Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 3951

GRB 050908: Swift-BAT refined analysis
2005-09-08T15:27:17Z (19 years ago)
Hans Krimm at NASA-GSFC <>
G. Sato (ISAS), L. Barbier (GSFC), S. Barthelmy (GSFC),
P. Boyd (GSFC/UMBC), J. Cummings (GSFC/NRC), D. Hullinger (GSFC/UMD),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/NRC), J. Tueller (GSFC), W. Voges (MPE),
on behalf of the Swift-BAT team:

Using the data set from T-60 to T+120 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050908
(trigger #154112)  (Goad, et al., GCN 3942).  The refined BAT ground position
is (RA,Dec) = 20.451,-12.962 {01h 21m 48s, -12d 57' 45"} [deg; J2000]
+- 1.6 arcmin, (radius, 90% containment, statistical plus systematic).
This is 35 arcsec from the optical position reported by the KAIT GRB team
in Li et al. 2005, GCN 3945.  The partial coding was 80%.

The mask-weighted BAT light curve shows a roughly triangular shape with a
single peak rising from T-8 sec to peak at T+2 sec and return to background
levels at T+15 sec. The duration T90 (15-350 keV) is 20 +/- 2 sec.
(estimated error including systematics). There is an indication of hard to
soft spectral  evolution.  The soft emission decays more slowly and in fact
the duration in the 50-300 keV band is T90 = 7 +/- 1 seconds.

The power law index of the time-averaged spectrum fit over T-10.3 to
T+15.4 sec is 1.93 +- 0.17.   The fluence in the 15-150 keV band is
(5.1 +/- 0.5) x 10^-7 erg/cm2.  The 1-s peak photon flux measured from
T+1.66 sec to T+2.66 sec in the 15-150 keV band is (0.7 +/- 0.1) ph/cm2/s.
All the quoted errors are at the 90% confidence level.

Given the measured redshift for this burst, z=3.35 (Fugazza et al., GCN 3948;
Foley et al., GCN 3949) and assuming a cosmology with Omega_M = 0.3,
Omega_lamda = 0.7, H0 = 65, we derive Eiso for this burst of 1.36 x 10^52 ergs
in  65.25 - 652.50 keV at the GRB rest frame.
Looking for U.S. government information and services? Visit