Compton Gamma Ray Observatory Status Report #190 Friday March 11, 1996 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: A new proposal season is rapidly bearing down upon us - don't forget, due date is April 19, 1996. For information on (mandatory) electronic form submission, send a blank e-mail message to "rps@legacy.gsfc.nasa.gov", or on the WWW under "http://cossc.gsfc.nasa.gov/cossc/cossc.html: under the item "The Cycle 6 remote proposal Submission Form ..." The procedure is similar to last years (minus some bugs), and similar to that of the other NASA High-Energy Missions. Report problems to Paul Barrett (barrett@compass.gsfc.nasa.gov, 301-286-1108), If you need hard copy of the NRA and appendices please let us know ASAP: send requests to Sandy Barnes at barnes@grossc.gsfc.nasa.gov (301-286-7780). You can download the various documents, minus the figures, from our WWW site, or by ftp: open grossc.gsfc.nasa.gov, cd nra, cd cycle6, ... At the very minimum, even if you've proposed many times in the past, PLEASE READ THE BULLETED LIST OF IMPORTANT CHANGES the beginning of the NRA (and replicated at the beginning of Appendix A). If all else fails, give me a call! The proposals will be evaluated by a peer-review committee, (under the supervision of NASA HQ) on June 24-26, 1996. If you are interested in volunteering to serve on a review committee, please contact Chris Shrader (shrader@grossc.gsfc.nasa.gov, 301-286-8434). The meeting will be in the Washington DC area. Its great fun! A change to the current viewing plan has been implemented by the project scientist to support Target-of-opportunity observations of GRO J1655-40; the effected Viewing Periods are 516 and 517; details will be posted on GRONEWS and the WWW imminently. A new piece of user-contributed software is available from CGRO-SSC; an alternate version of the EGRET maximum-likelihood point-source detection routine "LIKE", incorporating a number of improvements, has been contributed by Dr. John Mattox (Universty of Maryland). For details,and a copy of the software, retrieve the files in cossc.gsfc.nasa.gov, /pub/usr_contrib. CGRO will be 5 years old next month! (recall that launch was on April 5, 1991). Also, the CGRO exhibit at the National Air and Space Museum has opened last month! Both of these events both of these events will be celebrated in an event sponsered by TRW and the Air and Space Museum later this month! Congratulations to all who have contributed! Finally, we note that a CGRO (BATSE) image of GRO J1744-28 was pictured on the front page of USA Today (February 29 Issue). I have not thoroughly researched this, but will go out on a limb and venture that this is the first ever radon-transform image to adorn the cover of that particular publication! Instrument Team Reports EGRET EGRET operations were normal this monthly period. Delivery of the final phase 4 data to the GRO SSC is on schedule, and delivery of the phase 5 preliminary data to the GRO SSC is also on schedule. Interaction with guest investigators continues at a good level. A paper on PSR B1706 by D. J. Thompson et al. has recently been accepted by the Astrophysical Journal. In this paper, observations from 1991 to 1995 are summarized. An energy spectrum exists up to 30 GeV. It has a marked change in spectral slope at about 1 GeV. A detailed figure of the emission as a function of phase is also presented. In a paper by Fichtel et al. to appear in the proceedings of the Third Compton Gamma-Ray Burst meeting, there is an improved upper limit to microsecond bursts derived from the EGRET instrument which is capable of measuring them directly should they be present. Since the bursts that would have been seen would have been from our Galaxy within 100 pc, this limit is especially significant in terms of the prediction of such bursts by the Hawking model which attempts to make general relativity compatible with quantum mechanics. During March, EGRET will be viewing PKS 0208-512 and MRK 501. COMPTEL The COMPTEL instrument is performing well and continues routine observations. Quick-look analysis of data associated with the recent target-of-opportunity observation of the gamma-ray blazar 3C 279 shows no evidence to date for this source in the MeV range observable by COMPTEL; 3C 273 is seen, however. A further, more detailed analysis of these data is currently in progress. Several more gamma-ray bursts have occurred within the field of view of COMPTEL since the last report (GRBs 960207, 960208, 960214, and 960220). Once again, none of these was detected at MeV energies by COMPTEL, further extending the longest period (nine months and counting) without a field-of-view burst detection by COMPTEL. On a more positive note, a reanalysis of earlier COMPTEL data has uncovered a burst missed in the original processing, GRB 920627; further details on this event will soon appear on the new COMPTEL Burst Page on the WWW (at URL, http://wwwgro.unh.edu:8080/bursts/cgrbpage.html). A new release of COMPTEL data to the CGRO public archive at the COSSC is imminent. These data will include all remaining low-level and first high-level data products covering the balance of Phase 3 of the CGRO mission (VP 326 