So-called scaling relations based on oscillation frequencies have the potential to reveal the mass and radius of solar-like oscillating stars. In the derivation of these relations, it is assumed that ...the first adiabatic exponent at the surface (
$\Gamma _{\rm \negthinspace 1s}$
) of such stars is constant. However, by constructing interior models for the mass range 0.8–1.6 M⊙, we show that
$\Gamma _{\rm \negthinspace 1s}$
is not constant at stellar surfaces for the effective temperature range with which we deal. Furthermore, the well-known relation between large separation and mean density also depends on
$\Gamma _{\rm \negthinspace 1s}$
. Such knowledge is the basis for our aim of modifying the scaling relations. There are significant differences between masses and radii found from modified and conventional scaling relations. However, a comparison of predictions of these relations with the non-asteroseismic observations of Procyon A reveals that new scaling relations are effective in determining the mass and radius of stars. In the present study, solar-like oscillation frequencies of 89 target stars (mostly Kepler and CoRoT) were analysed. As well as two new reference frequencies (νmin1 and νmin2) found in the spacing of solar-like oscillation frequencies of stellar interior models, we also take into account νmin0. In addition to the frequency of maximum amplitude, these frequencies have a very strong diagnostic potential in the determination of fundamental properties. The present study applies the derived relations from the models to the solar-like oscillating stars, and computes their effective temperatures using purely asteroseismic methods. There are in general very close agreements between effective temperatures from asteroseismic and non-asteroseismic (spectral and photometric) methods. For the Sun and Procyon A, for example, the agreement is almost total.
ABSTRACT
Asteroseismology using space-based telescopes is vital to our understanding of stellar structure and evolution. CoRoT, Kepler, and TESS space telescopes have detected large numbers of ...solar-like oscillating evolved stars. Solar-like oscillation frequencies have an important role in the determination of fundamental stellar parameters; in the literature, the relations between the two is established by the so-called scaling relations. In this study, we analyse data obtained from the observation of 15 evolved solar-like oscillating stars using the Kepler and ground-based telescopes. The main purpose of the study is to determine very precisely the fundamental parameters of evolved stars by constructing interior models using asteroseismic parameters. We also fit the reference frequencies of models to the observational reference frequencies caused by the He ii ionization zone. The 15 evolved stars are found to have masses and radii within ranges of 0.79–1.47 M⊙ and 1.60–3.15 R⊙, respectively. Their model ages range from 2.19 to 12.75 Gyr. It is revealed that fitting reference frequencies typically increase the accuracy of asteroseismic radius, mass, and age. The typical uncertainties of mass and radius are ∼3–6 and ∼1–2 per cent, respectively. Accordingly, the differences between the model and literature ages are generally only a few Gyr.
ABSTRACT
The radii of planets serve as significant constraints for their internal structure. Despite the complexity of planetary internal structure compared to stars, substantial advancements have ...been made in this field. The most critical uncertainties stem from the chemical composition and equation of state of planetary material. Using the MESA code, we construct rotating and non-rotating interior models for Jupiter and Saturn and sought to align these models to the observed radii. Rotation exerts a significant influence on their structures, distorting planetary, and stellar structures in distinct ways. Regarding gas planets’ structure, two pivotal uncertain parameters depend on a possible separation between hydrogen and helium in the protosolar disc gas due to unequal evaporation between these two gases. In an extreme scenario where only hydrogen is lost and no heavy elements or helium are lost, Jupiter and Saturn would have a core mass of zero. However, this approach fails to yield a solution for Uranus and Neptune. Instead, our models indicate that hydrogen and helium were likely lost together during the protosolar disc phase, resulting in core masses of approximately 40, 25, 14, and 12 M⊕ for Jupiter, Saturn, Neptune, and Uranus, respectively. These findings are highly compatible with the observed mass–radius relationship of exoplanets, as well as the seismic and Juno data for Jupiter’s near-surface temperature.
