GRB 990915 (BATSE trigger # 7766) triggered BATSE at U.T. 83722.55. The detection was about 7 sigma. The burst was far off COMPTEL's axis (COMPTEL Zenith, Azimuth of 53.33, 73.00 degrees).

CGRO-COMPTEL + BATSE Sky-Map[color]

CGRO-COMPTEL 0.75-30 MeV light-curve

GRB 990728 (BATSE trigger # 7678) triggered BATSE at U.T. 39824.88. The detection was strong at about 15 sigma because it was very close on COMPTEL's axis (COMPTEL Zenith, Azimuth of 3.73, 93.99 degrees).

CGRO-COMPTEL + BATSE Sky-Map[color]

CGRO-COMPTEL 0.75-30 MeV light-curve

GRB 990123 (BATSE trigger # 7343), was so bright in >MeV gamma-rays that CGRO-COMPTEL was able to image it in a 10 sigma detection. (The preliminary COMPTEL detection, broadcast about 11 minutes after the BATSE trigger, was 8.2 sigma.) This, despite its being barely on the edge of the telescope field of view (COMPTEL Zenith, Azimuth of 58.38, 278.80 degrees). This event was observed simultaneously by several spacecraft (CGRO-BATSE: Kippen et al. GCN#224; BeppoSAX GRBM,WFC,NFI: Piro et al. GCN#199, 202, 203 and references therein; Ulysses: Hurley, Feroci et al. GCN 222) as well as later by ground-based radio and optical telescopes (Odewahn et al. GCN# 201; Frail et al. CGN# 211). In a sensational first detection, it was observed in optical by the ROTSE instrument during the course of the gamma-ray burst itself (Akerlof and McKay et al. GCN# 205). Below we have posted the combined CGRO-COMPTEL and BATSE/Huntsville 1,2 and 3 sigma location contours (systematic uncertainties included!), along with the IPN timing arc (Hurley, Feroci et al GCN# 222), and indications of the BeppoSAX X-ray, prompt optical (ROTSE), fading optical, and radio counterparts. GRB 990123 triggered BATSE at U.T. 35216.12, yet the MeV emission did not rise significantly until 18 seconds after BATSE's lower energy burst onset. Above an MeV, it lasted about 45 seconds, although clearly longer at lower energies. This is visible in the (preliminary!) COMPTEL low (0.2-1.6 MeV) and high (0.6-11 MeV) range burst mode, plus the 0.7-30 MeV telescope mode light-curves, also displayed below. For comparison we have indicated the times and rough magnitudes of the prompt optical emission measured by Akerlof, McKay et al. (GCN 205).

CGRO-COMPTEL + BATSE Sky-Map ---- [color] ---- [black and white] ---- [text]

CGRO-COMPTEL 0.2-1.6, 0.6-11 and 0.75-30 MeV light-curves ---- [black and white] ---- [text - qdp format]

GRB 980707 triggered CGRO-BATSE at 15:59:47.04 U.T. (No. 6904) - while COMPTEL computer systems were still being upgraded to solaris. Nevertheless R M Kippen, S Kappadath and A Young ground out an initial COMPTEL position about an hour from burst onset. Its roughly two dozen 0.75-30 MeV telescope photons were clusterd in a sharp spike (about 0.23 s long, according to a variant of J. Scargle 1998's Bayesian Blocks algorithm). This gave us about a 7 sigma imaging detection, despite being 47 degrees from telescope zenith. Combined CGRO-COMPTEL and BATSE/Huntsville 1,2 and 3 sigma location contours of this spike (systematic uncertainties included!), along with the IPN timing arc (Hurley et al via GCN) are displayed below. At lower energies there is a faint but visible tail lasting a few seconds after burst onset. These are both visible in the COMPTEL low (0.1-1.5 MeV0 and high (0.6-11 MeV) range burst mode, plus the 0.7-30 MeV telescope mode light-curves, also displayed below. There is a possible association with an RXTE/PCA source (Marshall, Takeshima, and Woods GCN 138).

