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GCN Circular 32800

Subject
GRB 221009A: Spectroscopic detection of emerging SN features
Date
2022-10-19T11:23:30Z (2 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
A. de Ugarte Postigo (OCA), L. Izzo (DARK/NBI), C. C. Thoene
 (ASU-CAS), J. P. U. Fynbo (DAWN/NBI), D. A. Kann (Goethe Univ.), 
J. F. Agui Fernandez (IAA-CSIC), N. R. Tanvir (Leicester Univ.) report:

We have been spectroscopically monitoring the evolution of the 
extremely bright GRB 221009A (Swift detection: Dichiara et al., 
GCN 32632; Fermi GBM detection: Veres et al., GCN 32636) using 
OSIRIS at the 10.4m GTC telescope. In a spectrum combining data 
taken on 16 and 17 October (at an average time of ~8 days after the 
burst), covering the spectral range between 3700 and 10000 AA, the 
emission is still clearly dominated by the afterglow. However, after 
subtracting a model of the continuum, the spectrum shows undulations 
characteristic of a GRB-SN. In particular we identify broad features at 
similar wavelengths (after correcting for the redshift difference) as 
those present in SN 1998bw, with somewhat larger velocities. This is 
indicative of the emergence of the associated supernova. Further 
follow-up observations are planned.
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