GCN Circular 18310

K.L. Page (U. Leicester), M. H. Siegel (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 150912A (Mereghetti et al. GCN Circ. 18291
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 ), collecting 4.7
ks of Photon Counting (PC) mode data between T0+32.6 ks and T0+50.4 ks.


No X-ray sources have been detected inside or close to the INTEGRAL
error region. The 3-sigma upper limit in the field ranges from ~0.002
to ~0.004 ct s^-1, corresponding to a 0.3-10 keV observed flux of
9.0e-14 to 1.5e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).

Two uncatalogued sources were detected too far from the GRB position to
be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020557.

Swift-UVOT also began settled observations of the field of GRB 150912A
32.6 ks after the INTEGRAL trigger. No optical afterglow consistent
with the INTEGRAL position is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial
exposures are:

Filter	       T_start(s)   T_stop(s)	   Exp(s)	  Mag

w2		 32643	      50446	    4789	 >21.2

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.42 in the direction of
the burst (Schlegel et al. 1998).

This circular is an official product of the Swift-XRT and UVOT teams.