{
  "bibcode": "2010GCN.10750....1P",
  "body": "D. A. Perley, C. R. Klein, and A. N. Morgan (UC Berkeley) report:\n\nWe began observing the location of the afterglow of GRB 100513A \n(Baumgartner et al., GCN 10746) at 04:06 UT using the Nickel 40-inch \ntelescope at Lick Observatory.  A total of fourteen 300-second images \nwere acquired in the R-band under clear sky conditions.\n\nA co-add of the first 9 images (midpoint 04:35 UT) reveals a faint point \nsource at the position reported by Morgan et al (GCN 10747).  The source \nis near the detection limit of the co-add and is not detected in \nindividual images.\n\nPhotometry of the object relative to three nearby SDSS stars (converted \nto Rc via the Lupton transformation equation) gives the following magnitude:\n\nR = 21.39 +/- 0.25    (t_mid = 2.46 hours)\n\nWe note that this is significantly fainter than expected from the \npreliminary JHK magnitudes of Morgan et al (GCN 10749).  The IR spectral \nindex is relatively flat (beta~0.5), suggesting little host extinction. \n  Assuming no extinction in addition to the Galactic value, a direct \npower-law extrapolation of the JHK data to R-band over-predicts the \nobserved flux by >2 magnitudes, strongly suggesting an R-band dropout \nand likely redshift of 4.6 < z < 6.0.  We note also that the X-ray \ncolumn is consistent with no absorption beyond Galactic (Baumgartner et \nal.), consistent with a high-redshift origin.\n\nWe encourage I/z/Y-band follow-up to better constrain the redshift and \ndust extinction.  Spectroscopic observations are planned.",
  "circularId": 10750,
  "createdOn": 1273734187000,
  "email": "dperley@astro.berkeley.edu",
  "subject": "GRB 100513A: Lick observations and R-band dropout",
  "submitter": "Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>",
  "eventId": "GRB 100513A"
}