{
  "bibcode": "2017GCN.22198....1S",
  "body": "S. Schmidl (TLS Tautenburg) and P. Schady (MPE Garching) report:\n\nWe observed the field of GRB 171205A (Swift trigger 794972; D'Elia et al.,\nGCN 22177) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla\nObservatory (Chile).\n\nObservations started at 07:30 UT on December 05, 2017, 10 minutes after\nthe GRB trigger. They were performed at an average seeing of 1.5\" and at\nan average airmass of 1.5.\n\nWe clearly detect the optical/NIR transient of GRB 171205A (Izzo et al.,\nGCN 22180; Emery & D'Elia, GCN 22181; Butler et al., GCN 22182; Mao et\nal., GCN 22186; de Ugarte Postigo et al., GCN 22187; Choi et al., GCN\n22188; Melandri et al., GCN 22189; Steeghs et al., GCN 22190; Cobb et al.,\nGCN 22192; Volnova et al., GCN 22193; Guidorzi et al., GCN 22197).\n\nBased on total exposures of 66 seconds in g'r'i'z', 60 seconds in JH and\n180 seconds in K at a midtime of 0.36 hours after the burst, we measure\nthe following preliminary magnitudes and upper limits (AB magnitude\nsystem):\n\ng' = 19.1 +/- 0.1 mag,\nr' = 18.9 +/- 0.1 mag,\ni' = 18.9 +/- 0.1 mag,\nz' = 18.8 +/- 0.1 mag,\nJ  = 18.4 +/- 0.2 mag,\nH  = 18.2 +/- 0.3 mag, and\nK  > 17.6 mag.\n\nMagnitudes and upper limits are calibrated against PanSTARRS and 2MASS\nfield stars and are not corrected for the Galactic foreground extinction\ncorresponding to a reddening of E_(B-V)= 0.05 mag in the direction of the\nburst (Schlegel et al. 1998).\n\nObservations are continuing.",
  "circularId": 22198,
  "createdOn": 1512657754000,
  "email": "schmidl@tls-tautenburg.de",
  "subject": "GRB 171205A: GROND observations of the optical/NIR transient",
  "submitter": "Sebastian Schmidl at TLS Tautenburg  <schmidl@tls-tautenburg.de>",
  "eventId": "GRB 171205A"
}