[vsnet-grb-info 15039] Swift Trigger 600114 in M31: Archival and Prompt UVOT Imaging

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16333
SUBJECT: Swift Trigger 600114 in M31: Archival and Prompt UVOT Imaging
DATE:    14/05/28 03:19:10 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel at swift.psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

Archival UVOT images of the transient reported in M31 (Barthelmy et al., GCN Circ. 16332)
from July 2009 and November 2011 show the known globular cluster B045-G108 at the reported
UVOT position, 4.5 arc-seconds from the position of the X-ray transient.  Although a direct comparison
is not possible at this time, we measure the following magnitudes for the object, before and after the
trigger, using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373):

Archival:
Filter            Mag
uvw2           19.4+-0.1
uvm2           19.6+-0.2
uvw1           18.2+-0.1

Prompt:
u              17.1+-0.2
white          16.9+-0.1

The post-explosion u magnitude would be roughly consistent with the pre-explosion NUV magnitudes
given the SED of a typical M31 globular cluster.  However, without processing of the full
post-outburst data set, we cannot determine if the source has varied in the UV since 2011.