Compton Observatory Science Report #132 Thursday, August 12, 1993 Eric Chipman, Compton Observatory Science Support Center Questions or comments can be sent to the Compton SSC. Phone 301/286-7764, e-mail SPAN GROSSC::CHIPMAN, Internet chipman@grossc.gsfc.nasa.gov. Science operations are continuing. Analysis of the reboost OATS burn test continues. There were 3 maneuvers this week. On Tuesday, August 10, there was a maneuver to the attitude of period 229 (z-axis target = GAL 5+05, x-axis target= Coma). The times were 1356Z to 1422Z, and the angle of the maneuver was 70.45 degrees. The HGA boom-equator angle was 37.88 degrees. On August 11 and 12, a maneuver was performed to orient the spacrcraft so that the bottom (-z-axis) would be in the direction of the Perseid meteor shower radiant, to minimize any chance of a particle creating a hole in the light shield for one of the anticoincidence domes on CGRO. The maneuver, of 64.36 degrees, was from 1641Z to 1702Z on the 11th. Then on the 12th, a maneuver back the period 229 attitude was done from 1401Z to 1421Z. BATSE ----- The newly discovered pulsar, GRO J1008-57, is fading rapidly. It reached its peak flux during the time interval from July 19 to July 29. At the present decay rate, it will no longer be observable by BATSE in another week or so. The BATSE collaborators at Caltech are performing timing analyses on the pulsed data obtained thus far. Over 160 abstracts have been received for the Huntsville Gamma-ray Burst Workshop, Oct. 20-22. The program committee, chaired by K. Hurley, is arranging the program, which will be mailed on or about Sept.18. The extreme interest in the Workshop may result in fewer and/or shorter talks. Beginning with this report, the BATSE burst and solar flare totals will be reported less frequently. COMPTEL ------- The COMPTEL instrument is performing well and continues routine observations. During the period of most intense activity predicted for the Perseid meteor shower this week, with the GRO spacecraft in a "shielded" orientation, the primary detector high voltages of COMPTEL were switched off, as an added safety precaution. Very preliminary analysis of the flight data received for the recent target-of-opportunity observation of the x-ray pulsar GRO J1008-57 shows no strong indication of emission from this object in the COMPTEL energy range at medium-energy gamma rays. ********** AS A SPECIAL ADDED BONUS TO THIS WEEK'S REPORT: YOU TOO CAN BECOME AN OFFICIAL FOB ("FRIEND OF BILL") (FvB = FREUND VON BILL?) THE PRESIDENT OF THE UNITED STATES IS NOW ON-LINE: BILL CLINTON, WASHINGTON, D.C. = president@whitehouse.gov SEND IN YOUR VOTE TODAY FOR INTEGRAL FUNDING! FOR A GRO MISSION EXTENSION! FOR GUARANTEED RESERVED SEATING FOR EUROPEAN VISITORS TO NEXT YEAR'S WORLD CUP! SAMPLE ACKNOWLEDGEMENT APPENDED (WITH THE LATEST POLITICAL JARGON). ***** WHITE HOUSE ACKNOWLEDGEMENT: >From autoresponder@WhiteHouse.Gov Mon Aug 9 14:30:33 1993 Return-Path: Received: from WhiteHouse.Gov by comptel.unh.edu.unh.EDU (4.1/SMI-4.1) id AA06858; Mon, 9 Aug 93 14:30:32 EDT Received: by WhiteHouse.Gov (5.65/fma/mjr-120691); id AA03137; Mon, 9 Aug 93 14:31:30 -0400 Date: Mon, 9 Aug 93 14:31:30 -0400 From: autoresponder@WhiteHouse.Gov Message-Id: <9308091831.AA03137@WhiteHouse.Gov> To: gstacy@comptel.unh.EDU (Greg Stacy) Status: OR Subject: Your mail has been received Thank you for sending in your thoughts and comments to the President via electronic mail. We are pleased to introduce this new form of communication into the White House for the first time in history. I welcome your response and participation. As we work to reinvent government and streamline our processes, this electronic mail experiment will help put us on the leading edge of progress. Please remember, though, this is still very much an experiment. Your message has been received, and we are keeping careful track of all the mail we are receiving electronically. We will be trying out a number of response-based systems shortly, and I ask for your patience as we move forward to integrate electronic