------------------------------------------------------------------- Compton Observatory Science Report #178, Friday March 6, 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 ------------------------------------------------------------------- Cycle-5 Proposals Just in case you had forgotten - Cycle-5 proposals are due one month from tomorrow! You can still request paper copies of the NRA and appendices by contacting the SSC (e.g. replying to this message), or download electronic copies via ftp (on grossc.gsfc.nasa.gov, under the nra/cycle5 directory via the Web at http://enemy.gsfc.nasa.gov/cossc/cossc.html. Also, keep in mind that electronic proposal form submissions required for Cycle 5. Look on the Web at the above URL, or send a blank e-mail message to rps@cossc.gsfc.nasa.gov for instructions. Instrument Reports EGRET EGRET operations were normal this biweekly period. Delivery of data to the GRO SSC remains on schedule. Interaction with guests investigators continues at a good level. As noted two week ago, careful studies are in progress on the whole gamma ray sky as observed by EGRET including all the refinements that currently exist. The first of these papers has been submitted to a journal; three more should be submitted over the next ten days. Five papers will be presented at the International Cosmic Ray Conference, and we are planning to submit ten or eleven to the Third Compton Symposium, including an invited summary talk. These latter papers should provide a good opportunity for the community to see the breadth of the results that have come from EGRET. At the moment EGRET has just begun to view a region centered at RA=90.1 and DEC=24.7; it includes the Galactic anticenter, the Crab, and PKS 0528+134. OSSE OSSE detector #1 failed three times on 28 February. Recovery from the first failure of the day took approximately 50 minutes and was accomplished without much difficulty. The second and third failures took considerably longer (17 hours total) to recover from. Commands sent to recover from the second failure involved moving the drive to a calibration position. During this motion a third failure occurred. These were the fifth, sixth, and seventh such events since launch. The motor drive positioning process, which in normal operation moves the detectors every 2 minutes, takes the detector off line when it detects a positioning error. Tests for pinpointing the cause of these drive failures are in the planning stages. OSSE is currently in normal operations on all four detectors. OSSE responded to a BATSE slew trigger during viewing period 411.5 on 23 February at 02:32 UT and mapped the region for 12 hours. The slewing response to BATSE burst triggers is currently disabled for viewing period 412 in order to conduct engineering tests. We will re-enable the slewing when the test period ends. In viewing period 411.5 (21-28 Feb), the Z-axis target is Mrk 3 (Guest Investigator P. Nandra), and the X-axis targets are QSO 2251+158 (PI team) and NGC 7172 and PKS 2155-304 (Guest Investigator L. Bassani). In viewing period 412 (28 Feb - 7 Mar), the Z-axis target is the Crab Pulsar (Engineering tests - PI team), and the X-axis targets are NGC 7172 and PKS 2155-304 (Guest Investigator L. Bassani). Data from viewing periods 308.0, 308.3, and 308.6 were delivered to the Compton GRO Science Support Center archive in the last two weeks. The targets during these viewing periods were the Virgo region sky survey, the galactic plane region near l=337 degrees, PSR 1800-21, Mrk 421, NGC 7213, and Sco X-1 (during reboost activities). Recent papers which have been accepted for publication include: "OSSE Observations of 1E 1740.7-2942 in 1992 September" by G.V. Jung et al. (A&A) "OSSE Observations of 3C 273" by W.N. Johnson et al. (ApJ) "Compton Gamma-Ray Observatory Observations of the Crab Pulsar" by M.P. Ulmer et al. (ApJ) "A Search for Fast Gamma Ray Pulsars with OSSE" by P. Hertz et al. (ApJ) "Highlights from OSSE on the Compton Observatory" by J.D. Kurfess (Proc. 17th Texas Symposium) "OSSE Observations of Gamma Ray Emission from Centaurus A" by R.L. Kinzer et al. (ApJ) A mailing including these preprints is planned in about 2 weeks. COMPTEL The COMPTEL instrument is performing well and continues routine observations. A weak cosmic gamma-ray burst was observed within the field of view of COMPTEL on 8 February 1995 (TJD 9756). The BATSE/BACODINE trigger intensity of this event was sufficiently weak that it did not meet the threshold for an automated rapid-response. From subsequent analysis the COMPTEL burst position is in good agreement with the best current BATSE/IPN position of (RA,DEC)=(338.29,56.33) degrees (J2000). BATSE BATSE continues to operate normally. The following sources were detected by the BATSE pulsed source monitor in the past two weeks: Her X-1, Cen X-3, 4U 1626-67, 2S 1417-624, OAO 1657-415, GX 1+4, Vela X-1, and GX 301-2. As of March 1 BATSE has detected 1235 gamma-ray bursts out of a total of 3341 on-board triggers in 1408 days of operation. There have been 749 triggers due to solar flares with emission above 60 keV.