Compton Observatory Science Report #160, Friday June 24, 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 Observatory, scientific instruments and all spacecraft subsystems continue to function nearly flawlessly. Science Support Center Activities Guest investigator activities at the CGRO-SSC have been on the upswing - several new IGORE (Interactive Gro Osse Reduction Environment) users have been utilizing SSC computing and archive facilities. Scientists utilizing EGRET and BATSE data and analysis software have also visited the SSC this month. Interest in the BATSE 2B catalog continues to be significant. Efforts to install the COMPTEL COMPASS data analysis sytem at the SSC are continuing. Preparations for the forthcoming Cycle-4 Proposal Review Meeting have been finalized. Additionally, the CGRO Users Committee will meet Thursday and Friday of next week. Dr. Alan Marscher (Boston University) is a new member of the Users Committee, and Dr. Kevin Hurley (UC Berkley) will take over charimanship of the committee after this meeting. Instrument Reports EGRET EGRET operations were normal during this biweekly period. Delivery of data to the GRO SSC is on schedule. A very severe, relatively sudden thunderstorm caused some damage to the EGRET computer systems, but it was possible to resume data reduction after about two days. Interaction with Guest Investigators remains at a good level. During standard basic analysis of EGRET data, it was discovered that the same source had been awarded to two guest investigators by the Phase-3 peer-review committee. There is also a serindipitous source involved. This matter has been brought to the attention of the project scientist for resolution. A summary of the current EGRET results will be presented at the COSPAR meeting in July, 1994. Several papers summarizing the results of phases 1 and 2 are in preparation and should be submitted for publication soon. OSSE OSSE operations are normal. In viewing period 330 (10-14 June), the Z-axis target was Cyg X-3 (PI team), and the X-axis target was GT 0236+610 (Guest Investigators M. Coe and M. Tavani). The Sun was not available on the OSSE scan plane, so the slewing burst response to BATSE solar flare triggers was disabled. In viewing period 331.5 (14-18 June), the Z-axis target was Cyg X-3 (PI team), and the X-axis targets were PSR 0611+22 (Guest Investigator J. Cordes) and 4U 0115+63 in its current outburst. The Sun was available on the scan plane, so the slewing response was enabled. For the first and last 24 hours of vp 331.0, we used two detectors to monitor the spectral state of Cyg X-1. In viewing period 332 (18 June - 5 July), the Z-axis target is a galactic plane scan near (l,b) = (20,0) (Guest Investigator H. Bloemen), and the X-axis targets are Cas A (PI team) and GT 0236+610 (Guest Investigators M. Coe and M. Tavani). The Sun is not available on the scan plane, so the slewing was once again disabled. For two 24-hour periods, we will monitor Cyg X-1 in place of Cas A. BATSE The pulsed flux from the x-ray binary 4U 0115+634 is declining, and is expected to drop below detection threshold in the next few days. The transient source has been detected by BATSE for most of the last 60 days. The BATSE pulsed source monitor is currently (TJD 9424) detecting pulsed flux from 4U0115+634, Cen X-3, OAO 1657-415, Vela X-1 and GX 301-2. This monitor is based on epoch folding of the BATSE 20-50 keV, 1.024 s resolution discriminator rates. Astronomers with correlative observing programs that would be interested being e-mailed the daily monitor report should contact Mark H. Finger at Finger@BATSE.msfc.nasa.gov or BATSE::Finger. BATSE folded-on-board data is currently being collected for the Crab, 4u0115+634, and Her X-1. As of June 20th, BATSE has detected 1020 cosmic gamma-ray bursts out of a total of 2931 on-board triggers in 1154 days of operation. There have been 733 triggers due to solar flares with emission above 60 keV. COMPTEL The COMPTEL instrument is performing well and continues routine observations. Several members of the team will be participating in the upcoming CGRO Cycle 4 Proposal Review next week near GSFC. It has been a busy (but somewhat disappointing) week of gamma-ray-burst-related activity within the COMPTEL team. A weak cosmic gamma-ray burst was recorded within the field of view of COMPTEL on Sunday, 19 June. The analysis of data from this burst was complicated by the fact that it occurred very near the Earth's limb, and was consequently highly contaminated by background events. A second burst from the same general direction, reported by BATSE on 22 June, was not seen by COMPTEL, primarily due to the high level of background observed in this direction during the current pointing. Finally, the COMPTEL rapid-response team was notified automatically by the BATSE BACODINE system of a third gamma-ray burst (in a different direction of the sky) within the field of view of the instrument early on Thursday, 23 June; unfortunately, no COMPTEL signal at MeV energies was measured for this last event. Summary information on GRB940619 follows: TITLE : COMPTEL BURST POSITION NOTICE: GRB940619 NOTICE_DATE: Wed Jun 22 15:51:19 GMT 1994 ORIG_SENDER: burst@comptel.unh.edu ***************************************************** BURST_DATE : 9522 TJD; 19-JUN-1994 BURST_TIME : 77480.00 SEC; 21:31:20 UT BURST_SCZEN: 27.3 Deg. BURST_SCAZI: 110.2 Deg. BURST_CLASS: Weak (Approx 29 events) ***************************************************** COORD_J2000: [RAsc Decl] [RAsc Decl] ============ =============== ====================== MAXLIK_POS : [297.7d -31.9d] = [19h50m38s -31d55m58s] ----------------------------------------------------- ERRBOX1_POS: [295.1d -32.7d] = [19h40m35s -32d40m21s] ERRBOX2_POS: [297.6d -30.3d] = [19h50m16s -30d16m41s] ERRBOX3_POS: [299.7d -31.8d] = [19h58m40s -31d45m54s] ERRBOX4_POS: [297.3d -34.2d] = [19h49m 3s -34d12m 2s] ***************************************************** COORD_B1950: [RAsc Decl] [RAsc Decl] ============ =============== ====================== MAXLIK_POS : [296.9d -32.1d] = [19h47m34s -32d 3m58s] ----------------------------------------------------- ERRBOX1_POS: [294.4d -32.8d] = [19h37m29s -32d47m40s] ERRBOX2_POS: [296.8d -30.4d] = [19h47m14s -30d24m39s] ERRBOX3_POS: [298.9d -31.9d] = [19h55m37s -31d54m27s] ERRBOX4_POS: [296.5d -34.3d] = [19h45m55s -34d19m55s]