TITLE: GCN CIRCULAR NUMBER: 9311 SUBJECT: GRB 090429D: Fermi GBM detection DATE: 09/04/30 22:09:24 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) reports on behalf of the Fermi GBM Team: "At 18:03:57.51 UT on 29 April 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090429D (trigger 262721039 / 090429753). The on-ground calculated location, using the GBM trigger data, is RA = 125.2, DEC = 6.2 (J2000 degrees, equivalent to 08 h 20.8 m, 06 d 12'), with an uncertainty of 4.6 degrees (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 33 degrees. [This burst was also independently detected by Konus Wind. Swift BAT confirms this GRB which occurred while it was slewing.] The GBM light curve consists of 3 short pulses (two which occurred before the trigger) with a duration (T90) of about 11 s (8-1000 keV). The time-averaged spectrum from T0-13.248 s to T0+1.088 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -0.87 +/- 0.27 and the cutoff energy, parametrized as Epeak, is 223 +/- 72.5 keV (chi squared 459 for 487 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.6 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0 s in the 8-1000 keV band is 0.86 +/- 0.16 ph/s/cm^2. [A Band function fits the spectrum equally well (chi squared 456 for 486 d.o.f.) with Epeak= 152.8 +/- 92.4 keV, alpha = -0.66 +/- 0.53 and beta = -1.88+/- 0.32.] The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."