TITLE:   GCN CIRCULAR
NUMBER:  23733
SUBJECT: GRB190114C: GRowth-India detection of optical afterglow
DATE:    19/01/16 07:33:37 GMT
FROM:    Varun Bhalerao at Indian Inst of Tech  <varunb@iitb.ac.in>

Harsh Kumar (IITB), Shubham Srivastav (IITB), Viraj karambelkar (IITB), Gaurav Waratkar(IITB), Tsewang Stanzin (IAO, IIA), Varun Bhalerao (IITB), G.C. Anupama (IIA) report on behalf of the GROWTH-India collaboration:

We observed the optical afterglow of GRB190114C (Gropp et al., GCN 23688) with the 0.7m robotic GROWTH-India telescope at the Indian Astronomical Observatory. Observation were started about 16.36 hrs after the initial alert. We observed the field using g,r,i filters with 600sec exposure in each filter. We clearly detected a faint afterglow source. Magnitudes were calibrated using PanSTARRs reference stars in the same field. The measured magnitudes are:

t-t0        MJD        Filt  Magnitude 
16.36hrs    58498.55    g    19.92 +- 0.24
16.68hrs    58498.56    r    19.29 +- 0.14
17.00hrs    58498.58    i    18.78 +- 0.19

Source has faded significantly as compared to its early time optical detection (Gropp et al., GCN 23688, Izzo et al. GCN 23699). Based on our data combined with other r band measurements (Selsing et al., GCN 23695; Bolmer et al., GCN 23702; D’Avanzo et al., GCN 23729; Kim et al., GCN 23732), we see that the source flux is fading approximately as a power law t^-alpha, with alpha = 0.7 +- 0.1.

GROWTH India telescope 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).