TITLE:   GCN CIRCULAR
NUMBER:  7573
SUBJECT: GRB 080409: Swift detection of a burst
DATE:    08/04/09 01:46:36 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. T. Holland (CRESST/USRA/GSFC), W. H. Baumgartner (GSFC/UMBC),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
K. M. McLean (GSFC/UMD), K. L. Page (U Leicester),
D. M. Palmer (LANL), R. L. C. Starling (U Leicester) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 01:22:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080409 (trigger=308812).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 84.333, +5.085 which is 
   RA(J2000) = 05h 37m 20s
   Dec(J2000) = +05d 05' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 10 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~0.7 sec after the trigger. 

The XRT began observing the field at 01:24:21.6 UT, 84.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 84.33035, 5.08523 which
is equivalent to:
  RA(J2000)  = 05h 37m 19.28s
  Dec(J2000) = +05d 05' 06.8"
with an uncertainty of 2.9 arcseconds (radius, 90% containment). This
location is 9.5 arcseconds from the BAT onboard position, within the
BAT error circle. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.34e+21
cm^-2, Kalberla et al. 2005), with an excess column of 4.5
(+4.33/-3.19) x 10^21 cm^-2 (90% confidence). The relation of Grupe et
al. (2007) implies that this burst has a redshift z<4.3, although high
redshift fits to the absorbed XRT spectrum are possible if paired with
an anomalously large column. A summary of the promptly downlinked data
is given at http://www.swift.ac.uk/sper/308812/. 

UVOT took a finding chart exposure of  95 seconds with the White (160-650 nm)
filter starting 87 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The 3-sigma upper limit is about 19.5 mag. 
No correction has been made for the expected extinction corresponding to E(B-V)
of 0.78 mag. 

Burst Advocate for this burst is S. T. Holland (sholland 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.)