The radius and mass of the subgiant star β Hyi from interferometry and asteroseismology

North, Julian; Davis, John; Bedding, Timothy R.; Ireland, Michael; Jacob, A. P.; O'Byrne, J. W.; Owens, S. M.; Robertson, James I.; Tango, W. J.; Tuthill, P. G.

doi:10.1111/j.1745-3933.2007.00355.x

Cited by 45 publications

(42 citation statements)

References 20 publications

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“…This has been done recently for a few nearby solar-like asteroseismic targets (see North et al 2007North et al , 2009) and yield T eff to about 50 K. Interferometric measurements of the relatively faint CoRoT targets (V 5−8) may be possible in the near future with the recently installed PAVO instrument at the CHARA array (Ireland et al 2008) or AMBER at VLTI (Petrov et al 2007). …”

Section: The Effective Temperaturementioning

confidence: 99%

Accurate fundamental parameters of CoRoT asteroseismic targets

Bruntt

2009

A&A

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Context. The CoRoT satellite has provided high-quality light curves of several solar-like stars. Analysis of these light curves provides oscillation frequencies that make it possible to probe the interior of the stars. However, additional constraints on the fundamental parameters of the stars are important for the theoretical modelling to be successful. Aims. We estimate the fundamental parameters (mass, radius, and luminosity) of the first four solar-like targets to be observed in the asteroseismic field. In addition, we determine their effective temperature, metallicity, and detailed abundance patterns.Methods. To constrain the stellar mass, radius and age we used the shotgun software, which compares the location of the stars in the Hertzsprung-Russell diagram with theoretical evolution models. This method takes the uncertainties of the observed parameters into account, including the large separation determined from the solar-like oscillations. We determined the effective temperatures and abundance patterns in the stars from the analysis of high-resolution spectra obtained with the HARPS, NARVAL, ELODIE and FEROS spectrographs. Results. We determined the mass, radius, and luminosity of the four CoRoT targets to within 5−10%, 2−4% and 5−13%, respectively. The quality of the stellar spectra determines how well we can constrain the effective temperature. For the two best spectra we get 1-σ uncertainties below 60 K and 100−150 K for the other two. The uncertainty on the surface gravity is less than 0.08 dex for three stars, while it is 0.15 dex for HD 181906. The reason for the larger uncertainty is that the spectrum has two components with a luminosity ratio of L p /L s = 0.50 ± 0.15. While Hipparcos astrometric data strongly suggest it is a binary star, we find evidence that the fainter star may be a background star, since it is less luminous but hotter.

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Section: The Effective Temperaturementioning

confidence: 99%

Accurate fundamental parameters of CoRoT asteroseismic targets

Bruntt

2009

A&A

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“…To compute the luminosity of β Hyi we used the same value for the bolometric flux as North et al (2007), F bol = (2.019 ± 0.05) × 10 9 W m −2 (Blackwell & Lynas-Gray 1998, the uncertainty on F bol is from di Benedetto 1998) and the revised Hipparcos parallax (van Leeuwen 2007). Adopting L = 3.842 × 10 26 W with an uncertainty of 0.4% (Bahcall et al 2001), we found L = 3.494 ± 0.087 L for β Hyi.…”

Section: Non-seismic Datamentioning

confidence: 99%

“…The radius was obtained by combining the interferometric angular diameter of the star, θ = 2.257 ± 0.019 mas (North et al 2007), with the revised Hipparcos parallax, π p = 134.07 ± 0.11 mas (van Leeuwen 2007).…”

Section: Non-seismic Datamentioning

confidence: 99%

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Asteroseismic modelling of the solar-type subgiant starβ Hydri

Brandão

Doğan

Christensen‐Dalsgaard

et al. 2011

A&A

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Context. Comparing models and data of pulsating stars is a powerful way to understand the stellar structure better. Moreover, such comparisons are necessary to make improvements to the physics of the stellar models, since they do not yet perfectly represent either the interior or especially the surface layers of stars. Because β Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims. The goal of the present work is to search for a representative model of the solar-type star β Hydri, based on up-to-date nonseismic and seismic data. Methods. We present a revised list of frequencies for 33 modes, which we produced by analysing the power spectrum of the published observations again using a new weighting scheme that minimises the daily sidelobes. We ran several grids of evolutionary models with different input parameters and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of β Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed frequencies of β Hydri: (i) we assume that the best model is the one that reproduces the star's interior based on the radial oscillation frequencies alone, to which we have applied the correction for the near-surface effects; (ii) we assume that the best model is the one that produces the lowest value of the chi-square (χ 2 ), i.e. that minimises the difference between the observed frequencies of all available modes and the model predictions, after all model frequencies are corrected for near-surface effects. Results. We show that after applying a correction for near-surface effects to the frequencies of the best models, we can reproduce the observed modes well, including those that have mixed mode character. The model that gives the lowest value of the χ 2 is a post-mainsequence model with a mass of 1.04 M and a metallicity slightly lower than that of the Sun. Our results underscore the importance of having individual frequencies to constrain the properties of the stellar model.

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“…1 and 2 that when these data are available, a direct estimation of the stellar mass and radius can be obtained (e.g., Silva Aguirre et al 2011;Stello et al 2008). These scaling relations seem to hold well for radius determinations (e.g., Huber et al 2012;North et al 2007;Silva Aguirre et al 2012;White et al 2013), while confirmation of masses is still under way using clusters and binaries. In order to determine ages for stars using the global seismic parameters, BASTA and BeSPP compare these quantities and the atmospheric parameters to those predicted by grids of models.…”

Section: The Bare Minimummentioning

confidence: 99%

Asteroseismic age determination for dwarfs and giants

Aguirre

Serenelli

2016

Astron Nachr

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Asteroseismology can make a substantial contribution to our understanding of the formation history and evolution of our Galaxy by providing precisely determined stellar properties for thousands of stars in different regions of the Milky Way. We present here the different sets of observables used in determining asteroseismic stellar properties, the typical level of precision obtained, the current status of results for ages of dwarfs and giants and the improvements than can be expected in the near future in the context of Galactic archaeology.

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The radius and mass of the subgiant star β Hyi from interferometry and asteroseismology

Cited by 45 publications

References 20 publications

Accurate fundamental parameters of CoRoT asteroseismic targets

Accurate fundamental parameters of CoRoT asteroseismic targets

Asteroseismic modelling of the solar-type subgiant starβ Hydri

Asteroseismic age determination for dwarfs and giants

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