TITLE:   GCN CIRCULAR
NUMBER:  7537
SUBJECT: GRB 080330: Swift detection of a burst with an optical counterpart
DATE:    08/03/30 04:02:22 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. Mao (INAF-OAB), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), K. M. McLean (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester), T. N. Ukwatta (GSFC/GWU) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:

At 03:41:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080330 (trigger=308041).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 169.302, +30.570 which is 
   RA(J2000) = 11h 17m 12s
   Dec(J2000) = +30d 34' 13"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiple-peak
structure with a duration of about 60 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 


The XRT began observing the field at 03:42:27.4 UT, 70.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 169.26095,
30.62298 which is equivalent to:
   RA(J2000)  = 11h 17m 2.63s
   Dec(J2000) = +30d 37' 22.7"
with an uncertainty of 3.077 arcseconds (radius, 90% containment). This
location is 229 arcseconds from the BAT onboard position, outside the
BAT error circle. 

A power-law fit to a spectrum formed from promptly downlinked event
data does not constrain the column density, so we cannot provide limits
on the redshift using spectroscopy and the relation from Grupe et al. 
(2007). A summary of the promptly downlinked data is given at
http://www.swift.ac.uk/sper/308041/. 

The initial flux in the 2.5 s image was 2.03e-09 erg cm^-2 s^-1 (0.2-10
keV). 


UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 82 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =	11:17:04.51 = 169.2688
  DEC(J2000) = +30:37:22.1  =  30.6228
with a 1-sigma error radius of about 1.0 arc sec. This position is 6.1 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 0.02. 




Burst Advocate for this burst is J. Mao (jirong.mao AT brera.inaf.it). 
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.)