GCN Circular 13666

S. T. Holland (STScI) and
C. Pagani (U Leicester)
report on behalf of the Swift/UVOT team:

     The Swift/UVOT observed the field of GRB 120815A starting 2672 s
after the BAT trigger (Pagani et al., 2012, GCNC 13645).  Settled
observations started at 2690 s.  We detect an uncatalogued source
inside the UVOT-enhanced XRT error circle (Goad et al., 2012, GCNC
13650) with preliminary coordinates

   RA (J2000.0)  18:15:49.88  =  273.95783 (deg)
  Dec (J2000.0) -52:07:52.1   =  -52.13114 (deg)

and an estimated uncertainty of 0.6 arcsec (radius, 90% confidence,
statistical + systematic).  The UVOT detection is consistent with the
optical afterglow reported by Sudilovsky et al. (2012, GCNC 13648)
Source magnitudes and 3-sigma upper limits at this location are given
below.  The afterglow is 4.27 arcsec northeast of the USNO-B1.0 source
0378-0977505, so the following photometry should be considered
preliminary.

Filter       TSTART   TSTOP   Exp Time       Mag  Err  Sigma
------------------------------------------------------------
    v         2847     3046        100     19.34 0.29    3.9
    b         3667     4120        226     20.11 0.24    4.7
    u         3462     3661        100    >20.5
 uvw1         3257     3457        100    >20.2
 uvm2         3052     3252        100    >19.9
 uvw2         4330     4530        100    >20.3
white         2690     2840         75     19.94 0.19    5.8
------------------------------------------------------------

    The quoted magnitudes and upper limits have not been corrected for
the Galactic extinction along the line of sight to this burst of
E_{B-V} = 0.10 mag (Schlafly et al. 2011, ApJS, 737, 103).