ABSTRACT
The observation of an unprecedented number of solar-like oscillating subgiant (SG) stars by the Kepler and TESS missions is crucial for the asteroseismic characterization of these stars, ...stellar population studies, and the study of stellar evolution theories. Owing to these missions, the fundamental parameters of the solar-like oscillating stars are precisely calculated from the evolution codes using the observed oscillation frequencies. Herein, we considered four solar-like oscillating SG stars. We obtained the fundamental parameters of the SG stars by constructing interior models using asteroseismic and non-asteroseismic observed parameters. The interior models of the four SG stars are constructed using the Modules for Experiments in Stellar Astrophysics code to effectively determine the fundamental properties. Using this method, the four solar-like oscillating SG stars are found to have masses and radii within the ranges of 1.16–1.75 M⊙ and 2.26–3.17 R⊙, respectively. The estimation accuracy of the typical asteroseismic radius, mass, and age is increased by fitting the observed and model reference frequencies. The typical uncertainties of the mass and radius are 3–4 ${{\ \rm per\ cent}}$ and 1–2 ${{\ \rm per\ cent}}$, respectively. Furthermore, the observed l = 1 frequencies, which showed a mixed mode for the first time, were also fitted to the models. Information regarding the gravity and density of the helium core was obtained by examining the mixed modes. Moreover, new asteroseismic methods for determining the age of SG stars are developed for the first time in this study.
ABSTRACT
Planets and planet candidates are subjected to great investigation in recent years. In this study, we analyse 20 planet and planet-candidate host stars at different evolutionary phases. We ...construct stellar interior models of the host stars with the mesa e.volution code and obtain their fundamental parameters under influence of observational asteroseismic and non-asteroseismic constraints. Model mass range of the host stars is 0.74–1.55 $\rm M_{\odot }$. The mean value of the so-called large separation between oscillation frequencies and its variation about the minima shows the diagnostic potential of asteroseismic properties. Comparison of variations of model and observed large separations versus the oscillation frequencies leads to inference of fundamental parameters of the host stars. Using these parameters, we revise orbital and fundamental parameters of 34 planets and four planet candidates. According to our findings, radius range of the planets is 0.35–16.50 $\rm R_{{\oplus }}$. The maximum difference between the transit and revised radii occurs for Kepler-444b-f is about 25 per cent.
It is already stated in the previous studies that the radius of the giant planets is affected by stellar irradiation. The confirmed relation between radius and incident flux depends on planetary mass ...intervals. In this study, we show that there is a single relation between radius and irradiated energy per gram per second (l
−), for all mass intervals. There is an extra increase in radius of planets if l
− is higher than 1100 times energy received by the Earth (l
⊕). This is likely due to dissociation of molecules. The tidal interaction as a heating mechanism is also considered and found that its maximum effect on the inflation of planets is about 15 per cent. We also compute age and heavy element abundances from the properties of host stars, given in the TEPCat catalogue (Southworth 2011). The metallicity given in the literature is as Fe/H. However, the most abundant element is oxygen, and there is a reverse relation between the observed abundances Fe/H and O/Fe. Therefore, we first compute O/H from Fe/H by using observed abundances, and then find heavy element abundance from O/H. We also develop a new method for age determination. Using the ages we find, we analyse variation of both radius and mass of the planets with respect to time, and estimate the initial mass of the planets from the relation we derive for the first time. According to our results, the highly irradiated gas giants lose 5 per cent of their mass in every 1 Gyr.
Comparison of Gaia and asteroseismic distances Yıldız, M; Çelik Orhan, Z; Örtel, S ...
Monthly notices of the Royal Astronomical Society. Letters,
09/2017, Letnik:
470, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Asteroseismology provides fundamental properties (mass, radius and effective temperature) of solar-like oscillating stars using so-called scaling relations. These properties allow the ...computation of the asteroseismic distance of stars. We compare the asteroseismic distances with the recently released Gaia distances for 74 stars studied in Yıldız et al. There is a very good agreement between these two distances; for 64 of these stars, the difference is less than 10 per cent. However, a systematic difference is seen if we use the effective temperature obtained by spectroscopic methods; the Gaia distances are about 5 per cent greater than the asteroseismic distances.
