{
  "bibcode": "2009GCN..8760....1A",
  "body": "GRB 081230: GROND confirmation of the afterglow \n\n\nP. Afonso (MPE), C. Clemens (MPE), S. Klose (Tautenburg), J. Greiner\n(MPE) and G. Szokoly (Eotvos Univ. Budapest) report on behalf of the\nGROND team: \n\nGROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI\ntelescope at La Silla Observatory (Chile) imaged the field of GRB 081230\n(Swift trigger 338633, La Parola et al., GCN #8753) simultaneously in\ng'r'i'z'JHK bands \n\nWe detected and confirm the afterglow candidate in all bands, at the \nposition: \n\nRA(J2000): 02:29:19.51\nDEC(J2000): -25:08:49.95 \n\nwith uncertainties of 0.5\" in each coordinate. \n\nThis position is compatible with UVOT (Oates et alia, GCN #8757) and\nROTSE-III (Yuan et alia, GCN #8754) reported positions. \n\nObservations started on Dec. 31 at 00h48 UT, 15123 seconds, or ~ 4.2 hours\nafter the burst. \n\nWe used 4 images of 375 s exposure in g'r'i'z' and 120 images of 10s\nexposure in JHK, for each epoch. \n\nThe images mid time for the 1st epoch is 5.99h (or 21564 seconds) after the \nburst. Observations were done at an average air mass = 1.128 and seeing ~ \n1.5''. \n\nWe took a 2nd epoch on January 1st, 2009, starting at 03h21 UT. \n\nThe images mid time for the 2nd epoch is 30.99h (or 111564 seconds) after \nthe burst. Observations were done at an average air mass = 1.334 and seeing \n~ 1.3''. \n\nThe preliminary data for the 2nd epoch clearly confirms the fading of the \nafterglow: \n\nWe present preliminary photometric results for g'r'i'z'. The AB magnitudes, \nusing GROND zero points are as follows: \n\n     1st epoch       2nd epoch \n\ng' = 21.32 +- 0.02   23.67 +- 0.08\nr' = 20.96 +- 0.01   23.07 +- 0.06\ni' = 20.74 +- 0.02   22.79 +- 0.09\nz' = 20.66 +- 0.03   22.84 +- 0.17 \n\nNo correction for galactic extinction was done. \n\nThe quoted error is statistical only. There is an additional\nsystematic error in the absolute calibration using the GROND zeropoints\nwhich is expected to be in the 0.2 mag range. \n\nFurther data analysis is ongoing for JHK - the aftegrlow being clearly \nvisible on the first epoch, but not on the 2nd.",
  "circularId": 8760,
  "createdOn": 1230823221000,
  "email": "pafonso@mpe.mpg.de",
  "subject": "GRB 081230: GROND confirmation of the afterglow",
  "submitter": "Paulo M. J. Afonso at MPE  <pafonso@mpe.mpg.de>",
  "eventId": "GRB 081230"
}