Asteroseismology of hot B subdwarf stars

Charpinet, S.; Grootel, Valérie Van; Brassard, P.; Fontaine, G.; Green, Elizabeth M.; Randall, S. K.

doi:10.1051/epjconf/20134304005

Cited by 17 publications

(7 citation statements)

References 39 publications

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“…The CBM at the border of the He-burning core is significantly less understood. While there are some physical arguments (e.g., Castellani et al 1985) and asteroseismic inferences (Charpinet et al 2013;Constantino et al 2015) in favor of the existence of CBM at convective boundaries, its extension is much less constrained. In the absence of a better constraint, we set f CHeB = 0.0174 (i.e., = 0.2 H P ) in our simulations for all stars.…”

Section: Convection and Convective Boundary Mixingmentioning

confidence: 99%

New models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae

Bertolami

Miguel²

2016

A&A

363

285

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Context. The post-asymptotic giant branch (AGB) phase is arguably one of the least understood phases of the evolution of low-and intermediate-mass stars. The two grids of models presently available are based on outdated micro-and macrophysics and do not agree with each other. Studies of the central stars of planetary nebulae (CSPNe) and post-AGB stars in different stellar populations point to significant discrepancies with the theoretical predictions of post-AGB models. Aims. We study the timescales of post-AGB and CSPNe in the context of our present understanding of the micro-and macrophysics of stars. We want to assess whether new post-AGB models, based on the latter improvements in TP-AGB modeling, can help us to understand the discrepancies between observation and theory and within theory itself. In addition, we aim to understand the impact of the previous AGB evolution for post-AGB phases. Methods. We computed a grid of post-AGB full evolutionary sequences that include all previous evolutionary stages from the zero age main sequence to the white dwarf phase. We computed models for initial masses between 0.8 and 4 M and for a wide range of initial metallicities (Z 0 = 0.02, 0.01, 0.001, 0.0001). This allowed us to provide post-AGB timescales and properties for H-burning post-AGB objects with masses in the relevant range for the formation of planetary nebulae (∼0.5−0.8 M ). We included an updated treatment of the constitutive microphysics and included an updated description of the mixing processes and winds that play a key role during the thermal pulses (TP) on the AGB phase.Results. We present a new grid of models for post-AGB stars that take into account the improvements in the modeling of AGB stars in recent decades. These new models are particularly suited to be inputs in studies of the formation of planetary nebulae and for the determination of the properties of CSPNe from their observational parameters. We find post-AGB timescales that are at least approximately three to ten times shorter than those of old post-AGB stellar evolution models. This is true for the whole mass and metallicity range. The new models are also ∼0.1−0.3 dex brighter than the previous models with similar remnant masses. Post-AGB timescales only show a mild dependence on metallicity. Conclusions. The shorter post-AGB timescales derived in the present work are in agreement with recent semiempirical determinations of the post-AGB timescales from the CSPNe in the Galactic bulge. The lower number of post-AGB and CSPNe predicted by the new models might help to alleviate some of the discrepancies found in the literature. As a result of the very different post-AGB crossing times, initial final mass relation and luminosities of the present models, the new models will have a significant impact on the predictions for the formation of planetary nebulae and the planetary nebulae luminosity function. In particular, the new models should help to understand the formation of low-mass CSPNe as inferred from asteroseismic and spectroscopic d...

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Section: Convection and Convective Boundary Mixingmentioning

confidence: 99%

New models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae

Bertolami

Miguel²

2016

A&A

363

285

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“…This feature is similar to the one already reported by Baran & Winans (2012) and becomes characteristic of the sdB interior. According to (Charpinet et al 2013(Charpinet et al , 2014a the feature could be caused by strong diffusion inside the stars.…”

Section: B3mentioning

confidence: 99%

Pulsating subdwarf B stars in the oldest open cluster NGC6791

Sanjayan,

Baran,

Ostrowski

et al. 2021

Preprint

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We report results of our analysis of the Kepler superaperture LC data of the open cluster NGC 6791 to search for pulsating sdB stars. We checked all pixels and we found only three sdB stars to be pulsating, KIC 2569576 (B3), KIC 2438324 (B4) and KIC 2437937 (B5). These stars were known to be pulsators before, though we extended data coverage detecting more frequencies and features in their amplitude spectra, i.e. new multiplets and more complete period spacing sequences that we used for identifying geometry of the pulsation modes. The multiplet splittings were also used to derive rotation periods. The remaining known sdBs do not show any pulsation-related light variation down to our detection thresholds. We analyzed already existing spectroscopic observations taken with the HECTOSPEC at the MMT telescope in Smithsonian Arizona and with the GMOS at the Gemini North telescope, and fitted atmospheric parameters using the Balmer lines. Four stars, B3 -B6, show atmospheric parameters that are consistent with g-mode dominated sdBs. We detected hints of radial velocity variability in B3, B5 and B6, indicating these three stars may be in binaries.

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“…We have recently decided to revisit the problem of the seismic modeling of white dwarf stars using current and proven techniques, typical of those used highly successfully for the class of pulsating hot subdwarf B stars as reviewed and used recently in Charpinet et al (2013) and Van Grootel et al (2013). Our approach rests on a new detailed parametrization of white dwarf models coupled to a double optimization procedure that insures an objective search in parameter space for the best fitting model.…”

Section: Astrophysical Contextmentioning

confidence: 99%

Ultra-high precision white dwarf asteroseismology

et al. 2015

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We present a brief progress report in our quest for deriving seismic models of pulsating white dwarfs that can account simultaneously for all the observed periods at the precision of the observations. We point out that this is possible from a pratical point of view only if parametrized models are used to complement evolutionary models. We adopt a double optimization procedure that insures that the best possible model in parameter space is found objectively and automatically. Our ultimate goal is to be able to account for the exquisite period data gathered with Kepler and Kepler-2 on key pulsating white dwarfs of both the DA (ZZ Ceti) and DB (V777 Her) type.

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Asteroseismology of hot B subdwarf stars

Cited by 17 publications

References 39 publications

New models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae

New models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae

Pulsating subdwarf B stars in the oldest open cluster NGC6791

Ultra-high precision white dwarf asteroseismology

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