Compton Gamma Ray Observatory Status Report #197 Friday October 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 NASA Headquarters released the final report from the 1996 Mission Operations and Data Analysis Senior Review. These recommendations of Senior Review Committee will serve as a guideline to NASA in establishing the funding levels of each of 8 astrophysics missions over the next two fiscal years (FY97 and 98), as well as baseline estimates for the subsequent two fiscal years. GRO did reasonably well in the review report, ranking in the middle of the eight reviewed missions in terms of science per dollar. A mission extension through the 2000 was recommended. Budgets will be tight though beyond 1997 due to the small total funding available for all extended missions. Cycle 6 officially begins next week, on October 15 1996. We are beginning tp process Cycle-6 grants at the CGRO-SSC. About 80% of the second-phase(budgetary) review process has been completed. Affected proposers will be contacted shortly. For the current timeline, and information on all targeted observations and current observing programs, refer to the CGRO-SSC pages on the World Web (see below). BATSE earth-occultation and pulsar data products, which have been delivered to the CGRO-SSC by the BATSE team, will be made available in simple (ASCII) formats via the World Wide Web in the very near future. An interface which allows a user to browse this data based interactively, and select desired portions of the data is undergoing beta-testing at the CGRO-SSC and at MSFC - stay tuned. CGRO-SSC pages: (http://www.cossc.gsfc.nasa.gov). Instrument Team Reports EGRET EGRET operations were normal this monthly period. Delivery of the final phase 4 data to the CGRO SSC is on schedule, and delivery of the phase 5 preliminary data to the CGRO SSC is also on schedule. Interaction with guest investigators continues at a good level. EGRET has now seen approximately sixty blazars, and a general picture is becoming clear. The ones observed typically have high-energy gamma-ray luminosities in the range of (10^47 to 10^49)f ergs s^-1 where f is the beaming fraction. If f is taken to be 10^-3, as is currently believed to be a reasonable number, then the energy emission would typically be 10^45 ergs s-1. Since a typical time for a high luminosity state for a blazar is of the order of 10^6 s, the total energy is about 10^51 ergs. If one considers that the size of the region is determined by the large variations sometimes occurring in about a day, then, considering the relativistic factor, the volume for these particles is about 10^47 cm^3. Hence, the energy density is of the order of 3 x 10^3 ergs cm-3, or the relativistic particle density is of the order of 10^6 cm-3. These particles must be collimated to avoid extremely rapid loss of energy, consistent with the current concept that they are moving outward relativistically in the jet. Recent radio results have shown that, for at least three blazars, a radio emitting region seems to move out rapidly from near the core of the jet following a high-energy gamma-ray increase. Hence, it appears that the relativistic particles originate at least reasonably close to the core of the jet, consistent with some of the current theories on the origin of these particles and the jets themselves. These results should give encouragement to theorists to pursue this work more quantitatively. Currently the EGRET telescope is observing PSR B1055-52 and will be until October 15, 1996. COMPTEL The COMPTEL instrument is performing well and continues routine operations. Members of the COMPTEL operations team will join representatives from the other instrument, spacecraft and ground-systems teams at a meeting of the Operations Working Group (OWG) at the NASA/GSFC on 15 October. Reboost planning and ground-systems upgrades are on the agenda. The long drought of non-detections of gamma-ray bursts occurring within the field of view of COMPTEL finally appears to be ending with the detection of the weak burst GRB 961001. An initial location for this event was distributed over the BATSE/COMPTEL/NMSU rapid-response network within a record 8.5 minutes of burst onset. More detailed follow-up information can be found on the COMPTEL gamma-ray burst page on the WWW. A major delivery of COMPTEL Cycle 4 data products to the COSSC public archive was recently completed. This included both low-level and high-level data products, including standard-processing skymaps, for viewing periods 401 to 411. A number of papers by COMPTEL team members and guest investigators were presented at the 2nd INTEGRAL Workshop in St. Malo, France. These included a review of radioactive gamma-ray line spectroscopy (Diehl), the latest all-sky maps at MeV energies (Strong et al), recent results on emission from the Orion region (Bloemen et al), pulsars (Hermsen et al), and the black-hole candidate GROJ 1655-40 (van Dijk et al). Evidence for MeV-emission that may be associated with high-velocity clouds was presented by Blom et al, and an update on 