{
  "bibcode": "2008GCN..7678....1P",
  "body": "D. A. Perley, J. S. Bloom (UC Berkeley), and J. X. Prochaska (UCO/Lick) \nreport:\n\nFurther to Bloom et al. (GCN 7667), we acquired additional imaging of \nthe probable short-hard (Ukwatta et al., GCN 7677) GRB 080503 (Mao et \nal., GCN 7665) with extended emission the night after the burst.   A \ntotal of 10 exposures of 180 seconds each were taken in r-band between \nUT 14:08 and 14:46 (2008-05-04), 26 hours after the BAT trigger, using \nGMOS on Gemini-North.  In addition, we report analysis of additional \nimaging taken between 1.0-2.5 hours after the burst in g, r, i, and z \nfilters.\n\nThe source noted in our previous circular, s1, does not appear to be \nvariable between images, and no other sources are detected in the XRT \nerror circle to a very deep limit of r >~ 26.5 during the first night. \nHowever, a new source (\"s2\") appears in the second night's observation \nthat was not detected in our r-band imaging during the first night.  If \nthis source is associated with GRB 080319B this would be extremely \nunusual behavior for a short gamma-ray burst.  It is possible that the \nrebrightening is the first example of the detection of a Li-Paczynski \n\"mini\"-supernova (1998ApJ...507L..59L; see also Kulkarni \nastro-ph/0510256). More tentatively, we note that s1 may the host galaxy \n(we note that all previous SHB's with extended emission have been seen \nat small offset from their host galaxies: Troja et al., astro-ph/0711.3034).\n\nThe source is located near the center of the enhanced XRT error circle \n(Goad et al, GCN 7669) at:\n\nRA=19:06:28.766  Dec=+68:47:35.53 (J2000)\n\n(uncertainty is 250 mas in both coordinates relative to the ICRS)\n\nAnd can be seen at the following links:\nhttp://lyra.berkeley.edu/~jbloom/grb080503-comp.png\nhttp://lyra.berkeley.edu/~jbloom/grb080503-rebrightening.mpeg\nhttp://lyra.berkeley.edu/~dperley/080503/080503_s2b.png\n\nWe report the following photometry, calibrated relative to USNO-B1.0:\n\nAcquisition r-band image (t=0.98 hr)\ns1: R = 25.56 +/- 0.33\ns2: R > 25.6\n\nFirst night r-band stack (t=1.5 hr)\ns1: R = 26.00 +/- 0.18\ns2: R >~ 26.5\n\nSecond night r-band stack (t=26.0 hr)\ns1: R = 25.70 +/- 0.12\ns2: R = 25.28 +/- 0.09\n\nUT_start exposure   filter magnitude\n13:23    1x180      r      R = 24.8 +/- 0.3\n13:38    1x30+2x300 R      R > 25.5 (2-sigma)\n13:47    5x180      r      R = 25.4 +/- 0.2\n\nPhotometric uncertainties do not include calibration uncertainties \nrelative to USNO-B1.0, which are at the level of 0.1 magnitude.  (This \ndoes not affect the relative magnitudes between the images).\n\nIn our images in other filters, s2 is not detected in i-band or z-band \nduring the first night.  It may be marginally detected in g-band imaging \nnear the limiting magnitude of that observation.\n\nFurther observations of this source are planned and strongly encouraged.",
  "circularId": 7678,
  "createdOn": 1209962989000,
  "email": "dperley@astro.berkeley.edu",
  "subject": "GRB 080503: Late-time Optical rebrightening (possible mini-SN)",
  "submitter": "Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>",
  "eventId": "GRB 080503"
}