On 1993 January 31 at 1857:12 Universal Time (UT), the Imaging Compton Telescope COMPTEL onboard the Compton Gamma Ray Observatory (CGRO) detected the cosmic gamma-ray burst GRB 930131. COMPTEL's MeV imaging capability was employed to locate the source to better than 2 deg (1 sigma error radius) within 7 hr of the event, initiating a world-wide search for an optical and radio counterpart. The maximum likelihood position of the burst from the COMPTEL data is alpha2000 = 12h 18m, delta2000 = -9 deg 42 min, consistent with independent CGRO-Burst and Transient Source Experiment (CGRO-BATSE) and Energetic Gamma Ray Experiment Telescope (EGRET) locations as well as with the triangulation annulus constructed using BATSE and Ulysses timing data. The combined COMPTEL and EGRET burst data yield a better estimate of the burst location: alpha2000 = 12h 18m and delta2000 = -10 deg 21 min, with a 1 sigma error radius of 32 min. In COMPTEL's energy range, this burst was short, consisting of two separate spikes occurring within a approximately 1 s interval with a low intensity tail for approximately 1 s after the second spike. No statistically significant flux is present for a 30 s period after the main part of the burst. This is consistent with the EGRET data. The COMPTEL telescope events indicate a hard, power-law emission extending to beyond 10 MeV with a spectral index of -1.8 +/- 0.4. The rapid fluctuations and high intensities of the gamma-ray flux greater than 10 MeV place the burst object no farther than 250 pc if the burst emission is not beamed.
American Astronomical Society
Digital Object Identifier (DOI)
J. Ryan, K. Bennett, W. Collmar, A. Connors, G. J. Fishman, J. Greiner, L. O. Hanlon, W. Hermsen, R. M. Kippen, C. Kouveliotou, L. Kuiper, G. Lichti, J. Macri, J. Mattox, M. McConnell, B. McNamara, C. Meegan, V. Schoenfelder, R. van Dijk, M. Varendorff, W. R. Webber, and C. Winkler, ‘COMPTEL measurements of the gamma-ray burst GRB 930131’, The Astrophysical Journal, vol. 422, p. L67, Feb. 1994.