GCN Circular 43529

N. J. Klingler (GSFC/UMBC/CRESSTII), R. Gupta (NASA GSFC),
J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
K. L. Page (U Leicester), T. M. Parsotan (GSFC) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 17:50:34 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 260127A (trigger=1444088).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 231.857, +6.758 which is 
   RA(J2000) = 15h 27m 26s
   Dec(J2000) = +06d 45' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed no
structure initially, typical of an image trigger, with a more 
classic pulse structure starting at ~T0+20 sec. The emission 
has a duration of about 50 sec.  The peak count rate was ~1460 
counts/sec (15-350 keV), at ~33 sec after the trigger.

The XRT began observing the field at 17:54:00.1 UT, 205.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 231.87885, 6.76345
which is equivalent to:
   RA(J2000)  = 15h 27m 30.92s
   Dec(J2000) = +06d 45' 48.4"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 80 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 https://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 (4.07 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2
(+2.30/-2.03) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 4.58e-10 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 213 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 none of
the XRT error circle. 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 0.049.

Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.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/)