GCN Circular 18343

S.J. Smartt, K. W. Smith,  ((Queen��<80><99>s University Belfast),K. Chambers,
M. Huber, E. Magnier, H. Flewelling, C. Waters, J. Tonry, A. Schultz,
N. Primak (IfA, University of Hawaii), D. Young, D. Wright
(Queen��<80><99>s University Belfast), C. Stubbs (Harvard)

Following our report of Pan-STARRS pointing coordinates for the field
of LIGO/Virgo G184098, we have carried out difference imaging of the
i, z and y-band exposures with respect to the Pan-STARRS1 3Pi
reference sky stacks. The nine Pan-STARRS fields were centred on the
��<80><9c>LIB��<80><9d> localisation map, although were observed during astronomical
twilight and airmass between 2.8 and 2. The difference images were
processed as described in Huber et al. (Atel 7153) and on the
Pan-STARRS Survey for Transients (PSST) pages
(http://star.pst.qub.ac.uk/ps1threepi/psdb/).
An initial sift through the data, with machine learning algorithms
and human eyeballing resulted in the following candidates within the
northern LIGO/Virgo error region for G184098. All candidates were detected
in two filters.

Three fairly secure candidates were discovered and about a dozen other
more marginal detections (variable stars and variable known AGNs are not considered).
We prefer to wait for another epoch to confirm/discount the other dozen or so
candidates. The three candidates which appear secure, and
are most likely supernovae are as follows (a sky map will be uploaded to
GraceDB). They lie within the central 20% probability map and
all have z-i colours which are not particularly red.

We emphasise that we did not dither and the GPC1 camera has an 80%
fill factor, therefore we do not claim to be complete in this region.

They all appear to be consistent with being normal population supernovae,
but spectroscopic observations would be useful.

PS15cbm
08:49:19.85 +03:48:17.9
i=18.6 +/- 0.1
12��<80><9d> from the core of galaxy 2MASX J08492024+0348280, located
within its visible optical disk.
With a spectroscopic z=0.059 (250 Mpc) it has M_i = -18.6 (A_i=0.07)
This is consistent with being a supernova

PS15cbj
08:38:49.71 +05:00:16.4
i=18.2 +/- 0.1
11��<80><9d> from the core of 2MASX J08385048+0500140
with spectroscopic z=0.076 (330 Mpc). Hence,
M_i = -19.5 (A_i=0.06)
This is consistent with being a supernova, although it
is quite bright and some 15kpc projected from the host.

PS15cbn
08:52:38.36 +06:49:50.4
i=18.8 +/- 0.1
3.7��<80><9d> from the galaxy SDSS J085238.20+064947.6
which has no spectroscopic redshift. The object appears
to be a supernova (A_i = 0.1)

[GCN OPS NOTE(19sep15): This Circular was originally published on 19:58 18-Sep-2015 UT.]