GCN 44191: GRB260402A: GROWTH-India Telescope optical upper limit

V. Vijaykumar, A. Khade, R. Arya, V. Swain, S. Patil, A.P. Saikia, T. Mohan, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team:

We observed the field of GRB260402A detected by SVOM/ECLAIRs (SVOM, GCN 44181), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-04-02 14:10:35 (UTC), i.e., 3.65 hours after the trigger, and obtained multiple exposures in the r' filter. We do not detect any transient in our image within the uncertainty region of source position reported by ECLAIRs and MXT  (Tan et al., GCN Circ. 44181, Gotz et al., GCN Circ.44182). The photometric upper limit is as follows:

| MJD (mid)    | Filter | tmid-t0 (hours) | Exposure Time (sec) | Magnitude (AB) |
| ------------ | ------ | -------------- | ------------------- | -------------- |
| 61132.590| r'    | 3.92           | 5x360               | 20.5 |


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

Our magnitude for the optical counterpart is consistent with other optical observations (GCN 44190 Li et al.; GCN 44189 Wu et al.; GCN 44185 Freeberg et al.; GCN 44184 Carrasco et al.; GCN 44183 Antier et al.)

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/.