Thermal imbalance effects on pulsational stability in stellar models

1985 ◽  
Vol 112 (1) ◽  
pp. 185-192
Author(s):  
N. S. Chauhan
Keyword(s):  
Stellar Models ◽  
Thermal Imbalance ◽  
Pulsational Stability

Pulsational Stability of Stars in Thermal Imbalance

1973 ◽  
Vol 182 ◽  
pp. 885 ◽  
Author(s):  
J. P. Cox ◽  
C. J. Hansen ◽  
William R. Davey
Keyword(s):  
Stability Of Stars ◽  
Thermal Imbalance ◽  
Pulsational Stability

scholarly journals A Search for β Cephei Pulsation in Extreme Composition Models

1974 ◽  
Vol 59 ◽  
pp. 73-73
Author(s):  
Arthur N. Cox ◽  
James E. Tabor
Keyword(s):  
Nuclear Reactions ◽  
Stellar Structure ◽  
Stellar Models ◽  
Composition Changes ◽  
Pulsational Stability ◽  
Hr Diagram

Following Davey (1973), we have considered the linear radial pulsational stability of stellar models in the region of the HR diagram populated by β Cephei stars. Instead of one composition, however, we have considered many compositions, some of them rather extreme. No consideration of composition changes for temperatures above a few-million degrees was given, and therefore the stellar structure and its pulsational stability may not be evaluated very accurately. Modulation of nuclear reactions was also neglected. In no case was radial pulsational instability found.

scholarly journals Estimation of singly transiting K2 planet periods with Gaia parallaxes

2019 ◽  
Vol 489 (3) ◽  
pp. 3149-3161 ◽  
Author(s):  
Emily Sandford ◽  
Néstor Espinoza ◽  
Rafael Brahm ◽  
Andrés Jordán
Keyword(s):  
Direct Measurement ◽  
Free Parameter ◽  
Broad Band ◽  
Long Period ◽  
Period Distribution ◽  
Typical Period ◽  
Stellar Models ◽  
Host Stars ◽  
Stellar Density ◽  
As If

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.

scholarly journals Influence of Rotation on the Stellar Parameters

1993 ◽  
Vol 137 ◽  
pp. 162-164 ◽  
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).

scholarly journals Testing convection in stellar models using detached eclipsing binaries

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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