Stellar model fits and inversions

Christensen‐Dalsgaard, J.

doi:10.1002/asna.201211836

Cited by 34 publications

(23 citation statements)

References 116 publications

(101 reference statements)

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“…Comparing the inferred stellar properties to the first case, 16 Cyg A yields slightly different uncertainties, 16 Cyg B is shifted within the uncertainties, and only the Sun shows marginally significant shifts in radius and mass. To probe the possible source of these biases, for the fifth case (labeled "surface term" in Table 1, AMP simulations 797, 798 and 799) we repeated the fourth case using the scaled solar surface correction of Christensen-Dalsgaard (2012) to replace the Kjeldsen et al (2008) prescription. The differences were insignificant for 16 Cyg A & B, but for the Sun the alternative surface correction effectively eliminated the biases.…”

Section: Results For 16 Cyg a And B And The Sunmentioning

confidence: 99%

ASTEROSEISMIC MODELING OF 16 Cyg A & B USING THE COMPLETE KEPLER DATA SET

Metcalfe

Creevey

Davies

2015

ApJ

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Asteroseismology of bright stars with well-determined properties from parallax measurements and interferometry can yield precise stellar ages and meaningful constraints on the composition. We substantiate this claim with an updated asteroseismic analysis of the solar-analog binary system 16 Cyg A & B using the complete 30-month data sets from the Kepler space telescope. An analysis with the Asteroseismic Modeling Portal (AMP), using all of the available constraints to model each star independently, yields the same age (t = 7.0 ± 0.3 Gyr) and composition (Z = 0.021 ± 0.002, Y i = 0.25 ± 0.01) for both stars, as expected for a binary system. We quantify the accuracy of the derived stellar properties by conducting a similar analysis of a Kepler-like data set for the Sun, and we investigate how the reliability of asteroseismic inference changes when fewer observational constraints are available or when different fitting methods are employed. We find that our estimates of the initial helium mass fraction are probably biased low by 0.02-0.03 from neglecting diffusion and settling of heavy elements, and we identify changes to our fitting method as the likely source of small shifts from our initial results in 2012. We conclude that in the best cases reliable stellar properties can be determined from asteroseismic analysis even without independent constraints on the radius and luminosity.

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Section: Results For 16 Cyg a And B And The Sunmentioning

confidence: 99%

ASTEROSEISMIC MODELING OF 16 Cyg A & B USING THE COMPLETE KEPLER DATA SET

Metcalfe

Creevey

Davies

2015

ApJ

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“…Dipole modes, given their p-g mixed character, do not follow the asymptotic relations for pressure modes, a certain regularity is expected, however, in the period spacing between consecutive radial orders (Beck et al 2011;Bedding et al 2011;Mosser et al 2011), for similarity with the asymptotic behaviour of pure gravity modes (Tassoul 1980). From the detected dipole modes we got a mean value of the period spacing of mixed modes (ΔP obs ) of the order of 53 s. This quantity is smaller than the asymptotic period spacing Mosser et al 2011;Christensen-Dalsgaard 2012;Mosser et al 2012;Montalbán et al 2013) which, according to the Mosser et al (2012) estimation for a RGB star with Δν ≈ 9.5 μHz, should be slightly lower than 80 s.…”

Section: Individual Frequency Modellingmentioning

confidence: 91%

Kepler-91b: a planet at the end of its life

Lillo-Box

Barrado

Moya

et al. 2014

A&A

116

113

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Context. The evolution of planetary systems is intimately linked to the evolution of their host stars. Our understanding of the whole planetary evolution process is based on the wide planet diversity observed so far. Only a few tens of planets have been discovered orbiting stars ascending the red giant branch. Although several theories have been proposed, the question of how planets die remains open owing to the small number statistics, making it clear that the sample of planets around post-main sequence stars needs to be enlarged. Aims. In this work we study the giant star Kepler-91 (KOI-2133) in order to determine the nature of a transiting companion. This system was detected by the Kepler Space Telescope, which identified small dims in its light curve with a period of 6.246580 ± 0.000082 days. However, its planetary confirmation is needed due to the large pixel size of the Kepler camera, which can hide other stellar configurations able to mimic planet-like transit events. Methods. We analysed Kepler photometry to 1) re-calculate transit parameters; 2) study the light-curve modulations; and 3) to perform an asteroseismic analysis (accurate stellar parameter determination) by identifying solar-like oscillations on the periodogram. We also used a high-resolution and high signal-to-noise ratio spectrum obtained with the Calar Alto Fiber-fed Échelle spectrograph (CAFE) to measure stellar properties. Additionally, false-positive scenarios were rejected by obtaining high-resolution images with the AstraLux lucky imaging camera on the 2.2 m telescope at the Calar Alto Observatory. −0.22 R away from the stellar atmosphere at the pericentre. We also detected three small dims in the phase-folded light curve. The combination of two of them agrees with the theoretical characteristics expected for secondary eclipse. Conclusions. Kepler-91b could be the previous stage of the planet engulfment, which has recently been detected for BD+48 740. Our estimations show that Kepler-91b will be swallowed by its host star in less than 55 Myr. Among the confirmed planets around giant stars, this is the closest to its host star. At pericentre, the star subtends an angle of 48• , covering around 10% of the sky as seen from the planet. The planetary atmosphere seems to be inflated probably due to the high stellar irradiation.

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“…This aspect of mixed modes has motivated extensive theoretical work (e.g. Dziembowski 1971;Scuflaire 1974;Osaki 1975;Aizenman et al 1977;Dziembowski et al 2001;Christensen-Dalsgaard 2004;Dupret et al 2009).…”

Section: Introductionmentioning

confidence: 99%

ASTEROSEISMOLOGY OF EVOLVED STARS WITH KEPLER : A NEW WAY TO CONSTRAIN STELLAR INTERIORS USING MODE INERTIAS

Benomar

Belkacem

Bedding

et al. 2014

ApJ

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Asteroseismology of evolved solar-like stars is experiencing a growing interest due to the wealth of observational data from space-borne instruments such as the CoRoT and Kepler spacecraft. In particular, the recent detection of mixed modes, which probe both the innermost and uppermost layers of stars, paves the way for inferring the internal structure of stars along their evolution through the subgiant and red giant phases. Mixed modes can also place stringent constraints on the physics of such stars and on their global properties (mass, age, etc...). Here, using two Kepler stars (KIC 4351319 and KIC 6442183), we demonstrate that measurements of mixed mode characteristics allow us to estimate the mode inertias, providing a new and additional diagnostics on the mode trapping and subsequently on the internal structure of evolved stars. We however stress that the accuracy may be sensitive to non-adiabatic effects.

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Stellar model fits and inversions

Cited by 34 publications

References 116 publications

ASTEROSEISMIC MODELING OF 16 Cyg A & B USING THE COMPLETE KEPLER DATA SET

ASTEROSEISMIC MODELING OF 16 Cyg A & B USING THE COMPLETE KEPLER DATA SET

Kepler-91b: a planet at the end of its life

ASTEROSEISMOLOGY OF EVOLVED STARS WITH KEPLER : A NEW WAY TO CONSTRAIN STELLAR INTERIORS USING MODE INERTIAS

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