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GCN Circular 34500

Subject
GRB 230812B: GIT Confirmation of SN rise
Date
2023-08-20T09:45:51Z (6 months ago)
From
Vishwajeet Swain at IIT Bombay <vishwajeet.s@iitb.ac.in>
Via
Web form
H. Kumar (IITB), V. Swain (IITB), R. Teja (IIA), R. Kumar (IITB), A. Salgundi (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), D.K. Sahu (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:

We continued observation of the field of the GRB230812B (Fermi GBM Team, GCN 34386) with 0.7m GROWTH-India Telescope (GIT). Starting at 15:26:30 UT on 2023-08-19, we took 18 exposures of 300 sec each in r' band and detected the optical source in our stacked images. We also observed the target with HCT (2x 25 min, PI: R Teja), and detect the source as well. The details of the photometry are given in the below table:


-------------------------------------------------------
JD (mid) | T-T0 (days)| Filter | Exposure (s) | Magnitude (AB) | Telescope

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

2460176.199743 | 6.90 | r' | 18 x 300 | 22.06 +/- 0.10 | GIT

2460176.196935 | 6.91 | r' | 2 x 1500 | 22.04 +/- 0.18 | HCT

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

Our photometry shows a significant deviation from the earlier estimated power-law decay (alpha = 1.23 +/- 0.04) and shows a rise by ~0.9 mag as compared to afterglow-only emission, suggesting the presence of a supernova component. Our results are consistent with A. S. Moskvitin et al., GCN 33475. Based on our SN + PL fits predict that the emission should rise slightly over next 15 days and will start decaying again once the SN peaks around T-T0 ~ 22 days.

We encourage the spectroscopic observation to confirm the presence of SN fully.

Also see: Zheng & Filippenko, GCN 34395, Lipunov et al., GCN 34396, Salgundi et al., GCN 34397, Ackley et al., GCN 34398, Kuin et al. GCN 34399, Mao et al., GCN 34404, Odeh et al., GCN 34405, Moskvitin et al., GCN 34406, Leonini et al., GCN 34408, de Ugarte Postigo et al. GCN 34409, 34410 & 34468, Belkin et al., GCN 34412, and N. Ruocco et al., GCN 34413, N. Ruocco et al., GCN 34413, M. Shrestha et al., GCN 34416, C. Adami et al., GCN 34418, L. Moretti et al., GCN 34419, R. Kumar et al., GCN 33420, S. Belkin et al., GCN 33421, 33423, 33432, O. Pyshna et al., GCN 34425, A. S. Moskvitin et al., GCN 33428, 33442, 33461 33471, 33475 & 33496, U.Quadri and L.Strabla GCN 33430, B. Mihov et al., GCN 33431, Lauren Rhodes et al., GCN 33433, S. Klose et al., GCN  33435, Giulio Scarfì et al., GCN 33436, F.D. Romanov GCN 33443, Lopresti et al., GCN 33445, J. Vinko et al., GCN 33463.

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/.
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