2018ApJ...857...97M -
Astrophys. J., 857, 97-97 (2018/April-3)
Evidence for a sub-Chandrasekhar-mass Type Ia supernova in the Ursa Minor dwarf galaxy.
McWILLIAM A., PIRO A.L., BADENES C. and BRAVO E.
Abstract (from CDS):
A long-standing problem is identifying the elusive progenitors of Type Ia supernovae (SNe Ia), which can roughly be split into Chandraksekhar and sub-Chandrasekhar-mass events. An important difference between these two cases is the nucleosynthetic yield, which is altered by the increased neutron excess in Chandrasekhar progenitors due to their pre-explosion simmering and high central density. Based on these arguments, we show that the chemical composition of the most metal-rich star in the Ursa Minor dwarf galaxy, COS 171, is dominated by nucleosynthesis from a low-metallicity, low-mass, sub-Chandrasekhar-mass SN Ia. Key diagnostic abundance ratios include Mn/Fe and Ni/Fe, which could not have been produced by a Chandrasekhar-mass SN Ia. Large deficiencies of Ni/Fe, Cu/Fe and Zn/Fe also suggest the absence of alpha-rich freeze-out nucleosynthesis, favoring low-mass white dwarf progenitors of SNe Ia, near 0.95 M☉, from comparisons to numerical detonation models. We also compare Mn/Fe and Ni/Fe ratios to the recent yields predicted by Shen et al., finding consistent results. To explain the [Fe/H] at -1.35 dex for COS 171 would require dilution of the SN Ia ejecta with ∼104 M☉ of material, which is expected for an SN remnant expanding into a warm interstellar medium with n ∼ 1 cm–3. In the future, finding more stars with the unique chemical signatures we highlight here will be important for constraining the rate and environments of sub-Chandrasekhar SNe Ia.
Abstract Copyright:
© 2018. The American Astronomical Society.
Journal keyword(s):
galaxies: dwarf - nuclear reactions, nucleosynthesis, abundances - stars: abundances - supernovae: general
Simbad objects:
9
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