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GCN Circular 31014

Subject
GRB 211024A: Possible afterglow candidate from GIT
Date
2021-10-27T11:35:56Z (2 years ago)
From
Harsh Kumar at Indian Inst of Tech,Bombay <harshkosli13@gmail.com>
H. Kumar(IITB), V. Swain (IITB), U. Stanzin (IAO), V. Bhalerao(IITB), G. C.
Anupama(IIA), S. Barway(IIA) report on behalf of the GIT team:

We observed GRB 211024A detected by Fermi GBM (GCN 30962), localisation
further refined by Swift/BAT-GUANO

A. Tohuvavohu et al., (GCN #31006), with 0.7m GROWTH-India Telescope (GIT).
We obtained 2 exposures of 300 sec each in the r' filter, separated by ~15
min. We detected a potential candidate in our subtracted image at R.A.=
1:52:46.98 , DEC.= -7:00:27.30. This is coincident with an X-ray source
(#4) by Swift-XRT ToO observations (M. Perri et al. GCN # 31013). The
photometric results follow as:

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

 JD (Start) | T_start-T0(days) | Filter | Magnitude (AB) |

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

 2459514.2264 | 2.66 | r' | 19.83 +/- 0.038|

 2459514.2373 | 2.67 | r' | 19.87 +/- 0.046 |

-------------------------------------------------------------------
There was an underlying source at the position of the target in the raw
image which was subtracted using reference images from PanSTARRS. The
source magnitude is 17.86 mag in the r band with phot_z = 0.2108 +/- 0.02
(SDSS Release 12: Alam+, 2015). This may be the host galaxy of the GRB.
There is no minor planet at the location of the candidate in MPC. The gap
between exposures was not sufficient to measure any decay. Further
observations are planned. Follow-up observations for this source are
strongly encouraged.

The magnitudes are calibrated against PanSTARRS (Flewelling et al., 2018)
and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics (IIA) and the
Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and
IUSSTF. It is located at the Indian Astronomical Observatory (Hanle),
operated by IIA. We acknowledge funding by the IITB alumni batch of 1994,
which partially supports operations of the telescope. Telescope technical
details are available at https://sites.google.com/view/growthindia/.
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