Determining the Best Method of Calculating the Large Frequency Separation For Stellar Models

Viani, Lucas S.; Basu, Sarbani; Corsaro, E.; Ball, Warrick H.; Chaplin, W. J.

doi:10.3847/1538-4357/ab232e

Cited by 22 publications

(11 citation statements)

References 59 publications

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“…4.4), we measure ∆ν also by fitting individual radial-mode frequencies (also known as 'peakbagging') following the approach presented in Davies et al (2016). The latter approach allows for a definition of ∆ν closer to that adopted in our models, as described in Sections 2.4 and 3 (see also Khan et al 2019 andViani et al 2019). Since measuring individual-mode frequencies is not a fully automated procedure yet, we apply this approach to the limited set of stars which we then use to make detailed, precise inferences on mass loss and age.…”

Section: Asteroseismic Constraintsmentioning

confidence: 99%

Age dissection of the Milky Way discs: Red giants in theKeplerfield

Miglio

Chiappini

Mackereth

et al. 2021

A&A

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147

124

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Ensemble studies of red-giant stars with exquisite asteroseismic (Kepler), spectroscopic (APOGEE), and astrometric (Gaia) constraints offer a novel opportunity to recast and address long-standing questions concerning the evolution of stars and of the Galaxy. Here, we infer masses and ages for nearly 5400 giants with available Kepler light curves and APOGEE spectra using the code PARAM, and discuss some of the systematics that may affect the accuracy of the inferred stellar properties. We then present patterns in mass, evolutionary state, age, chemical abundance, and orbital parameters that we deem robust against the systematic uncertainties explored. First, we look at age-chemical-abundances ([Fe/H] and [α/Fe]) relations. We find a dearth of young, metal-rich ([Fe/H] > 0.2) stars, and the existence of a significant population of old (8−9 Gyr), low-[α/Fe], super-solar metallicity stars, reminiscent of the age and metallicity of the well-studied open cluster NGC 6791. The age-chemo-kinematic properties of these stars indicate that efficient radial migration happens in the thin disc. We find that ages and masses of the nearly 400 α-element-rich red-giant-branch (RGB) stars in our sample are compatible with those of an old (∼11 Gyr), nearly coeval, chemical-thick disc population. Using a statistical model, we show that the width of the observed age distribution is dominated by the random uncertainties on age, and that the spread of the inferred intrinsic age distribution is such that 95% of the population was born within ∼1.5 Gyr. Moreover, we find a difference in the vertical velocity dispersion between low- and high-[α/Fe] populations. This discontinuity, together with the chemical one in the [α/Fe] versus [Fe/H] diagram, and with the inferred age distributions, not only confirms the different chemo-dynamical histories of the chemical-thick and thin discs, but it is also suggestive of a halt in the star formation (quenching) after the formation of the chemical-thick disc. We then exploit the almost coeval α-rich population to gain insight into processes that may have altered the mass of a star along its evolution, which are key to improving the mapping of the current, observed, stellar mass to the initial mass and thus to the age. Comparing the mass distribution of stars on the lower RGB (R < 11 R⊙) with those in the red clump (RC), we find evidence for a mean integrated RGB mass loss ⟨ΔM⟩ = 0.10 ± 0.02 M⊙. Finally, we find that the occurrence of massive (M ≳ 1.1 M⊙) α-rich stars is of the order of 5% on the RGB, and significantly higher in the RC, supporting the scenario in which most of these stars had undergone an interaction with a companion.

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Section: Asteroseismic Constraintsmentioning

confidence: 99%

Age dissection of the Milky Way discs: Red giants in theKeplerfield

Miglio

Chiappini

Mackereth

et al. 2021

A&A

Self Cite

147

124

View full text Add to dashboard Cite

show abstract

“…We started by measuring the large frequency separation, Δν, and the frequency of maximum oscillation amplitude, n max , using a range of well-tested automated analysis methods (Huber et al 2009;Mosser & Appourchaux 2009;Mathur et al 2010;Corsaro & De Ridder 2014;Campante et al 2017Campante et al , 2019García Saravia Ortiz de Montellano et al 2018;Lightkurve Collaboration et al 2018;Viani et al 2019;Corsaro et al 2020), which have previously been extensively applied to Kepler/K2 data. Returned values were subject to a preliminary step that involved the rejection of outliers following Peirce's criterion (Peirce 1852;Gould 1855).…”

Section: Global Oscillation Parametersmentioning

confidence: 99%

Asteroseismology of iota Draconis and Discovery of an Additional Long-period Companion

Hill

Kane

Campante

et al. 2021

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Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise ratio follow-up measurements. Here, we report on new observations of the bright (V ∼ 3.3) giant star ι Draconis (ι Dra), known to host a planet in a highly eccentric ∼511 day period orbit. TESS observations of the star over 137 days reveal asteroseismic signatures, allowing us to constrain the stellar radius, mass, and age to ∼2%, ∼6%, and ∼28%, respectively. We present the results of continued radialvelocity monitoring of the star using the Automated Planet Finder over several orbits of the planet. We provide more precise planet parameters of the known planet and, through the combination of our radial-velocity measurements with Hipparcos and Gaia astrometry, we discover an additional long-period companion with an orbital period of ~-+ 68 36 60 yr. Mass predictions from our analysis place this substellar companion on the border of the planet and brown dwarf regimes. The bright nature of the star combined with the revised orbital architecture of the system provides an opportunity to study planetary orbital dynamics that evolve as the star moves into the giant phase of its evolution.

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“…The large separation ∆ν for the models were calculated from the frequencies of their radial modes, which in turn were calculated with the code of Antia & Basu (1994). The large separations were corrected for the surface term by applying the correction obtained by Viani et al (2019).…”

Section: Grid-based Modelingmentioning

confidence: 99%

Magnetic and Rotational Evolution of $ρ$ CrB from Asteroseismology with TESS

Metcalfe,

van Saders,

Basu

et al. 2021

Preprint

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During the first half of main-sequence lifetimes, the evolution of rotation and magnetic activity in solar-type stars appears to be strongly coupled. Recent observations suggest that rotation rates evolve much more slowly beyond middle-age, while stellar activity continues to decline. We aim to characterize this mid-life transition by combining archival stellar activity data from the Mount Wilson Observatory with asteroseismology from the Transiting Exoplanet Survey Satellite (TESS). For two stars on opposite sides of the transition (88 Leo and ρ CrB), we independently assess the mean activity levels and rotation periods previously reported in the literature. For the less active star (ρ CrB), we detect solar-like oscillations from TESS photometry, and we obtain precise stellar properties from asteroseismic modeling. We derive updated X-ray luminosities for both stars to estimate their mass-loss rates, and we use previously published constraints on magnetic morphology to model the evolutionary change in magnetic braking torque. We then attempt to match the observations with rotational evolution models, assuming either standard spin-down or weakened magnetic braking. We conclude that the asteroseismic age of ρ CrB is consistent with the expected evolution of its mean activity level, and that weakened braking models can more readily explain its relatively fast rotation rate. Future spectropolarimetric observations across a range of spectral types promise to further characterize the shift in magnetic morphology that apparently drives this mid-life transition in solar-type stars.

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Determining the Best Method of Calculating the Large Frequency Separation For Stellar Models

Cited by 22 publications

References 59 publications

Age dissection of the Milky Way discs: Red giants in theKeplerfield

Age dissection of the Milky Way discs: Red giants in theKeplerfield

Asteroseismology of iota Draconis and Discovery of an Additional Long-period Companion

Magnetic and Rotational Evolution of $ρ$ CrB from Asteroseismology with TESS

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