Abstract
Abstract Many young, massive stars are found in close binaries. Using population synthesis simulations we predict the likelihood of a companion star being present when these massive stars end their lives as core-collapse supernovae (SNe). We focus on stripped-envelope SNe, whose progenitors have lost their outer hydrogen and possibly helium layers before explosion. We use these results to interpret new Hubble Space Telescope observations of the site of the broad-lined Type Ic SN 2002ap, 14 years post-explosion. For a subsolar metallicity consistent with SN 2002ap, we expect a main-sequence (MS) companion present in about two thirds of all stripped-envelope SNe and a compact companion (likely a stripped helium star or a white dwarf/neutron star/black hole) in about 5% of cases. About a quarter of progenitors are single at explosion (originating from initially single stars, mergers, or disrupted systems). All of the latter scenarios require a massive progenitor, inconsistent with earlier studies of SN 2002ap. Our new, deeper upper limits exclude the presence of an MS companion star >8–10 M ⊙ , ruling out about 40% of all stripped-envelope SN channels. The most likely scenario for SN 2002ap includes nonconservative binary interaction of a primary star initially ≲ 23 M ⊙ . Although unlikely (<1% of the scenarios), we also discuss the possibility of an exotic reverse merger channel for broad-lined Type Ic events. Finally, we explore how our results depend on the metallicity and the model assumptions and discuss how additional searches for companions can constrain the physics that govern the evolution of SN progenitors.
Highlights
Massive stars end their lives when their cores collapse under their own weight and form either a neutron star or black hole (e.g., Baade & Zwicky 1934; Bethe et al 1979; Woosley et al 2002)
We follow the evolution of each simulation from the onset of central hydrogen burning until the final fate as a compact remnant using the evolutionary algorithms for single stars provided by Hurley et al (2000)
In our variation with an efficiency parameter (aCE) = 5, where there is an increase of the number of systems that successfully eject their envelope and prevent coalescence, we find a larger contribution of stripped SNe with the presence of a compact companion
Summary
Massive stars end their lives when their cores collapse under their own weight and form either a neutron star or black hole (e.g., Baade & Zwicky 1934; Bethe et al 1979; Woosley et al 2002). A series of progenitor nondetections (e.g., Van Dyk et al 2003; Maund & Smartt 2005; Maund et al 2005; Smartt et al 2009; Eldridge et al 2013; Van Dyk 2016) seemingly argues against the single-star model ( the nondetections can be explained if WR progenitors become optically faint at the very end of their lives or if they are obscured and highly reddened by mass loss in the very late phases of their evolution; see Yoon et al 2012; Eldridge et al 2013, and Tramper et al 2015) These nondetections are, consistent with the binary scenario, in which the expected progenitors are lower mass helium giants that can more elude detection. If wind mass-loss rate estimates are reduced due to the effect of clumping on wind diagnostics, this will exacerbate the problems with attributing stripped-envelope SNe to wind mass loss alone (Smith 2014)
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