[vsnet-grb-info 15574] GRB 140930B: MMT confirmation of the optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16863
SUBJECT: GRB 140930B: MMT confirmation of the optical afterglow
DATE:    14/10/01 06:47:14 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong at email.arizona.edu>

W. Fong (U. Arizona), M. Calkins (SAO), and E. Berger (Harvard) report:

"We observed the location of the short-duration GRB 140930B (De Pasquale et
al., GCN 16857) with MMTCam mounted on the 6.5-m MMT starting on 2014 Oct
1.144 UT (7.76 hr post-burst). We obtained 4x300-sec of r-band observations
in 1" seeing. We detect a source at the position of the candidate optical
afterglow (Tanvir et al., GCN 16861) with a magnitude of r~24.0 +/- 0.2
(calibrated to SDSS), indicating that the source faded by ~2.2 mag between
3.0 hr and 7.8 hr post-burst. The fading confirms that this source is the
optical afterglow of GRB 140930B. Assuming a single power-law decline
between these two epochs, the decay index is alpha~-2.1.

We thank Nelson Caldwell for the rapid scheduling of these observations."