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SN 2011hs: a fast and faint Type IIb supernova from a supergiant progenitor

Bufano, F and Pignata, G and Bersten, M and Mazzali, PA and Ryder, SD and Margutti, R and Milisavljevic, D and Morelli, L and Benetti, S and Cappellaro, E and Gonzalez-Gaitan, S and Romero-Canizales, C and Stritzinger, M and Walker, ES and Anderson, JP and Contreras, C and de Jaeger, T and Foerster, F and Gutierrez, C and Hamuy, M and Hsiao, E and Morrell, N and Olivares E, F and Paillas, E and Parker, S and Pian, E and Pickering, TE and Sanders, N and Stockdale, C and Turatto, M and Valenti, S and Fesen, RA and Maza, J and Nomoto, K and Phillips, MM and Soderberg, A (2014) SN 2011hs: a fast and faint Type IIb supernova from a supergiant progenitor. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 439 (2). pp. 1807-1828. ISSN 0035-8711

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Observations spanning a large wavelength range, from X-ray to radio, of the Type IIb supernova (SN) 2011hs are presented, covering its evolution during the first year after explosion. The optical light curve presents a narrower shape and a fainter luminosity at peak than previously observed for Type IIb SNe. High expansion velocities are measured from the broad absorption H I and He I lines. From the comparison of the bolometric light curve and the time evolution of the photospheric velocities with hydrodynamical models, we found that SN 2011hs is consistent with the explosion of a 3–4 M⊙ He-core progenitor star, corresponding to a main-sequence mass of 12–15 M⊙, that ejected a mass of 56Ni of about 0.04 M⊙, with an energy of E = 8.5 × 1050 ERG. Such a low-mass progenitor scenario is in full agreement with the modelling of the nebular spectrum taken at ∼215 d from maximum. From the modelling of the adiabatic cooling phase, we infer a progenitor radius of ≈500–600 R⊙, clearly pointing to an extended progenitor star. The radio light curve of SN 2011hs yields a peak luminosity similar to that of SN 1993J, but with a higher mass-loss rate and a wind density possibly more similar to that of SN 2001ig. Although no significant deviations from a smooth decline have been found in the radio light curves, we cannot rule out the presence of a binary companion star.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record MNRAS (April 01, 2014) 439 (2): 1807-1828 is available online at: http://dx.doi.org/10.1093/mnras/stu065
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Related URLs:
Date Deposited: 08 Feb 2016 11:03
Last Modified: 08 Feb 2016 11:03
DOI or Identification number: 10.1093/mnras/stu065
URI: http://researchonline.ljmu.ac.uk/id/eprint/2858

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