Journal Article

Cas A and the Crab were not stellar binaries at death

C. S. Kochanek

in Monthly Notices of the Royal Astronomical Society

Published on behalf of Royal Astronomical Society

Volume 473, issue 2, pages 1633-1643
ISSN: 0035-8711
Published online September 2017 | e-ISSN: 1365-2966 | DOI:
Cas A and the Crab were not stellar binaries at death

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The majority of massive stars are in binaries, which implies that many core collapse supernovae should be binaries at the time of the explosion. Here we show that the three most recent, local (visual) SNe (the Crab, Cas A and SN 1987A) were not stellar binaries at death, with limits on the initial mass ratios of q = M2/M1 ≲ 0.1. No quantitative limits have previously been set for Cas A and the Crab, while for SN 1987A we merely updated existing limits in view of new estimates of the dust content. The lack of stellar companions to these three ccSNe implies a 90 per cent confidence upper limit on the q ≳ 0.1 binary fraction at death of fb < 44 per cent. In a passively evolving binary model (meaning no binary interactions), with a flat mass ratio distribution and a Salpeter IMF, the resulting 90 per cent confidence upper limit on the initial binary fraction of F < 63 per cent is in tension with observed massive binary statistics. Allowing a significant fraction fM ≃ 25 per cent of stellar binaries to merge reduces the tension, with [math], but allowing for the significant fraction in higher order systems (triples, etc.) reintroduces the tension. That Cas A was not a stellar binary at death also shows that a surviving massive binary companion at the time of the explosion is not necessary for producing a Type IIb SNe. Much larger surveys for binary companions to Galactic SNe will become feasible with the release of the full Gaia proper motion and parallax catalogues providing a powerful probe of the statistics of such binaries and their role in massive star evolution, neutron star velocity distributions and runaway stars.

Keywords: stars: massive; supernovae: general; supernovae: individual: Cas A, Crab, SN 1987A

Journal Article.  9917 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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