{
  "bibcode": "2015GCN.17522....1K",
  "body": "D. A. Kann (TLS Tautenburg), C. Delvaux and J. Greiner (both MPE Garching)\nreport on behalf of the GROND team:\n\nWe observed the field of GRB 150301B (Swift trigger 633180; Lien et al.,\nGCN #17515) 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 00:09 UT on 2015-03-02, 4.5 hrs after the GRB\ntrigger. They were performed at an average seeing of 1\".0 and at an\naverage airmass of 1.1.\n\nWe detect the optical afterglow candidate reported by Lien et al. (GCN\n#17515) and Buckley et al. (GCN #17518).\n\nBased on 7.7 min of total exposure time in g'r'i'z' and 8.0 min in JHK, \ncentered 5 hrs after the GRB, we estimate the following preliminary\nmagnitudes (all in AB system):\n\ng' = 21.7 +/- 0.2 mag,\nr' = 21.4 +/- 0.1 mag,\ni' = 21.2 +/- 0.1 mag,\nz' = 21.0 +/- 0.1 mag,\nJ = 20.5 +/- 0.3 mag,\nH = 20.6 +/- 0.4 mag, and\nK > 17.9 mag.\n\nGiven magnitudes are calibrated against GROND zeropoints (g'r'i'z') as\nwell as 2MASS field stars and are not corrected for the expected Galactic \nforeground extinction corresponding to a reddening of E_(B-V)=0.08 mag in\nthe direction of the burst (Schlegel et al. 1998).",
  "circularId": 17522,
  "createdOn": 1425261337000,
  "email": "kann@tls-tautenburg.de",
  "subject": "GRB 150301B: GROND afterglow observations",
  "submitter": "Alexander Kann at TLS Tautenburg  <kann@tls-tautenburg.de>",
  "eventId": "GRB 150301B"
}