{
  "bibcode": "2013GCN.15034....1T",
  "body": "M. Tanga (MPE Garching), F. Olivares E. (UNAB, MCSS), and J. Greiner\n(MPE Garching) report on behalf of the GROND team:\n\nWe observed the field of GRB 130725B (Swift trigger 564028; Swenson et al.,\nGCN #15029) 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\nSilla Observatory (Chile).\n\nObservations started at 00:47 UT on July 26, 2013, 7.1 hours after the\nGRB trigger. They were performed at an average seeing of 1.5\" and at\nan average airmass of 1.2.\n\nWe detect the afterglow at the position of Siegel et al. (GCN #15032), and\nbased on the first images with total exposures of 4.4 minutes in g'r'i'z'\nand 8 minutes in JHK, we estimate preliminary magnitudes (all in AB) of\n\ng' = 21.1 +/- 0.1 mag,\nr' = 20.5 +/- 0.1 mag,\ni' = 20.4 +/- 0.1 mag,\nz' = 20.4 +/- 0.1 mag,\nJ = 20.4 +/- 0.3 mag,\nH = 19.9 +/- 0.3 mag, and\nK = 19.5 +/- 0.4 mag.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as\n2MASS field stars and are not corrected for the expected Galactic\nforeground extinction corresponding to a reddening of E(B-V) = 0.061 mag in\nthe direction of the burst (Schlegel et al. 1998).",
  "circularId": 15034,
  "createdOn": 1374816618000,
  "email": "felipe@mpe.mpg.de",
  "subject": "GRB 130725B: GROND Detection of the Optical/NIR Afterglow",
  "submitter": "Felipe Olivares Estay at MPE  <felipe@mpe.mpg.de>",
  "eventId": "GRB 130725B"
}