HE 0430-2457: a post merger extremely low-mass pre-white dwarf in a wide binary posing as an extreme horizontal branch star

Abstract

We report the discovery of HE 0430-2457, the first extremely low-mass pre-white dwarf (ELM pre-WD) in a long period binary (P = 771 +- 3 d). The spectroscopic parameters of the primary are determined to be Teff = 26200 +- 1500 K and logg = 5.40 +- 0.35, placing it in the region occupied by core He-burning hot subdwarf B stars. By comparing the spectroscopic parameters of the K-type companion to stellar models, and using the mass ratio, the mass of the hot primary is determined to be 0.23 Msun. Given that this is too low for core He-burning, the primary in HE 0430-2457 is not an EHB star but a pre WD of the ELM type. As the lifetime of ELM pre-WDs in this region of the HR diagram populated by EHBs is thought to be very short, they are not considered to be part of the observed EHBs. However, the discovery of this system indicates that the percentage of ELM pre-WDs in the observed EHB population might be higher than previously thought. Binary evolution models indicate that HE 0430-2457 is likely formed by a merger of the inner binary in a hierarchical triple system.

arXiv comment5 pages, 3 figures, Accepted for publication in MNRAS

References in corpus (34)

• emcee: The MCMC Hammer
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• Evolution of binary stars and the effect of tides on binary populations
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The Origin of Subdwarf B Star (I): the Formation Channels
• Tertiary companions to close spectroscopic binaries
• Hot subluminous stars
• Post-common-envelope binaries from SDSS. IX: Constraining the common-envelope efficiency
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Three in one go: consequential angular momentum loss can solve major problems of CV evolution
• The Yale-Potsdam Stellar Isochrones (YaPSI)
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• The ELM Survey. VII. Orbital Properties of Low Mass White Dwarf Binaries
• Grid Search in Stellar Parameters: a software for spectrum analysis of single stars and binary systems
• Post-common envelope binaries from SDSS-X: The origin of low-mass white dwarfs
• The ELM Survey. V. Merging Massive White Dwarf Binaries
• The timescale of low-mass proto-helium white dwarf evolution
• The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
• The orbits of subdwarf-B + main-sequence binaries: III. The period - eccentricity distribution
• Bayesian mass and age estimates for transiting exoplanet host stars
• The orbits of subdwarf B + main-sequence binaries. I: The sdB+G0 system PG 1104+243
• Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars
• Composite hot-subdwarf binaries -- I. The spectroscopically confirmed sdB sample
• CoRoT's view on variable B8/9 stars: spots versus pulsations: Evidence for differential rotation in HD 174648
• White Dwarf based evaluation of the GALEX absolute calibration
• The origin of single low-mass WDs: another problem that consequential angular momentum loss in CVs might solve
• The Merger Rate of Extremely Low Mass White Dwarf Binaries: Links to the Formation of AM CVn Stars and Underluminous Supernovae
• The DEBCat detached eclipsing binary catalogue
• Evolutionary Constraints on the Long-period Subdwarf B Binary PG 1018-047

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• The ELM Survey. VIII. 98 Double White Dwarf Binaries
• Gaia Data Release 2 Catalogue of Extremely-low Mass White Dwarf Candidates
• Alone but not lonely: Observational evidence that binary interaction is always required to form hot subdwarf stars
• Self-lensing Discovery of a $0.2M_{\odot }$ White Dwarf in an Unusually Wide Orbit Around a Sun-like Star
• Observed binary populations reflect the Galactic history. Explaining the orbital period-mass ratio relation in wide hot subdwarf binaries
• The ELM Survey. IX. A Complete Sample of Low Mass White Dwarf Binaries in the SDSS Footprint
• The sdA problem - II. Photometric and Spectroscopic Follow-up
• The sdA problem - III. New extremely low-mass white dwarfs and their precursors from Gaia astrometry
• Most EL CVn systems are inner binaries of hierarchical triples
• The McDonald Observatory search for pulsating sdA stars: asteroseismic support for multiple populations
• No longer impossible: the self-lensing binary KIC 8145411 is a triple
• The first heavy-metal hot subdwarf composite binary SB 744
• Orbital and atmospheric parameters of two wide O-type subdwarf binaries: BD$-$11${}^{\mathrm{o}}$162 and Feige 80
• The first massive compact companion in a wide orbit around a hot subdwarf star
• Dynamically Forming Extremely Low-Mass White Dwarf Binaries in Wide Orbits
• Four New Self-lensing Binaries from Kepler: Radial Velocity Characterization and Astrophysical Implications
• One of Everything: The Breakthrough Listen Exotica Catalog