Nebular phase observations of the type-Ib supernova iPTF13bvn favour a binary progenitor

H. KUNCARAYAKTI; K. MAEDA; M. C. BERSTEN

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2015

0004-6361

Aims. We present and analyse late-time observations of the type-Ib supernova with possible pre-supernova progenitor detection, iPTF13bvn, taken at ∼300 days after the explosion, and discuss these 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 close binary system. Methods. Our observations show that the supernova has entered the nebular phase, with the spectrum dominated by Mg~I] lambda lambda 4571, [O~I] lambda lambda 6300, 6364, and [Ca~II]lambda lambda 7291, 7324 emission lines. We measured the emission line fluxes to estimate the core oxygen mass and compare 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 Msun, which implies initial progenitor mass not exceeding ∼15 -- 17 Msun . Since the derived mass is too small 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.