[vsnet-grb-info 27551] GRB 210306A: HCT optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29654
SUBJECT: GRB 210306A: HCT optical upper limit
DATE:    21/03/13 04:44:34 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13 at gmail.com>

H. Kumar (IITB), A. Dutta (IIA), R. Gupta (ARIES), V. Bhalerao (IITB), G.
C. Anupama (IIA), S. Barway (IIA), D.K. Sahu (IIA),  A. Kumar (ARIES),
Dimple (ARIES), A. Ghosh (ARIES), S. B. Pandey (ARIES), and K. Misra
(ARIES) report:

We observed GRB 210306A detected by Swift Burst Alert Telescope (V. D'Elia
et. al., GCN 29597) and optical afterglow confirmed by Alan M. Watson et.
al., (GCN 29598) with the 2.0m Himalayan Chandra Telescope (HCT) of the
Indian Astronomical Observatory. We obtained 6 exposures of 300 sec each in
the Bessell R filter. We did not detect the afterglow in our stacked image.
The photometric upper limit is:

--------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Filter | Lim_mag (5-sigma) |

--------------------------------------------------------

2459282.110905 | 58.76 | Bessell R | > 23.22 |

--------------------------------------------------------

The magnitudes are in the AB system of magnitude calibrated against PanSTARRS
(Flewelling et al., 2018) using Lupton's transformation equations available
at http://classic.sdss.org/dr4/algorithms/sdssUBVRITransform.html#Lupton2005.
The magnitudes are not corrected for galactic extinction.

These observations were carried out under the ToO program HCT-2021-C1-P2.
We thank the HCT staff for their support during the observations. The
Indian Astronomical Observatory is operated by the Indian Institute of
Astrophysics, Bengaluru, India.