Compton Gamma Ray Observatory Status Report #193 Monday, June 10 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: The 231 Cycle-6 proposals have now been distributed to teams of anonymous referees. A peer-review meeting will occur later this month, followed by a timeline development meeting in July. Once the timeline has been developed, and a final list of accepted proposals thus determined, budget requests will be solicited from selected proposals (probably during August). Cycle-6 begins on October 30, 1996. The CGRO User's Committee is preparing for the written and oral presentations to the NASA HQ MO&DA Senior Review. In this review, CGRO and will be jointly evaluated and budgeting priorities for FY 97-00 will be established. The User's Committee will also meet during July to establish guidelines for the Cycle-7 program. Major topics under consideration include reinstitution and emphasis on Key projects, revision of the proprietary data rights period (downward from 1 year to 0-3 months) usage of the remaining EGRET gas, and funding priorities in an era of shrinking budgets. Please feel free to discuss any ideas you may have on these issues with a User's Committee member; the committee members are: khurley@sunspot.ssl.berkeley.edu !Kevin Hurley (Chair) cordes@astrosun.tn.cornell.edu !Jim Cordes josh@cfa255.harvard.edu !Josh Grindlay donk@pulsar.hsc.edu !Don Kniffen gok@mpe-garching.mpg.de !Gottfried Kanbach kroeger@osse.nrl.navy.mil !Dick Kroeger kurfess@osse.nrl.navy.mil !Jim Kurfess liang@spacsun.rice.edu !Edision Liang marscher@buast0.bu.edu !Al Marscher paciesas@ssl.msfc.nasa.gov !Bill Paciesas prince@caltech.edu, !Tom Prince jryan@comptel.unh.edu !Jim Ryan vos@mpe-garching.mpg.de !Volker Schoenfelder aew@ipac.caltech.e !Ann Wehrle gfb@iftcr.mi.cnr.it !Giovanni Bignami fichtel@lheavx.gsfc.nasa.gov !Carl Fichtel fishman@ssl.msfc.nasa.gov !Jerry Fishman NASA Exofficio Members ------------------------------------------------------- abunner@hq.nasa.gov !Alan Bunner gehrels@lheavx.gsfc.nasa.gov !Neil Gehrels norris@grossc.gsfc.nasa.gov !Jay Norris shrader@grossc.gsfc.nasa.gov !Chris Shrader 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. In case that you missed it last month, information on EGRET is now available on the World Wide Web. You may access it through: http://lheawww.gsfc.nasa.gov/docs/gamcosray/EGRET/egret.html The material includes a discussion of the EGRET instrument and the scientific goals, the institutions involved, a list of some major EGRET discoveries, guest invesitgator information in relation to the GRO Science Support Center, a list of EGRET papers in refereed journals, and some EGRET preprints that have been accepted by journals, but have not yet appeared in print, as well as other material such as a picture of the instrument and the high-energy gamma-ray all-sky map. A paper by Reshmi Muknerjee and others on the high-energy gamma-ray flare from PKS 0528+134 has been accepted by the Astrophysical Journal. Both the history of this object and the multiwavelength coverage are described. A detailed relativistic SSC jet model agrees well with the flare multiwavelength spectrum. At the forthcoming AAS meeting in Madison, Wisconsin, Bob Hartman and his co-authors will be reporting on the large increase seen in 3C 279 recently and on the related multi-wavelength coverage, as well as giving a discussion of the scientific implications. Carl Fichtel and his co-authors at the same meeting will describe the BL Lac blazars that have been seen in high-energy gamma radiation. The report will show a comparison of the z distribution to that of those seen in the radio region and will describe the luminosity and spectral shape of these objects as seen in the high-energy gamma-ray region. Also, Joe Esposito and colleagues will describe his work on the high-energy gamma-ray emission from supernovae. Currently, the EGRET telescope is pointed at GRO J0516-609 and will move to CEN X-3 on June 11, 1996. 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 was enabled on day 96/135. Since this time there have been no burst triggers sent from BATSE that met the OSSE slewing criteria. A paper detailing results of OSSE observations of the Orion complex has been submitted for publication in ApJ (Murphy at al.). Flux levels reported by COMPTEL of gamma-ray line emission in the 3 - 7 MeV range suggest that if the origin of the emission were a point source at the center of the OSSE field of view then OSSE observations of the region would result in significant detections of line emission near 4.4 and 6.1 MeV. The lack of compelling evidence for an OSSE detection in this region requires that any source of this emission must be more extended than the distibution of the intense CO emission localized around Orion A and Orion B. Recent observations are listed in the following table. View period Dates Target (owner) ----------------------------------------------------------- 519 23 Apr-7 May Arp 220 (GI: C. Dermer) Mrk 590 (not assigned) GPLANE 95 (GI: J. Skibo) 520 7-21 May PKS 0528+134 (PI team) M 31 (PI team) Cyg X-2 (not assigned) 520.4 21-28 May PKS 2155-304 (GI: M. Urry) PKS 0235+164 (PI team) 521 28 May-11 June PKS 0506-612 (PI team) NGC 2110 (GI: L. Bassani) Data through viewing period 411.5 have been delivered to the Compton GRO Science Support Center archive. Also, OSSE high level data products covering viewing periods 209, 210, 331.5, 332 and 333 were delivered to the CGRO-SSC. Refer to the CGRO-SSC page on the WWW (http://cossc.gsfc.nasa.gov), or contact Tom Bridgman (bridgman@grossc.gsfc.nasa.gov) for more information. COMPTEL The COMPTEL instrument is performing well and continues routine operations. During May three gamma-ray bursts were observed by COMPTEL without detection (GRBs 960518, 960528, and 960530). The collaboration notes (with regret) that M. Kippen, stalwart of the COMPTEL rapid burst-response effort, has moved on to join the BATSE team in Huntsville, to be a few minutes closer to those burst trigger messages; the newly designated Keeper of the Beeper for the rapid analysis of COMPTEL bursts is A. Connors of UNH. Recent COMPTEL results on solar flares will be presented (by Ryan et al. and Rank et al.) at the upcoming 188th meeting of the AAS in Madison, Wisconsin. Lastly, the countdown has begun toward the start of the 83rd Tour de France ... BATSE The following was reported in IAU circular 6395: GRO J1744-28 C. Kouveliotou, Universities Space Research Association (USRA); K. Deal, P. Woods, M. Briggs, University of Alabama in Huntsville (UAH); B. A. Harmon, G. J. Fishman, Marshall Space Flight Center, NASA; J. van Paradijs, UAH and University of Amsterdam; M. H. Finger, USRA; and J. Kommers and W. H. G. Lewin, Massachusetts Institute of Technology, report: "BATSE is no longer detecting bursts or persistent emission from the bursting pulsar GRO J1744-28. A total of 3080 bursts were detected from this source (not corrected for earth occultation or other deadtime effects) between its onset on 1995 Dec. 2 until its cessation on 1996 May 3. During most of this 152-day interval, the burst rate was fairly constant at an average of about 20 bursts/day, but after Apr. 27 the rate declined rapidly. The last detected event had a fluence of 1.2 x 10E-7 erg cmE-2. The pulsing signal in the persistent emission was last detected on Apr. 26; after this date, the pulsed flux was below 7 x 10E-10 erg cmE-2 sE-1 (r.m.s., between 20 and 40 keV). Between Apr. 30 and May 6, earth-occultation measurement yields a 3-sigma upper limit on the total flux above 20 keV of 2.7 x 10E-9 erg cmE-2 sE-1, or about 150 mCrab." The following was reported in IAU circular 6405: CYGNUS X-1 S. N. Zhang, W. S. Paciesas, B. A. Harmon, G. J. Fishman, and D. Crary, Marshall Space Flight Center, NASA, report for the Compton Gamma Ray Observatory BATSE team: "Cygnus X-1 has been decreasing rapidly in intensity in the band 20-200 keV, as observed by BATSE, roughly coincident in time with the increased 2- to 12- keV flux reported by ASM/RXTE (see IAUC 6404). The flux changed from 1.0 +/- 0.02 Crab units (20-100 keV) on May 11 to 0.5 +/- 0.02 on May 19-20. The energy spectrum also becomes softer during this time (the Optically Thin Thermal Bremsstrahlung model temperature being from 80 to about 50 keV). The r.m.s. fraction (0.01-0.488 Hz) also decreased from a typical value of 8 +/- 0.5 to 5 +/- 0.5 percent during this period." The following was reported in IAU circular 6411: GRS 1915+105 S. N. Zhang, C. R. Robinson, B. A. Harmon, W. S. Paciesas, and G. J. Fishman, Marshall Space Flight Center, NASA, report for the Compton Gamma Ray Observatory BATSE team: "A hard x-ray outburst from GRS 1915+105 is being detected by BATSE/CGRO. Its 20- to 100- keV flux has increased almost linearly from an upper limit of about 50 mCrab on May 15-18 to about 250 mCrab on May 24 and remained bright with significant day-to-day variations of 20-50 percent as of May 27. This flux level is slightly below the average peak flux (about 300 mCrab) of this source during previous outbursts." The following was reported in IAU circular 6413: EXO 2030+375 M. T. Stollberg, University of Alabama in Huntsville; R. B. Wilson, Marshall Space Flight Center; M. H. Finger, Universities Space Research Association; and T. A. Prince, California Institute of Technology, report for the Compton Gamma Ray Observatory BATSE team: "Pulsations from the Be/x-ray transient pulsar EXO 2030+375 have been observed during Apr. 1-7 and May 17-22. Outbursts began 4-5 days before the periastron passages predicted by the orbital model of Stollberg et al. (1993, AIP Conference Proc. 308, 255). All prior outbursts observed by BATSE occurred after periastron. The measured pulse period for the first outburst, after correcting for orbital motion, was 41.6773 +/- 0.0015 s on 1996 Apr. 2.5 UT. The rms pulsed flux (20-50 keV) peaked on that day at 16 +/- 3 mCrab. The second outburst had an orbit-corrected pulse period of 41.67781 +/- 0.00083 s on 1996 May 19.5. The rms pulsed flux (20- 50 keV) peaked at 15 +/- 3 mCrab on May 21.5. Thirteen consecutive outbursts were observed previously by BATSE from 1992 Feb. 8 to 1993 Aug. 28. During that time, the pulse period of EXO 2030+375 decreased from 41.6839 +/- 0.0011 s on 1992 Feb. 10.5 to 41.6708 +/- 0.0015 s on 1993 Aug. 23.5 for a mean period rate of -8.5 ms/yr. Over the 21 orbital periods during which the source was not detected, the mean period rate was +2.3 ms/yr. The next periastron passage is predicted to occur on 1996 July 7." During the last month the following pulsed sources have been detected by the BATSE pulsed source monitor: Her X-1, Cen X-3, 4U 1626-67, EX 02030+375, 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 50-300 keV energy range. As of June 6 BATSE has detected 1550 gamma-ray bursts out of a total of 5382 on-board triggers in 1871 days of operation. There have been 767 triggers due to solar flares, 10 due to SGR events, 54 due to terrestrial gamma-ray flashes, and 1477 due to the bursting pulsar GRO J1744-28. A series of 20 triggers in a row has occurred that were all gamma-ray bursts.