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GCN Circular 25664

GRB190829A: Keck LRIS spectroscopic confirmation of the accompanying supernova
2019-09-05T03:11:38Z (5 years ago)
Giacomo Terreran at Northwestern/CIERA <>
G. Terreran, W. Fong, R. Margutti, A. Miller, K. Alexander, P. Blanchard, D. Coppejans, K. Paterson (Northwestern) report:

We observed the optical afterglow of GRB 190829A (Fermi Collab. et al., GCN 25551; Dichiara et al., GCN 25552) with the Low Resolution Imaging Spectrometer (LRIS) mounted on the 10-m Keck I telescope at a mid-time of 14:15 UT on 2019 Sep 4 (5.76 days after the Swift trigger). We obtained 3x1200-s of spectroscopy covering a wavelength range of ~3200-10200 Ang.

The spectrum appears very red and shows features consistent with a broad-line SN one week before maximum light. In particular, a very broad and shallow feature is present at 7800 Ang, possibly associated with O I. We find the best match to be with SN 2006aj a few days post explosion. However, a reddening correction with E(B-V) of ~0.6-0.9 mag is necessary to match the slope of the continuum of SN 2006aj at these phases. The high reddening inferred from the optical spectrum is consistent with the relatively high absorption column density reported by J.P. Osborne et al. (GCN 25568) in their X-ray analysis.

The emergence of the supernova light is consistent with the reported photometric flattening (J. Bolmer et al., GCN 25651; V. Lipunov et al., GCN 25652) and re-brightening (D. A. Perley and A. M. Cockeram; GCN 25657) of the optical source.

Giacomo Terreran
Postdoctoral Associate
Northwestern University
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