{
  "bibcode": "2013GCN.14656....1C",
  "body": "S. B. Cenko (UC Berkeley), A Cucchiara (UCSC), D. Xu (DARK/NBI), and A. J.\nLevan (U. Warwick) report on behalf of a larger collaboration:\n\nWe obtained a single 240 s r'-band image of the field of GRB 130515A\n(Malesani et al., GCN 14650) with the Gemini Multi-Object Spectrograph\nmounted on the 8 m Gemini South telescope.  The observation commenced at\n01:59 UT (~ 38 min after the Swift trigger) under poor seeing conditions.\n\nWe identify the same 3 sources in the vicinity of the XRT error circle as\nXu et al. (GCN 14653).  For reference, we measure J2000.0 positions for\nthese sources with respect to nearby point sources from the 2MASS catalog\nto be:\n\nS1: 18:53:45.79, -54:16:47.1\n\nS2: 18:53:45.23, -54: 16:44.4\n\nS3: 18:53:46.13, -54:16:41.2\n\nWe have compared photometry from our Gemini images directly with that\nobtained by the VLT approximately 50 minutes later. For these three point\nsources, we measure the following change in magnitude (VLT - Gemini):\n\nS1: -0.37 +/- 0.18 mag\n\nS2: -0.03 +/- 0.10 mag\n\nS3: -0.03 +/- 0.10 mag\n\nThere is this marginal evidence that S1 has brightened between the two\nepochs.  However, we cannot rule out that the discrepancy results from a\ncolor difference between the two images (r' vs R).\n\nFurther observations are planned.\n\n[GCN OPS NOTE(15may13): Per author's request, the 14653 reference was\ncorrected to \"Xu et al\".]",
  "circularId": 14656,
  "createdOn": 1368599578000,
  "email": "cenko@srl.caltech.edu",
  "subject": "GRB 130515A: Gemini/GMOS Observations",
  "submitter": "S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>",
  "eventId": "GRB 130515A"
}