Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations

Abstract

We have determined the angular diameters of two metal-poor stars, HD 122563 and Gmb 1830, using CHARA and Palomar Testbed Interferometer observations. For the giant star HD 122563, we derive an angular diameter theta_3D = 0.940 +- 0.011 milliarcseconds (mas) using limb-darkening from 3D convection simulations and for the dwarf star Gmb 1830 (HD 103095) we obtain a 1D limb-darkened angular diameter theta_1D = 0.679 +- 0.007 mas. Coupling the angular diameters with photometry yields effective temperatures with precisions better than 55 K (Teff = 4598 +- 41 K and 4818 +- 54 K --- for the giant and the dwarf star, respectively). Including their distances results in very well-determined luminosities and radii (L = 230 +- 6 L_sun, R = 23.9 +- 1.9 R_sun and L = 0.213 +- 0.002 L_sun, R = 0.664 +- 0.015 R_sun, respectively). We used the CESAM2k stellar structure and evolution code in order to produce models that fit the observational data. We found values of the mixing-length parameter alpha (which describes 1D convection) that depend on the mass of the star. The masses were determined from the models with precisions of <3% and with the well-measured radii excellent constraints on the surface gravity are obtained (log g = 1.60 +- 0.04, 4.59 +- 0.02, respectively). The very small errors on both log g and Teff provide stringent constraints for spectroscopic analyses given the sensitivity of abundances to both of these values. The precise determination of Teff for the two stars brings into question the photometric scales for metal-poor stars.

accepted A&A, 8 dbl-column pages, incl. 7 tables and 4 figures

References in corpus (8)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• A new implementation of the infrared flux method using the 2MASS catalogue
• CESAM: a free code for stellar evolution calculations
• Non-LTE line formation for heavy elements in four very metal-poor stars
• Oscillating K giants with the WIRE satellite: determination of their asteroseismic masses
• The radii of the nearby K5V and K7V stars 61 Cyg A & B - CHARA/FLUOR interferometry and CESAM2k modeling
• Angular Diameters of the G Subdwarf $\mu$ Cassiopeiae A and the K Dwarfs $\sigma$ Draconis and HR 511 from Interferometric Measurements with the CHARA Array
• Modelling the components of binaries in Hyades: The dependence of the mixing-length parameter on stellar mass

Cited by in corpus (22)

• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Three Ancient Halo Subgiants: Precise Parallaxes, Compositions, Ages, and Implications for Globular Clusters
• The Hamburg/ESO R-process Enhanced Star survey (HERES) X. HE 2252-4225, one more r-process enhanced and actinide-boost halo star
• A large sample of calibration stars for Gaia: log g from Kepler and CoRoT
• 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
• Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-Variable Horizontal-Branch Stars. I. M3, M15, and M92
• Detailed Abundance Analysis of the Brightest Star in Segue 2, the Least Massive Galaxy
• Element abundance patterns in stars indicate fission of nuclei heavier than uranium
• Fundamental stellar parameters of benchmark stars from CHARA interferometry. I. Metal-poor stars
• Planet and star synergy at high spectral resolution. A rationale for the characterisation of exoplanet atmospheres. I. The Infrared
• Influence of Collisions with Hydrogen on Titanium Abundance Determinations in Cool Stars
• Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars. IV. Oxygen diagnostics in extremely metal-poor red giants with infrared OH lines
• From the stellar properties of HD219134 to the internal compositions of its transiting exoplanets
• Optical interferometry and Gaia measurement uncertainties reveal the physics of asymptotic giant branch stars
• 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
• Calibrating the α parameter of convective efficiency using observed stellar properties
• Theoretical predictions of surface light element abundances in protostellar and pre-Main Sequence phase
• Asteroseismic analysis of 15 solar-like oscillating evolved stars
• LOTUS: A (non-)LTE Optimization Tool for Uniform derivation of Stellar atmospheric parameters
• Benchmarking the effective temperature scale of red giant branch stellar models: the case of the metal-poor halo giant HD 122563