Compton Observatory Science Report #166, Friday, September 16, 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 Remarkably, a large number of overseas CGRO Guest Investigators have not yet received their Cycle-4 proposal notification letters. We apologize for this inconvenience and note that a list of accepted Cycle-4 programs is available on GRONEWS (telnet to gronews.gsfc.nasa.gov and login as "gronews", or access through Xmosaic, URL http://enemy.gsfc.nasa.gov/cossc/cossc.html). An addendum to this status report describes a forthcoming workshop on "HIGH VELOCITY NEUTRON STARS AND GAMMA RAY BURSTS", and includes preliminary registration information. This information, and announcements regarding other CGRO related meetings and workshops are posted on GRONEWS. The first announcement of opportunity for the 1995/96 CGRO Postdoctoral Fellowship Program has been released. Applications are due by December 12, 1994. Additional information is available on GRONEWS, or by sending an inquiry to grofellow@grossc.gsfc.nasa.gov. Instrument Reports EGRET EGRET operations were normal this biweekly period. Delivery of data to the GRO SSC remains on schedule. Interaction with guest investigators remains at a good level. A major paper on active galaxies has been accepted by the Astrophysical Journal. In it, the properties of gamma-ray emission from active galaxies are described. The paper includes gamma-ray spectra and time dependent gamma-ray fluxes of detected sources. For sources where the information is available in the literature, multifrequency spectra covering the range from radio to gamma rays are also included. Constraints which the EGRET observations place upon various emission models are discussed. The paper should appear early next year. At the present time we are continuing the observation of the Vela Pulsar following the glitch. OSSE The OSSE on-board slew response to BATSE gamma-ray burst triggers continues to be disabled. The duration of the burst trigger signal from BATSE to OSSE is used to encode OSSE's scan angle to the burst; however there appears to be some occasional confusion in either the generation or readout of this signal. The cause is still under investigation. In viewing period 338.5 (31 Aug - 20 Sep), the Z-axis target is the Vela pulsar region (Guest Investigator A. Harding), and the X-axis target is 3C273 (PI team). During intervals when both of these targets are occulted detectors 1 and 2 stare at PSR J0437-47 (Guest Investigator M. Bailes). Data from viewing periods 223 and 224 were delivered to the Compton GRO Science Support Center archive this week. The targets during period 223 were 1E 1740-2942, CYG X-1, and GT 0236+610. The targets during period 224 were SMC X-1 and 3C 120. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The Universe has been fairly quiet recently in medium-energy gamma-rays. The routine production processing of incoming flight data is proceeding on schedule, and progress continues on a number of scientific investigations at the various COMPTEL sites. At least one COMPTEL Co-PI (who shall remain nameless), however, currently in mourning due to the premature demise of the professional baseball season, is finding it particularly hard to concentrate of late. BATSE The following items were included in IAU Circular 6075: 2S 1417-624 C. A. Wilson and R. B. Wilson, Marshall Space Flight Center, NASA; M. H. Finger and S. N. Zhang, University Space Research Association; and D. Chakrabarty and T. A. Prince, California Institute of Technology, report for the Compton Observatory BATSE Team: "An outburst of the transient x-ray binary pulsar 2S 1417-624 is currently being observed. Pulsations in the energy band 20-50 keV were first detected on Aug. 26 at a frequency consistent with the discovery observation of this source (Kelley et al. 1981, Ap.J. 243, 251). On Sept. 4-5, the source was detected between 20 and 70 keV with a phase-averaged pulsed flux of 10 +/- 2 mCrab and a total flux of 75 +/- 15 mCrab. The pulse phases between Aug. 26 and Sept. 6 are consistent with a barycentric pulse frequency of 5.666395(5) x 10E-2 Hz