{
  "bibcode": "2009GCN..9481....1C",
  "body": "B. E. Cobb (UC Berkeley) reports:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained\noptical/IR imaging of the error region of GRB 090531b (GCN 9461, Cummings\net al.) over two epochs with mid-exposure times of 2009-06-01 02:56 UT\nand 2009-06-02 05:26 UT (8.3 and 34.8 hours post-burst). Total summed \nexposure times for each observation amounted to 36 minutes in R and\n30 minutes in J.\n\nWhile there are a number of sources in and around the position of\nthe GRB X-ray afterglow (GCN 9463, Sbarufatti et al.; GCN 9480, Rossi\net al.), image differencing of the two epochs using the ISIS image\nsubtraction program does not reveal any significant variable source.  The\nsky limiting magnitude of the images is I>21.1 and J>18.5 (where optical\nphotometry is calibrated using USNO-B1 stars and IR photometry with 2MASS;\nthese limits have not been corrected for Galactic reddening).",
  "circularId": 9481,
  "createdOn": 1243979432000,
  "email": "bcobb@astro.berkeley.edu",
  "subject": "GRB 090531b, SMARTS optical/IR observations",
  "submitter": "Bethany Cobb at UC Berkeley  <bcobb@astro.berkeley.edu>",
  "eventId": "GRB 090531B"
}