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. From grodis@ascasrv.gsfc.nasa.gov Thu Nov 9 18:18 EST 1995 Return-Path: Received: from ascasrv.gsfc.nasa.gov by circe.lhea (5.x/SMI-SVR4) id AA08519; Thu, 9 Nov 1995 18:18:35 -0500 Received: from (localhost [127.0.0.1]) by ascasrv.gsfc.nasa.gov (LHEA9404/940426.s1) with SMTP id SAA16191 for ; Thu, 9 Nov 1995 18:21:35 -0500 Errors-To: dpf@egret.gsfc.nasa.gov Date: Thu, 9 Nov 1995 18:21:35 -0500 Message-Id: <951109181526.20c00285@grossc.gsfc.nasa.gov> Errors-To: dpf@egret.gsfc.nasa.gov Reply-To: SHRADER@grossc.gsfc.nasa.gov Originator: grodis@athena.gsfc.nasa.gov Sender: grodis@athena.gsfc.nasa.gov Precedence: bulk From: SHRADER@grossc.gsfc.nasa.gov To: scott@circe.gsfc.nasa.gov Subject: CGRO Status Report for November 1995 X-Listprocessor-Version: 6.0c -- ListProcessor by Anastasios Kotsikonas Content-Type: text Content-Length: 8291 Compton Gamma Ray Observatory Status Report #187 Thursday November 9, 1995 Questions or comments can be sent to Chris Shrader at the CGRO-SSC. Phone: 301/286-8434 e-mail: shrader@grossc.gsfc.nasa.gov Guest Investigator News The revised EGRET software and data products (described in detail below in the EGRET report) are in the process of being installed at the GRO-SSC and will be available for public use shortly. During Cycle-5 there are several viewing periods for which, due to a number of pointing constraints, there are no OSSE secondary targets scheduled (VP 515, 518 and 530). This means that there were no approved Cycle-5 GI targets, nor any targets previously observed by CGRO along the accessible region of the OSSE scan-plane for those particular Z- and X-axis orientations. This is not to say that there are no objects of interest there - we may just not know about them! Maybe you have some ideas! Details on the specific pointing constraints and how to submit a "mini-proposal" for some target of interest will be appearing soon as on the GRO-SSC WWW home page: URL http://cossc.gsfc.nasa.gov/cossc/cossc.html. 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 also on schedule. Interaction with guest investigators continues at a good level. As noted in last month's report, a very extensive review and analysis of the whole data set has been underway to improve the normalization values. In addition to the improvement due to the existence of the substantial amount of data, (1) there is a change due to small corrections to the instrument live time. (This is not a uniform correction over the EGRET field-of-view and typically shows a maximum deviation of ~ 15%.) and (2) there has been the introduction of small corrections arising from excluding very short time intervals when the instrument was in improper operational modes. There is also now the introduction of energy dependent scale factors. (These factors are primarily important towards the end of an EGRET spark chamber gas fill before the gas is replaced.) The INTMAP program, that generates the exposure and intensity maps, is modified to use the energy dependent scale factors. The scale factor file (scale.factor) that is accessed by the INTMAP code currently includes the new energy dependent factors. The SPECTRAL program has also been updated to incorporate energy dependent scale factors. This entire work has now been completed for all of the publicly available data in the GRO Science Support Center. In addition, the normalization factors are available for all data through vieing period 427; normalization for subsequent viewing period will be made available as the analyses are complete. In a recent IAU circular, Lundgren and colleagues reported: "An ouburst was detected 8-22 August 1995 from the unidentified EGRET source 2EG J0432+2910, now believed to be an AGN. Premlinary analysis indicates the gamma-ray flux above 100 MeV during the flare was enhanced by a factor of 5 over the average flux from this source in 1991-1993 observations ----- The combination of a gamma-ray flare, radio variability in a candidate flat spectrum counterpart, and possible optical and X-ray counterparts provides strong evidence that the source is in the blazar class of radio-loud AGN." Beginning on October 31, 1995, EGRET has been turned off to conserve the remaining spark chamber gas while observations are being made which are of primary interest to those using the other instruments on GRO. EGRET will be turned on again November 28, 1995 to observe CTA 102 and the neighboring region. OSSE OSSE operations are normal. The instrument is working as designed, with all subsystems in complete and full operation. 