Context. The Transiting Exoplanet Survey Satellite (TESS) is observing bright known planet-host stars across almost the entire sky. These stars have been subject to extensive ground-based ...observations, providing a large number of radial velocity measurements. Aims. The objective of this work is to use the new TESS photometric observations to characterize the star λ2 Fornacis, and following this to update the parameters of the orbiting planet λ2 For b. Methods. We measured the frequencies of the p-mode oscillations in λ2 For, and in combination with non-seismic parameters estimated the stellar fundamental properties using stellar models. Using the revised stellar properties and a time series of archival radial velocities from the UCLES, HIRES and HARPS instruments spanning almost 20 years, we refit the orbit of λ2 For b and searched the residual radial velocities for remaining variability. Results. We find that λ2 For has a mass of 1.16 ± 0.03 M⊙ and a radius of 1.63 ± 0.04 R⊙, with an age of 6.3 ± 0.9 Gyr. This and the updated radial velocity measurements suggest a mass of λ2 For b of 16.8−1.3+1.2 M⊕, which is ∼5M⊕ less than literature estimates. We also detect an additional periodicity at 33 days in the radial velocity measurements, which is likely due to the rotation of the host star. Conclusions. While previous literature estimates of the properties of λ2 For are ambiguous, the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase. Typically only short time series of photometric data are available from TESS, but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground. This prompts a reexamination of archival radial velocity data that have been accumulated in the past few decades in order to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible.
ABSTRACT
Data from the space missions Gaia, Kepler, CoRoT and TESS, make it possible to compare parallax and asteroseismic distances. From the ratio of two densities ρsca/ρπ, we obtain an empirical ...relation fΔν between the asteroseismic large frequency separation and mean density, which is important for more accurate stellar mass and radius. This expression for main-sequence (MS) and subgiant stars with K-band magnitude is very close to the one obtained from interior MS models by Yıldız, Çelik & Kayhan. We also discuss the effects of effective temperature and parallax offset as the source of the difference between asteroseismic and non-asteroseismic stellar parameters. We have obtained our best results for about 3500 red giants (RGs) by using 2MASS data and model values for fΔν from Sharma et al. Another unknown scaling parameter $f_{\nu _{\rm max}}$ comes from the relationship between the frequency of maximum amplitude and gravity. Using different combinations of $f_{\nu _{\rm max}}$ and the parallax offset, we find that the parallax offset is generally a function of distance. The situation where this slope disappears is accepted as the most reasonable solution. By a very careful comparison of asteroseismic and non-asteroseismic parameters, we obtain very precise values for the parallax offset and $f_{\nu _{\rm max}}$ for RGs of –0.0463 ± 0.0007 mas and 1.003 ± 0.001, respectively. Our results for mass and radius are in perfect agreement with those of APOKASC-2: the mass and radius of ∼3500 RGs are in the range of about 0.8–1.8 M⊙ (96 per cent) and 3.8–38 R⊙, respectively.
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.
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.
Context.
The Transiting Exoplanet Survey Satellite (TESS) is observing bright known planet-host stars across almost the entire sky. These stars have been subject to extensive ground-based ...observations, providing a large number of radial velocity measurements.
Aims.
The objective of this work is to use the new TESS photometric observations to characterize the star
λ
2
Fornacis
, and following this to update the parameters of the orbiting planet
λ
2
For b
.
Methods.
We measured the frequencies of the
p
-mode oscillations in
λ
2
For
, and in combination with non-seismic parameters estimated the stellar fundamental properties using stellar models. Using the revised stellar properties and a time series of archival radial velocities from the UCLES, HIRES and HARPS instruments spanning almost 20 years, we refit the orbit of
λ
2
For b and searched the residual radial velocities for remaining variability.
Results.
We find that
λ
2
For has a mass of 1.16 ± 0.03
M
⊙
and a radius of 1.63 ± 0.04
R
⊙
, with an age of 6.3 ± 0.9 Gyr. This and the updated radial velocity measurements suggest a mass of
λ
2
For b of 16.8
−1.3
+1.2
M
⊕
, which is ∼5
M
⊕
less than literature estimates. We also detect an additional periodicity at 33 days in the radial velocity measurements, which is likely due to the rotation of the host star.
