Considering the Single and Binary Origins of the Type IIP SN 2017eaw

Abstract

Current population synthesis modeling suggests that 30%–50% of Type II supernovae originate from binary progenitors; however, the identification of a binary progenitor is challenging. One indicator of a binary progenitor is that the surrounding stellar population is too old to contain a massive single star. Measurements of the progenitor mass of SN 2017eaw are starkly divided between observations made temporally close to core collapse, which show a progenitor mass of 13–15 M _⊙ (final helium-core mass ${M}_{\mathrm{He},\mathrm{core}}=4.4\mbox{--}6.0\,{M}_{\odot }$ —which is a more informative property than initial mass) and those from the stellar population surrounding the SN, which find M ≤ 10.8 M _⊙ ( ${M}_{\mathrm{He},\mathrm{core}}\leqslant 3.4\,{M}_{\odot }$ ). In this paper, we reanalyze the surrounding stellar population with improved astrometry and photometry, finding a median age of ${16.8}_{-1.0}^{+3.2}$ Myr for all stars younger than 50 Myr ( ${M}_{\mathrm{He},\mathrm{core}}=4.7{M}_{\odot }$ ) and ${85.9}_{-6.5}^{+3.2}$ Myr for stars younger than 150 Myr. 16.8 Myr is now consistent with the helium-core mass range derived from the temporally near-explosion observations for single stars. Applying the combined constraints to population synthesis models, we determine that the probability of the progenitor of SN 2017eaw being an initially single star is 65% compared to 35% for prior binary interaction. 85.9 Myr is inconsistent with any formation scenarios. We demonstrate that combining progenitor age constraints with helium-core mass estimates from red supergiant SED modeling, late-time spectra, and indirectly from light-curve modeling can help to differentiate single and binary progenitor scenarios and provide a framework for the application of this technique to future observations.

Keywords

• Stellar populations
• Binary stars
• Type II supernovae
• Stellar evolutionary models
• Late stellar evolution
• Massive stars