TITLE: GCN CIRCULAR NUMBER: 16334 SUBJECT: Swift Trigger 600114: Preliminary BAT analysis DATE: 14/05/28 05:58:06 GMT FROM: Craig Markwardt at NASA/GSFC W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+180 sec from a recent telemetry downlink, we report preliminary analysis of BAT trigger 600114, tentatively associated with the M31 galaxy (Barthelmy, et al., GCN Circ. 16332). The BAT ground-calculated position is RA, Dec = 10.371, 41.520 deg which is RA(J2000) = 00h 41m 29.0s Dec(J2000) = +41d 31' 11.7" with an uncertainty of 3.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%. The mask-weighted light curve is consistent with a sharp rise (~10 sec rise time) near T+0sec, followed by a ~60 sec decay. The excess counts are primarily in the 15-50 keV band. T90 (15-350 keV) is 55.2 +- 15.9 sec (estimated error including systematics). The time-averaged spectrum from T-4 to T+55 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.35 +- 0.57. The fluence in the 15-150 keV band is (3.1 +- 1.1) x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+22.42 sec in the 15-150 keV band is 0.6 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. We caution that this is a faint BAT transient and the significance is lower than typical for GRBs. We urge confirmation at other wavelengths. Significance, light curve and spectral properties may be revised after further refined analysis. If confirmed as real and associated with the M31 galaxy at a distance of 778 kpc, the mean luminosity averaged over the T90 duration in the 15-150 keV band would be 2-6 x 10^41 erg/s. Such a luminosity, if isotropic, would be highly super Eddington for a 1 solar mass object (by a factor in the 2000-5000 range). Alternatively, the source could be highly beamed in our observer direction. Although either interpretation suggests a tantalizingly energetic event as the progenitor, we again urge caution until the presence of a bright source at this location is confirmed independently. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/600114/BA/