TITLE: GCN CIRCULAR NUMBER: 21142 SUBJECT: GRB 170524B: Swift detection of a burst DATE: 17/05/25 18:29:03 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), and T. Sakamoto (AGU), report on behalf of the Swift Team: At 10:40:40 UT on 2017-05-24, the Swift Burst Alert Telescope (BAT) triggered on GRB 170524B (trigger=754265). However, on-board analysis was truncated by a pre-planned slew to a scheduled target. Subsequent ground analysis using data from T+2 to T+101 s finds the source at a location of RA, Dec 90.864, -17.086, which is RA(J2000) = 06h 03m 27s Dec(J2000) = -17d 05' 11" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a complex structure about 50 seconds long. The raw peak count rate was ~18000 counts/sec (15-350 keV), at ~7 sec after the trigger. T90 (15-350 keV) estimated using the raw light curve is 46.4 +- 1.6 sec (estimated error including systematics). The time-averaged spectrum from T+1.8 to T+49.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.15 +- 0.06. The fluence in the 15-150 keV band is (6.6 +/- 0.2) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+6.70 sec in the 15-150 keV band is 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. This event was also detected by CALET, KONUS-Wind, and INTEGRAL SPI ACS. A Swift Target of Opportunity observation has been requested. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/00753445006/BA/