Discovery of A New Class of Pulsating Stars: Gravity-Mode Pulsators among Subdwarf B Stars

Green, E. M.; Fontaine, G.; Reed, M. D.; Callerame, K.; Seitenzahl, Ivo R.; White, Benjamin Thomas; Hyde, E. A.; Østensen, R. H.; Cordes, O.; Brassard, P.; Falter, S.; Jeffery, Elizabeth; Dreizler, S.; Schuh, S.; Giovanni, M. K.; Edelmann, H.; Rigby, J. Keith; Bronowska, A.

doi:10.1086/367929

Cited by 235 publications

(63 citation statements)

References 28 publications

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“…Green et al (2003) published the discovery of pulsations in V1093 Her, with periods between one half and two hours, and reported that as many as 75% of sdB stars cooler than 30 kK display some level of pulsations at these periods. The V1093 Her stars span the EHB from the coolest sdBs at around 24 kK up to the domain of the V361 Hya stars (Fig.…”

Section: Asteroseismologymentioning

confidence: 99%

Asteroseismology and evolution of EHB stars

Østensen¹

2009

cia

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The properties of the Extreme Horizontal Branch stars are quite well understood, but much uncertainty surrounds the many paths that bring a star to this peculiar configuration. Asteroseismology of pulsating EHB stars has been performed on a number of objects, bringing us to the stage where comparisons of the inferred properties with evolutionary models becomes feasible. In this review I will outline our current understanding of the formation and evolution of these stars, with emphasis on recent progress. The aim is to show how the physical parameters derived by asteroseismology can enable the discrimination between different evolutionary models.

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Section: Asteroseismologymentioning

confidence: 99%

Asteroseismology and evolution of EHB stars

Østensen¹

2009

cia

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“…The analyses for the three pulsators estimate the convection zone to extend out to M cc = 0. 22 [14]. In the last case two equally probable solutions were found.…”

Section: Subdwarf B Starsmentioning

confidence: 88%

Asteroseismic Constraints on the Models of Hot B Subdwarfs: Convective Helium-Burning Cores

2017

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Abstract.Asteroseismology of non-radial pulsations in Hot B Subdwarfs (sdB stars) offers a unique view into the interior of core-helium-burning stars. Ground-based and space-borne high precision light curves allow for the analysis of pressure and gravity mode pulsations to probe the structure of sdB stars deep into the convective core. As such asteroseismological analysis provides an excellent opportunity to test our understanding of stellar evolution. In light of the newest constraints from asteroseismology of sdB and red clump stars, standard approaches of convective mixing in 1D stellar evolution models are called into question. The problem lies in the current treatment of overshooting and the entrainment at the convective boundary. Unfortunately no consistent algorithm of convective mixing exists to solve the problem, introducing uncertainties to the estimates of stellar ages. Three dimensional simulations of stellar convection show the natural development of an overshooting region and a boundary layer. In search for a consistent prescription of convection in one dimensional stellar evolution models, guidance from three dimensional simulations and asteroseismological results is indispensable. Hot Subdwarf B starsSubdwarf B (sdB) stars are a class of hot (T eff = 20, 000−40, 000 K) and compact (log g = 5.0−6.2) stars with very thin hydrogen envelopes (M H < 0.01 M ) [1,2]. They form the so-called extreme horizontal branch (EHB) in the Hertzsprung-Russell diagram, where most of them quietly burn helium in their cores for ∼10 8 years. A violent process stripped them of most of their hydrogen envelope before they underwent the helium flash near the tip of the red giant branch (RGB). As a consequence they will not climb up the asymptotic giant branch (AGB) once their core helium is exhausted, but rather evolve directly to become white dwarfs.Although some sdB stars appear to be single and others occur in wide binaries, surveys have concluded that the majority are in close binaries with white dwarf or lowmass main sequence companions [3][4][5]. A small fraction of the latter exhibit eclipses, offering insight into the orbital parameters and masses of the systems. These HW Virginis stars, named after the discovery system, play a crucial role in determining the mass distribution of sdB stars. The median mass of sdB stars estimated from these binaries is 0.469 M [6].The formation scenarios for sdB stars have to explain their existence in both single and binary systems as well as introduce a process by which the hydrogen envelope of the progenitor stars can be lost. Common envelope ejection (CE) or stable Roche lobe overflow (RLOF) during binary evolution result in systems with close and wide e-mail: jtschindler@email.arizona.edu separations, respectively, [7]. Population synthesis models can well explain the occurrence of binary systems and the mass distribution of the primary and secondary components [8]. To explain the existence of single sdB stars, extreme mass loss on the RGB [9-11] as well as white dwarf mergers...

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“…The short periods of the EC 14026 stars [10] are of the order of minutes and have amplitudes of a few tens mmag, while the longer periods in the PG 1716 stars [11] range from 30 to 80 mins at even lower amplitudes of a few mmag. Typical light curves are compiled in Fig.…”

Section: Pulsating Subdwarf B Starsmentioning

confidence: 99%

“…Only a fraction of the sdB stars with otherwise identical effective temperature, surface gravity and photospheric metallicity are pulsators; they co-exist with non-variable stars in the same region of the HRD and fall into two groups, the short-period p-mode and the longer-period g-mode prototype [11] (V 1093 Her)…”

Section: Pulsating Subdwarf B Starsmentioning

confidence: 99%

Observations of compact pulsators: the subdwarf B variables

Schuh¹

2008

J. Phys.: Conf. Ser.

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Discovery of A New Class of Pulsating Stars: Gravity-Mode Pulsators among Subdwarf B Stars

Cited by 235 publications

References 28 publications

Asteroseismology and evolution of EHB stars

Asteroseismology and evolution of EHB stars

Asteroseismic Constraints on the Models of Hot B Subdwarfs: Convective Helium-Burning Cores

Observations of compact pulsators: the subdwarf B variables

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