{
  "bibcode": "2006GCN..5238....1B",
  "body": "GRB 060502B: A Bright Early-type Galaxy as Putative Host of the Short  \nBurst\n\nJ. S. Bloom, D. Perley, D. Kocevski, N. Butler (UC Berkeley), J. X.  \nProchaska (UCO/Lick), and H.-W. Chen report:\n\nOn 31 May 2006 UT, using Keck I (+LRIS), we obtained spectra of a  \nbright red extended source (\"G*\"; RA, DEC J2000 = 18:35:45.7,  \n+52:37:37) that is 11.2 arcsec South of the southern edge of the  \nrevised XRT error circle (Troja et al. GCN 5093). Strong absorption  \nfeatures, which we identify as Ca II H+K, indicate a redshift for  \nthis early type galaxy of z=0.287. Weak [OII] emission can be seen  \nindicating some low level of active star formation.\n\nWe advance the hypothesis that this galaxy is the host of short burst  \nGRB 060502B (Troja et al. GCN 5055) based on several points:\n\n      1. The galaxy is a massive early-type similar to the putative  \nhosts of 050509B [1] and 050724 [2].\n\n      2. The redshift inferred of the hosts of 050509b (z=0.225) and  \n050724 (z=0.258) are remarkably similar to that of G* indicating  \ncomparable energetics of the respective bursts.\n\n      3. At the redshift of z=0.287, the burst location would be  \nbetween 47 - 67 kpc in projection from the center of the putative  \nhost, similar to the offset (39 +/- 13 kpc) inferred for 050509b.  \nThere are viable progenitors scenarios (e.g. degenerate binary  \nmergers) where bursts occur at such distances from their birthsite.\n\n      4. Weak X-ray afterglow and no detected optical afterglow would  \nseem to indicate a low density circumburst environment, as would be  \nexpected if the GRB originated far from the progenitor birthsite.\n\nWe recognize the difficulty of now confirming this hypothesis but  \nnote that in the striking similarity of the host, redshift,  \nafterglow, and offset configuration to GRB 050509b, these  \nobservations and inferences have a priori precedent.\"\n\nA false color image will be posted at:\n   http://astro.berkeley.edu/~jbloom/grb060502B_color_keck1.gif\n\nThis message may be cited.\n\n[1] Bloom et al. 2006ApJ...638..354B (astro-ph/0505480); Gehrels et  \nal. 2005Natur.437..851G (astro-ph/0505630)\n[2] Berger et al. Nature 438 (2005) 988-990 (astro-ph/0508115)",
  "circularId": 5238,
  "createdOn": 1149676609000,
  "email": "jbloom@astron.berkeley.edu",
  "subject": "GRB 060502B: A Bright Early-type Galaxy as Putative Host of the Short Burst",
  "submitter": "Josh Bloom at UC Berkeley  <jbloom@astron.berkeley.edu>",
  "eventId": "GRB 060502B"
}