Detection of the emerging supernova spectrum from the afterglow of GRB221009A
ATel #15712; J. Vinko (Konkoly, UT Austin), J. C. Wheeler (UT Austin)
on 22 Oct 2022; 21:27 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)
Subjects: Optical, Gamma-Ray Burst, Supernovae
We report an optical spectrum on the afterglow of the extremely strong, long Gamma-Ray Burst
GRB221009A/Swift J1913.1+1946 (ATel #15653, #15655, #15660, #15663, #15671, #15685) taken with the LRS2-R spectrograph (wavelength range: 6450-10500 Angstroms, resolving power: 1800) of the 10m Hobby-Eberly Telescope at McDonald Observatory on 2022-10-21.1 UT. The spectrum shows a redward slope due to high extinction of Milky Way dust. Below 8000 Angstrom the spectrum is dominated by the synchrotron emission from the GRB afterglow. Above 8000 Angstrom, however, broad spectral features are clearly visible that are probably due to the radiation from the emerging supernova ejecta.
According to the SuperNova IDentification Tool (SNID, Blondin and Tonry 2007, Ap.J., 666, 1024), the best-matching template is that of the broad-lined Ic SN 2010bh at +1.2 days after maximum light. The redshift of the best-matching template is z ~ 0.149 +/- 0.04, which matches the reported redshift of the host galaxy, z = 0.151 (de Ugarte Postigo et al. GCN Circular #32648).
GRB221009A HET spectrum
