Compton Observatory Science Report #167, Monday October 3, 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 Final preparation for the start of Cycle-4, including plans for data distribution and implemenation GI programs are underway. If you have an approved Cycle-4 program and have any questions about your planned observations, data delivery, analysis software or tecnical support please contact the appropriate CGRO-SSC Instrument Specialist or contact the SSC directly. Cycle-4 starts tomorrow (10/04/94)! A CD Rom containing all Gamma-Ray Burst data from the 2B catalog and solar flare data for approximately the first 500 triggers is being prepared by the SSC and the BATSE team. It is expected to be ready for distribution in the December 1994 - January 1995 time frame. It will be distrubted at future CGRO related science meetings or upon request to the SSC. Instrument Reports EGRET EGRET Operations were normal this biweekly period. Delivery of data to the CGRO SSC remains on schedule. Interaction with Guest Investigators continues at a good level. An article setting an upper limit for the microsecond high-energy gamma-ray bursts, predicted by Steven Hawking to be produced by the decay of small black holes in the early universe, will appear in the October 20, 1994 issue of the Astrophysical Journal. Preparation has begun on the second EGRET catalog of sources; it will include both Phase 1 and 2 data. With the addition of the Phase 2 data and an improved model of the galactic diffuse radiation, the second catalog will show some sources with improved position locations and revised flux estimates relative to the first catalog. Also, the statistical significance in many cases will improve. In order to avoid confusion between the two catalogs, a new source naming convention is necessary. This matter has been discussed with the Project Scientist. The second catalog will use 2EG Jhhmm(+/-)ddmm - a form specified by the IAU. OSSE OSSE operations are normal. Following some small modifications to BATSE and OSSE flight software, we re-enabled the on-board slewing response to BATSE gamma-ray burst triggers. Bursts within 11 degrees of OSSE's scan plane will be observed for twelve hours in a search for persistent low-level emission. We expect of order one trigger per month. In viewing period 339 (20 Sep - 4 Oct), the Z-axis target is PG 1416-129 (Guest Investigator R. Staubert), and the X-axis target is MCG-5-23-16 (PI team). Data from viewing period 226 were delivered to the Compton GRO Science Support Center archive this week. The targets during period 226 were the galactic plane near (l,b) = (355,0), and the Coma cluster. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The COMPTEL Burst Rapid Response Team set a new record recently in the rapid location of a gamma-ray burst occurring within the field of view of the telescope. Following the receipt of a BACODINE trigger message on 21 September (=TJD 9616), the position of GRB940921 was determined and broadcast over the network 1 hour and 25 minutes after the event occurred (15 minutes faster than the previous best response time). This processing time likely approaches the fastest possible turnaround achievable with the procedures currently in place. The team continues to actively investigate alternative processing methods and procedures that could lower this time further, for rapid counterpart searches at other wavelengths. The particulars on GRB940921 follow: TITLE : COMPTEL BURST POSITION NOTICE: GRB940921 NOTICE_DATE: Fri Sep 23 22:39:25 GMT 1994 ORIG_SENDER: burst@comptel.unh.edu ***************************************************** BURST_DATE : 9616 TJD; 21-SEP-1994 BURST_TIME : 18493.00 SEC; 5: 8:13 UT BURST_SCZEN: 31.3 Deg. BURST_SCAZI: 0.7 Deg. BURST_CLASS: Medium (Approx 86 events) ***************************************************** COORD_J2000: [RAsc Decl] [RAsc Decl] ============ =============== ====================== MAXLIK_POS : [206.8d -16.8d] = [13h47m 3s -16d45m27s] ----------------------------------------------------- ERRBOX1_POS: [207.2d -15.7d] = [13h48m45s -15d43m 0s] ERRBOX2_POS: [208.0d -17.4d] = [13h52m 3s -17d23m22s] ERRBOX3_POS: [206.8d -17.9d] = [13h47m21s -17d55m 0s] ERRBOX4_POS: [206.0d -16.2d] = [13h44m 5s -16d14m21s] ***************************************************** COORD_B1950: [RAsc Decl] [RAsc Decl] ============ =============== ====================== MAXLIK_POS : [206.1d -16.5d] = [13h44m27s -16d29m53s] ----------------------------------------------------- ERRBOX1_POS: [206.5d -15.5d] = [13h46m10s -15d27m29s] ERRBOX2_POS: [207.4d -17.1d] = [13h49m27s -17d 7m59s] ERRBOX3_POS: [206.2d -17.7d] = [13h44m45s -17d39m26s] ERRBOX4_POS: [205.4d -16.0d] = [13h41m31s -15d58m41s] The members of the COMPTEL collaboration formerly resident in Leiden announce the following change in contact information: As a result of an internal reorganization of SRON (the Space Research Organization of the Netherlands), its laboratories in Groningen, Leiden, and Utrecht have been combined into one organizational entity, effective since March 1. The SRON laboratories in Leiden and Utrecht are now being combined into one laboratory, SRON-Utrecht. This move will be completed by the end of October. Our new address is: SRON-Utrecht Sorbonnelaan 2 3584 CA Utrecht The Netherlands Tel: (31) 30 535600 Fax: (31) 30 540860 Internet: user@sron.ruu.nl (already effective in addition to our current address) The e-mail user names are of the form .: H.Aarts, H.Bloemen, H.Blom, J.denHerder, H.Deutekom, C.deVries, L.Dubbeldam, W.Hermsen, F.Jansen, J.Kaastra, A.Klumper, L.Kuiper, E.Philippus, A.Nieuwenhuizen, B.Swanenburg, J.Talsma, R.vanderA, K.vanderBent, R.vanDijk. BATSE The following was submitted for inclusion in an IAU Circular: X-RAY NOVA IN SCORPIUS B. A. Harmon, C. A. Wilson, W. S. Paciesas, S. N. Zhang and G. J. Fishman, report for the BATSE/Compton Observatory Team: We have been observing GROJ1655-40 (X-Ray Nova Scorpii 1994) in the 20-100 keV band at a level of 75 mCrab(+/- 30%) since Sept. 17. This followed a more intense period which began on Sept. 6 (IAU Cir. No. 6075) and ended approximately on Sept. 16, where the source showed daily variations between 200 and 900 mCrab. The spectrum continues to be well-represented by a power law between 20 and 200 keV with an index of approximately -3 in the Sept. 6-16 time period. GX 339-4 We are currently observing a hard (low) state outburst of the black hole candidate GX 339-4. Between Sept. 24 and 26, its intensity in the 20-100 keV band gradually increased from 150 to 200 mCrab (+/-15%). Due to the recent activity of several hard x-ray sources in the Scorpius-Ara sky region, it is difficult at this time to establish when the outburst began. Preliminary indications are that the source was first detectable around Sept. 5-10. Based on the behavior of previous outbursts, the measured thermal bremsstrahlung temperature of kT = 73+/-8 keV is consistent with the source being a few weeks to a month into its outburst. There has been much of activity among the x-ray binary pulsars in the last two weeks. The outburst from 2S 1417-624 is still continuing, but the flux is now declining. Small outburst from A0535+262 and 4U 1145+619 were observed. Other sources detected by the BATSE pulsed source monitor were Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. On September 19, BATSE revised the burst trigger criteria. We are now using channels 3 and 4 (> 100 keV), rather than channels 2 and 3 ( 50 - 300 keV). The main reason for the change is to try to get a better sample of the atmospheric gamma-ray flashes, which have particularly hard spectra. The burst data will be kept in a separate catalog, and may provide additional insights into distributions of spectral properties. We find that the new energy range results in significantly more triggers on entry into the SAA. There is a revision to the SAA boundaries currently in progress, which will eliminate most of these false triggers. At some undetermined future date, we will also spend some time triggering on channels 1 and 2 (25 - 100 keV), to optimize for SGR's. THE THIRD HUNTSVILLE GAMMA-RAY BURST WORKSHOP The BATSE group is planning to host the Third Huntsville Gamma-ray Burst Workshop (to take place in Huntsville, AL) in October 1995. The first circular for the workshop will be sent out in December or January.