scholarly journals Tidal Disruptions of Main-sequence Stars. III. Stellar Mass Dependence of the Character of Partial Disruptions

2020 ◽  
Vol 904 (2) ◽  
pp. 100 ◽  
Author(s):  
Taeho Ryu ◽  
Julian Krolik ◽  
Tsvi Piran ◽  
Scott C. Noble
Keyword(s):  
Main Sequence ◽  
Stellar Mass ◽  
Mass Dependence ◽  
Main Sequence Stars ◽  
Tidal Disruptions

scholarly journals Testing planet formation theories with giant stars

2007 ◽  
Vol 3 (S249) ◽  
pp. 209-222
Author(s):  
Luca Pasquini ◽  
M.P. Döllinger ◽  
A. Hatzes ◽  
J. Setiawan ◽  
L. Girardi ◽  
...  
Keyword(s):  
Main Sequence ◽  
Planet Formation ◽  
Mass Range ◽  
Stellar Mass ◽  
Giant Planets ◽  
Main Sequence Stars ◽  
Giant Stars ◽  
Solar Type ◽  
The Subject ◽  
Host Stars

AbstractPlanet searches around evolved giant stars are bringing new insights to planet formation theories by virtue of the broader stellar mass range of the host stars compared to the solar-type stars that have been the subject of most current planet searches programs. These searches among giant stars are producing extremely interesting results. Contrary to main sequence stars planet-hosting giants do not show a tendency of being more metal rich. Even if limited, the statistics also suggest a higher frequency of giant planets (at least 10%) that are more massive compared to solar-type main sequence stars.The interpretation of these results is not straightforward. We propose that the lack of a metallicity-planet connection among giant stars is due to pollution of the star while on the main sequence, followed by dillution during the giant phase. We also suggest that the higher mass and frequency of the planets are due to the higher stellar mass. Even if these results do not favor a specific formation scenario, they suggest that planetary formation might be more complex than what has been proposed so far, perhaps with two mechanisms at work and one or the other dominating according to the stellar mass. We finally stress as the detailed study of the host stars and of the parent sample is essential to derive firm conclusions.

scholarly journals Significant uncertainties from calibrating overshooting with eclipsing binary systems

2018 ◽  
Vol 618 ◽  
pp. A177 ◽  
Author(s):  
Thomas Constantino ◽  
Isabelle Baraffe
Keyword(s):  
Stellar Evolution ◽  
Binary Stars ◽  
Binary Systems ◽  
Precise Measurement ◽  
Main Sequence ◽  
Stellar Mass ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
The Masses ◽  
Convective Boundaries

The precise measurement of the masses and radii of stars in eclipsing binary systems provides a window into uncertain processes in stellar evolution, especially mixing at convective boundaries. Recently, these data have been used to calibrate models of convective overshooting in the cores of main sequence stars. In this study we have used a small representative sample of eclipsing binary stars with 1.25 ≤ M/M⊙ < 4.2 to test how precisely this method can constrain the overshooting and whether the data support a universal stellar mass–overshooting relation. We do not recover the previously reported stellar mass dependence for the extent of overshooting and in each case we find there is a substantial amount of uncertainty, that is, the same binary pair can be matched by models with different amounts of overshooting. Models with a moderate overshooting parameter 0.013 ≤ fos ≤ 0.014 (using the scheme from Herwig et al. 1997, A&A, 324, L81) are consistent with all eight systems studied. Generally, a much larger range of f is suitable for individual systems. In the case of main sequence and early post-main sequence stars, large changes in the amount of overshooting have little effect on the radius and effective temperature, and therefore the method is of extremely limited utility.

scholarly journals Tidal Disruptions of Main-sequence Stars. V. The Varieties of Disruptions

2020 ◽  
Vol 904 (1) ◽  
pp. 68 ◽  
Author(s):  
Julian Krolik ◽  
Tsvi Piran ◽  
Taeho Ryu
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Tidal Disruptions

scholarly journals Revisiting the mass-luminosity relation with an effective temperature modifier

2018 ◽  
Vol 619 ◽  
pp. L1 ◽  
Author(s):  
Jifei Wang ◽  
Zehao Zhong
Keyword(s):  
Effective Temperature ◽  
Main Sequence ◽  
Mass Range ◽  
Estimating Equation ◽  
Stellar Mass ◽  
Estimation Accuracy ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Mass Estimation ◽  
Stellar Masses

The mass-luminosity relation (MLR) is commonly used to estimate the stellar mass. The classical MLR can hardly fit data of all the stellar mass range, thus researchers have generally adopted piecewise MLRs based on the classical MLR with different exponents for different mass ranges. However, varying turning points for the piecewise MLRs and for the exponent of each segment were used, and the estimated stellar masses are not always as good as those obtained by dynamical methods. We suggest an alternative way to improve the mass estimation accuracy: adding an effective temperature modifier to modify every segment MLR. We use a corresponding estimating equation for G- and K-type main-sequence stars, and verify this equation on two eclipsing binary catalogs. We compare the estimated results with those from a classical MLR and several piecewise MLRs. We find that the new estimates are significantly more accurate than those from the classical MLR and some piecewise MLRs, and they are not inferior to the stellar masses from other piecewise MLRs. This indicates that the temperature modifier can effectively help improve the estimation accuracy. In addition, we discuss the effect of adding the temperature modifier on the practicability of estimating stellar masses.

scholarly journals The occurrence and the distribution of masses and radii of exoplanets

2010 ◽  
Vol 6 (S276) ◽  
pp. 3-12
Author(s):  
Geoffrey W. Marcy ◽  
Andrew W. Howard ◽  
Keyword(s):  
Orbital Period ◽  
Main Sequence ◽  
Stellar Mass ◽  
Population Synthesis ◽  
Actual Number ◽  
Main Sequence Stars ◽  
Solar Type ◽  
Low Mass ◽  
High Integrity ◽  
Orbital Periods

AbstractWe analyze the statistics of Doppler-detected planets and Keplere-detected planet candidates of high integrity. We determine the number of planets per star as a function of planet mass, radius, and orbital period, and the occurrence of planets as a function of stellar mass. We consider only orbital periods less than 50 days around Solar-type (GK) stars, for which both Doppler and Kepler offer good completeness. We account for observational detection effects to determine the actual number of planets per star. From Doppler-detected planets discovered in a survey of 166 nearby G and K main sequence stars we find a planet occurrence of 15+5−4% for planets with M sin i = 3–30 ME and P < 50 d, as described in Howard et al. (2010). From Keplere, the planet occurrence is 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2–4, 4–8, and 8–32 RE, consistent with Doppler-detected planets. From Keplere, the number of planets per star as a function of planet radius is given by a power law, df/dlog R = kRRα with kR = 2.9+0.5−0.4, α = −1.92 ± 0.11, and R = RP/RE. Neither the Doppler-detected planets nor the Keplere-detected planets exhibit a “desert” at super-Earth and Neptune sizes for close-in orbits, as suggested by some planet population synthesis models. The distribution of planets with orbital period, P, shows a gentle increase in occurrence with orbital period in the range 2–50 d. The occurrence of small, 2–4 RE planets increases with decreasing stellar mass, with seven times more planets around low mass dwarfs (3600–4100 K) than around massive stars (6600–7100 K).

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

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