A. M. Parsons (GSFC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL) and E. Troja (U Leicester/INAF-IASFPA) report on
behalf of the Swift Team:
At 21:22:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080517 (trigger=311874). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 102.255, +50.731 which is
RA(J2000) = 06h 49m 01s
Dec(J2000) = +50d 43' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peaked
structure with a duration of about 20 sec. The peak count rate
was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 21:24:57.5 UT, 125.5 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 102.24274,
50.73512 which is equivalent to:
RA(J2000) = 06h 48m 58.26s
Dec(J2000) = +50d 44' 06.4"
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This
location is 31 arcseconds from the BAT onboard position, within the BAT
error circle. We note that a known, 18th magnitude optical source lies
within our error circle; this is identified as a galaxy, EO0691-0008689,
in the APM-North survey.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.12e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.70/-1.44) x 10^21 cm^-2 (90% confidence). The relation of Grupe et
al. (2007) implies that this burst has a redshift z<4.8, 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/311874/.
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 130 seconds after the BAT trigger. A
400 second exposure with the V filter was taken starting 236 seconds
after the BAT trigger. There is no evidence for an afterglow,
however there is a known object within the XRT error circle visible
in the UVOT images. The 2.7'x2.7' sub-image covers 100% of the XRT
error circle. The typical 3-sigma upper limit has been about 18.5
mag in both images. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.11.
Burst Advocate for this burst is A. M. Parsons (parsons 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.)