{
  "bibcode": "2004GCN..2514....1F",
  "body": "D.B. Fox and S.B. Cenko (Caltech) with R. Phelps (NSF) report:  \n\n\"We have observed the error circle of the Integral GRB 040106\n(Mereghetti et al., GCN 2505) on a second occasion with the Swope\n40-inch telescope at Las Campanas Observatory, commencing Jan 8.28 UT.\nObservations consisted of 2x600 s exposures in I-band, reaching R ~ 21\nmag.\n\nComparison of these images to our first-epoch T2-band imaging (Price\net al., GCN 2509) reveals that the two faint sources (a) and (b) which\nlie within the region of the XMM X-ray afterglow localization (Ehle,\nGonzalez-Riestra & Gonzalez-Garcia, GCN 2508) have not changed in\nbrightness since our first epoch, retaining the same flux to +/- 0.1\nmag.\n\nThe two brighter sources within the XMM localization, which are\nvisible in the archival images of the DSS2, have also not varied\nsignificantly in brightness between our two epochs (+/- 0.1 mag).  We\nthus identify no candidate optical counterparts within the XMM\nlocalization, and establish a limit of R>~21 on the brightness of any\ntypical such counterpart at either of our epochs of observation.\"",
  "circularId": 2514,
  "createdOn": 1073625707000,
  "email": "derekfox@astro.caltech.edu",
  "subject": "GRB040106: Second Epoch Optical Observations",
  "submitter": "Derek Fox at CIT  <derekfox@astro.caltech.edu>",
  "eventId": "GRB 040106"
}