Testing Metal-poor Stellar Models and Isochrones withHSTParallaxes of Metal-poor Stars

ABSTRACT When a planet is only observed to transit once, direct measurement of its period is impossible. It is possible, however, to constrain the periods of single transiters, and this is desirable as they are likely to represent the cold and far extremes of the planet population observed by any particular survey. Improving the accuracy with which the period of single transiters can be constrained is therefore critical to enhance the long-period planet yield of surveys. Here, we combine Gaia parallaxes with stellar models and broad-band photometry to estimate the stellar densities of K2 planet host stars, then use that stellar density information to model individual planet transits and infer the posterior period distribution. We show that the densities we infer are reliable by comparing with densities derived through asteroseismology, and apply our method to 27 validation planets of known (directly measured) period, treating each transit as if it were the only one, as well as to 12 true single transiters. When we treat eccentricity as a free parameter, we achieve a fractional period uncertainty over the true single transits of $94^{+87}_{-58}{{\ \rm per\ cent}}$, and when we fix e = 0, we achieve fractional period uncertainty $15^{+30}_{-6}{{\ \rm per\ cent}}$, a roughly threefold improvement over typical period uncertainties of previous studies.

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Influence of Rotation on the Stellar Parameters

International Astronomical Union Colloquium ◽

10.1017/s0252921100017668 ◽

1993 ◽

Vol 137 ◽

pp. 162-164 ◽

Cited By ~ 2

Author(s):

V. Wenske ◽

D. Schönberner

Keyword(s):

Lower Surface ◽

Equatorial Region ◽

Star Formation History ◽

Rotational Rate ◽

Visible Part ◽

Photometric Observations ◽

Formation History ◽

Inclination Angles ◽

Stellar Models ◽

Stellar Masses

For several years it has become quite common to derive stellar parameters like effective temperature, Teff, and surface acceleration, g, by means of properly calibrated photometric indices, and to use these values for the derivation of important properties of stellar aggregates (viz. ages, star formation history, distances, etc.). Photometric observations, however, fail to give informations about one important property of a star: its rotational rate!The main effect of rotation is to increase the size of the star, mainly in the equatorial region, leading to lower surface temperatures and accelerations. Since in non–spherical stars Teff and g depend on the latitude, the observed values, which are, of course, averages over the visible hemisphere, depend on the angle of inclination, i. Collins & Sonneborn (1977) utilized the rigidly rotating stellar models of Sackmann and Anand (1970) to compute emergent fluxes and photometric indices for various stellar masses, inclination angles i and rotational parameters being the break–up rotational rate. These indices, viz. C0 and β, represent then averages over the visible part of the rotally distorted stellar models. Closer inspections indicated also that emergent fluxes and line profiles of rotationally distorted stars can be matched by the predictations of standard model atmospheres to a very high accuray, even for w close to unity (Wenske 1992, Diplom Thesis).

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Testing convection in stellar models using detached eclipsing binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307000336 ◽

2006 ◽

Vol 2 (S239) ◽

pp. 157-159

Author(s):

John Southworth ◽

Hans Bruntt

Keyword(s):

Binary Stars ◽

Eclipsing Binaries ◽

Eclipsing Binary ◽

Fundamental Properties ◽

Eclipsing Binary Stars ◽

Average System ◽

Stellar Models

AbstractThe fundamental properties of detached eclipsing binary stars can be measured very accurately, which could make them important objects for constraining the treatment of convection in theoretical stellar models. However, only four or five pieces of information can be found for the average system, which is not enough. We discuss studies of more interesting and useful objects: eclipsing binaries in clusters and eclipsing binaries with pulsating components.

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Developments in Physics of Massive Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308020449 ◽

2007 ◽

Vol 3 (S250) ◽

pp. 147-160 ◽

Cited By ~ 3

Author(s):

Georges Meynet ◽

Sylvia Ekström ◽

André Maeder ◽

Raphael Hirschi ◽

Cyril Georgy ◽

...

Keyword(s):

Massive Star ◽

Massive Stars ◽

Stellar Models

AbstractNew constraints on stellar models are provided by large surveys of massive stars, interferometric observations and asteroseismology. After a review of the main results so far obtained, we present new results from rotating models and discuss comparisons with observed features. We conclude that rotation is a key feature of massive star physics.

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