Conclusions.
While previous literature estimates of the properties of
λ
2
For are ambiguous, the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase. Typically only short time series of photometric data are available from TESS, but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground. This prompts a reexamination of archival radial velocity data that have been accumulated in the past few decades in order to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible.
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.
A&A 641, A25 (2020) The Transiting Exoplanet Survey Satellite (TESS) is observing bright known
planet-host stars across almost the entire sky. These stars have been subject
to extensive ground-based ...observations, providing a large number of radial
velocity (RV) measurements. In this work we use the new TESS photometric
observations to characterize the star $\lambda^2$ Fornacis, and following this
to update the parameters of the orbiting planet $\lambda^2$ For b. We measure
the p-mode oscillation frequencies in $\lambda^2$ For, and in combination with
non-seismic parameters estimate the stellar fundamental properties using
stellar models. Using the revised stellar properties and a time series of
archival RV data from the UCLES, HIRES and HARPS instruments spanning almost 20
years, we refit the orbit of $\lambda^2$ For b and search the RV residuals for
remaining variability. We find that $\lambda^2$ For has a mass of
$1.16\pm0.03$M$_\odot$ and a radius of $1.63\pm0.04$R$_\odot$, with an age of
$6.3\pm0.9$Gyr. This and the updated RV measurements suggest a mass of
$\lambda^2$ For b of $16.8^{+1.2}_{-1.3}$M$_\oplus$, which is $\sim5$M$_\oplus$
less than literature estimates. We also detect a periodicity at 33 days in the
RV measurements, which is likely due to the rotation of the host star. While
previous literature estimates of the properties of $\lambda^2$ are ambiguous,
the asteroseismic measurements place the star firmly at the early stage of its
subgiant evolutionary phase. Typically only short time series of photometric
data are available from TESS, but by using asteroseismology it is still
possible to provide tight constraints on the properties of bright stars that
until now have only been observed from the ground. This prompts a reexamination
of archival RV data from the past few decades to update the characteristics of
the planet hosting systems observed by TESS for which asteroseismology is
possible.
The Transiting Exoplanet Survey Satellite (TESS) is observing bright known planet-host stars across almost the entire sky. These stars have been subject to extensive ground-based observations, ...providing a large number of radial velocity (RV) measurements. In this work we use the new TESS photometric observations to characterize the star \(\lambda^2\) Fornacis, and following this to update the parameters of the orbiting planet \(\lambda^2\) For b. We measure the p-mode oscillation frequencies in \(\lambda^2\) For, and in combination with non-seismic parameters estimate the stellar fundamental properties using stellar models. Using the revised stellar properties and a time series of archival RV data from the UCLES, HIRES and HARPS instruments spanning almost 20 years, we refit the orbit of \(\lambda^2\) For b and search the RV residuals for remaining variability. We find that \(\lambda^2\) For has a mass of \(1.16\pm0.03\)M\(_\odot\) and a radius of \(1.63\pm0.04\)R\(_\odot\), with an age of \(6.3\pm0.9\)Gyr. This and the updated RV measurements suggest a mass of \(\lambda^2\) For b of \(16.8^{+1.2}_{-1.3}\)M\(_\oplus\), which is \(\sim5\)M\(_\oplus\) less than literature estimates. We also detect a periodicity at 33 days in the RV measurements, which is likely due to the rotation of the host star. While previous literature estimates of the properties of \(\lambda^2\) are ambiguous, the asteroseismic measurements place the star firmly at the early stage of its subgiant evolutionary phase. Typically only short time series of photometric data are available from TESS, but by using asteroseismology it is still possible to provide tight constraints on the properties of bright stars that until now have only been observed from the ground. This prompts a reexamination of archival RV data from the past few decades to update the characteristics of the planet hosting systems observed by TESS for which asteroseismology is possible.
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