TITLE:   GCN CIRCULAR
NUMBER:  33636
SUBJECT: GRB 230414B: 3.6m DOT Optical observations, slow decay at early epochs
DATE:    23/04/16 19:21:38 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Amit K. Ror, Rahul Gupta, S. B. Pandey, A. Aryan, K. Misra (ARIES), A. J.
Castro-Tirado (IAA-CSIC), D. Bhattacharya (Ashoka University/IUCAA), and V.
Bhalerao (IITB) report on behalf of a larger collaboration:

We observed the field of GRB 230414B (D'Ai et al. GCN 33612; and Evans et
al. GCN 33613) using the TANSPEC mounted at the axial port of the 3.6m
Devasthal Optical Telescope (DOT) of ARIES Nainital. We have taken multiple
frames with an exposure time of 300 sec each in r, and i filters on
2023-04-14 and successive nights. We clearly detect the optical afterglow
(Pankov et al. GCN 33615; Lu et al. GCN 33616; Raman et al. GCN 33618;
Ghosh et al. GCN 33620; Moskvitin et al. GCN 33622; Malesani et al. GCN
33623; Zhu et al. GCN 33625; Belkin et al. GCN 33628; Fernandez et al. GCN
33629; Quadri et al. GCN 33630; and Leonini et al. GCN 33634) in each
individual image taken on 2023-04-14. We report the preliminary brightness
of the afterglow to be i = 19.95 +/- 0.16 mag ~ 43 minutes after the BAT
trigger. By combining our i-band magnitude with the observations of Raman
et al. GCN 33618, we determine the preliminary flux decay index of 0.60
+/-0.08. Our observations indicate the slow flux decay behavior of the
afterglow at the early epoch, as also noted by Malesani et al. GCN
33623. Late-time
observations will further provide insight into jet geometry, circumburst
medium, and the total energy of the burst.

The magnitude quoted is not corrected for the Galactic and host extinctions
in the direction of the burst. Photometric calibration is performed using
the standard stars from the PanSTARRS catalog.


This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is the
recently commissioned facility in the Northern Himalayan region of India
(long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the
Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (
https://www.aries.res.in). Authors of this GCN circular thankfully
acknowledge consistent support from the staff members to run and maintain
the 3.6m DOT.