through VP 339). A general team meeting of the collaboration was held during the week of 27 February to 1 March at SRON-Utrecht in The Netherlands. OSSE The OSSE status report will be circulated separately as an addendum to this report. BATSE The following was reported in IAU Circular 6335: GRO J1744-28 B. A. Harmon, Marshall Space Flight Center, NASA; J. van Paradijs and W. S. Paciesas, University of Alabama, Huntsville; and S. N. Zhang and C. Kouveliotou, Universities Space Research Association, report for the BATSE Team: "The 20- to 100-keV flux of GRO J1744-28, as measured with BATSE using earth occultations, has steadily decreased from 0.9 photon cmE-2 sE-1 on Feb. 19 to 0.5 photon cmE-2 sE-1 on Mar. 2. This may signal the upcoming end of the outburst of this unique source. No convincing optical/infrared counterpart of the source has so far been found, likely due to its high interstellar extinction (Augusteijn et al., IAUC 6326). The non-detection of a V-band counterpart implies that the interstellar column density, NH, is at least 2 x 10E22 cmE-2. At a source distance of 7 kpc, the unabsorbed apparent K magnitude is expected to be about 13. Since the K-band extinction, A(K), increases with column density by A(K)/NH about 7.5 x 10E-23 mag cm^2, the only way to identify a counterpart would appear to be deep K-band imaging centered on the variable radio source (IAUC 6323) down to at least mag 19. In view of the possible upcoming termination of the outburst, we urge observers that such images be made as soon as possible." During the past 30 days (TJD 10119 - 10149) the following pulsed sources have been detected by the BATSE pulsed source monitor: GRO J1744-28, 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. The burst trigger is currently using count rates from 20-300 keV energy range. As of 8 March BATSE has detected 1472 gamma-ray bursts out of a total of 5062 on-board triggers in 1781 days of operation. There have been 766 triggers due to solar flares, 10 due to SGR events, and 54 due to terrestrial gamma-ray flashes. There have been 1138 triggers due to bursts from GRO J1744-28. From grodis@ascasrv.gsfc.nasa.gov Tue Mar 12 10:31:23 1996 Received: from circe.lhea (circe.gsfc.nasa.gov [128.183.126.90]) by rosserv.gsfc.nasa.gov (LHEA9504/950407.s1) with SMTP id KAA13339 for ; Tue, 12 Mar 1996 10:31:11 -0500 Received: from ascasrv.gsfc.nasa.gov by circe.lhea (5.x/SMI-SVR4) id AA11208; Tue, 12 Mar 1996 08:55:23 -0500 Received: from (localhost [127.0.0.1]) by ascasrv.gsfc.nasa.gov (LHEA9404/940426.s1) with SMTP id JAA06511 for ; Tue, 12 Mar 1996 09:00:50 -0500 Date: Tue, 12 Mar 1996 09:00:50 -0500 Message-Id: <960312085441.21000684@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@ascasrv.gsfc.nasa.gov Precedence: bulk From: SHRADER@grossc.gsfc.nasa.gov To: scott@circe.gsfc.nasa.gov Subject: Addendum to CGRO March Status report X-Listprocessor-Version: 6.0c -- ListProcessor by Anastasios Kotsikonas Status: RO Addendum to CGRO March Status report OSSE Instrument Team report: 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 remains disabled because of the bursting pulsar, GRO J1744-28. OSSE observations of this new source in December and January were particularly fruitful. In the following IAU circular, we reported the discovery that pulses within bursts lag those at times away from bursts. A paper summarizing spectroscopy and timing of the bursts and the pulsar is in the final stages of preparation. GRO J1744-28 (IAUC 6321) G. V. Jung and B. F. Phlips, Universities Space Research Association; J. D. Kurfess, J. E. Grove, M. S. Strickman, W. N. Johnson, C. D. Dermer, and G. H. Share, Naval Research Laboratory (NRL); and S. J. Sturner, NRL and National Research Council, on behalf of the Gamma Ray Observatory OSSE team, report: "OSSE has observed the 467-ms pulsed emission from the bursting x-ray pulsar GRO J1744-28 (IAUC 6285), in both the steady source and during bursts. Using the pulsar ephemeris supplied by BATSE (M. Finger, private communication), we epoch-folded and co-added data from the brightest 2 s of each burst in a sample of 104 bursts observed by OSSE between Jan. 18 and 30. We find that the pulsed emission during the bursts lags the non-bursting pulsed emission; the lag amounts to 0.155 +/- 0.007 of a pulsar period at the peak of the burst. The magnitude of the phase lag follows the average intensity profile of the burst sample. This result suggests that the burst-emitting region is physically offset from the region that produces the persistent emission, which could be caused by azimuthal asymmetries from accreting matter constrained to move along different field lines." An important paper summarizing OSSE spectra of Cyg X-1 has been accepted for publication in ApJ (Phlips et al.). Although we have measured a new minimum in the hard X-ray flux from the source, no evidence was found for either a broad 1 MeV feature or a narrow 511 keV line previously reported in association with a low flux state. Preprints are available through on the World Wide Web at URL http://osse-www.nrl.navy.mil/osselib.htm. Data through viewing period 405 have been delivered to the Compton GRO Science Support Center archive.