{
  "bibcode": "2006GCN..5387....1P",
  "body": "D. A. Perley, R. J. Foley, J. S. Bloom and N. R. Butler (UCB) report:\n\nOn the night of 2006 July 25 (UT), we imaged the field of GRB051109B \n(GCN 4222) for 630 seconds in g' and 600 seconds in R using Keck I (+ \nLRIS).  There is a bright (R ~ 14.5) spiral galaxy close to the XRT \nposition (GCN 4226), also visible in DSS and other surveys.  In our \nimaging, the galaxy is observed to be a barred spiral of type SBa.  The \npresence of a faint tidal bridge indicates that the galaxy has recently \ninteracted with a neighboring galaxy 60\" to the north.\n\nUsing 25 X-ray sources and 51 DSS sources in the field, we calculate an \nimproved XRT position of RA = 23:01:50.21, dec = +38:40:46.0 (with a 90% \nuncertainty radius of 2.2\", including an estimate of the systematic \nerror.)  This position lies inside an outer spiral arm of the galaxy, \nidentifying it as the GRB host.  In addition, both our position and the \noriginal XRT error circle include a faint optical point-like source at \nRA = 23:01:50.30, dec = +38:40:46.7 (0.5\" uncertainty).\n\nWe obtained spectroscopy of the host galaxy and optical source the \nfollowing night.  The galaxy is observed to be at a redshift of z = \n0.080, and lacks any strong emission features.  Spectroscopy of the \npoint source inside the XRT error circle shows no evidence for a \nnebular-phase supernova; however, there are emission lines indicating \nactive star formation in this region.\n\nThe offset of the position of the optical source to the galaxy center is \n14.1\", or 20.9 kpc at the observed redshift.  This is the largest offset \nyet seen in a long GRB in angular or physical scale.  Using the 15-150 \nkeV gamma-ray fluence (GCN 4237), E_iso for this GRB is 4.1 x 10^48 \nergs, comparable to that observed for GRB980425 but less than that of \nany other GRB.  GRB980425/SN1998bw was also seen in a spiral galaxy at \nlarge offset, and also lacked a detected optical afterglow.\n\nGiven the low redshift of this system, inspection of archival images for \nthe presence or absence of supernova emission is strongly encouraged. \nWe also encourage radio and X-ray observations to look for a late-time \nafterglow or supernova.\n\nAdditional information on this GRB, including an image of the field, is \navailable at:\n\nhttp://lyra.berkeley.edu/~dperley/051109b/host.html",
  "circularId": 5387,
  "createdOn": 1154494263000,
  "email": "dperley@astro.berkeley.edu",
  "subject": "GRB 051109B:  Bright spiral host galaxy at low redshift",
  "submitter": "Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>",
  "eventId": "GRB 051109B"
}