TITLE: GCN CIRCULAR NUMBER: 16766 SUBJECT: GRB 140903A: Coincident galaxy cluster in archival images DATE: 14/09/03 18:53:21 GMT FROM: Derek Fox at PSU Derek B. Fox (PSU) and J. R. Cummings (NASA/UMBC) report: "The BAT (Cummings, GCN 16765) and XRT (Kennea & Cummings, GCN 16764) localizations of GRB 140903A (Cummings et al., GCN 16763) are located within 2.5' (<0.2 Mpc projected) of the center of the galaxy cluster NSC J155202+273349, as cataloged by the Northern Optical Cluster Survey (Gal et al. 2003, AJ, 125, 2064). While the photometric redshift for the cluster is provided as z=0.2955 in the catalog, four of the five SDSS-resolved galaxies nearest the XRT position have spectroscopic redshifts (SDSS and 2MASX surveys, as retrieved from the NASA Extragalactic Database) within the range z=0.074 +/- 0.001. In particular, the two nearest galaxies with known redshifts are SDSS J155208.34+273631.8 at z=0.073 (1.05' distance) and 2MASX J15520787+2735016 at z=0.075 (1.47' distance). Given past associations (and proposed associations) of short bursts with evolved galaxies and galaxy clusters at z<~0.3 we consider the presence of this coincident galaxy cluster at z~0.074 suggestive." This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.