GRB 070920

D. Grupe (PSU), N. Gehrels (NASA/GSFC), F. E. Marshall (NASA/GSFC),
C. Pagani (PSU), D. M. Palmer (LANL), J. L. Racusin (PSU),
G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU),
T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the
Swift Team:

At 04:00:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070920 (trigger=291614). 
The BAT on-board calculated location is 
RA, Dec 100.932, +72.227 which is 
   RA(J2000) = 06h 43m 44s
   Dec(J2000) = +72d 13' 38"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is often the case with 64-second
image triggers, the BAT light curve shows no obvious
variation in the count rate. 

Because Swift is in the process of returning to normal operations, 
automatic slewing to GRBs is currently disabled.  Therefore, there 
are no prompt XRT or UVOT observations of this burst. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 070920 detected by SWIFT
(trigger 291614) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 544.7s after the GRB trigger
(6.8s after the notice). The elevation of the field increased from
from 57 degrees above horizon and weather conditions
were excellents.

The date of trigger : t0 = 2007-09-20T04:00:14.112

The first image is 90.0s exposure in tracking mode:
t0+544.7s to t0+634.7s : R > 18.2

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=142.6283 lat=+25.1560
and the galactic extinction in R band is 0.3 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.

L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-119 to T+300 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070920 (trigger #291614)
(Grupe, et al., GCN Circ. 6805
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 100.968, 72.250 deg which is 
   RA(J2000) =  06h 43m 52.2s 
   Dec(J2000) = 72d 14' 59" 
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted lightcurve shows a single peak (with structure) starting
at ~T-15 sec, broadly peaking at ~T+25 sec, and ending at ~T+140 sec.
T90 (15-350 keV) is 56 +- 1 sec (estimated error including systematics).
 
The time-averaged spectrum from T+15.1 to T+75.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.69 +- 0.21.  The fluence in the 15-150 keV band is 5.1 +- 0.7 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+30.45 sec in the 15-150 keV band
is 0.3 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.