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) 502 17-31 Oct Geminga (PI team) NGC 3227 (not assigned) NGC 4388 (PI team) M87 (PI team) NGC 1068 (not assigned) 505 31 Oct - 7 Nov N Ecl Pole survey (PI team) Mrk 464 (not assigned) 506 7-14 Nov N Ecl Pole survey (PI team) NGC 5548 (not assigned) Data up to viewing period 336.5 have been delivered to the Compton GRO Science Support Center archive. The following paper has recently been accepted for publication: "OSSE Observations of the Vela and Geminga Pulsars" by M. S. Strickman et al. (ApJ) COMPTEL The COMPTEL instrument is performing well and continues routine observations. A number of team results related to gamma-ray bursts were presented at the recent 3rd Gamma Ray Burst Symposium organized by the BATSE team in Huntsville. A preprint of COMPTEL contributions to the proceedings volume for the conference is being prepared for distribution, and an electronic version will also be made available on the WWW. In further burst news, the paper on "COMPTEL observations of the strong gamma ray burst GRB 940217" (Winkler et al.) has just recently appeared in A&A Vol 302, 765, 1995. A number of gamma-ray bursts have occurred within the field of view of COMPTEL since the last report (GRBs 951013, 951014, 951030, 951030b, 951104, and 951107). Unfortunately, none of these was detected at MeV energies by COMPTEL. Additional details on such field-of-view burst events will soon be available on the COMPTEL pages of the WWW. A first circular has just recently been distributed on the NATO Advanced Study Institute on "The Many Faces of Neutron Stars," to be held from 1-10 October 1996 in Lipari, Sicily. Further information can be obtained via e-mail request to NATO96@areapa.area.pa.cnr.it, or on the WWW at URL http://www-NATO96.area.pa.cnr.it. BATSE The third Huntsville Symposium which took place October 25-27, was the biggest ever. Over 200 scientists gathered in Huntsville and contributed approximately 70 oral presentations and 170 posters. The meeting was very successful with many exciting new results, mainly based on the newly released 3B catalog. Theoreticians are still working on the GRB origin problem. The meeting proceedings will be published in a two volume AIP series; the editors will be C. Kouveliotou, M. S. Briggs and G. J. Fishman. The transient sources GX 339-4 and GRS 1915+105 were active over the past month. GX 339-4 is undergoing a long low intensity outburst (more than 6 months). It is averaging less than 75 mCrab in the 20-100 keV band, and has been decreasing in intensity very gradually over the past few weeks. GRS 1915+105 is bright (typically 200-300 mCrab) with daily flux variations and no discernable trends in the light curve. During the past 30 days (TJD 9999 - 100029) the following pulsed sources have been detected by the BATSE pulsed source monitor: Her X-1, Cen X-3, 4U 1626-67, OAO 1657-415, GX 1+4, GRO J2058+42, Vela X-1, and GX 301-2. BATSE has returned to its standard trigger criteria, with triggers based on discriminator channels 2+3 (~50-300 keV). As of November 6 BATSE has detected 1398 gamma-ray bursts out of a total of 3793 on-board triggers in 1658 days of operation. There have been 766 triggers due to solar flares, 10 due to SGR events, and 49 due to terrestrial gamma-ray flashes. The BATSE Science Team can provide preliminary, quick-look observations of bright sources observed by BATSE using earth occultation and pulse timing analysis. This service is intended primarily for those planning observations by spacecraft and balloon-borne experiments. Requests for the service should be made by the research team leader to the BATSE P.I., Jerry Fishman (fishman@ssl.msfc.nasa.gov).