TITLE: GCN CIRCULAR NUMBER: 18343 SUBJECT: LIGO/Virgo G184098: Pan-STARRS1 observations of the northern sky region DATE: 15/09/20 02:00:26 GMT FROM: S. J. Smartt at Queens U Belfast S.J. Smartt, K. W. Smith, ((Queenâ<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 (Queenâ<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 â<80><9c>LIBâ<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 12â<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 11â<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 3.7â<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.]