[vsnet-grb-info 4171] GRB 061222A: Confirmation of Gemini Afterglow Candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5978
SUBJECT: GRB 061222A: Confirmation of Gemini Afterglow Candidate
DATE:    06/12/24 19:33:26 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko at srl.caltech.edu>

S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:

We have further refined the processing of our first epoch of Gemini
Ks-band imaging of GRB061222A (see GCN 5975).  Using 12 2MASS stars in the
field, we report a refined position for the afterglow candidate of:

	RA: 23:53:03.419
	Dec: +46:31:58.60

with an uncertainty of +/- 0.2" in each coordinate (J2000.0).  Using our
full set of Ks-band images, we calculate a magnitude of Ks = 20.7 +/- 0.3
at a mean epoch of 5:35 Dec. 22 UT (~ 2.1 hr after the burst).

We obtained a second epoch of Ks-band imaging from Gemini on the following
evening (mean epoch 4:53 Dec. 23 UT, ~ 25.4 hr after the burst).  The
object reported above faded by ~ 1.2 mag, confirming this source as the
afterglow of GRB061222A.  The corresponding decay rate is quite shallow,
with a decay index alpha ~ 0.4 (assuming no contribution from the host
galaxy).