Atmospheric parameters of 82 red giants in the<i>Kepler</i>field

Thygesen, A. O.; Frandsen, S.; Bruntt, H.; Kallinger, T.; Andersen, M. Fredslund; Elsworth, Y.; Hekker, S.; Karoff, C.; Stello, Dennis; Brogaard, K.; Burke, Christopher J.; Caldwell, Douglas A.; Christiansen, Jessie L.

doi:10.1051/0004-6361/201219237

Cited by 88 publications

(115 citation statements)

References 37 publications

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“…Yet, it calls for an observational calibration of surface abundances versus the global stellar parameters, such as mass and log g, which in return requires a high-precision mass assessment. The asteroseismology of oscillating red giants comes to the rescue, as it can indirectly provide measures of log g from seismic scaling laws as precise as ∼1% (see, e.g., Basu et al 2011;Morel et al 2013;Thygesen et al 2012). Once this is relaxed, surface abundance ratios might serve as an alternative technique in estimating the masses of stars when seismic and/or binarity information is missing.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Moravveji¹,

Guinan²,

Khosroshahi³

et al. 2013

200

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α 1 Her is the second closest asymptotic giant branch (AGB) star to the Sun, and the variable luminous M5 Ib-II member of a triple-stellar system containing G8 III and A9 IV-V components. However, the mass of this important star was previously uncertain, with published values ranging from ∼2-15 M . As shown by this study, its fortuitous membership in a nearby resolved triple-star system makes it possible to determine its fundamental properties including its mass and age. We present over 20 years of VRI photometry of α 1 Her as well as Wing intermediate-band near-IR TiO and NIR continuum photometry. We introduce a new photometry-based calibration technique and extract the effective temperature and luminosity of α 1 Her, in agreement with recent interferometric measures. We find average values of T eff = 3280 ± 87 K and log(L/L ) = 3.92 ± 0.14. With the MESA code, we calculate a dense grid of evolutionary tracks for Galactic low-to intermediate-mass (1.3 to 8 M ) rotating stars from the pre-main sequence phase to the advanced AGB phase. We include atomic diffusion and rotation mechanisms to treat the effects of extra elemental mixing. Based on the observed properties of the α Herculis stars, we constrain the age of the system to lie in the range 0.41 to 1.25 Gyr. Thus, the mass of α 1 Her lies in the range 2.175 M/M 3.250. We compare our model-based age inference with recent tracks of the Geneva and STAREVOL codes, and show their agreement. In the prescribed mass range for α 1 Her, the observed 12 C/ 13 C and 16 O/ 17 O ratios are consistent (within 2σ ) with the ratios predicted by the MESA, Geneva, and STAREVOL codes.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

Moravveji¹,

Guinan²,

Khosroshahi³

et al. 2013

200

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“…Stellar fundamental parameters have been computed with the method described by Kallinger et al (2010b), where we use ν max , Δν, and T eff as an input for the LC sample and ν max and T eff for the SC sample. Effective temperatures are taken from the Kepler Input Catalog (KIC; Brown et al 2011) and corrected according to Thygesen et al (2012).…”

Section: Granulation Amplitudesmentioning

confidence: 99%

The connection between stellar granulation and oscillation as seen by theKeplermission

