{
  "bibcode": "2009GCN..8914....1P",
  "body": "D. A. Perley, J. S. Bloom, and N. R. Butler (UC Berkeley) report:\n\nGRB 081211B was discovered in the Swift-BAT slew survey (Copete et al, \nGCN 8661) and, based on observations by Konus-Wind (Golenetskii et al., \nGCN 8676), was classified as a possible short burst with an extended \nemission component.  We note that the GRB localization lies within a \nvisual galaxy overdensity in SDSS archival imaging, and near the centers \nof several reported clusters in the literature, which likely correspond \nto the same physically extended structure: ZW 3893, Abell 1196, and \nMaxBCG J168.22310+53.83028.\n\nRedshifts from the Sloan Digital Sky Survey of the brightest two \napparent cluster members place this cluster at a probable redshift of \nz=0.216.\n\nOn the night of 2009-02-19 (UT) we observed the field with Keck I (+ \nLRIS) for an exposure time of 990 sec (g-band) and 870 sec (R-band) \nsimultaneously through thin cloud cover.  No host galaxy underlying the \nXRT position (Page et al., GCN 8666) is detected to approximately R > \n25, g > 26 mag.  The nearest catalogued objects are:\n\nSDSS J111303.09+534953.8  g=21.26 r=20.26 i=20.03 (7\" = 24 kpc)\nSDSS J111304.73+534959.5  g=20.56 r=19.25 i=18.84 (16\" = 56 kpc)\n\nAn additional very faint extended object is located 3\" west of the \ncenter of the XRT position, outside the 90% confidence error circle. \nImages of the field (from our observations and from SDSS) are posted to:\n\nhttp://lyra.berkeley.edu/~dperley/081211b/081211b_keck.png \nhttp://lyra.berkeley.edu/~dperley/081211b/081211b_sdss.png\n\nIf the BAT detection represents extended emission from this event and no \nfainter host galaxy is found, this would constitute an additional case \nof a short GRB event with detected extended emission occurring without a \ncoincident host galaxy (after GRB 080503 - arXiv:0811.1044), as well as \nan additional example of a short burst occurring within a galaxy cluster \n(see also e.g. GRBs 050509B, 050813, 051210, 061201).  The isotropic \ngamma-ray energy release at the cluster redshift would be 7 x 10^49 erg \nin the BAT bandpass, comparable to values measured for other short GRBs.\n\nWe encourage deeper observations of the field.",
  "circularId": 8914,
  "createdOn": 1235366722000,
  "email": "dperley@astro.berkeley.edu",
  "subject": "GRB 081211B: Nearby cluster",
  "submitter": "Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>",
  "eventId": "GRB 081211B"
}