{
  "bibcode": "2010GCN.10734....1S",
  "body": "P. Schady, F. Olivares, (MPE Garching), A. Rossi (Tautenburg Obs.) and J.\nGreiner (MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of GRB 100508A (Swift trigger 421386; Margutti et\nal., GCN #10728) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.\n2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla\nObservatory (Chile).\n\nObservations started at 22:50 UT on date, 13.5 hrs after the GRB trigger,\nand were performed in poor seeing conditions and high airmass.\n\nWe detect an extended source in all four optical filters within the 1.7\nSwift-XRT refined error circle reported by Beardmore et al. (GCN #10731),\nand at a position consistent with the UVOT position reported by Landsman\net al. (GCN #10730).\n\nBased on 15.3 min of total exposures in g'r'i'z' and 16 min in JHK, we\nestimate preliminary magnitudes and upper limits in the optical and IR\nrespectively (all in AB system) of\n\ng' = 22.0 +- 0.1 mag\nr' = 21.8 +- 0.1 mag\ni' = 21.5 +- 0.1 mag\nz' = 21.7 +- 0.2 mag\nJ > 21.4\nH > 20.8\nK > 20.1\n\nat the UVOT position using aperture photometry.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as 2MASS\nfield stars and are not corrected for the expected Galactic foreground\nextinction corresponding to a reddening of E_(B-V)=0.029 in the direction\nof the burst (Schlegel et al. 1998). No correction has been applied to the\noptical magnitudes for the possible contribution from the underlying host\ngalaxy.",
  "circularId": 10734,
  "createdOn": 1273379780000,
  "email": "pschady@mpe.mpg.de",
  "subject": "GRB 100508A: GROND Detection of the optical afterglow",
  "submitter": "Patricia Schady at MPE/Swift  <pschady@mpe.mpg.de>",
  "eventId": "GRB 100508A"
}