GCN Circular 4604
Subject
GRB 060121: Probable Detection of NIR Afterglow
Date
2006-01-26T22:50:50Z (18 years ago)
From
Don Lamb at U.Chicago <lamb@oddjob.uchicago.edu>
GRB 060121: Probable Detection of NIR Afterglow
F. Hearty (Colorado), M. Bayliss (Chicago), D. Q. Lamb (Chicago), G.
Gyuk (Chicago), M. Hammergren (Adler Planetarium), A. Puckett
(Chicago), B. Ketzeback (APO), J. Barentine (APO), J. Dembicky (APO),
R. McMillan (APO), and D. G. York (Chicago) report:
We observed the afterglow (Malesani et al. GCN 4561, Levan et al. GCN
4562) of GRB 060121, a bright short/hard burst localized by HETE-2
(Arimoto et al. GCN 4550, Prigozhin et al. GCN 4551, Boer et al. GCN
4552), on the night of January 22nd, using NIC-FPS on the ARC 3.5-meter
telescope at Apache Point Observatory. The observation began at 7.25
UT on 23 January (32.83 hours after the burst) and ended at 8.63 UT on
23 January (34.21 hours after the burst). The observation consisted of
a series of 180 20-second exposures in Ks. We have constructed from
them a stacked image of the GRB field, corresponding to a 60-minute
exposure.
We detect an object at the 5-sigma confidence level within 1" of the
location of the optical afterglow and well within the revised XRT
error circle (Mangano et al. GCN 4560). The PSF of the object is
consistent with that of a point source. We therefore identify the
object as the probable NIR afterglow of GRB 060121. We measure Ks ~ 20
mag, calibrated relative to four 2MASS stars in the field.
Extended emission is visible about 1" SE and NE of the probable NIR
afterglow, but is detected at less than the 2-sigma confidence level.
Therefore the emission might be due to nearby galaxies (possibly
including the host of GRB060121) or merely to a background fluctuation.
Further observations are in progress.
NIC-FPS is currently in its commissioning phase.