The fundamental parameters of the roAp star alpha Circini

Abstract

We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of alpha Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, alpha Cir being the brightest member of its class. We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967+-0.066 Rs. We have constrained the bolometric flux from calibrated spectra to determine an effective temperature of 7420+-170 K. This is the first direct determination of the temperature of an roAp star. Our temperature is at the low end of previous estimates, which span over 1000 K and were based on either photometric indices or spectroscopic methods. In addition, we have analysed two high-quality spectra of alpha Cir, obtained at different rotational phases and we find evidence for the presence of spots. In both spectra we find nearly solar abundances of C, O, Si, Ca and Fe, high abundance of Cr and Mn, while Co, Y, Nd and Eu are overabundant by about 1 dex. The results reported here provide important observational constraints for future studies of the atmospheric structure and pulsation of alpha Cir.

Accepted by MNRAS (9 pages, 3 figures, 6 tables)

References in corpus (11)

• Evolutionary state of magnetic chemically peculiar stars
• New grids of ATLAS9 atmospheres I: Influence of convection treatments on model structure and on observable quantities
• Asteroseismology and Interferometry
• New Hipparcos-based Parallaxes for 424 Dim Stars
• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• Abundance analysis of targets for the COROT / MONS asteroseismology missions II. Abundance analysis of the COROT main targets
• The complementary roles of interferometry and asteroseismology in determining the mass of solar-type stars
• The Core-Wing Anomaly of Cool Ap Stars: Abnormal Balmer Profiles
• Pulsation tomography of rapidly oscillating Ap stars. Resolving the third dimension in peculiar pulsating stellar atmospheres
• Stellar model atmospheres with magnetic line blanketing
• The Sydney University Stellar Interferometer: A Major Upgrade to Spectral Coverage and Performance

Cited by in corpus (27)

• Chemically peculiar stars and their temperature calibration
• The VLT/NaCo Large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits: I- Sample definition and characterization
• Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2
• Discovery of 17 new sharp-lined Ap stars with magnetically resolved lines
• Theoretical light curves of dipole oscillations in roAp stars
• Testing excitation models of rapidly oscillating Ap stars with interferometry
• On the first $\delta$ Sct--roAp hybrid pulsator and the stability of p and g modes in chemically peculiar A/F stars
• Asteroseismic analysis of the roAp star alpha Circini: 84 days of high-precision photometry from the WIRE satellite
• TESS Cycle 1 observations of roAp stars with 2-min cadence data
• A self-consistent empirical model atmosphere, abundance and stratification analysis of the benchmark roAp star alpha Circini
• Addressing Systematics in the Traceback Age of the $\beta$ Pictoris Moving Group
• HD 24355 observed by the Kepler K2 mission: A rapidly oscillating Ap star pulsating in a distorted quadrupole mode
• The radius and effective temperature of the binary Ap star beta CrB from CHARA/FLUOR and VLT/NACO observations
• The fundamental parameters of the roAp star $\gamma$ Equulei
• Statistical analysis of roAp, He-weak and He-rich stars
• Fundamental parameters of bright Ap stars from wide-range energy distributions and advanced atmospheric models
• Hot Grain Dynamics by Electric Charging and Magnetic Trapping in Debris Disks
• Fundamental parameters and evolutionary status of the magnetic chemically peculiar stars HD 188041 (V1291 Aquilae), HD 111133 (EP Virginis), and HD 204411. Spectroscopy versus interferometry
• The fundamental parameters of the roAp star 10 Aql
• Fundamental properties of a selected sample of Ap stars: Inferences from interferometric and asteroseismic constraints
• Interferometry of chemically peculiar stars: theoretical predictions vs. modern observing facilities
• K2 observations of the rapidly oscillating Ap star 33 Lib (HD 137949): new frequencies and unique non-linear interactions
• Search for exoplanets and brown dwarfs with VLBI
• The roAp star $\alpha$ Circini as seen by BRITE-Constellation
• New BRITE-Constellation observations of the roAp star Alpha Circini
• SALT HRS capabilities for time resolved pulsation analysis: a test with the roAp star $\alpha$ Circini
• Pushing the limit of instrument capabilities