AT2018cow: detection of an underlying broad-line SN Ic
ATel #11753; L. Izzo (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann (HETH/IAA-CSIC), C. C. Thoene (HETH/IAA-CSIC), G. Leloudas (DARK/NBI), M. Blazek (HETH/IAA-CSIC), K. Bensch (HETH/IAA-CSIC), R. Sanchez-Ramirez (INAF-IAPS), S. Schulze (Weizmann), N. R. Tanvir (U. Leicester), A. Sagues Carracedo (NOT), M. Della Valle (INAF-Naples), N. Castro-Rodriguez (GTC), A. Tejero (GTC)
on 21 Jun 2018; 15:30 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Antonio de Ugarte Postigo (adeugartepostigo@gmail.com)
Subjects: Optical, Gamma-Ray Burst, Supernovae, Transient
We observed ATLAS18qqn/AT2018cow (ATels: #11727, #11729, #11732, #11734, #11736, #11737, #11738, #11740, #11741, #11742, #11743, #11744, #11748, #11749, #11750, #11751, #11752) with OSIRIS/GTC on June 21, 2018 starting at 03:20 UT. Spectra were obtained with the R1000B and R2500I grisms with an exposure time of 2x120s each in each grism, covering the wavelength range between 3700 and 10000 AA.
The spectrum is dominated by a power-law continuum (probably due to the tail of the very hot black body mentioned in ATel #11742) with superposed undulations. By subtracting this continuum we find similarities with a broad-line type Ic supernova spectrum (see also ATel #11740), although a direct match is not obvious. The spectrum is dominated by a peak at 5460 AA, bluewards of which there is an absorption feature that could be interpreted as FeII 5169 AA expanding at 20000 km/s.
