GCN Circular 10863

J. K. Cannizzo (NASA/UMBC), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC),
J. Mao (INAF-OAB), R. Margutti (INAF-OAB), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/IASFPA),
M. H. Siegel (PSU), M. A. Stark (PSU) and T. N. Ukwatta (GSFC/GWU)
report on behalf of the Swift Team:

At 00:21:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100619A (trigger=424998).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 84.615, -27.001 which is 
   RA(J2000) = 05h 38m 28s
   Dec(J2000) = -27d 00' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed two well-separated
peaks about 90 seconds apart with an overall duration of about 120 sec. 
The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after
the trigger for the first peak, and 5000 counts/sec (15-350 keV) at
~95 sec after the trigger for the second peak. 

The XRT began observing the field at 00:22:23.7 UT, 76.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
84.6227, -27.0049 which is equivalent to:
   RA(J2000)  = 05h 38m 29.46s
   Dec(J2000) = -27d 00' 17.8"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 27 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2e+20
cm^-2, Kalberla et al. 2005), with an excess column of 3.8
(+1.95/-1.69) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 0.1 s image was 5.61e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter starting 87 seconds after the BAT trigger. No credible
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 typical
3-sigma upper limit has been about 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 0.03. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo 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.)