Orbital Characteristics of the Subdwarf-B and F V Star Binary EC~20117-4014(=V4640 Sgr)

Abstract

Among the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC~20117-4014 (=V4640~Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion (O'Donoghue et al. 1997), however the period and the orbit semi-major axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic Observed minus Calculated (O-C) variations were detected in the two highest amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system's precise orbital period (P = 792.3 days) and the light-travel time amplitude (A = 468.9 s). This binary shows no significant orbital eccentricity and the upper limit of the eccentricity is 0.025 (using 3 $\sigma$ as an upper limit). This upper limit of the eccentricity is the lowest among all wide sdB binaries with known orbital parameters. This analysis indicated that the sdB is likely to have lost its hydrogen envelope through stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB stars. In addition to those results, the underlying pulsation period change obtained from the photometric data was $\dot{P}$ = 5.4 ($\pm$0.7) $\times$ $10^{-14}$ d d${}^{-1}$, which shows that the sdB is just before the end of the core helium-burning phase.

References in corpus (31)

• 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
• The Origin of Subdwarf B Star (I): the Formation Channels
• The origin of sdB stars (II)
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• Pulsating White Dwarf Stars and Precision Asteroseismology
• The Potential of Asteroseismology for Hot, Subdwarf B Stars: A New Class of Pulsating Stars?
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• Origin of apparent period variations in eclipsing post-common-envelope binaries
• HS0702+6043: A star showing both short-period p-mode and long-period g-mode oscillations
• The orbital periods of subdwarf B binaries produced by the first stable Roche overflow channel
• Eclipsing time variations in close binary systems: Planetary hypothesis vs. Applegate mechanism
• A survey for pulsating subdwarf B stars with the Nordic Optical Telescope
• A pulsation zoo in the hot subdwarf B star KIC 10139564 observed by Kepler
• Testing eccentricity pumping mechanisms to model eccentric long period sdB binaries with MESA
• Composite hot-subdwarf binaries -- I. The spectroscopically confirmed sdB sample
• Detection of a tertiary brown dwarf companion in the sdB-type eclipsing binary HS 0705+6700
• PG1018-047: the longest period subdwarf B binary
• Subdwarf B stars from the common envelope ejection channel
• How to Make a Singleton sdB Star via Accelerated Stellar Evolution
• Tatooine's Future: The Eccentric Response of Kepler's Circumbinary Planets to Common-Envelope Evolution of their Host Stars
• Observations and asteroseismological analysis of the rapid subdwarf B pulsator EC 09582-1137
• Binary star influence on post-main-sequence multi-planet stability
• Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234
• Two New Long-Period Hot Subdwarf Binaries with Dwarf Companions
• Rapid orbital decay in detached binaries: evidence for circumbinary disks
• PG 1613+426: a new sdB pulsator
• Structure and evolution of pulsating hot subdwarfs

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