[vsnet-grb-info 5727] GRB 080310: Swift detection of a burst with optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7382
SUBJECT: GRB 080310: Swift detection of a burst with optical afterglow
DATE:    08/03/10 08:58:27 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc at milkyway.gsfc.nasa.gov>

J. R. Cummings (NASA/UMBC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
P. A. Evans (U Leicester), E. A. Hoversten (PSU),
S. D. Hunsberger (PSU), C. B. Markwardt (CRESST/GSFC/UMD),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), R. L. C. Starling (U Leicester),
G. Tagliaferri (INAF-OAB) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift Team:

At 08:37:58 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080310 (trigger=305288).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 220.081, -0.166 which is 
   RA(J2000) = 14h 40m 19s
   Dec(J2000) = -00d 09' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a precursor at
T-24 seconds and multiple peaks from T-10 to T+6 seconds. The peak count 
rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 08:39:27.9 UT, 89.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 220.0566, -0.1756 which is equivalent to:
   RA(J2000)  = 14h 40m 13.5s
   Dec(J2000) = -00d 10' 32.1"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 94 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to assess possible
redshift constraints using X-ray spectroscopy and the nH-z relation
from Grupe et al. (2007). 

UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 99 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =	14:40:13.80 = 220.0575
  DEC(J2000) = -00:10:29.6  =  -0.1749
with a 1-sigma error radius of about 0.6 arc sec. This position is 4.1 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 18.8 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.04. 

Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.nasa.gov). 
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.)