CGRO-COMPTEL + BATSE Sky-Map [color] ---- [black and white]

CGRO-COMPTEL 0.1-1.5, 0.6-11 and 0.75-30 MeV light-curves [color] ---- [black and white]

GRB 980329 triggered CGRO-BATSE at 03:44:35 U.T. (No. 6665; Briggs et al. 1998, IAUC 6856). Although very bright at lower energies, this was a weak COMPTEL detection (33 events, about 4.3 sigma) at about 40 degrees telescope zenith. The position was broadcast world-wide about 45 minutes after burst onset. The 0.1-1, 0.6-10 and 0.75-30 MeV COMPTEL light-curves (low and high range burst-mode and telescope mode, respectively; see below) show the rise of the >1 MeV emission slightly preceding the BATSE trigger time, and the lower energy peaks broader than those at higher energies. It was a spectacularly bright BeppoSAX WFC detection (Fronterra et al. 1998, IAUC 6853) with a subsequent X-ray afterglow detection ('t Zand et al. 1998, IAUC 6854); possible faint R, I and K band detections (Djorgovski et al. 1998, CGN#41; Klose 1998, GCN#43; Larkin et al. 1998, CGN#44; repectively) as well as radio (Taylor et al. GCN#40). Together with the high energy light curve, below is a color plot showing the combined CGRO COMPTEL and BATSE-Huntsville 1, 2 and 3 sigma location contours (systematic errors included), with the IPN timing ARC (Hurley et al. via GCN) and the BeppoSAX position ('t Zand et al. 1998 IAUC 6854).

CGRO-COMPTEL + BATSE Sky-Map [color] ---- [black and white]

CGRO-COMPTEL 0.1-1.5, 0.6-10 and 0.75-30 MeV light-curves [color] ---- [black and white]

This COMPTEL telescope detection occurred on 24 January 1998 at 06:34:35.20 UT. The event was about 20 degrees from telescope zenith, but bright enough so that about sixty 0.75-30 MeV burst photons were detected in the first peak, lasting about 14 seconds. The first and second peaks are visible in the COMPTEL 0.1-1.6 MeV (Burst-mode low range) and 0.6-10 MeV (Burst-mode high range), with the second barely visible in telescope-mode (0.75-30 MeV) light-curves (below). We have also posted both the CGRO-COMPTEL-only map from just the first peak; and a combined COMPTEL + BATSE/Huntsville map, using COMPTEL data from the first and second bright peaks. The BATSE/Huntsville data are courtesy of the GCN network, R.M. Kippen and V. Connaughton. We have plotted BATSE one and two sigma circles indicating 1 and 2 sigma statistical + systematic uncertainties; plus the COMPTEL 1, 2, and 3 sigma location contours, in R.A. and Decl. 2000.

CGRO-COMPTEL + BATSE Sky-Map ---- [postscript]

CGRO-COMPTEL Sky-Map, 1st peak ---- [postscript]

CGRO-COMPTEL 0.1-1.5, 0.6-10 and 0.75-30 MeV light-curves ---- [postscript]

The latest COMPTEL telescope detection occurred on 7 August 1997 at 18:29:09.09 UT. The event was about 20 degrees from telescope zenith, but bright enough so that about thirty 0.75-30 MeV burst photons were detected in about 25 seconds. On rare occasions, the automatic estimate of the burst interval is not optimal, and the duty scientist must re-calculate the burst position with better time limits, delaying the procedure by tens of minutes. The faint but long light-curve of GRB 970807 caused just this difficulty, so launch of the burst position to the world-wide BCN network of ground-based observers was delayed until about 45 minutes after burst onset. The preliminary most probable position is (R.A. 284.73, Decl. -39.25 degrees, epoch 2000) with an error of approximately +/-2.4 degrees (95% confidence). This is consistent with the BATSE/IPN location of (R.A. 287.076, Decl. -36.518 degrees, epoch 2000).

