[vsnet-grb-info 27436] GRB 210217A: 1.3m DFOT optical detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29539
SUBJECT: GRB 210217A: 1.3m DFOT optical detection
DATE:    21/02/19 19:32:22 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515 at gmail.com>

Amit Kumar (ARIES), Rahul Gupta (ARIES), Ankur Ghosh (ARIES), Dimple
(ARIES), Tushar Tripathi (ARIES), Shubham Kishore (ARIES), Amar Aryan
(ARIES), Shashi B. Pandey (ARIES), Brajesh Kumar (ARIES), and Kuntal Misra
(ARIES) report:

We observed the optical afterglow of the Swift detected GRB 210217A
(Simpson et al. GCN 29521; Evans et al., GCN 29525) with the 1.3m Devsthal
Fast Optical Telescope (DFOT) at Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital (India), on 2021-02-18 from UT
17:31:22 to 19:09:31 (corresponding to 18.094 to 19.730 hours from the GRB
trigger time). We observed a series of 30x120s exposures in the Bessel R
filter and a series of 20x120s exposures in the Bessel I filter. We clearly
detected the optical afterglow of GRB 210217A in the stacked frames within
the Swift XRT error circle (Simpson et al. GCN 29521) as also reported by
Zhu et al., GCN 29523; Zheng & Filippenko GCN 29533; Shrestha et al. GCN
29535.

The estimated preliminary magnitudes are as follows:

T_start-T0 (hours) Start Date (UTC) Filter Magnitude (mag)
-----------------------------------------------------------
-----------------------------------------------------------
18.09 2021-02-18T17:31:22 R 21.80 +- 0.08
19.73 2021-02-18T19:09:31 I 21.56 +- 0.12

The magnitudes are not corrected for the Galactic extinction in the
direction of the burst. Photometric calibration is performed using the
standard stars from the USNO-B1.0 catalog.

This circular may be cited.