[vsnet-grb-info 25464] GRB 200412B: Optical afterglow detection with 1.3m DFOT

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27564
SUBJECT: GRB 200412B: Optical afterglow detection with 1.3m DFOT
DATE:    20/04/13 09:14:18 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515 at gmail.com>

TITLE:   GCN CIRCULAR
NUMBER:  27563
SUBJECT: GRB 200412B: Optical afterglow detection with 1.3m DFOT
DATE:    20/04/13 09:05:41 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515 at gmail.com,
amit at aries.res.in>

A. Kumar (ARIES), A. Aryan (ARIES),  S. B. Pandey (ARIES), S. Mishra
(ARIES), R. Gupta (ARIES), A. Ghosh (ARIES), Dimple (ARIES), and K. Misra
(ARIES) report:

We observed the optical afterglow of the Fermi GBM detected GRB 200412B
(GCN 27547, Lipunov et al., GCN 27555, GCN 27561)
with the 1.3m Devsthal Fast Optical Telescope (DFOT) at Aryabhatta Research
Institute of Observational Sciences (ARIES), Nainital
(India),
from 2020-04-12 UT 22:03:14 to 2020-04-12 UT 23:29:44 (corresponding to
12.90 to 14.46 hours from the GRB trigger time). We observed a series of
9x300s exposures in Bessel R filter and a series of 7x360s exposures in
Bessel I filter. We stacked the images and detected the optical afterglow
of GRB 200412B in both Bessel R and I filters which is consistent with
optical detections by Lipunov et al., GCN 27555, 27556.

The observed magnitudes are as follows:

T_start-T0 (hours)   Start Date (UTC)             End Date
(UTC)                  Filter            Magnitudes
---------------------------------------------------------------------------------------------------------------
12.90               2020-04-12 UT 22:03:14          2020-04-12 UT
22:46:11          R               18.90 +- 0.03
13.72               2020-04-12 UT 22:52:02          2020-04-12 UT
23:29:44          I               17.54 +- 0.02


Photometry is done based on the USNO-B1.0 catalog. The quoted magnitudes
are not corrected for Galactic extinction.