GRB 050827: Swift-BAT refined analysis

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 3894
SUBJECT: GRB 050827: Swift-BAT refined analysis
DATE: 05/08/27 23:39:07 GMT
FROM: Hans Krimm at NASA-GSFC krimm@milkyway.gsfc.nasa.gov

T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (LANL), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:

Using the full data set from T-300 to T+300 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050827 (trigger #152325) (Capalbi, et al., GCN 3893). The refined BAT ground position is (RA,Dec) = 64.297,+18.217 {04h 17m 11s, +18d 13′ 01″} [deg; J2000] +-1.3 arcmin, (90% containment). The partial coding was 61%.

The mask-weighted light curve shows two peaks, with the first peak significantly larger than the second. The first peak is triangular in shape beginning at T-15 sec, rising to a maximum at T+0 and returning to background at T+9 sec. This peak shows a hint of spectral hardening as it progresses. There is a smaller second peak of duration ~3 sec, beginning at T+25 sec and a hint of a ~4-sec peak at T+31 sec. T90 (15-350 keV) is (49 +- 2) seconds (estimated error including systematics).

The power law index of the time-averaged spectrum is 1.37 +- 0.10. The fluence in the 15-150 keV band is (2.11 +- 0.12) x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.5 sec in the 15-150 keV band is (1.78 +- 0.19) ph/cm2/sec. All the quoted errors are at the 90% confidence level.

[GCN OPS NOTE(28aug05): The “05027: in the subject-line was changed to “050827”.]