{
  "bibcode": "2013GCN.15319....1P",
  "body": "D. A. Perley (Caltech) reports:\n\nI imaged the location of GRB 131004A (GCN 15303) in Ks-band with MOSFIRE \non the Keck I telescope on the night of 2013-10-07 for a total \nintegration time of 291 seconds under good seeing conditions but some \ncloud cover.  The midpoint of the integration was 07:21 UT, 2.40 days \nafter the GRB.\n\nAt the location of the optical transient reported by Xu et al. (GCN \n15304), no source is detected to a limiting magnitude of Ks > 20.6.  The \nnearest detected object to this location is a faint (Ks = 19.7), compact \nsource approximately 1.4 arcsec to the west, at RA=19:44:26.99, \ndec=-02:57:30.15.\n\nGiven the moderate redshift of z=0.717 (Chornock et al., GCN 15307), \nthese results suggest either that the host of this event is a relatively \nlow-mass galaxy or that the GRB exploded outside the bulk of the stellar \nlight of its host.  The >1.5 sec duration and significant lag reported \nin the BAT refined analysis (Lien et al., GCN 15316) may suggest the \nformer interpretation is more likely.\n\nI thank D. Malesani for providing the NOT image to verity the location \nof the optical transient.",
  "circularId": 15319,
  "createdOn": 1381224690000,
  "email": "dperley@astro.caltech.edu",
  "subject": "GRB 131004A: MOSFIRE NIR imaging",
  "submitter": "Daniel Perley at Caltech  <dperley@astro.caltech.edu>",
  "eventId": "GRB 131004A"
}