{
  "bibcode": "2012GCN.13267....1P",
  "body": "D. A. Perley (Caltech), A. Cucchiara (UCO/Lick), S. B. Cenko (UC \nBerkeley), A. J. Levan (Warwick), S. R. Kulkarni, S. Ben-Ami, and Y. Cao \n(Caltech) report:\n\nWe conducted a second epoch of imaging at the position of GRB 120422A \n(Troja et al., GCN 13243) with GMOS-N on Gemini-North starting at 05:42 \nUT on 2012-04-26 in each of the griz filters.  Seeing conditions were \nexcellent (0.7\"), cleanly resolving the transient previously identified \nby Cucchiara et al. (GCN 12345) from its putative host galaxy.  A curved \nbridge of emission connects the transient with the host, suggesting it \noccurred either in a spiral arm (however no counter-arm is visible on \nthe far side of the galaxy) or within an interacting companion.  An \nimage is posted to:\n\nhttp://www.astro.caltech.edu/~dperley/gcn/120422a/120422a_gmos.png\n\nThe transient has clearly faded since the last observations, and is now \nat r = 22.05 +/- 0.09 mag, i = 22.31 +/- 0.07 mag (using a 0.7\" radius \naperture and calibrating relative to SDSS standards, with the \nuncertainties due almost entirely to the systematics of the color \ncomparison).  This would indicate a relatively blue color.  However, the \n(nearly contemporaneous) g-band flux lies approximately 1 magnitude \nbelow a simple extrapolation of the r-i color, indicating that the SED \npeaks in or near the r-band range.\n\nAs previously noted by Schulze et al. (GCN 13257) on the basis of the \nblue UVOT color, this type of SED is very unusual for traditional GRB \nafterglows (which normally are power-laws in the optical band) but \nsimilar properties have been seen at early times in GRBs 060218 (e.g. \nCampana et al., Nature 442:1008), as well as GRBs 100316D (Starling et \nal. 2011, MNRAS 411:2792), and 101225 (Th�ne et al. 2011, Nature \n480:72).  We suggest that the apparent color evolution of the peak \nwavelength of the transient from the UV to the optical and NIR is likely \nto continue in subsequent days, and encourage multi-band photometric \nfollow-up as well as spectroscopy.\n\nAdditionally, on the night of 2012-04-27 UT we acquired 30 minutes of \nspectroscopy using LRIS on the Keck 10m telescope.  A preliminary flux \ncalibration of the spectrum shows a similar signature as evident in the \nphotometry, with a pronounced, smooth peak around 6500 Angstroms.  No \nobvious absorption or emission features are evident except for the \nnarrow emission lines from the underlying host, previously mentioned by \nTanvir et al. (GCN 13251) and Schulze et al. (GCN 13257).   In \nparticular, we do not yet recognize any broad supernova signatures. \nFurther observations are planned.",
  "circularId": 13267,
  "createdOn": 1335545133000,
  "email": "dperley@astro.caltech.edu",
  "subject": "GRB 120422A: Additional Gemini observations and Keck/LRIS spectroscopy",
  "submitter": "Daniel Perley at Caltech  <dperley@astro.caltech.edu>",
  "eventId": "GRB 120422A"
}