{
  "bibcode": "2012GCN.13891....1K",
  "body": "F. Knust, P. Schady and J. Greiner (all MPE Garching) report on behalf  \nof the GROND team\n\nWe observed the field of GRB 121024A (Pagani et al., GCN 13886)  \nsimultaneously in g'r'i'z' with GROND (Greiner et al. 2008, PASP, 120,  \n405) mounted on the 2.2 m MPG/ESO telescope at La Silla Observatory  \n(Chile).\n\nDue to clouds, observations only started at 05:53 UT no 24th October,  \n3 hours after the GRB trigger, and continued until the end of the  \nnight, 3.8 hours later. They were performed at an average seeing of  \n1.4\" and at an average airmass of 1.1.\n\nWe find a single point source within the 0.8 arcsec Swift/UVOT error  \ncircle reported by Pagani et al. (GCN 13886) at\n\nRA (J2000.0) = 04:41:53.30\nDec (J2000.0) = -12:17:26.5\n\nwith an uncertainty of 0.4\" in each coordinate.\n\nBased on the first 142 sec integration in g'r'i'z' and 240 sec  \nintegration in JHK taken at a mid-time of 05:58 UT and 05:54 UT in the  \noptical and NIR respectively, we estimate preliminary magnitudes (all  \nin AB system) of\n\ng' = 21.0 +/- 0.2 mag\nr' = 20.1 +/- 0.2 mag\ni' = 19.8 +/- 0.2 mag\nz' = 19.5 +/- 0.2 mag\nJ = 18.7 +/- 0.1 mag\nH = 18.4 +/- 0.1 mag\nK = 17.9 +/- 0.1 mag\n\nGiven magnitudes are calibrated against GROND zeropoints in the  \noptical, and 2MASS field stars in the NIR, and are not corrected for  \nthe expected Galactic foreground extinction corresponding to a  \nreddening of E(B-V) = 0.1 mag in the direction of the burst (Schlegel  \net al. 1998).",
  "circularId": 13891,
  "createdOn": 1351078270000,
  "email": "pschady@mpe.mpg.de",
  "subject": "GRB 121024A: GROND Detection of the Optical/NIR Afterglow",
  "submitter": "Patricia Schady at MPE/Swift  <pschady@mpe.mpg.de>",
  "eventId": "GRB 121024A"
}