The large separations between the oscillation frequencies of solar-like stars are measures of stellar mean density. The separations have been thought to be mostly constant in the observed range of ...frequencies. However, detailed investigation shows that they are not constant, and their variations are not random but have very strong diagnostic potential for our understanding of stellar structure and evolution. In this regard, frequencies of the minimum large separation are very useful tools. From these frequencies, in addition to the large separation and frequency of maximum amplitude, Yıldız et al. recently have developed new methods to find almost all the fundamental stellar properties. In the present study, we aim to find metallicity and helium abundances from the frequencies, and generalize the relations given by Yıldız et al. for a wider stellar mass range and arbitrary metallicity (Z) and helium abundance (Y). We show that the effect of metallicity is significant for most of the fundamental parameters. For stellar mass, for example, the expression must be multiplied by (Z/Z⊙)0.12. For arbitrary helium abundance, M ∝ (Y/Y⊙)0.25. Methods for determination of Z and Y from pure asteroseismic quantities are based on amplitudes (differences between maximum and minimum values of Δν) in the oscillatory component in the spacing of oscillation frequencies. Additionally, we demonstrate that the difference between the first maximum and the second minimum is very sensitive to Z. It also depends on
${\nu _{\rm min}}_1/{\nu _{\rm max}}$
and small separation between the frequencies. Such a dependence leads us to develop a method to find Z (and Y) from oscillation frequencies. The maximum difference between the estimated and model Z values is about 14 per cent. It is 10 per cent for Y.
Low amplitude is the defining characteristic of solar-like oscillations. The space projects Kepler and CoRoT give us a great opportunity to successfully detect such oscillations in numerous targets. ...Achievements of asteroseismology depend on new discoveries of connections between the oscillation frequencies and stellar properties. In the previous studies, the frequency of the maximum amplitude and the large separation between frequencies were used for this purpose. In the present study, we confirm that the large separation between the frequencies has two minima at two different frequency values. These are the signatures of the He ii ionization zone, and as such have very strong diagnostic potential. We relate these minima to fundamental stellar properties such as mass, radius, luminosity, age and mass of convective zone. For mass, the relation is simply based on the ratio of the frequency of minimum Δν to the frequency of maximum amplitude. These frequency comparisons can be very precisely computed, and thus the mass and radius of a solar-like oscillating star can be determined to high precision. We also develop a new asteroseismic diagram which predicts structural and evolutionary properties of stars with such data. We derive expressions for mass, radius, effective temperature, luminosity and age in terms of purely asteroseismic quantities. For solar-like oscillating stars, we now will have five very important asteroseismic tools (two frequencies of minimum Δν, the frequency of maximum amplitude, and the large and small separations between the oscillation frequencies) to decipher properties of stellar interior astrophysics.
ABSTRACT
The Transiting Exoplanet Survey Satellite (TESS) is recording short-cadence, high duty-cycle timeseries across most of the sky, which presents the opportunity to detect and study ...oscillations in interesting stars, in particular planet hosts. We have detected and analysed solar-like oscillations in the bright G4 subgiant HD 38529, which hosts an inner, roughly Jupiter-mass planet on a $14.3\, \mathrm{d}$ orbit and an outer, low-mass brown dwarf on a $2136\, \mathrm{d}$ orbit. We combine results from multiple stellar modelling teams to produce robust asteroseismic estimates of the star’s properties, including its mass $M=1.48\pm 0.04\, \mathrm{M}_\odot {}$, radius $R=2.68\pm 0.03\, \mathrm{R}_\odot {}$, and age $t=3.07\pm 0.39\, \mathrm{Gyr}{}$. Our results confirm that HD 38529 has a mass near the higher end of the range that can be found in the literature and also demonstrate that precise stellar properties can be measured given shorter timeseries than produced by CoRoT, Kepler, or K2.
PDF
