The Correlation between Mixing Length and Metallicity on the Giant Branch: Implications for Ages in the Gaia Era

Tayar, Jamie; Somers, Garrett; Pinsonneault, Marc H.; Stello, Dennis; Mints, A.; Johnson, Jennifer A.; Zamora, Olga; García-Hernández, D. A.; Maraston, Claudia; Serenelli, Aldo; Prieto, C. Allende; Bastien, Fabienne A.; Basu, Sarbani; Bird, Jonathan C.; Cohen, Roger E.; Cunha, Kátia; Elsworth, Y.; García, Rafael A.; Girardi, L.; Hekker, S.; Holtzman, Jon A.; Huber, Daniel; Mathur, S.; Mészáros, Szabolcs; Mosser, B.; Shetrone, Matthew; Aguirre, V. Silva; Stassun, Keivan G.; Stringfellow, Guy S.; Zasowski, Gail; Roman-Lopes, Alexandre

doi:10.3847/1538-4357/aa6a1e

Cited by 110 publications

(130 citation statements)

References 79 publications

(104 reference statements)

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“…In this work, six oscillating red giants in eclipsing binaries were used to calibrate these parameters for evolved stars. Our main conclusions from the results are summarised as follows: (i) The average mixing-length parameter of the six red giants is ∼ 1.14 ± 0.07 times the calibrated solar value, which is similar with the previous results based on the APOGEE sample (Tayar et al 2017).…”

Section: Discussionsupporting

confidence: 89%

“…Their grid models for the red giants within the range of metallicity ([Fe/H]) from −0.5 to +0.4 required a ∼8% larger α than the Sun to fit the observations. Tayar et al (2017) also suggested a linear correlation between α and [Fe/H]. However, we did not obtain a clear dependence between the two parameters in our stars.…”

Section: The Mixing-length Parametercontrasting

confidence: 73%

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Modelling Kepler red giants in eclipsing binaries: calibrating the mixing-length parameter with asteroseismology

Bedding

Huber

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Stellar models rely on a number of free parameters. High-quality observations of eclipsing binary stars observed by Kepler offer a great opportunity to calibrate model parameters for evolved stars. Our study focuses on six Kepler red giants with the goal of calibrating the mixing-length parameter of convection as well as the asteroseismic surface term in models. We introduce a new method to improve the identification of oscillation modes which exploits theoretical frequencies to guide the mode identification ('peak-bagging') stage of the data analysis. Our results indicate that the convective mixing-length parameter (α) is ≈14% larger for red giants than for the Sun, in agreement with recent results from modelling the APOGEE stars. We found that the asteroseismic surface term (i.e. the frequency offset between the observed and predicted modes) correlates with stellar parameters (T eff , log g) and the mixing-length parameter. This frequency offset generally decreases as giants evolve. The two coefficients a −1 and a 3 for the inverse and cubic terms that have been used to describe the surface term correction are found to correlate linearly. The effect of the surface term is also seen in the p-g mixed modes, however, established methods for correcting the effect are not able to properly correct the g-dominated modes in late evolved stars.

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Section: Discussionsupporting

confidence: 89%

Section: The Mixing-length Parametercontrasting

confidence: 73%

Modelling Kepler red giants in eclipsing binaries: calibrating the mixing-length parameter with asteroseismology

Bedding

Huber

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…These cases provide valuable opportunities to enhance our knowledge of stellar astrophysics by leveraging APOGEE-2 spectra together with complementary observations exploring other wavelength regimes and/or observational sampling. This is exemplified by recent results from the APOKASC (Tayar et al 2017) and CoRoGEE (Anders et al 2017) samples, and a plethora of additional opportunities lie with optical spectroscopic surveys such as GALAH (Martell et al 2017) and GES (Gilmore et al 2012). Targets selected to be in common with other data sets, spectroscopic and photometric, have the targeting bit APOGEE2_TARGET2=5 set, as well as bits for specific surveys ( Table 1).…”

Section: Cross-and Inter-survey Calibrationmentioning

confidence: 98%

Target Selection for the SDSS-IV APOGEE-2 Survey

Zasowski

Cohen

Chojnowski

et al. 2017

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APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing ∼3×10 5 stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding on APOGEE's goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch and red clump stars, RR Lyrae, lowmass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.