Kallinger

Ridder

Hekker

et al. 2014

A&A

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224

352

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Context. The long and almost continuous observations by Kepler show clear evidence of a granulation background signal in a large sample of stars, which is interpreted as the surface manifestation of convection. It has been shown that its characteristic timescale and rms intensity fluctuation scale with the peak frequency (ν max ) of the solar-like oscillations. Various attempts have been made to quantify the observed signal, to determine scaling relations for its characteristic parameters, and to compare them to theoretical predictions. Even though they are consistent on a global scale, large systematic differences of an unknown origin remain between different methods, as well as between the observations and simulations. Aims. We aim to study different approaches to quantifying the signature of stellar granulation and to search for a unified model that reproduces the observed signal best in a wide variety of stars. We then aim to define empirical scaling relations between the granulation properties and ν max and various other stellar parameters. Methods. We use a probabilistic method to compare different approaches to extracting the granulation signal. We fit the power density spectra of a large set of Kepler targets, determine the granulation and global oscillation parameter, and quantify scaling relations between them. Results. We establish that a depression in power at about ν max /2, known from the Sun and a few other main-sequence stars, is also statistically significant in red giants and that a super-Lorentzian function with two components is best suited to reproducing the granulation signal in the broader vicinity of the pulsation power excess. We also establish that the specific choice of the background model can affect the determination of ν max , introducing systematic uncertainties that can significantly exceed the random uncertainties. We find the characteristic frequency (i.e., inverse timescale) and amplitude of both background components to tightly scale with ν max for a wide variety of stars (about 2-2000 μHz in ν max ), and quantify a mass dependency of the latter. To enable comparison with theoretical predictions (which do not include the observed power depression), we computed effective timescales and bolometric intensity fluctuations and found them to approximately scale as τ eff ∝ g −0.85 T −0.4 and A gran ∝ (g 2 M) −1/4 (or more conveniently R/M 3/4 ), respectively. Similarly, the bolometric pulsation amplitude scales approximately as A puls ∝ (g 2 M) −1/3 (or R 4/3 /M), which implicitly verifies a separate mass and luminosity dependence of A puls . We have also checked our scaling relations with solar reference values and find them in good agreement. Conclusions. We provide a thorough analysis of the granulation background signal in a large sample of stars, from which we establish a unified model that allows us to accurately extract the granulation and global oscillation parameter. The resulting scaling relations allow a simple estimate of the overall spectral shape of any solar-ty...

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“…We expect the differences between all the measurements to increase the dispersion of the residuals and to decrease the dependence of the calibrations with metallicity. Noting in brackets the percentage of stars found and used in this work 1 , our established priority order is: Morel et al (2014) [0%], Thygesen et al (2012) [0%], Bruntt et al (2012) The final sample contained 2334 stars when considering the extinction, red giants selection, multiplicity, metallicity and the photometric constraints on the G and K s bands. Subsamples were then generated for each colour-colour relation depending on the other photometric bands used (see later in Table 4 the final sizes for every fit).…”

Section: Metallicitymentioning

confidence: 99%

Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

Ruiz-Dern

Babusiaux

Arenou

et al. 2018

A&A

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Context. Gaia Data Release 1 allows to recalibrate standard candles such as the Red Clump stars. To use those, they first need to be accurately characterised. In particular, colours are needed to derive the interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. Aims. The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia Red Clump stars of the solar neighbourhood, through colour-colour, effective temperature-colour and absolute magnitude-colour relations, from the Gaia, Johnson, 2MASS, Hipparcos, Tycho-2, APASS-SLOAN and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. Methods. We used a 3D extinction map to select low reddening red giants. To calibrate the colour-colour and the effective temperaturecolour relations, we developed a MCMC method which accounts for all variable uncertainties and selects the best model for each photometric relation. We estimate the Red Clump absolute magnitude through the mode of a kernel-based distribution function. Results. We provide 20 colour vs G − K s relations and the first T eff vs G − K s calibration. We obtained the Red Clump absolute magnitudes for 15 photometric bands with, in particular, M Ks = (−1.606±0.009) and M G = (0.495±0.009)+(1.121±0.128) (G − K s − 2.1). We present an unreddened Gaia-TGAS HR diagram and use the calibrations to compare its Red Clump and its Red Giant Branch Bump with the Padova isochrones.

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Atmospheric parameters of 82 red giants in theKeplerfield

Cited by 88 publications

References 37 publications

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

The connection between stellar granulation and oscillation as seen by theKeplermission

Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

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Atmospheric parameters of 82 red giants in theKeplerfield

Cited by 88 publications

References 37 publications

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M☉⩽ 8.0

The connection between stellar granulation and oscillation as seen by theKeplermission

Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

Contact Info

Product

Resources

About

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0

THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽M/M_☉⩽ 8.0