[vsnet-grb-info 12626] GRB 121123A: NOT optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13986
SUBJECT: GRB 121123A: NOT optical observations
DATE:    12/11/23 21:31:18 GMT
FROM:    Dong Xu at DARK/NBI  <dong.dark at gmail.com>

D. Xu, T. Kruehler, D. Malesani (DARK/NBI), G. Leloudas (OKC Stockholm
and DARK/NBI) I. Ilyin (AIP), J. Clasen (NOT), P. Jakobsson (U.
Iceland), J. P. U. Fynbo (DARK/NBI) report on behalf of a larger
collaboration:

We observed the field of GRB 121123A (Helder et al., GCN 13982) using
the 2.5m Nordic Optical Telescope (NOT) equipped with StanCam.
Observations started at 20:03:43 UT on 2012-11-23 (i.e., 9.972 hr
after the BAT trigger) and 5x300s R-band frames were obtained with
mid-time of 10.218 hr post-trigger.

The afterglow is clearly detected in the stacked image at coordinates

R.A.(J2000)= 20:29:16.289
Dec.(J2000)=-11:51:35.87

with R=19.65+/-0.03 mag, calibrated with the #0781-0714632 star
(R1=R2=17.17 mag with a scatter of 0.3 mag) in the USNO B1 catalog.

We note that our measurement is only modestly fainter than the one
reported by Zhao et al. (GCN 13983) at 1.5 hr after the BAT trigger,
indicating a shallow decay or an irregular light curve.