[vsnet-grb-info 23855] GRB 191004B: NOT optical photometry

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25954
SUBJECT: GRB 191004B: NOT optical photometry
DATE:    19/10/05 03:58:45 GMT
FROM:    Kasper Elm Heintz at Univ. of Iceland and DAWN/NBI  <keh14 at hi.is>

K. E. Heintz (Univ. of Iceland), D. B. Malesani (DTU space), and S. Moran (NOT), report on behalf of a larger collaboration:

We observed the field of the Swift-detected GRB 191004B (Cenko et al., GCN 25947) with the Nordic Optical Telescope (NOT) equipped with StanCAM. We obtained 3x300s exposures with the Bessel R filter starting at 02:30:07 UT on October 5 (i.e. 4.94 hr post-burst). We clearly detect the optical afterglow (Cenko et al., GCN 25947; Lipunov et al., GCN 25948; Strausbaugh & Cucchiara, GCN 25949) and measure a magnitude of R = 20.87 +/- 0.05 mag in the stacked image. We calibrated the photometry assuming for the USNO star at (RA, Dec) = (03:16:54.39, -39:37:41.5) a magnitude of R = 16.97 mag. The derived magnitude for the GRB afterglow is not corrected for the Galactic extinction.