TITLE: GCN CIRCULAR NUMBER: 10977 SUBJECT: GRB 100724B: Fermi GBM detection DATE: 10/07/24 23:28:20 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) reports on behalf of the Fermi GBM Team: "At 00:42:05.98 UT on 24 July 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100724B (trigger 301624927 / 100724029). The on-ground calculated location, using the GBM trigger data, is RA = 124.16, DEC = 74.42 (J2000 degrees, equivalent to 08 h 16.6 m, 74 d 25.2 '), with an uncertainty of 1.0 degree (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 52 degrees. GBM triggered an automatic repoint request to the Fermi Observatory to execute a maneuver following this trigger and track the burst location for the next 5 hours. However due to spacecraft constraints, the slew did not commence until 2733 s after the trigger. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of several pulses with a duration (T90) of about 111.6 s (50-300 keV). The time-averaged spectrum from T0-5.12 s to T0+140.29 s is best fit by a Band function with Epeak = 467.8 +15.3/-13.1 keV, alpha = 0.84 +/- 0.01, and beta = -1.84 +/- 0.01 (Cstat 18069 for 736 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.44 +/- 0.006)E-04 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+52 s in the 8-1000 keV band is 7.06 +/- 0.01 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."