GCN Circular 4538

J. Cummings (GSFC/NRC),  L. Barbier (GSFC), S. Barthelmy (GSFC)
E. Fenimore (LANL), N. Gehrels (GSFC), K. Gendreau (GSFC),
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), P. Meszaros (PSU), J. Norris (GSFC),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC)
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 BAT GRB 060117 (trigger
#177666) (Campana, et al., GCN 4533
Not found
 
 
).  The BAT ground-calculated
position is RA,Dec = 327.917, -59.967 {21h 51m 40s, -59d 58' 1"}
(J2000) +- 1.0 arcmin, (radius, sys+stat, 90% containment).  This
position includes a small correction for small  BAT image distortions.
We note that this error circle formally excludes the position of IRAS
21482-6015 (GCN 4533
Not found
 
 
, GCN4534
Not found
 
 
).  We also note that fading afterglow
discovered by the FRAM telescope group (Jelinek et al, GCN 4536
Not found
 
 
) is
0.8 arc min from the center of the BAT 90% error circle.  The partial
coding was 25%.

The light curve has multiple peaks, with the main peaks spanning the
time range T-1 to T+17.  T90 (15-350 keV) is (16 +- 1) sec (estimated
error including systematics).  There does appear to be weak emission
extending out to T+100 seconds.

The best fit to the spectral data for the time averaged period from
T-1.98 to T+26.99 seconds is a power law with an exponential cutoff.
This fit gives a photon index 1.51 +- 0.13, and Epeak of 71 +- 5 keV
(chi squared 40 for 59 d.o.f).  For this model the total fluence in the
15-150 keV band is (2.04 +- 0.04) x 10^-05 erg/cm2 and the 1-sec peak
flux measured from T+11.12 sec is 48.9 +- 1.6 ph/cm2/sec.   A fit to a
simple power law gives a photon index of 1.93 +- 0.03  (chi square 68
for 59 d.o.f.)  All the quoted errors are at the 90% confidence level.

Using the lag-luminosity method of Norris et al. (2000),
and a lag measurement of 25 ms +- 5 ms (1 sigma; 100-350 keV
to 25-50 keV bands), yields a pseudo-redshift of z ~ 1.3 +- 0.3
(includes spectral uncertainties).

The remainder of the expected event data for this burst (from T-300 to T-60
sec and from T+120 to T+300) has not yet been received on the ground.  If
we see evidence for emission after T+120 sec in these data, we will
issue another circular.