A realistic two-dimensional model of Altair
arXiv:1912.03138 · doi:10.1051/0004-6361/201936830
Abstract
Fast rotation is responsible for important changes in the structure and evolution of stars. Optical long baseline interferometry now permits the study of its effects on the stellar surface, mainly gravity darkening and flattening. We aim to determine the fundamental parameters of the fast-rotating star Altair, in particular its evolutionary stage, mass, and differential rotation, using state-of-the-art stellar interior and atmosphere models together with interferometric, spectroscopic, and asteroseismic observations. We use ESTER 2D stellar models to produce the relevant surface parameters needed to create intensity maps from atmosphere models. Interferometric and spectroscopic observables are computed from these intensity maps and several stellar parameters are then adjusted using the MCMC algorithm Emcee. We determined Altair's equatorial radius to be 2.008 +/- 0.006 Rsun, the position angle 301.1 +/- 0.3 degrees, the inclination 50.7 +/- 1.2 degrees, and the equatorial angular velocity 0.74 +/- 0.01 times the Keplerian angular velocity. This angular velocity leads to a flattening of 0.220 +/- 0.003. We also deduce from the spectroscopically derived vsini ~ 243 km/s, a true equatorial velocity of ~314 km/s corresponding to a rotation period of 7h46m (~3 c/d). The data also impose a strong correlation between mass, metallicity, hydrogen abundance, and core evolution. Thanks to asteroseismic data, we constrain the mass of Altair to 1.86 +/- 0.03 Msun and further deduce its metallicity Z = 0.019 and its core hydrogen mass fraction Xc = 0.71, assuming an initial solar hydrogen mass fraction X = 0.739. These values suggest that Altair is ~100 Myrs old. Finally, the 2D ESTER model also gives the internal differential rotation of Altair, showing that its core rotates approximately 50% faster than the envelope, while the surface differential rotation does not exceed 6%.
arXiv comment20 pages, 20 figures, accepted for publication in A&A
References in corpus (39)
- emcee: The MCMC Hammer
- Validation of the new Hipparcos reduction
- Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
- A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
- Presupernova Evolution of Rotating Massive Stars II: -- Evolution of the Surface Properties
- PIONIER: a 4-telescope visitor instrument at VLTI
- Imaging the Surface of Altair
- Interferometric Observations of Rapidly Rotating Stars
- Gravity darkening in rotating stars
- Rotational velocities of A-type stars IV. Evolution of rotational velocities
- The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars
- CESAM: a free code for stellar evolution calculations
- Acoustic oscillations of rapidly rotating polytropic stars. II. Effects of the Coriolis and centrifugal accelerations
- A new method to compute limb-darkening coefficients for stellar atmosphere models with spherical symmetry: the space missions TESS, Kepler, Corot, and MOST
- Populations of rotating stars. - I. Models from 1.7 to 15 Msun at Z = 0.014, 0.006, and 0.002 with Ω/Ωcrit between 0 and 1
- Self-consistent 2D models of fast rotating early-type star
- Automated spectroscopic abundances of A and F-type stars using echelle spectrographs II. Abundances of 140 A-F stars from ELODIE and CORALIE
- Asymptotic analysis of high-frequency acoustic modes in rapidly rotating stars
- High-Precicison Limb-Darkening Measurement of a K3 Giant Using Microlensing
- An algorithm for computing the 2D structure of fast rotating stars
- Resolving the Effects of Rotation in Altair with Long-Baseline Interferometry
- Regular patterns in the acoustic spectrum of rapidly rotating stars
- Geometry of giant star model atmospheres: A consistency test
- Observational - relation for Sct stars using eclipsing binaries and space photometry
- Altair: The Brightest Delta Scuti Star
- High precision transit observations of the exoplanet WASP-13b with the RISE instrument
- Mode visibilities in rapidly rotating stars
- Altair - the 'hottest' magnetically active star in X-rays
- Modelling of the fast rotating delta Scuti star Altair
- Spherically symmetric model stellar atmospheres and limb darkening II: limb-darkening laws, gravity-darkening coefficients and angular diameter corrections for FGK dwarf stars
- Critical angular velocity and anisotropic mass loss of rotating stars with radiation-driven winds
- Regular Oscillation Sub-spectrum of Rapidly Rotating Stars
- Asymmetric Surface Brightness Distribution of Altair Observed with the Navy Prototype Optical Interferometer
- Chemical abundances of fast-rotating massive stars. I. Description of the methods and individual results
- Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey
- Altair's inclination from line profile analysis
- A near-infrared interferometric survey of debris-disk stars. VI. Extending the exozodiacal light survey with CHARA/JouFLU
- Differential Rotation in F Stars
- The evolved fast rotator Sargas. Stellar parameters and evolutionary status from VLTI/PIONIER and VLT/UVES
Cited by in corpus (24)
- Probing the interior physics of stars through asteroseismology
- Solar structure and evolution
- MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars
- A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper-Centaurus Lupus
- Gaia Data Release 3: Pulsations in main sequence OBAF-type stars
- Asteroseismology of the young open cluster NGC 2516 I: Photometric and spectroscopic observations
- The first two-dimensional stellar structure and evolution models of rotating stars
- Detecting deep axisymmetric toroidal magnetic fields in stars. The traditional approximation of rotation for differentially rotating deep spherical shells with a general azimuthal magnetic field
- Oscillations of 2D ESTER models. I. The adiabatic case
- Analysis of high-resolution FEROS spectroscopy for a sample of variable B-type stars assembled from TESS photometry
- Seismology of Altair with MOST
- The Habitable Zones of Rapidly Rotating Main Sequence A/F Stars
- Spectroscopic detection of Altair's non-radial pulsations
- Synthetic Spectra of Rotating Stars
- Asteroseismic Determination of Stellar Rotation: On Synchronization in the Close Eclipsing Binaries AB Cas and OO Dra
- The A-shell star Phi Leo revisited: its photospheric and circumstellar spectra
- High contrast imaging with Fizeau interferometry: The case of Altair
- RUBIS: a simple tool for calculating the centrifugal deformation of stars and planets
- The first radio spectrum of a rapidly rotating A-type star
- Probing stellar rotation in the Pleiades with gravity-mode pulsators
- Photometric determination of rotation axis inclination, rotation rate, and mass of rapidly rotating intermediate-mass stars
- A Lagrangian construction of rotating stars
- Pulsation and Rotation of the EL CVn-type Eclipsing Binary 1SWASP J024743.37-251549.2
- Fundamental properties of two rapidly rotating stars: Rasalhague and Alkaid