{
  "bibcode": "2010GCN.10683....1O",
  "body": "F. Olivares, T. Kruehler and J. Greiner (all MPE Garching) report on \nbehalf of the GROND team:\n\nWe observed the field of GRB 100425A (Swift trigger 420398; Grupe et \nal., GCN 10673) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. \n2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla \nObservatory (Chile).\n\nObservations started at 05:17 UT on April 25, 2.4 hours after the GRB \ntrigger, and were initially performed through thin cloud coverage.\n\nThe optical afterglow candidate reported by Malesani et al. (GCN 10680, \nsource 'B') is found to be clearly variable. Between 2.9 and 5.9 hours \nafter the burst, the source decayed roughly 0.5 mag in the r' band. At a \nmidtime of 08:45 UT we measure the following preliminary magnitudes (all \nin the AB system) in stacked images with a total integration time of 24 \nmin in g'r'i'z' and 20 min in JHK:\n\ng = 21.5 +- 0.2\nr = 21.0 +- 0.1\ni = 20.8 +- 0.1\nz = 20.5 +- 0.1\nJ = 20.1 +- 0.2\nH = 19.9 +- 0.2\nK = 19.6 +- 0.2\n\ncalibrated against the GROND zeropoints and 2MASS field stars, and not \ncorrected for the expected foreground extinction of E(B-V)=0.15 \n(Schlegel et al. 1998).",
  "circularId": 10683,
  "createdOn": 1272192415000,
  "email": "kruehler@mpe.mpg.de",
  "subject": "GRB 100425A: GROND afterglow observation",
  "submitter": "Thomas Kruehler at MPE/MPI  <kruehler@mpe.mpg.de>",
  "eventId": "GRB 100425A"
}