mail from the public into the White House. Again, on behalf of the President, thank you for your message and for taking part in the White House electronic mail project. Sincerely, Marsha Scott, Deputy Assistant to the President and Director of Correspondence [You will only receive one automated response per day] EGRET ----- EGRET operations were normal this week. Work continues on the Compton Symposium presentations. Three papers are being submitted to the burst conference in October. Interactions with guest investigators continues at a normal level. We are watching the instrument for any indication of an abnormality due to the meteor shower. Dr. Ramana Murthy will be joining the EGRET science team as a guest on the first of September. He will be a Senior National Research Council Associate. OSSE ---- OSSE operations are normal. For viewing periods 229 and 229.5, the Z-axis target is the galactic plane at 5 degrees longitude (PI team), and the X-axis target is the Coma Cluster (GI: Y Rephaeli). The viewing strategy near the galactic center employs large source and background offsets from the galactic plane to measure the extent of the bulge in the diffuse continuum and annihilation radiation. When neither target is above the Earth's limb, engineering data are being collected to improve our calibration of the neutron v. gamma-ray pulse-shape discrimination efficiency. Because the Sun is not available on the OSSE scan plane, the slewing response to BATSE solar flare triggers is disabled. There have been no slews to the Sun since the last report. During the brief reorientation for the Perseid meteor shower, OSSE's single target was the radio pulsar PSR 1509-58. The instrument configuration was optimized to give maximum sensitivity to pulsed emission. Data from viewing periods 1 and 2.0 have been delivered to the Compton Science Support Center Archive. These data have now been screened with the same techniques as the subsequent viewing periods already delivered to the archive. We issue the following science report on the extended Target of Opportunity pointing at the recent supernova in M81. --- Preliminary OSSE Results on SN 1993J --- OSSE observed SN 1993J during three different intervals, approximately 9--15, 23--36, and 93--121 days after outburst. There is some evidence for continuum emission below 200 keV in the first two of these periods. Power-law fits yield intensities at 100 keV of (1.82+-0.39)e-3 photons cm-2 s-1 MeV-1 and (0.89+-0.35)e-3 photons cm-2 s-1 MeV-1, and photon indices of -2.3+-0.5 and -2.2+-0.9, respectively. There is no evidence for any emission in the longer, more sensitive, third observation. These measured continua are probably too bright to be entirely due to Comptonized gamma-rays from radioactive 56Ni and 56Co alone. A power-law of fixed photon index -1.2 fit to the first OSSE observation extrapolates approximately to the total luminosity measured by ASCA (Tanaka IAU Circ. 5753) from 1--10 keV one day earlier. This emission cannot be unambiguously attributed to SN 1993J. Because of the large OSSE field of view, SN 1993J cannot be separated from other sources such as the nucleus of M81 or even M82. However, OSSE did observe this region twice earlier, 597 and 443 days before SN 1993J and no continuum emission was detected at either time. It might be possible to attribute the OSSE emission to SN 1993J by correlating its variations with other observations, e.g. ASCA or ROSAT, of SN 1993J. No evidence for line emission is seen in any observation. In the third OSSE observation of SN 1993J, the time when gamma-ray lines were most likely to be detectable, preliminary measured fluxes of 847 and 1238 keV lines are (1.6+-2.1)e-05 photons cm-2 s-1 and (0.7+-1.9)e-05 photons cm-2 s-1, respectively. These limits do not include OSSE data stored on-board GRO during periods of no real-time TDRS coverage, which will probably add 20-30 percent additional data on SN 1993J. Combining these OSSE data with COMPTEL results will provide the best overall search for 56Co line emission from SN 1993J.