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GCN Circular 16863

GRB 140930B: MMT confirmation of the optical afterglow
2014-10-01T06:47:14Z (10 years ago)
Wen-fai Fong at U of Arizona <>
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."
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