The diameters of Alpha Centauri A and B - A comparison of the asteroseismic and VINCI/VLTI views

TL;DR

This study precisely measures the angular diameters of Alpha Centauri A and B using VLTI interferometry and compares these measurements with model diameters derived from asteroseismic data, providing valuable insights into stellar parameters.

Contribution

The paper presents the first direct interferometric angular diameter measurements of Alpha Centauri A and B, and compares them with asteroseismic model diameters, enhancing stellar parameter accuracy.

Findings

Measured angular diameters with 0.2-0.6% precision.

Derived linear diameters consistent with previous mass estimates.

Validated model diameters against direct interferometric measurements.

Abstract

We compare the first direct angular diameter measurements obtained on our closest stellar neighbour, Alpha Centauri, to recent model diameters constrained by asteroseismic observations. Using the VINCI instrument installed at ESO's VLT Interferometer (VLTI), the angular diameters of the two main components of the system, Alpha Cen A and B, were measured with a relative precision of 0.2% and 0.6%, respectively. Particular care has been taken in the calibration of these measurements, considering that VINCI is estimating the fringe visibility using a broadband K filter. We obtain uniform disk angular diameters for Alpha Cen A and B of UD[A] = 8.314 +/- 0.016 mas and UD[B] = 5.856 +/- 0.027 mas, and limb darkened angular diameters of LD[A] = 8.511 +/- 0.020 mas and LD[B] = 6.001 +/- 0.034 mas. Combining these values with the parallax from Soderhjelm (1999), we derive linear diameters of D[A] = 1.224 +/- 0.003 Dsun and D[B] = 0.863 +/- 0.005 Dsun. These values are compatible with the masses published by Thevenin et al.(2002) for both stars.