44Ti emission from the Cas A SNR by Iyudin et al. Knoedlseder and Leising reported on indications for a local extended glow of 26Al emission, both from COMPTEL imaging as well as from a comparison with OSSE and SMM data. OSSE OSSE operations are currently normal. The instrument is working as designed, with all subsystems in complete and full operation following a temporary failure of the drive system on detector 1 on day 96/269. Analysis of the failure indicates the detector 1 drive motor failed to step when commanded by the flight software to step from the OSSE X-axis target to the Z-axis target. The detector motion was disabled from 02:43:01 UT until 14:22:11 UT. A study of possible flight software solutions to prevent this failure from occurring is underway. The slewing response to BATSE burst triggers is enabled and the solar window was enabled on day 96/262. This solar window enables slewing to the position of the Sun if the scan angle reported on board by BATSE for a slewable burst trigger is within a programmable range of scan angles from the current position of the Sun. OSSE slewed in response to BATSE trigger #5601 on day 96/256 (TJD: 10338) at 13:57:27 UT and to BATSE trigger #5617 on day 96/271 (TJD: 10353) at 03:47:18 UT and mapped each of the areas for 3 hours. The configuration of the "burst-regulated spectrum multiscale" data has been modified as follows: 256-ms samples in 64 channels, giving 16.384 second buffer covering the energy range 200 keV - 8 MeV. Recent observations are listed in the following table. View period Dates Target (owner) ------------------------------------------------- 529.5 27 Aug - 6 Sep CGRO J1655-40 (PI team) NGC 2992 (public) 530 6 Sep - 3 Oct 4U 0115+634 (PI team) (4 days @100% response, 22 days @50%, 1 day @100%) SCAN -6.5 (public) (gal plane study at (l,b)=(123.7,0.0)) NGC 4151 (GI:Zdziarski) Low-level OSSE data products through viewing period 423 and high-level data products through viewing period 220 have been delivered to the Compton CGRO Science Support Center archive. In addition, by special request all subsequent public Cyg X-1 data sets, both low and high level, have been delivered. 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. BATSE BATSE operations for September have been normal. A gamma-ray burst on September 24 was the brightest yet detected by BATSE. The event was featured on the World Wide Web on October 1 as the astronomy picture of the day. A non-technical description of the burst may be found at http://wwwssl.msfc.nasa.gov/newhome/headlines/ast26sep96_1.htm. The Third BATSE Gamma Ray Burst Catalog appeared in the September issue of ApJ Supplements (Meegan et al., ApJS, 106,65). This includes all bursts detected by BATSE as of 1994 September 19, a total of 1122 events. The BATSE team is currently working on the next catalog, which will be treated separately because of the different trigger criteria which have been implemented at various times in the interim. As of October 1 BATSE has detected 1660 gamma-ray bursts out of a total of 5514 on-board triggers in 1988 days of operation. There have been 768 triggers due to solar flares, 10 due to SGR events, 63 due to terrestrial gamma-ray flashes, and 1477 due to the bursting pulsar CGRO J1744-28. During the last month the following pulsed sources have been detected by the BATSE pulsed source monitor: Her X-1, 4U 0115+634,Cen X-3, 4U 1626-67, OAO 1657-415, Vela X-1, and GX 301-2. The following regarding the non-detection of GX 1+4 was reported in IAU Circular 6478: GX 1+4 D. Chakrabarty, Massachusetts Institute of Technology (MIT); M. H. Finger, Universities Space Research Association; and T. A. Prince, California Institute of Technology, report for the Compton Observatory BATSE team: "The accreting x-ray pulsar GX 1+4 has been undetected by BATSE since Aug. 18, with a 90-percent-confidence upper limit of 15 mCrab (20-60 keV) for the pulsed intensity. This is the first time that GX 1+4 has remained below our 15-mCrab detection threshold for longer than a month, since we began continuous BATSE monitoring of its pulsed flux in 1991. When last detected on Aug. 18.5 UT, the phase-averaged pulsed intensity of GX 1+4 was 29 +/- 4 mCrab and the barycentric pulse frequency was (8.0381 +/- 0.0001) x 10E-3 Hz. The pulse frequency derivative changed from (-3.7 +/- 0.2) x 10E-12 Hz sE-1 during May 28-June 12, to (0.0 +/- 0.2) x 10E-12 Hz sE-1 during July 27-Aug. 6, suggesting that a torque reversal may have occurred in early Aug. (cf. IAUC 6105, 6153). The phase-averaged pulsed intensity flared from 59 +/- 5 mCrab on June 4.5 to a maximum of 204 +/- 5 mCrab on Aug. 5.5, before dropping below our detection threshold." The outburst of 4U 0115 + 634 observed by RXTE reported in IAUC 6482 was observed by BATSE very weakly on Oct. 1-3,1996. The outburst of 4U 1145-619 observed by RXTE reported in IAUC 6486 was observed by BATSE starting on Oct. 1,1996, with the outburst still in progress as of the date of this report. The source reached a level of about 140 mCrab in the 20-50 keV band.