin board facility. Spacecraft Status The Z-axis of GRO was maneuvered to target 310, GEMINGA on 1 December. As of December 2, 1993 the Compton GRO orbit had an apogee of 452.0KM and a perigee of 409.6KM. The GRO Z-axis will be maneuvered to target 311.0, VIRGO 284+75 on 13 December. The final three, Phase II, reboost burns are scheduled for December 15, 16, and 17. Instruments will be commanded to the reboost configurations during this period. These burns will raise perigee with a resulting circular orbit of approximately 450KM. The Australian TDRS ground station (GRTS - GRO Remote Terminal System) is nearly complete and the drift of TDRS-1 has begun. Five minutes of test data were transmitted through this system on December 6, 1993. Short tests will continue until the reboost (December 15-17). After the reboost, the length of time for the GRTS passes will be increased. Instrument Reports OSSE OSSE operations are normal. GRO reboost activities occurred in viewing period 308.3 (19-Nov-93 to 23-Nov-93). OSSE was placed in a low-power mode during the portion of each day that reboost operations were in progress. The instrument was then returned to a normal operating mode for the remainder of each day. During these times, engineering tests were performed and some science data was collected from the target Sco X-1. In viewing period 308.6 (23-Nov-93 to 01-Dec-93), the Z-axis target was the Virgo sky survey region (Key project) centered at (l,b) = (283,+75), and the X-axis target was the galactic plane near (337,0) (Key project). When neither target was available, i.e. when both were occulted by the Earth, OSSE observed the targets Mrk 421 and NGC 7213. In viewing period 310 (01-Dec-93 to 13-Dec-93), the Z-axis target is Geminga (PI team) and the X-axis target is NGC 4151 (GI: G. Reichert). The OSSE observation of NGC 4151 is part of a multi-wavelength AGN Watch campaign to simultaneously observe NGC 4151 from infrared to gamma-rays. During the period 3-Nov-93 through 29-Nov-93, OSSE responded to BATSE solar flare triggers with slews to the Sun on the following occasions (TJD=Truncated Julian Day): TJD 9297.8556 (Nov. 6) & TJD 9307.2045 (Nov. 16) EGRET EGRET operations were normal this week. Currently, the deep survey is being interrupted for the Geminga observation. The final part of the reboost will occur towards the end of the coming week. Interaction with guest investigators continues at a good level. The study involving a search for microsecond bursts of gamma rays over the first 2.5 years is nearing completion. The EGRET preprints for the Second Compton Symposium should be mailed shortly. COMPTEL The COMPTEL instrument is performing well and continues routine observations. Low-level and first high-level data products for Viewing Periods 14 through 20 were delivered to the Science Support Center last week, for inclusion in the GRO public archive. Preparations for future deliveries of COMPTEL data encompassing the balance of Phase 1 are ongoing. During the final series of reboost maneuvers of the GRO spacecraft, scheduled for December 15-17, COMPTEL will once again be placed in a low-power mode as a safety precaution; no scientific observation will be carried during this three-day period. BATSE The following report was published in IAU circular 5900: X-RAY NOVA IN OPHIUCHUS B. A. Harmon and G. J. Fishman, Marshall Space Flight Center, NASA; W. S. Paciesas, University of Alabama, Huntsville; and S. N. Zhang, Universities Space Research Association, report for the Compton Observatory BATSE Team: "The hard x-ray transient GRO J1719-24 has been remarkable in its steady, persistent, high level of emission. It reached a peak intensity of about 1.4 Crab (20-100 keV) five days after discovery (IAUC 5874) on Sept. 30. The 1/e decay time is about 300 days from a fit of occultation data obtained during Oct. 1-Nov. 22, although a linear fit to the light curve is equally good, with intensity dropping at about 0.3 +/- 0.05 percent per day relative to the peak. This is believed to be the slowest decay of any hard x-ray nova observed. Power-law fits to the spectrum in the band 20-100 keV showed the spectrum softening from -2.0 to -2.3 (+/- 0.05) during the rise, then softening more gradually since the end of September; it continues to be the brightest source in the sky in this energy range." A very strong burst occurred on Dec.4 (TJD 9325), BATSE Trigger #2676, with a peak count rate of over 120,000 cps. It triggered the BATSE Quick-Alert burst notification system. This system provides rough locations (~4 deg.) for coordinated observations within hours of the event. Persons who could benefit from this service, who are not already on the notification list, should contact Dr. C. Kouveliotou (kouveliotou@ssl.msfc.nasa.gov). They should include a short description of their coordinated observation plans or other need for the service. As of December 7th, BATSE has detected 837 cosmic gamma-ray bursts out of a total of 2577 on-board triggers in 959 days of operation. There have been 689 triggers due to solar flares with emission above 60 keV. From server@athena.gsfc.nasa.gov Fri Dec 10 18:07:39 1993 Received: from athena.gsfc.nasa.gov by xtelab.gsfc.nasa.gov (4.1/1.35) id AA08941; Fri, 10 Dec 93 18:07:32 EST Received: by athena.gsfc.nasa.gov (Smail3.1.28.1 #3) id m0p8GtS-0004L6a; Fri, 10 Dec 93 18:05 EST Date: Fri, 10 Dec 93 18:05 EST Sender: server@athena.gsfc.nasa.gov (listserv server) Message-Id: <931210180153.22803fbc@GROSSC.GSFC.NASA.GOV> Errors-To: jacobs@thuban.gsfc.nasa.gov Reply-To: SHRADER@GROSSC.GSFC.NASA.GOV Originator: grodisb@athena.gsfc.nasa.gov Sender: grodisb@athena.gsfc.nasa.gov Precedence: bulk From: SHRADER@GROSSC.GSFC.NASA.GOV To: scott@xtelab.gsfc.nasa.gov Subject: Correction to CGRO Weekly Report X-Listprocessor-Version: 6.0 -- ListProcessor by Anastasios Kotsikonas Status: R Todays CGRO Weekly report inadvertantly included last weeks OSSE status report. The correct version is appended: - C.Shrader OSSE operations are normal. In viewing period 310 (01-Dec-93 to 13-Dec-93), the Z-axis target is Geminga (PI team) and the X-axis target is NGC 4151 (Guest Investigator: G. Reichert). The OSSE observation of NGC 4151 is part of a multi-wavelength AGN Watch campaign to observe NGC 4151 simultaneously from infrared to gamma rays. The Sun is not accessible along the OSSE scan plane, and the slewing response to BATSE solar flare triggers is disabled. Data from viewing periods 22, 23, 24.0, 26, and 28 will be delivered to the Compton GRO Science Support Center Archive today. The targets during these periods are given in the following table. Viewing periods 24.5, 25, and 27 are still being screened. vp targets 22 Mrk 279, N Cyg 1992. 23 PSR 1509-58, NGC 253. 24.0 Galactic Center region, NGC 4151, NGC 7582. 26 Mrk 335, Vela pulsar. 28 Mrk 335, Vela pulsar. The most recent, configured version of the standard OSSE data analysis system, Igore v7.3, has also been delivered to the GROSSC.