HV2112, a Thorne-A >> ytkow object or a super asymptotic giant branch star

Christopher A. Tout, Anna N. Zytkow, Ross Church, Herbert H. B. Lau, Carolyn L. Doherty, Robert G. Izzard

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The very bright red star HV2112 in the Small Magellanic Cloud could be a massive Thorne-A >> ytkow object (TA >> O), a supergiant-like star with a degenerate neutron core. With a luminosity of over 10(5) L-aS (TM), it could also be a super asymptotic giant branch (SAGB) star, a star with an oxygen/neon core supported by electron degeneracy and undergoing thermal pulses with third dredge up. Both TA >> Os and SAGB stars are expected to be rare. Abundances of heavy elements in HV2112's atmosphere, as observed to date, do not allow us to distinguish between the two possibilities based on the latest models. Molybdenum and rubidium can be enhanced by both the irp-process in a TA >> O or by the s-process in SAGB stars. Lithium can be generated by hot bottom burning at the base of the convective envelope in either. HV2112's enhanced calcium could thus be the key determinant. Neither SAGB stars nor TA >> Os are known to be able to synthesize their own calcium but it may be possible to produce it in the final stages of the process that forms a TA >> O, when the degenerate electron core of a giant star is tidally disrupted by a neutron star. Hence, it is more likely, on a fine balance, that HV2112 is indeed a genuine TA >> O.
    Original languageEnglish
    Pages (from-to)L36-L40
    JournalMonthly Notices of the Royal Astronomical Society
    Volume445
    Issue number1
    DOIs
    Publication statusPublished - 2014

    Subject classification (UKÄ)

    • Astronomy, Astrophysics and Cosmology

    Free keywords

    • stars: abundances
    • stars: AGB and post-AGB
    • binaries: close
    • stars:
    • evolution
    • stars: individual: HV2112

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