Massive white Dwarf from Two Stars Merging:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Mar 2, 2020.

  1. paddoboy Valued Senior Member

    Messages:
    27,543
    https://phys.org/news/2020-03-stars-merged-massive-white-dwarf.html

    Two stars merged to form massive white dwarf:

    Please Register or Log in to view the hidden image!


    Artist's impression of two white dwarfs in the process of merging. Depending on the combined mass, the system may explode in a thermonuclear supernova, or coalesce into a single heavy white dwarf, as with WDJ0551+4135. Credit: University of Warwick/Mark Garlick
    A massive white dwarf star with a bizarre carbon-rich atmosphere could be two white dwarfs merged together according to an international team led by University of Warwick astronomers, and only narrowly avoided destruction.

    They have discovered an unusual ultra-massive white dwarf around 150 light years from us with an atmospheric composition never seen before, the first time that a merged white dwarf has been identified using its atmospheric composition as a clue.

    The discovery, published today (2 March) in the journal Nature Astronomy, could raise new questions about the evolution of massive white dwarf stars and on the number of supernovae in our galaxy.
    more at link.....

    the paper:
    https://www.nature.com/articles/s41550-020-1028-0

    An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant:

    Abstract:
    White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen1, or oxygen and neon (with a few per cent carbon) at higher initial stellar masses2. These stellar cores are enveloped by a shell of helium, which in turn, is usually surrounded by a layer of hydrogen, generally prohibiting direct observation of the interior composition. However, carbon is observed at the surface of a sizeable fraction of white dwarfs3,4, sometimes with traces of oxygen, and is thought to be dredged up from the core by a deep helium convection zone5,6. In these objects, only traces of hydrogen are found7,8, as large masses of hydrogen are predicted to inhibit hydrogen–helium convective mixing within the envelope9. We report the identification of WD J055134.612+413531.09, an ultra-massive (1.14 solar masses (M⊙)) white dwarf with a unique carbon–hydrogen mixed atmosphere (atomic ratio C∕H = 0.15). Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single-star evolution10: less than 10−9.5 and 10−7.0, respectively. Due to the fast kinematics (129 ± 5 km s−1 relative to the local standard of rest), large mass and peculiar envelope composition, we argue that WD J0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system11,12,13,14.


     

Share This Page