[vsnet-grb-info 3373] GRB 060602B: Swift-BAT Refined Analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5208
SUBJECT: GRB 060602B: Swift-BAT Refined Analysis
DATE:    06/06/04 00:00:01 GMT
FROM:    Hans Krimm at NASA-GSFC  <krimm at milkyway.gsfc.nasa.gov>

D. Palmer (LANL),  L. Barbier (GSFC),  S. Barthelmy (GSFC),
J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), M. Koss (GSFC/UMD), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (GSFC/JSPS/USRA), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
on behalf of the Swift-BAT team:

Using the data set from T-119.1 to T+182.9 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 060602B
(trigger #213190)  (Schady, et al., GCN 5200).  The BAT 
ground-calculated position
is (RA,Dec) = 267.368, -28.121 deg {17h 49m 28.2s, -28d 7' 15.5"} (J2000)
+- 1.4 arcmin, (radius, sys+stat, 90% containment).  The partial 
coding was 100%.

The light curve shows a single boxcar shaped peak from ~T-1.0 to ~T+12.0 sec.
The peak is strongest in the 15-25 keV band and is not seen above 50 keV.
T90 (15-350 keV) is 9.0 +- 2 sec (estimated error including systematics).

The time-averaged spectrum from T-1.1 to T+8.8 is best fit by
a simple power-law model.   The power law index of the time-averaged
spectrum is 5.02 +- 0.52. The fluence in the 15-150 keV band is
1.8 +- 0.2 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from
T+5.94 sec in the 15-150 keV band is 0.8 +- 0.1 ph/cm2/sec.  All the quoted
errors are at the 90% confidence level.

We note that this is one of the softest spectra yet seen in the BAT for a GRB.
The spectra plus the galactic coordinates of the source:  galactic lon, lat:
1.15, -0.30 deg suggest that this source may be an X-ray burster rather than
a classical GRB.  Analysis of XRT and other ground and satellite based
observations will help to settle this question.  Therefore further observations
are encouraged.