Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAsteroseismic analysis of Kepler target KIC 2837475
97
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The ratios $r_{01}$ and $r_{10}$ of small to large separations of KIC 2837475 primarily exhibit an increase behavior in the observed frequency range. The calculations indicate that only the models with overshooting parameter $delta_{rm ov}$ between approximately 1.2 and 1.6 can reproduce the observed ratios $r_{01}$ and $r_{10}$ of KIC 2837475. The ratios $r_{01}$ and $r_{10}$ of the frequency separations of p-modes with inner turning points that are located in the overshooting region of convective core can exhibit an increase behavior. The frequencies of the modes that can reach the overshooting region decrease with the increase in $delta_{rm ov}$. Thus the ratio distributions are more sensitive to $delta_{rm ov}$ than to other parameters. The increase behavior of the KIC 2837475 ratios results from a direct effect of the overshooting of convective core. The characteristic of the ratios provides a strict constraint on stellar models. Observational constraints point to a star with $M=1.490pm0.018$ $M_{odot}$, $R=1.67pm0.01$ $R_{odot}$, age $=2.8pm0.4$ Gyr, and $1.2lesssim$ $delta_{rm ov}$ $lesssim1.6$ for KIC 2837475.
rate research
Read More
We present results of an asteroseismic study on the $gamma$ Dor type {it Kepler} target KIC,6462033. {it Kepler} photometry is used to derive the frequency content and principal modes. High-dispersion ground-based spectroscopy is also carried out in order to determine the atmospheric parameters and projected rotational velocity. From an analysis of the {it Kepler} long cadence time series, we find that the light curve of KIC,6462033 is dominated by three modes with frequencies $f_{1}$=0.92527, $f_{2}$=2.03656 and $f_{3}$=1.42972 d$^{-1}$ as well as we detect more than a few hundreds of combination terms. However, two other independent frequencies appear to have lower amplitudes in addition to these three dominant terms. No significant peaks are detected in the region $>$ 5 d$^{-1}$. We therefore confirm that KIC,6462033 pulsates in the frequency range of $gamma$ Dor type variables, and a future study will allow us to investigate modal behaviour in this star.
The high precision data obtained by the {it Kepler} satellite allows us to detect hybrid type pulsator candidates more accurately than the data obtained by ground-based observations. In this study, we present preliminary results on the new analysis of the {it Kepler} light curve and high resolution spectroscopic observations of pulsating Am star KIC,9204718. Our tentative analysis therefore show that the star has hybrid pulsational characteristics.
The frequency ratios and of HD 49933 exhibit an increase at high frequencies. This behavior also exists in the ratios of other stars, which is considered to result from the low signal-to-noise ratio and the larger line width at the high-frequency end and could not be predicted by stellar models in previous work. Our calculations show that the behavior not only can be reproduced by stellar models, but can be predicted by asymptotic formulas of the ratios. The frequency ratios of the Sun, too, can be reproduced well by the asymptotic formulas. The increased behavior derives from the fact that the gradient of mean molecular weight at the bottom of the radiative region hinders the propagation of p-modes, while the hindrance does not exist in the convective core. This behavior should exist in the ratios of stars with a large convective core. The characteristic of the ratios at high frequencies provides a strict constraint on stellar models and aids in determining the size of the convective core and the extent of overshooting. Observational constraints point to a star with $M=1.28pm0.01 M_{odot}$, $R=1.458pm0.005 R_{odot}$, $t=1.83pm0.1$ Gyr, $r_{cc}=0.16pm0.02 R_{odot}$, $alpha=1.85pm0.05$, and $delta_{ov}=0.6pm0.2$ for HD 49933.
The satellite CoRoT (Convection, Rotation, and planetary Transits) has provided high-quality data for almost six years. We show here the asteroseismic analysis and modeling of HD169392A, which belongs to a binary system weakly gravitationally bound as the distance between the two components is of 4250 AU. The main component, HD169392A, is a G0IV star with a magnitude of 7.50 while the second component is a G0V-G2IV star with a magnitude of 8.98. This analysis focuses on the main component, as the secondary one is too faint to measure any seismic parameters. A complete modeling has been possible thanks to the complementary spectroscopic observations from HARPS, providing Teff=5985+/-60K, log g=3.96+/-0.07, and [Fe/H]=- 0.04+/-0.10.
The frequency ratios $r_{01}$ and $r_{10}$ of KIC 11081729 decrease firstly and then increase with the increase in frequency. For different spectroscopic constraints, all models with overshooting parameter $delta_{mathrm{ov}}$ less than 1.7 can not reproduce the distributions of the ratios. However, the distributions of the ratios can be directly reproduced by models with $delta_{mathrm{ov}}$ in the range of about $1.7-1.8$. The estimations of mass and age of the star can be affected by spectroscopic results, but the determination of the $delta_{mathrm{ov}}$ is not dependent on the spectroscopic results. A large overshooting of convective core may exist in KIC 11081729. The characteristics of $r_{01}$ and $r_{10}$ of KIC 11081729 may result from the effects of the large overshooting of convective core. The distributions of $r_{01}$ and $r_{10}$ of different stars with a convective core can be reproduced by the function $B( u_{n,1})$. If the value of the critical frequency $ u_{0}$ is larger than the value of frequency of maximum oscillation power $ u_{max}$, a star may have a small convective core and $delta_{rm ov}$. But if the value of $ u_{0}$ is less than that of $ u_{max}$, the star may have a large convective core and $delta_{mathrm{ov}}$. The function aids in determining the presence of convective core and the size of the convective core including overshooting region from observed frequencies. The determination is not dependent on the calculation of stellar models.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
