M. Stamatikos (NASA/ORAU), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. Immler (GSFC/USRA), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (NASA/ORAU), P. Schady (MSSL-UCL) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:
At 04:44:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070220 (trigger=261299). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 34.819, +68.818 which is
RA(J2000) = +02h 19m 17s
Dec(J2000) = +68d 49' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple peaks
with a duration of about 60 sec. The peak count rate
was ~7000 counts/sec (15-350 keV), at ~15 sec after the trigger.
The XRT began observing the field at 04:45:51 UT, 79 seconds after the
BAT trigger. XRT found a bright, fading, uncatalogued X-ray source
located at RA, Dec 34.7765, +68.8052 which is
RA(J2000) = 02h 19m 06.3s
Dec(J2000) = 68d 48' 18.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment).
This location is 72 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 4.5e-09 erg/cm2/s (0.2-10 keV).
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 88 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 in a 100s white band exposure is 19.6 mag. The 8'x8'
region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about
18 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.90.