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“…In addition, 36 stars (12 in NGC 6791, 20 in NGC 6819, and 4 in NGC 6811) have new temperatures determined from spectroscopy with ASPCAP (APOGEE Stellar Parameters and Chemical Abundances Pipeline, Zasowski et al 2013;Nidever et al 2015;Holtzman et al 2015;García Pérez et al 2016;Majewski et al 2017), using the Data Release 13 (DR13, SDSS Collaboration 2016) of SDSS IV (Blanton et al 2017), which includes the post-release metallicity correction (see Holtzman et al, in prep.). We therefore use ASPCAP temperatures, available from the latest release of the APOKASC catalog (Pinsonneault et al 2014;Tayar et al 2017), to apply a zero point shift to the temperatures from SDSS and correct them for the different cluster extinctions, which were based on the KIC map (Brown et al 2011) in the work by Pinsonneault et al (2012). In this way we put the temperatures from SDSS on the same scale as ASPCAP and we adopt the typical ASPCAP total temperature uncertainty (including both systematic and random effect) of ∼69 K as a reference (see Holtzman et al, in prep.…”

Section: Effective Temperaturesmentioning

confidence: 99%

Metallicity effect on stellar granulation detected from oscillating red giants in open clusters

Corsaro

Mathur

García

et al. 2017

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Context. The effect of metallicity on the granulation activity in stars, and hence on the convective motions in general, is still poorly understood. Available spectroscopic parameters from the updated APOGEE-Kepler catalog, coupled with high-precision photometric observations from NASA's Kepler mission spanning more than four years of observation, make oscillating red giant stars in open clusters crucial testbeds. Aims. We aim to determine the role of metallicity on the stellar granulation activity by discriminating its effect from that of different stellar properties such as surface gravity, mass, and temperature. We analyze 60 known red giant stars belonging to the open clusters NGC 6791, NGC 6819, and NGC 6811, spanning a metallicity range from [Fe/H] −0.09 to 0.32. The parameters describing the granulation activity of these stars and their frequency of maximum oscillation power, ν max , are studied while taking into account different masses, metallicities, and stellar evolutionary stages. We derive new scaling relations for the granulation activity, re-calibrate existing ones, and identify the best scaling relations from the available set of observations. Methods. We adopted the Bayesian code Diamonds for the analysis of the background signal in the Fourier spectra of the stars. We performed a Bayesian parameter estimation and model comparison to test the different model hypotheses proposed in this work and in the literature. Results. Metallicity causes a statistically significant change in the amplitude of the granulation activity, with a dependency stronger than that induced by both stellar mass and surface gravity. We also find that the metallicity has a significant impact on the corresponding time scales of the phenomenon. The effect of metallicity on the time scale is stronger than that of mass. Conclusions. A higher metallicity increases the amplitude of granulation and meso-granulation signals and slows down their characteristic time scales toward longer periods. The trend in amplitude is in qualitative agreement with predictions from existing 3D hydrodynamical simulations of stellar atmospheres from main sequence to red giant stars. We confirm that the granulation activity is not sensitive to changes in the stellar core and that it only depends on the atmospheric parameters of stars.

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The Correlation between Mixing Length and Metallicity on the Giant Branch: Implications for Ages in the Gaia Era

Cited by 110 publications

References 79 publications

Modelling Kepler red giants in eclipsing binaries: calibrating the mixing-length parameter with asteroseismology

Modelling Kepler red giants in eclipsing binaries: calibrating the mixing-length parameter with asteroseismology

Target Selection for the SDSS-IV APOGEE-2 Survey

Metallicity effect on stellar granulation detected from oscillating red giants in open clusters

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