{
  "bibcode": "2012GCN.13335....1R",
  "body": "A. Rossi (TLS Tautenburg), M. Nardini (Universita' degli Studi\nMilano-Bicocca), S. Klose (TLS Tautenburg), and J. Greiner (MPE\nGarching) report on behalf of the GROND team:\n\nWe observed the field of GRB 120521A (Swift trigger 522578; Chester\net al., GCN 13302) simultaneously in g'r'i'z'JHKs with GROND (Greiner\net al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at\nLa Silla Observatory (Chile).\n\nObservations started at 22:53 UT on 2012-05-21, 16.9 h after the GRB\n  trigger, and lasted for 100 minutes.  They were performed under good\n  sky conditions at an average seeing of 0.9 and at an average airmass\n  of 1.1.\n\nUsing an exposure of 50 minutes in the optical and 40 minutes in the\nNIR we do not detect any source within the Swift-XRT error circle\nreported by Goad et al. (GCN 13304).  Preliminary observed upper\nlimits (AB mags) are:\n\ng' > 25.5\nr' > 25.0\ni' > 24.0\nz' > 23.7\nJ > 20.9\nH > 20.3\nK > 19.1\n\nThe given limits are derived based on calibrating the images against\nGROND zeropoints (g'r'i'z') and 2MASS stars (JHK).  We note that the\nGalactic reddening along the line of sight is E_(B-V)= 0.43 mag\n(Schlegel et al. 1998).",
  "circularId": 13335,
  "createdOn": 1337706693000,
  "email": "rossi@tls-tautenburg.de",
  "subject": "GRB 120521A: GROND Upper limits",
  "submitter": "Andrea Rossi at TLS Tautenburg  <rossi@tls-tautenburg.de>",
  "eventId": "GRB 120521A"
}