Benchmarking the effective temperature scale of red giant branch stellar models: the case of the metal-poor halo giant HD 122563

Abstract

There is plenty of evidence in the literature of significant discrepancies between the observations and models of metal-poor red giant branch stars, in particular regarding the effective temperature, teff, scale. We revisit the benchmark star HD 122563 using the most recent observations from Gaia Data Release 3, to investigate if these new constraints may help in resolving this discrepancy. We review the most recent spectroscopic determinations of the metallicity of HD 122563 [Fe/H], and provide a new assessment of its fundamental parameters, i.e. bolometric luminosity, teff, surface gravity, plus a photometric determination of its metal content. Using these constraints, we compare the position of the star in the Hertzsprung-Russell (H-R) diagram with various recent sets of stellar evolution tracks. The H-R diagram analysis reveals a significant disagreement between observed and theoretical teff values, when adopting the most recent spectroscopic estimate of [Fe/H]. On the other hand, by using the photometric determination of [Fe/H] some of the selected sets of stellar tracks appear in fair agreement with observations. The sets with discrepant teff can be made to agree with observations either by modifying the prescription adopted to calculate the models' outer boundary conditions, and/or by reducing the adopted value of the mixing length parameter with respect to the solar-calibration. A definitive assessment of whether the teff scale of metal-poor stellar red giant branch models is consistent with observations requires an even more accurate determination of the fundamental parameters of HD 122563 and also a larger sample of calibrators. From the theoretical side, it is crucial to minimise the current uncertainties in the treatment (boundary conditions, temperature gradient) of the outer layers of stellar models with convective envelopes.

arXiv commentaccepted for publication in A&A

References in corpus (61)

• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Gaia Data Release 3: Summary of the content and survey properties
• Validation of the new Hipparcos reduction
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
• Gaia Data Release 2: using Gaia parallaxes
• Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry
• Nominal values for selected solar and planetary quantities: IAU 2015 Resolution B3
• The Updated BaSTI Stellar Evolution Models and Isochrones: I. Solar Scaled Calculations
• Gaia FGK Benchmark Stars - Metallicity
• The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models
• Preparation of Kepler lightcurves for asteroseismic analyses
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - I. Methods and General Properties
• Gaia Data Release 3: Analysis of RVS spectra using the General Stellar Parametriser from spectroscopy
• Gaia Data Release 3: Astrophysical parameters inference system (Apsis) I -- methods and content overview
• Observational constraints on the origin of the elements. IV: The standard composition of the Sun
• Red Giant Branch stars: the theoretical framework
• The updated BaSTI stellar evolution models and isochrones: II. alpha-enhanced calculations
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Age dissection of the Milky Way discs: red giants in the Kepler field
• Gaia Data Release 3: External calibration of BP/RP low-resolution spectroscopic data
• Improvements to stellar structure models, based on a grid of 3D convection simulations. II. Calibrating the mixing-length formulation
• Gaia FGK benchmark stars: abundances of alpha and iron-peak elements
• The Stagger-grid: A grid of 3D stellar atmosphere models - III. The relation to mixing-length convection theory
• The Correlation Between Mixing Length and Metallicity on the Giant Branch: Implications for Ages in the Gaia Era
• Towards stellar effective temperatures and diameters at one per cent accuracy for future surveys
• The brightness of the Red Giant Branch tip: Theoretical framework, a set of reference models, and predicted observables
• First Results From The Hertzsprung Song Telescope: Asteroseismology Of The G5 Subgiant Star {\Mu}Her
• Not All Stars Are the Sun: Empirical Calibration of the Mixing Length for Metal-Poor Stars Using One-dimensional Stellar Evolution Models
• Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission
• Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $\nu$ Indi
• Changing the ${\nu }_{\max }$ Scaling Relation: The Need For a Mean Molecular Weight Term
• Gaia FGK Benchmark stars: Opening the black box of stellar element abundance determination
• The empirical Gaia G-band extinction coefficient
• Evolutionary and structural properties of mirror star MACHOs
• Improvements to Stellar Structure Models, Based on a Grid of 3D Convection Simulations. I. $T(\tau )$-Relations
• Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations
• On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models
• Benchmark stars for Gaia: fundamental properties of the Population II star HD140283 from interferometric, spectroscopic and photometric data
• Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563 and HD 103095 from CHARA interferometry
• Probing the deep end of the Milky Way with \emph{Kepler}: Asteroseismic analysis of 854 faint Red Giants misclassified as Cool Dwarfs
• The benchmark halo giant HD 122563: CNO abundances revisited with three-dimensional hydrodynamic model stellar atmospheres
• Stellar models with mixing length and T(tau) relations calibrated on 3D convection simulations
• Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars
• Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models
• Stellar models with the ML2 theory of convection
• Asteroseismic versus Gaia distances: a first comparison
• The Chemical Compositions of Very Metal-Poor Stars HD 122563 and HD 140283; A View From the Infrared
• Detections of solar-like oscillations in dwarfs and subgiants with Kepler DR25 short-cadence data
• On the Red Giant Branch: Ambiguity in the Surface Boundary Condition Leads to ~100 K Uncertainty in Model Effective Temperatures
• Stellar evolution and large extra dimensions
• Evidence of structural discontinuities in the inner core of red-giant stars
• Chemical evolution of the metal poor Globular Cluster NGC 6809
• Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars. V. Oxygen abundance in the metal-poor giant HD 122563 from OH UV lines
• First detection of oscillations in the Halo giant HD 122563: validation of seismic scaling relations and new fundamental parameters
• Models for Metal-Poor Stars with Different Initial Abundances of C, N, O, Mg, and Si. III. Grids of Isochrones for $-2.5\le$ [Fe/H] $\le -0.5$ and Helium Abundances $Y=0.25$ and $0.29$ at Each Metallicity
• M92 (NGC~6341) Is a Metal-Complex Globular Cluster with an Atypical Primordial Population

Cited by in corpus (1)

• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) II. Unveiling the formation and evolution of the kinematically selected Thick and Thin Discs