TITLE: GCN CIRCULAR NUMBER: 27598 SUBJECT: GRB200412B: GROWTH India detection of afterglow DATE: 20/04/17 06:59:26 GMT FROM: Varun Bhalerao at Indian Inst of Tech H. Kumar, M. Khandagale, K. Deshmukh, V. Bhalerao(IITB), G. C. Anupama, B. Kumar, A. Singh, A. Dutta, S. Barway(IIA), P. Dorji (IAO), U. Stanzin (IAO), report on behalf of the GROWTH collaboration: We observed GRB200412B reported by Fermi GBM Team (GCN 27547) and Burgess J. et al, (GCN 27548) with 0.7m robotic GROWTH-India telescope. We switched from tiled observations to targeted follow-up based on the afterglow identification by Lipunov V. et al, (GCN 27555) at RA(J2000) = 18:33:15.33 Dec(J2000) = +62:31:57.0 . The field was observed multiple times in g and r filters with 550 sec exposure time, starting about 7.4 hours after the trigger. We clearly detect the afterglow emission. The decay is well-described by a power law with alpha = 1.05 +/- 0.14 for g band data and 0.85 +/- 0.17 for r band data. We obtained the following results: ------------------------------------------------------------------ JD(Start)| Exposure(sec) | Filter | Mag | lim_Mag | ------------------------------------------------------------------ 2458952.1903 | 550 | g | 18.301+/-0.034 | 20.92 2458952.3277 | 550 | g | 18.590+/-0.039 | 20.54 2458952.3601 | 550 | g | 18.761+/-0.040 | 20.52 2458952.3768 | 550 | g | 18.826+/-0.039 | 20.56 2458952.4216 | 550 | g | 18.984+/-0.041 | 20.65 2458952.1982 | 550 | r | 17.854+/-0.027 | 20.83 2458952.3356 | 550 | r | 17.998+/-0.036 | 20.32 2458952.3681 | 550 | r | 18.231+/-0.031 | 20.58 2458952.3847 | 550 | r | 18.314+/-0.039 | 20.65 2458952.4295 | 550 | r | 18.379+/-0.033 | 20.77 ------------------------------------------------------------------ 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 and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).