on Aug. 31.0 UT, with a frequency derivative of 2.936(9) x 10E-11 Hz/s. A search of the 20- to 50-keV BATSE data from 1991 April to date revealed no previous outbursts. Optical observations of the proposed Be-star companion (Grindlay et al. 1984, Ap.J. 276, 621) are encouraged." X-RAY NOVA IN SCORPIUS W. S. Paciesas, S. N. Zhang, C. A. Wilson, and B. A. Harmon report for the Compton Gamma Ray Observatory BATSE team: "We have detected a second outburst of this object (GRO J1655-40), beginning on Sept. 6. The hard x-ray (20-100 keV) flux from this source had declined rapidly from about 700 to about 150 mCrab over a few-day period beginning about Aug. 12 and remained at or below that level through Sept. 5. Our preliminary flux estimates for Sept. 6 and 7 are 440 +/- 50 and 370 +/- 30 mCrab, respectively. The rapid decline of the first x-ray outburst coincides well with the calculated emission time of the expanding radio lobe (IAUC 6073). The reflare may portend further interesting radio and/or optical activity." The flux from 2S 1417-624 continues to increase. Other x-ray binaries being detected during the last week by the BATSE pulsed source monitor are Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. As of September 14th, BATSE has detected 1116 cosmic gamma-ray bursts out of a total of 3063 on-board triggers in 1240 days of operation. There have been 740 triggers due to solar flares with emission above 60 keV. Addendum: ******************************************************************* --- First Announcement --- WORKSHOP ON HIGH VELOCITY NEUTRON STARS AND GAMMA RAY BURSTS 15 -- 17 March 1995 University of California, San Diego This workshop will focus on the major breakthrough in our understanding of some, if not all, gamma ray bursters that has resulted from two very exciting recent developments -- the evidence suggesting that most neutron stars are born with high velocities -- and the apparent identification of the three known soft gamma ray bursters with young, (high velocity?) neutron stars still associated with supernova remnants. Multiwavelength observations are providing a wealth of new information about the nature of these sources, which may have important implications for the origin of all gamma ray bursts. Invited and contributed talks will examine the following: HIGH VELOCITY NEUTRON STARS -- Observational evidence. Other related properties - intense B fields? - ms periods? Theories of their formation - asymmetric SN? SOFT GAMMA RAY BURSTERS -- General properties of bursts. Identification with SNRs and plerions - high velocity NS? Multiwavelength observations. Burst energetics and emission mechanisms. CLASSICAL GAMMA RAY BURSTERS -- Burst properties and systematics. Temporal and spectral comparisons with soft bursters. High velocity neutron star models of their origin. -- ORGANIZING COMMITTEE -- R.E. Rothschild (Chrmn), A.S. Burrows, J.M. Cordes, E.E. Fenimore, D.A. Frail, K. Hurley, S.R. Kulkarni, D.Q. Lamb, R.E. Lingenfelter, I. Mitrofanov, T. Murakami, R. Ramaty, M. Ruderman, V.L. Trimble, and S.E. Woosley If you wish to attend please respond soon, because the facility capacity will limit attendance to about 50. A modest registration fee will cover conference proceedings, &c. **************************************************************************** **************************************************************************** PRELIMINARY RESPONSE WORKSHOP ON HIGH VELOCITY NEUTRON STARS AND GAMMA RAY BURSTS 15--17 March 1995 University of California, San Diego NAME: (Last, First) E-MAIL ADDRESS: FAX: TELEPHONE: POSTAL ADDRESS: I WOULD LIKE TO:(Select/Delete) ATTEND BUT NOT PRESENT A PAPER OR POSTER ATTEND AND PRESENT A PAPER (10 min) ATTEND AND PRESENT A POSTER TENTATIVE TITLE: ****** PLEASE SEND THIS RESPONSE BY E-MAIL (IF POSSIBLE) TO: ****** workshop@mamacass.ucsd.edu (DO NOT REPLY TO GROSSC) OR (IF NECESSARY) BY FAX TO (619)534-2294 OR (AS A LAST RESORT) BY MAIL TO: R. Rothschild, CASS 0111, Univ. of California, 9500 Gilman Dr., La Jolla, CA 92093-0111, USA ****************************************************************************