Compton Observatory Science Report #159, Friday June 10, 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 News Several typographical errors to the Gamma-Ray Burst Basic Information Table on GRONEWS were noted by the BATSE Instrument Team. They have been corrected and a revised version installed (see the BATSE Instrument Report below). The Burst Catalog has been an extremely popular item - approximately 150 downloads per week have occurred since it was first announced. The 236 Cycle 4 Guest Investigator Proposals have all been distributed to panels of anonymous referees. A peer-review meeting later this month, followed by the detailed timeline devlopment during early July will determine what subset of these proposals will be approved for Cycle 4. Instrument Reports EGRET EGRET operations were normal during this biweekly period. Delivery of data to the GRO-SSC is on schedule. Interaction with guest investigators remains at a good level. Several papers were presented at the AAS meeting, including the results on the February 17, 1994 gamma-ray burst event described here two weeks ago. Dr. Joe Espositio described the statistically quite significant correlation between unidentified sources in the plane and supernova remnants. Because the size of the emission region cannot be distinguished from a point source, pulsars not seen in the radio wavelength range are a possible origin of the radiation as well as diffuse emission. Other talks on pulsars and the galactic diffuse radiation were also presented. A paper by Dr. Stan Hunter and others on rho Ophiucus was accepted by the Astrophysical Journal; in this paper, they show that the emission is consistent with cosmic rays at the local intensity level interacting with the material and photons in the region. OSSE OSSE operations are normal. In viewing period 329 (31 May - 7 June), the Z-axis target was PSR J0437-47 (Guest Investigator M. Bailes) and the X-axis target was the Crab Nebula and Pulsar (Guest Investigator J. Cordes). The Sun was not available on the OSSE scan plane. During the Crab observations, the housekeeping telemetry was modified to retrieve a limited amount of calibration data to monitor the pulse-shape discrimination efficiency in detector 1. In viewing period 331.0 (7-10 June), the Z-axis target is Cyg X-3 (PI team), and the X-axis targets are PSR 0611+22 (Guest Investigator J. Cordes) and 4U 0115+63 in its current outburst. The Sun is not available on the scan plane, so the slewing response to BATSE solar flare triggers is disabled. For the first 24 hours of vp 331.0, we used two detectors to monitor the spectral state of Cyg X-1. OSSE reports on SN1993J (M.D. Leising et al., ApJL), on NGC 1275 (C.Y. Osaka et al., ApJ), and on NGC 253 and M82 (D. Bhattacharya et al., ApJ) have recently been accepted for publication. Preprints will be distributed shortly. Data from viewing period 211 were delivered to the Compton GRO Science Support Center archive this week. The targets during period 211 were 4U0115+63, NGC 253, 47 Tuc, and SMC X-1. BATSE BATSE's 1000th gamma-ray burst (trigger # 2996) occurred on May 27th. The BATSE Science Team wishes to express their extreme gratitude to all of the wonderful people associated with the Compton Observatory who have helped us to achieve this important milestone. We are especially grateful to the outstanding GRO project office at GSFC, the TRW personnel who designed, assembled, and tested one of the finest (and largest) spacecraft in the history of NASA, and the dedicated and conscientious GSFC/TRW/Allied-Signal operations team who continue to provide us with high quality data in a timely manner. At Marshall SFC a contest to guess the date of the 1000th burst was held. This was won by Georgia Richardson. Zamir Sariff won an award for doing the burst processing for the day the burst occurred. A party was held in the burst's honor at the residence of P.I. Jerry Fishman. The following was included in IAU Circular 5999: 4U 0115+634 R. B. Wilson, M. H. Finger, and D. M. Scott report for the Compton Gamma Ray Observatory BATSE pulsar team: "The outburst from the x-ray binary pulsar 4U 0115+634 previously reported on IAUC 5990 continues as of May 30. The flux in the energy band 20-50 keV rose at a constant rate from the onset of detection on May 8 to about 65 mCrab on May 18, increased at a lesser rate to about 75 mCrab on May 28, then increased more rapidly, reaching about 180 mCrab on May 30." The source is still currently being detected. As of June 8th, BATSE has detected 1009 cosmic gamma-ray bursts out of a total of 2915 on-board triggers in 1125 days of operation. There have been 733 triggers due to solar flares with emission above 60 keV. An error in the names of 16 bursts (col 2) in the BASIC table of the 2nd burst catalog was found. This problem is now corrected in the table available from the GROSSC. COMPTEL The COMPTEL instrument is performing well and continues routine observations. The collaboration forwarded this week to the CGRO public archive at the Science Support Center low-level and first high-level COMPTEL data products for Viewing Periods 29-44 of Phase 1. With the exception of a few files of processed burst spectra, currently being prepared, these data complete the delivery by COMPTEL of initial Sky Survey datasets to the CGRO archive.