The subgiant HR 7322 as an asteroseismic benchmark star

Stokholm, Amalie; Nissen, P. E.; Aguirre, V. Silva; White, T. R.; Lund, Mikkel N.; Mosumgaard, J. R.; Huber, Daniel; Jessen-Hansen, J.

doi:10.1093/mnras/stz2222

Cited by 19 publications

(23 citation statements)

References 113 publications

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“…There is no obvious connection between these stars other than their best-fitting masses all being greater than 1.3 M . We also note that, at least in the Birmingham team's models, the dipole-mode frequencies are all increasing while the star's radius is staying roughly constant, as Stokholm et al (2019) also found for HR 7322. Because the star's mean density is therefore roughly constant, one would expect purely acoustic mode frequencies to be roughly constant too.…”

Section: Precise Age Estimatessupporting

confidence: 74%

“…Such precise ages for subgiants and low-luminosity red giants have been encountered before (e.g. Deheuvels & Michel 2011;Ball & Gizon 2017;Stokholm et al 2019;Li et al 2020) but in most cases, the mass uncertainties are sufficiently precise that the age uncertainties are still consistent. We note, however, that Stokholm et al (2019) inferred very precise ages for the bright subgiant HR 7322 (KIC 10005473) and discuss the constraining power of its mixed modes in detail.…”

Section: Precise Age Estimatesmentioning

confidence: 71%

“…Deheuvels & Michel 2011;Ball & Gizon 2017;Stokholm et al 2019;Li et al 2020) but in most cases, the mass uncertainties are sufficiently precise that the age uncertainties are still consistent. We note, however, that Stokholm et al (2019) inferred very precise ages for the bright subgiant HR 7322 (KIC 10005473) and discuss the constraining power of its mixed modes in detail. Li et al (2020) also report age uncertainties that are more precise than the naïve estimate for the stars KIC 6766513, KIC 7199397, KIC 10147635, KIC 11193681 and KIC 11771760.…”

Section: Precise Age Estimatesmentioning

confidence: 99%

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Robust asteroseismic properties of the bright planet host HD 38529

Ball

Chaplin

Nielsen

et al. 2020

Monthly Notices of the Royal Astronomical Society

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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 d orbit and an outer, low-mass brown dwarf on a 2136 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 ± 0.04 M⊙, radius R = 2.68 ± 0.03 R⊙ and age t = 3.07 ± 0.39 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.

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Section: Precise Age Estimatessupporting

confidence: 74%

Section: Precise Age Estimatesmentioning

confidence: 71%

Section: Precise Age Estimatesmentioning

confidence: 99%

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Robust asteroseismic properties of the bright planet host HD 38529

Ball

Chaplin

Nielsen

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Using different approaches and input physics each team returned estimates of the physical properties of the star that were consistent to within 1 − 2σ, suggesting that the application of asteroseismic constraints produces more robust estimates of the stellar properties. For the mass and radius, which are typically well constrained by asteroseismology (Lebreton & Goupil 2014;Stokholm et al 2019), we adopted the overall values M = 1.16 ± 0.03 M and R = 1.63 ± 0.04 R . Together with a surface temperature of T eff = 5829 ± 80 K. Previous literature estimates suggest λ 2 For could be anything from an early G dwarf to a late G-type subgiant; however, multiple modeling teams using asteroseismic constraints all place the star firmly at the start of the subgiant phase of its evolution.…”

Section: Discussionmentioning

confidence: 99%

TESS asteroseismology of the known planet host star λ² Fornacis

Nielsen

Ball

Standing

et al. 2020

A&A

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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.

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“…This makes their seismic modeling challenging. Recently, increasing efforts have been made to model subgiants (Huber et al 2019;Stokholm et al 2019;Metcalfe et al 2020;Deheuvels et al 2020;Li et al 2019Li et al , 2020, driven by both their great physical interest and the sudden increase of seismic data for these stars. Most of those works focused on finding the optimal stellar parameters for one or several subgiants.…”

Section: Introductionmentioning

confidence: 99%

Probing core overshooting using subgiant asteroseismology: The case of KIC10273246

Noll

Deheuvels

Ballot

2021

A&A

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Context. The size of convective cores remains uncertain, despite their substantial influence on stellar evolution, and thus on stellar ages. The seismic modeling of young subgiants can be used to obtain indirect constraints on the core structure during main sequence, thanks to the high probing potential of mixed modes. Aims. We selected the young subgiant KIC10273246, observed by Kepler, based on its mixed-mode properties. We thoroughly modeled this star, with the aim of placing constraints on the size of its main-sequence convective core. A corollary goal of this study is to elaborate a modeling technique that is suitable for subgiants and can later be applied to a larger number of targets. Methods. We first extracted the parameters of the oscillation modes of the star using the full Kepler data set. To overcome the challenges posed by the seismic modeling of subgiants, we propose a method that is specifically tailored to subgiants with mixed modes and uses nested optimization. We then applied this method to perform a detailed seismic modeling of KIC10273246. Results. We obtain models that show good statistical agreements with the observations, both seismic and non-seismic. We show that including core overshooting in the models significantly improves the quality of the seismic fit, optimal models being found for αov = 0.15. Higher amounts of core overshooting strongly worsen the agreement with the observations and are thus firmly ruled out. We also find that having access to two g-dominated mixed modes in young subgiants allows us to place stronger constraints on the gradient of molecular weight in the core and on the central density. Conclusions. This study confirms the high potential of young subgiants with mixed modes to investigate the size of main-sequence convective cores. It paves the way for a more general study including the subgiants observed with Kepler, TESS, and eventually PLATO.

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The subgiant HR 7322 as an asteroseismic benchmark star

Cited by 19 publications

References 113 publications

Robust asteroseismic properties of the bright planet host HD 38529

Robust asteroseismic properties of the bright planet host HD 38529

TESS asteroseismology of the known planet host star λ² Fornacis

Probing core overshooting using subgiant asteroseismology: The case of KIC10273246

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The subgiant HR 7322 as an asteroseismic benchmark star

Cited by 19 publications

References 113 publications

Robust asteroseismic properties of the bright planet host HD 38529

Robust asteroseismic properties of the bright planet host HD 38529

TESS asteroseismology of the known planet host star λ2 Fornacis

Probing core overshooting using subgiant asteroseismology: The case of KIC10273246

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TESS asteroseismology of the known planet host star λ² Fornacis