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Optical and near-infrared spectroscopy of SN 2013ak (= PSN J08070669-2803101)

ATel #4943; D. Milisavljevic (Harvard-Smithsonian Center for Astrophysics, CfA), G. H. Marion (CfA), E. Y. Hsiao, (Las Campanas Observatory), A. Soderberg (CfA), R. Margutti (CfA), M. Drout (CfA), N. Sanders (CfA), P. Challis (CfA), R. Kirshner (CfA), R. Chornock (CfA), R. Foley (CfA), and J. Skinner (Dartmouth College)
on 3 Apr 2013; 18:33 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: D. Milisavljevic (dmilisav@cfa.harvard.edu)

Subjects: Supernovae, Transient

Referred to by ATel #: 4944, 4945, 4946, 4947

We report on low-dispersion optical and near-infrared spectra of SN 2013ak (= PSN J08070669-2803101; ATel #4874; CBET 3437) that show the supernova to be gradually exhibiting features consistent with a Type IIb classification. Optical spectra (range 345-730 nm) were obtained 2013 March 18 UT with the F. L. Whipple Observatory 1.5m telescope (+ FAST), and 2013 March 30 with the 2.4m Hiltner telescope (+ CCDS). Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) and GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) produces reasonable matches with 1987K, 1996cb, 2008D, and 2008ax within two weeks of maximum light. The measured velocities of the broad line features associated with H_alpha, He I, Ca II, and Fe II remain high, and the changes in these velocities between epochs are small. Using a redshift of z = 0.0037 (ATel #4874), the velocity of the H_alpha absorption feature on March 30 is approximately -16500 km/s, which is slower by only 2000 km/s when compared to a previous spectrum obtained March 11 (ATel #4874).

Near-infrared spectra (range 800-2400 nm) of SN 2013ak were obtained on 2013 March 20, 25 and April 1 with the FoldedPort Infrared Echellette (FIRE) spectrograph on the 6.5-m Magellan Baade Telescope. These spectra show absorption features with the same high velocities and slow changes between epochs as the features seen in the optical spectra. Absorptions associated with the He I lines at 1.0830 and 2.0581 micron are observed blueshifted some -15000 km/s, and features from the Pachen series are evident.