Multi-Instrument Sky-Map ---- [postscript]

COMPTEL Telescope Lightcurve ---- [postscript]

The previous COMPTEL telescope detection occurred on 12-December 1996 at 04:07:51 UT. The event was about 42 degrees from telescope zenith, but bright enough so that about thirty 0.75-30 MeV burst photons were detected in about 1.5 seconds. On rare occasions, the automatic estimate of the burst interval is not optimal, and the duty scientist must re-calculate the burst position with better time limits, delaying the procedure by about 7 minutes. The single-spike light-curve of GRB 961212 caused just this difficulty, so launch of the burst position to the world-wide BCN network of ground-based observers was delayed until about 15 minutes after burst onset. The preliminary most probable position is (R.A. 180.1, Decl. 33.7 degrees, epoch 2000) with an error of approximately +/-2 degrees (95% confidence). This is consistent with the BATSE location of (R.A. 182.8, Decl. 34.5 degrees, epoch 2000). No IPN detection was available for this burst

COMPTEL Sky-Map ---- [postscript]

COMPTEL Telescope Lightcurve ---- [postscript]

The gamma-ray burst which triggered BATSE/BACODINE on 01-Oct-1996 at 20:53:05 UT was detected by the COMPTEL telescope with a significance of about 4 sigma. An initial localization of this burst was distributed to the BCN observer network only 8.5 minutes after the trigger. Unfortunately, the localization is not very accurate due to few events and the proximity of the source to the earth's limb. The burst was also detected by Ulysses, providing an IPN timing annulus. The preliminary most probable COMPTEL/IPN position of GRB 961001 is (R.A. 40.60, Decl. 57.78 degrees, epoch 2000) with an error of approximately -/+ 2 degrees (95% confidence) along the IPN arc. This is consistent with the BATSE/IPN location of (R.A. 40.73, Decl. 57.73 deg).

Multi-Instrument Sky-Map ---- [postscript]

COMPTEL Telescope Lightcurve ---- [postscript]

The bright gamma-ray burst which occurred on 08-August-1996 at 16:42:03 UT was detected by the COMPTEL telescope with a significance of about 6.3 sigma. This burst ends a period of more than a year during which no strong bursts were detected. The preliminary most probable COMPTEL position of GRB 960808 is (R.A. 86.38 , Decl. 36.53 degrees, epoch 2000) with an error raduis of approximately 1 degree (68% confidence). The COMPTEL localization is consistent with the BATSE location of (R.A. 85.28, Decl. 36.95 deg; error radius about 1.6 deg). Unfortunately, the BACODINE system did not respond to this burst so that rapid follow up observations could not be obtained.

Multi-Instrument Sky-Map ---- [postscript]

COMPTEL Telescope Lightcurve ---- [postscript]

The relatively bright (by BATSE standards) gamma-ray burst which occurred on 09-April-1996 at 21:25:44.96 UT was marginally detected by the COMPTEL telescope with a significance of about 2.5 sigma. Because this burst was only a marginal detection, the COMPTEL localization is rather crude (-/+ several degrees). It is, however, consistent with the more accurate localizations of BATSE and BATSE/Ulysses triangulation.

At the time of this burst, Comet Hyakutake was within 3 degrees of the best weighted BATSE / COMPTEL / Ulysses burst position. There is therefore the possibility that serendipitous optical observations exist. If you know of any such observations, or would like more information, please contact Dr. Thomas Harrison (New Mexico State University) at telephone 505-646-3628 (email tharriso@nmsu.edu).

Information from IAU Circular #6384 ---- [postscript]

BACODINE / BATSE / IPN Localization Information

Multi-Instrument Sky-Map ---- [postscript]

COMPTEL Telescope Lightcurve ---- [postscript]

Back to the COMPTEL Burst Page

Creation Date: Mon Jan 1, 1996