Abstract
ABSTRACTMany characteristics of dwarf carbon stars are broadly consistent with a binary origin, including mass transfer from an evolved companion. While the population overall appears to have old-disc or halo kinematics, roughly 2 per cent of these stars exhibit Hα emission, which in low-mass main-sequence stars is generally associated with rotation and relative youth. Its presence in an older population therefore suggests either irradiation or spin-up. This study presents time-series analyses of photometric and radial-velocity data for seven dwarf carbon stars with Hα emission. All are shown to have photometric periods in the range 0.2–5.2 d, and orbital periods of similar length, consistent with tidal synchronization. It is hypothesized that dwarf carbon stars with emission lines are the result of close-binary evolution, indicating that low-mass, metal-weak, or metal-poor stars can accrete substantial material prior to entering a common-envelope phase.
Highlights
Binary-star evolution is responsible for a wide array of astrophysical phenomena, including blue stragglers, Type-Ia supernovae, and gravitational waves (Maeder 1987; Webbink 1984; Abbott et al.D Roche-lobe overflow, and more-recent models such as wind–Rochelobe overflow (Abate et al 2013)
This study investigates the possibility that emission lines observed in some dwarf carbon (dC) stars arise because of illuminate the nature of the source: (1) Green 2013; (2) Whitehouse et al 2018; (3) Mould et al 1985; (4) Rossi et al 2011; (5) Liebert et al 1994
If the white dwarf is at the Gaia parallax distance of d =
Summary
Binary-star evolution is responsible for a wide array of astrophysical phenomena, including blue stragglers, Type-Ia supernovae, and gravitational waves (Maeder 1987; Webbink 1984; Abbott et al. D Roche-lobe overflow, and more-recent models such as wind–Rochelobe overflow (Abate et al 2013). Metal-poor stars are significantly more susceptible to atmospheric pollution through external carbon enrichment processes. Interactions between binary components may result in deviations from the course of typical single-star evolution, through. N A prime example of how binary interactions can influence stellar evolution is given by dwarf carbon (dC) stars. These low-mass, Liebert et al 1994; Green 2013). Recent observational evidence supports a binary formation channel for dC stars.
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