Compton Observatory Science Report #184, Wednesday, August 9 1995 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 Guest Investigator News Notification letters for all Cycle-5 Guest Investigator proposals were mailed out during July. A list of accepted programs (titles and abstracts) as well as the Cycle-5 Viewing Plan and a list of all scheduled targets are available on GRONEWS. You can access GRONEWS by telnet'ing to grossc.gsfc.nasa.gov (login as GRONEWS) or via the WWW GRO-SSC home page on the World Wide Web: (http://cossc.gsfc.nasa.gov/cossc/cossc.html). The long-awaited BATSE 3B Gamma-Ray Burst Catalog has been delivered to the SSC by the BATSE Team!!! (see the BATSE instrument report below). It is available for browsing and/or downloads on GRONEWS. Portions of the JPL Enhanced Earth Occultation analysis Package (EBOP) are now available for general GI use at the SSC. About 250 days of data (from phase 1 and 2) for use with EBOP are online. Anyone interested in using this data and software should contact the SSC. Consultation with JPL is also strongly recommended, particularly in interpretation of results (JPL contact is Jim Ling, jling@jplsp.jpl.nasa.gov). Work to make the software more user- friendly is ongoing as a collaborative effort between JPL and the SSC. OSSE high-level data products (currently for the first 16 viewing periods) are now available at the SSC. See the "OSSE" item on our WWW home page. These include PostScript plots, summed background subtracted spectra in IGORE and XSPEC compatible formats, as well as simple ascii text files containing approximate photon fluxes vs energy - and much more! For more information contact Tom Bridgman (bridgman@grossc.gsfc.nasa.gov). A second announcement for the 3'rd Huntsville Gamma-Ray Burst Workshop (October 1995) is appended to this report. Instrument Reports EGRET EGRET operations were normal this monthly period. Delivery of the final phase 3 data to the GRO SSC remains on schedule and delivery of the phase 4 preliminary data to the GRO SSC is now running ahead of schedule. Interaction with guest investigators continues at a good level. The viewing plan for phase 5 has been received. For most of the viewing periods, EGRET will be in the narrow field viewing mode to conserve the remaining spark chamber gas. For four weeks, it will be in the fan mode, and for thirteen weeks it will be turned off. The approved targets for each viewing period have been received and are being loaded into the EGRET computer so that guest investigators may be informed when results exist, as in previous cycles. On August 8, 1995, the pointing direction changes to the anticenter and, on August 22, 1995, the pointing direction moves to Galactic coordinates (l=154o, b=-10o). OSSE OSSE operations are normal. The slewing response to BATSE burst triggers has been enabled since 30 June. Recent observations are listed in the following table. View period Dates Target (owner) 424 10-25 Jul Cen A (GI H. Steinle) PSR J0631+10 (GI J. Cordes) 425 25 Jul - 8 Aug 4C 15.05 (PI team) 3C 109 (GI L. Bassani) 426 8-22 Aug Crab pulsar (PI team) NGC 4388 (GI L. Piro) Data up to viewing period 324 have been delivered to the Compton GRO Science Support Center archive. OSSE papers on the Crab pulsar (Ulmer et al.), PSR B1259-63 (Grove et al.), and Cen A (Kinzer et al.) have recently appeared in ApJ. A few members of the OSSE team will present recent results at the 24th International Cosmic Ray Conference at the end of the month. COMPTEL The COMPTEL instrument is performing well and continues routine observations. Members of the COMPTEL team have carried out an accelerated processing of the data associated with the recent target-of-opportunity observations of the gamma-ray-bright quasar PKS 1622-297. There is NO strong evidence for this source in the COMPTEL band at MeV energies in either the quick-look or standard processing for Viewing Periods 423 and 423.5. Nor is there any evidence at present of the other prominent source reported by the EGRET team, GRO J1629-49. A more refined analysis of these data is currently in progress. An article by Morris et al. on "Neutron measurements in near-Earth orbit with COMPTEL" has recently appeared in JGR, Vol. 100, No. A7, pp. 12,243-12,249 (1995). Also, a review article on "High-Energy Particles in Solar Flares" (Hudson and Ryan) will soon appear in the 1995 volume of the Annual Reviews of Astronomy and Astrophysics. A COMPTEL preprint has also recently been distributed containing contributed papers by team members and collaborators presented at the 29th ESLAB Symposium "Towards the Source of Gamma-Ray Bursts." Attendees of the The 3rd Compton Symposium recently held in Munich should note that contributions to the proceedings volume for the symposium are now due by October 1. BATSE The electronic version of the 3B burst catalog was delivered to the GROSSC on August 8. This catalog comprises 1122 bursts and extends from launch until 19 September 1994. The locations of all bursts have been recomputed using an improved algorithm. The systematic error in the 3B locations is estimated to be 1.6 degrees. The outbursts of GX 339-4 and GRO J1719-24 continue to be detectable using BATSE occultation monitoring, and new active episodes have been observed during July in GRS 1915+105 and GRO J1655-40. The latter activity was reported in IAU Circular No. 6196 as follows: X-RAY NOVA 1994 IN SCORPIUS B. A. Harmon, M. L. McCollough, S. N. Zhang, W. S. Paciesas and C. A. Wilson report, for the Compton Observatory/BATSE Team: "The x-ray/radio transient GRO J1655-40 is undergoing a bright outburst in hard x-rays above 20 keV. The source became detectable around July 22; its intensity exceeded 300 mCrab on July 27 and increased to 400 mCrab (+/- 10 percent) on July 29-30. This is the brightest outburst in hard x-rays since that of February-April (IAUC 6143, 6147). The spectrum on July 29-30 extends to at least 200 keV and is well fitted by a power law with spectral index -2.4 +/- 0.1." The following sources have been detected by the BATSE pulsed source monitor in the last month : Her X-1, Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. BATSE monitoring of Cygnus X-1 shows that the source is currently in a state of high flickering, as evidenced by visual inspection of the raw data as well as an increased number of false burst triggers attributable to fluctuations from Cyg X-1. The energy range for the BATSE burst trigger was changed on July 24 from 25-100 keV to E > 25 keV. During the final four days using the 25-100 keV interval, single-detector triggers were accepted in order to collect data on phosphorescent events for studies of systematics. As of August 6, BATSE has detected 1331 gamma-ray bursts out of a total of 3644 on-board triggers in 1566 days of operation. There have been 757 triggers due to solar flares, 9 due to SGR events, and 48 due to terrestrial gamma-ray flashes. 3'rd Huntsville Symposium on Gamma-Ray Bursts Third Huntsville Symposium on Gamma-Ray Bursts October 25-27, 1995 Invited Speakers Opening Remarks G. Fishman Closing Remarks C. Kouveliotou Spatial & Intensity Properties and Implications E. Fenimore D. Hartmann D. Lamb C. Meegan Temporal Properties I. Mitrofanov J. Norris Spectral Properties D. Band M. Briggs Counterparts K. Hurley F. Vrba Models C. Thompson S. Woosley For further information: Email your address to workshop@batse.msfc.nasa.gov, or consult the WWW page http://xanth.msfc.nasa.gov/astro/batse/events/hgrbw_third.shtml The deadline for abstracts is September 7th.