{
  "bibcode": "2012GCN.13840....1S",
  "body": "S. Schmidl (TLS Tautenburg), D. A. Kann (MPE Garching), S. Klose (TLS\nTautenburg), and J.Greiner (MPE Garching) report on behalf of the GROND\nteam:\n\nWe observed the field of GRB 121001A (Swift trigger 535026, D'Elia et al.,\nGCN # 13831) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla\nObservatory (Chile).\n\nObservations started on October 01, 2012, at 23:37 UT, 5.23 hr after the\nGRB trigger. They were performed at an average seeing of 2\".7 (in r') and\nat an average airmass of 1.2.\n\nWe found a source in the z', J, H and K bands at coordinates (J2000):\n\nRA   =  18:24:07.84\n\nDec. = -05:39:55.30\n\nwith an error of 0\".3 in each coordinate.\n\nThis is consistent with the afterglow positions reported by Andreev et al.\n(GCN # 13833) and Tello et al. (GCN # 13835), but slightly outside the\nrefined XRT position reported by Evans et al. (GCN # 18837).\n\nBased on 1380 s of total exposures in g'r'i'z' (mean time 0.2415 days\nafter the trigger) and 1920 s in JHK (mean time 0.2363 days after the\ntrigger) we estimate preliminary AB magnitudes (upper limits are 3 sigma) of\n\ng' > 23.6,\n\nr' > 22.9,\n\ni' > 22.2,\n\nz' = 21.7 +/- 0.2,\n\nJ  = 19.5 +/- 0.4,\n\nH  = 18.4 +/- 0.1 and\n\nK  = 17.94 +/- 0.06.\n\nGiven magnitudes are calibrated against GROND zeropoints in the optical as\nwell as 2MASS field stars in the NIR and are not corrected for the high\nGalactic foreground reddening of E_(B-V) ~ 1.3 mag (Schlegel et al. 1998).\n\nOur r'- and i'-band non-detections vs. the detections reported by Andreev\net al. (GCN # 13833) and Tello et al. (GCN # 13835) confirm that this is\nthe afterglow of GRB 121001A. Furthermore, the bright source we detect in\nK is not detected in 2MASS, while nearby sources of similar magnitude are\nclearly visible in 2MASS.",
  "circularId": 13840,
  "createdOn": 1349221574000,
  "email": "kann@tls-tautenburg.de",
  "subject": "GRB 121001A: GROND Afterglow Confirmation",
  "submitter": "Alexander Kann at TLS Tautenburg  <kann@tls-tautenburg.de>",
  "eventId": "GRB 121001A"
}