Nebular phase observations of the Type-Ib supernova iPTF13bvn favour a binary progenitor ⋆
1 Millennium Institute of Astrophysics, Casilla 36-D, Santiago, Chile
2 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
3 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, 606-8502 Kyoto, Japan
4 Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, 277-8583 Chiba, Japan
5 Instituto de Astrofísica de La Plata (IALP), CCT-CONICET-UNLP, Paseo del Bosque S/N, B1900 FWA La Plata, Argentina
6 Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile
7 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 763 0355, Santiago, Chile
8 Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, 739-8526 Hiroshima, Japan
9 Core of Research for the Energetic Universe, Hiroshima University, Higashi-Hiroshima, 739-8526 Hiroshima, Japan
Received: 31 December 2014
Accepted: 7 April 2015
Aims. We present and analyse late-time observations of the Type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, which were done ~300 days after the explosion. We discuss them in the context of constraints on the supernova’s progenitor. Previous studies have proposed two possible natures for the progenitor of the supernova, i.e. a massive Wolf-Rayet star or a lower-mass star in a close binary system.
Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg I]λλ4571, [O I]λλ6300, 6364, and [Ca II]λλ7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compared the [O I]/[Ca II] line ratio with other supernovae.
Results.The core oxygen mass of the supernova progenitor was estimated to be ≲0.7 M⊙, which implies initial progenitor mass that does not exceed ~15–17 M⊙.Since the derived mass is too low for a single star to become a Wolf-Rayet star, this result lends more support to the binary nature of the progenitor star of iPTF13bvn. The comparison of [O I]/[Ca II] line ratio with other supernovae also shows that iPTF13bvn appears to be in close association with the lower mass progenitors of stripped-envelope and Type-II supernovae.
Key words: supernovae: general / supernovae: individual: iPTF13bvn / stars: massive
Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU); Chilean Telescope Time Allocation Committee proposal CN2014A-91.
© ESO, 2015