TITLE: GCN CIRCULAR NUMBER: 20938 SUBJECT: GRB 170325A, Swift-BAT detection of a short GRB DATE: 17/03/26 04:36:10 GMT FROM: David Palmer at LANL GRB 170325A, Swift-BAT detection of a short GRB D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): GRB 170325A was detected by Swift/BAT at 2017-03-25 07:56:57.95 UTC. Because the spacecraft was slewing at that time, there was no onboard triggers, and the burst was found later in the ground analysis in response to Fermi-GBM trigger #512121423. Using the data set from T-16 to T+92 sec from the recent telemetry downlink, The BAT ground-calculated position is RA, Dec = 127.483, 20.526 deg which is RA(J2000) = 08h 29m 55.9s Dec(J2000) = +20d 31' 32.5" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The mask-weighted light curve shows a single FRED-like pulse that starts and peaks at ~T0, and ends at ~T+0.4 s. T90 (15-350 keV) is 0.3 +- 0.1 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+0.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.06 +- 0.26. The fluence in the 15-150 keV band is 8.8 +-1.3 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band is 1.1 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.