Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 32850

GRB 221009A: spectroscopic confirmation of SN in LBT spectra
2022-10-25T16:50:09Z (2 years ago)
Andrea Rossi at INAF <>
E. Maiorano, E. Palazzi, A. Rossi (INAF-OAS), V. D'Elia (SSDC & 
INAF-OAR), and A. Melandri (INAF-OAR) on behalf of the CIBO 
collaboration, and F. Cusano (INAF-OAS), L. Izzo (DARK/NBI) report:

We report the results of the spectroscopic follow-up observations of the 
afterglow of GRB 221009A (Dichiara et al., GCN 32632; Fermi GBM 
detection: Veres et al., GCN 32636). The optical spectra were obtained 
with the Multi-Object Double Spectrographs (MODS) instrument mounted on 
the 2x8.4-m LBT telescope (Mt. Graham, AZ, USA) at 3 UT on 2022-10-18, 
8.56 days after the burst trigger. The spectra cover the wavelength 
range 3200-10000 AA, and we obtained a total of 6 exposures of 900 s.

After correction for the foreground Galactic extinction (E(B-V)=1.324, 
Schlafly & Finkbeiner 2011), we find that the resulting spectrum is 
clearly dominated by the afterglow. We subtracted the afterglow 
contribution assuming a spectral slope -0.7 (using the convention F_nu ~ 
nu^-beta), anchored to the simultaneous NIR flux. This value has been 
obtained modeling the NIR light curve of the afterglow (Ferro et al., 
GCN 32804; D'Avanzo et al., GCN 32755). The remaining low S/N spectrum 
shows features typical of type Ic-BL supernovae. Therefore, we confirm 
the emerging contribution of SN 2022xiw (de Ugarte Postigo et al. et al. 
TNSCR, 2022-3047) as reported by de Ugarte Postigo et al. (GCN 32800).

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly A. Becker and D. G. Huerta, in obtaining these observations.
Looking for U.S. government information and services? Visit