{
  "bibcode": "2000GCN...586....1R",
  "body": "James Rhoads and Andy Fruchter (STScI) report:\n\nWe observed the proposed afterglow of GRB 000301c with the NASA IRTF + NSFCam\nin K' band (2.1 microns) on March 4.640, and in J band (1.25 microns) on\nMarch 4.652.  The data were photometrically calibrated by observations\nof UKIRT faint standard 27.  Seeing was approximately 0.85\" in K'\nand 0.95\" in J.\n\nWe find K'=17.65 +- 0.04 and J=19.10 +- 0.05 (statistical error only)\nfor the candidate afterglow.  Aperture photometry was performed using a\n0.9\" (3 pixel) radius aperture, corrected to an effective aperture of\n2.7\" radius using aperture corrections derived from the brighter star\n5.7\" W and 1\" S of the proposed OT.  For reference, this star had\nmagnitudes K'=15.96 +- 0.02 and J=16.63 +- 0.01.\n\nNo correction was made for atmospheric extinction or color terms; however,\nthese are expected to be small.  (The standard was observed at airmass 1.09,\nand the GRB field at airmass 1.02.)\n\nWe detect a faint object, quite possibly a galaxy, approximately 2\" N and\n1\" E of the candidate OT; this could be the host galaxy if the OT is\nreal.  This object has approximate magnitudes K'=19.8, J=20.8.\n\nThis K' flux shows no significant decline from the earlier reported\nobservations (Stecklum et al, GCNC 572; Kobayashi et al, GCNC 577), \nwhile it would be expected to decay by 0.44 magnitudes from Kobayashi's\ndata point for a t^-1.0 power law.  This relative constancy of the near-IR\nflux, despite optical fading, is difficult to reconcile with GRB afterglow\nmodels, especially if it persists for more than a day.  \n\nWe note that many classes of variable objects (other than\nafterglows) show stronger variability at bluer wavelengths.\nThe weak or nonexistent variability in the K' filter is therefore\na cause for concern, and we urge continued followup at both optical\nand IR wavelengths.\n\nWe thank the staff of the IRTF for help with these service observations.",
  "circularId": 586,
  "createdOn": 952235305000,
  "email": "rhoads@stsci.edu",
  "subject": "GRB 000301c near-IR observations",
  "submitter": "James Rhoads at STScI  <rhoads@stsci.edu>",
  "eventId": "GRB 000301C"
}