TITLE: GCN CIRCULAR NUMBER: 10451 SUBJECT: GRB 100224A SHB found in ground analysis of BAT data DATE: 10/02/25 20:00:59 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. R. Cummings (GSFC/UMBC), H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC), and D. M. Palmer (LANL) report on behalf of the Swift team: At 15:20:10 UTC, Swift-BAT rate-triggered on GRB 100224A (trigger# 413805). No source was found on board. A source was found in ground analysis at RA, Dec 83.467, -7.994, which is RA (J2000) = 05h 33m 52.1s Dec (J2000) = -07d 59' 37" with an estimated error of 3 arcmin (90% containment). The burst had two main peaks, the first larger, at T+0.2 and T+0.5 sec, the first about 0.1 sec long, the second about 0.3 sec long. The spectrum is well fit by a simple powerlaw with a photon index of 0.98 +- 0.23. The fluence (15-150 keV) from T+0.17 to T+0.625 sec was 3.2 +- 2 x 10^-8 ergs/cm^2/sec (1 sigma error estimates). Since the source was not detected onboard, there are no automated products for this burst. Since the burst is old for a SHB, there are currently no plans for Swift followup observations.