GCN Circular 23797

S. D. Barthelmy (GSFC), J. A. Kennea (PSU), N. J. Klingler (PSU),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), B. Sbarufatti (PSU)
and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 00:56:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located MAXI J1348-630 (trigger=885960).  Swift slewed immediately to the source. 
The BAT on-board calculated location is 
RA, Dec 207.035, -63.268 which is 
   RA(J2000) = 13h 48m 08s
   Dec(J2000) = -63d 16' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is normal for an image trigger, the 
light-curve showed no significant structure. 

The XRT began observing the field at 00:59:18.9 UT, 189.3 seconds after
the BAT trigger. XRT found a bright X-ray source located
at RA, Dec 207.0558, -63.2733 which is equivalent to:
   RA(J2000)  = 13h 48m 13.39s
   Dec(J2000) = -63d 16' 23.9"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy. 

The initial flux in the 2.5 s image was 1.09e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 197 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	13:48:12.84 = 207.05348
  DEC(J2000) = -63:16:28.5  = -63.27458
with a 90%-confidence error radius of about 0.61 arc sec. This position is 5.9
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.99 with a 1-sigma error of about  0.14. No correction has been made for the
large, but uncertain, extinction expected. This source is consistent with the
location of the previously reported optical transient associated with MAXI J1348-630
(ATEL #12430).