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GCN Circular 38754

Subject

GRB 250101A : GIT optical detection

Date

2025-01-01T14:35:06Z (8 days ago)

From

V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in>

Via

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T. Mohan, V. Swain, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:

We observed the field of Swift GRB 250101A (Page et. al., GCN 38752

) with 0.7m GROWTH-India Telescope (GIT) in r' filter. We started the observation at 2025-01-01 13:55:28 UT, i.e., 32.6 mins after the Swift Bat trigger. The source is detected at UVOT position and photometry result follows as:

JD (mid)	t-t0 (mins)	Filter	Exposure (s)	Mag (AB)
2460677.080185	34.6	r'	240	18.36 +/- 0.08

More broadband observations are ongoing. Our result is consistent with GMG Optical Observation (Li et. al., GCN 38753

) The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT; Kumar et al. 2022) 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 the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.