GCN Circular 32638
Subject
Swift J1913.1+1946: Liverpool Telescope imaging and spectroscopy
Date
2022-10-09T21:53:41Z (2 years ago)
From
Daniel Perley at Liverpool JMU <d.a.perley@ljmu.ac.uk>
D. A. Perley (LJMU) reports:
Imaging and spectroscopy were acquired of the optical counterpart of Swift J1913.1+1946 (Dichiara et al., GCN 32632; Lipunov et al., GCN 32634), potentially the optical afterglow of GRB 221009A (Kennea & Williams, GCN 32635; Veres et al., GCN 32636).
The spectrum, taken with SPRAT between 20:49 and 21:06 UT on 2022-10-09, covers a wavelength range of 4000-8000 Angstroms and reveals a red continuum with no strong features. Due to the low resolution of the spectrograph, we cannot rule out potential narrow absorption lines. The shape is consistent with a heavily dust-reddened afterglow. Galactic extinction towards this direction is about 3.52 mag in r-band (from the NED extinction calculator).
Imaging was acquired using IO:O in the SDSS g, r, i, and z filters between 21:18 and 21:23 UT on the same night. We measure the following magnitudes, calibrating relative to local PS1 secondary standards:
MJD filter mag emag
59861.88806 g 18.53 0.06
59861.88896 r 17.00 0.03
59861.88982 i 15.98 0.03
59861.89069 z 15.32 0.03
Analysis is ongoing, and additional observations are planned.
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