[vsnet-grb-info 6573] GRB 080905: Swift detection of a probably-short burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8180
SUBJECT: GRB 080905: Swift detection of a probably-short burst
DATE:    08/09/05 12:19:45 GMT
FROM:    Claudio Pagani at PSU/Swift-XRT  <pagani at astro.psu.edu>

C. Pagani (PSU), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), D. Grupe (PSU),
S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA),
J. Mao (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Preger (ASDC), J. L. Racusin (PSU),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA),
P. Schady (MSSL-UCL), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU),
E. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU)
report on behalf of the Swift Team:

At 11:58:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080905 (trigger=323870).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 287.662, -18.877 which is 
   RA(J2000) = 19h 10m 39s
   Dec(J2000) = -18d 52' 37"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows 3 peaks with a total 
duration of about 2 sec.  The spectrum is hard, with most response above
25 keV in the BAT energy range. The peak count rate was ~4500 counts/sec 
(15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 12:01:05.3 UT, 130.4 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 287.67363,
-18.87986 which is equivalent to:
   RA(J2000)  = 19h 10m 41.67s
   Dec(J2000) = -18d 52' 47.5"
with an uncertainty of 2.8 arcseconds (radius, 90% containment). This
location is 40 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 consistent with the Galactic value of
8.95e+20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm)  filter starting 114 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 at the location of the XRT position is 17.8 mag.  No
correction has been made for the expected extinction corresponding to
E(B-V) of 0.14. 

Burst Advocate for this burst is C. Pagani (pagani 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.)