Resolving Vega and the inclination controversy with CHARA/MIRC

TL;DR

This study uses advanced interferometry to clarify Vega's rotation and inclination, resolving previous discrepancies and refining its physical and evolutionary parameters.

Contribution

The paper provides new interferometric observations that reconcile Vega's inclination and rotation rate, updating its physical and evolutionary models.

Findings

Vega is rotating less rapidly than previously thought.

Vega's inclination angle is smaller, consistent with pole-on viewing.

Vega's age is estimated at approximately 700 million years.

Abstract

Optical and infrared interferometers definitively established that the photometric standard Vega (alpha Lyrae) is a rapidly rotating star viewed nearly pole-on. Recent independent spectroscopic analyses could not reconcile the inferred inclination angle with the observed line profiles, preferring a larger inclination. In order to resolve this controversy, we observed Vega using the six-beam Michigan Infrared Combiner on the Center for High Angular Resolution Astronomy Array. With our greater angular resolution and dense (u,v)-coverage, we find Vega is rotating less rapidly and with a smaller gravity darkening coefficient than previous interferometric results. Our models are compatible with low photospheric macroturbulence and also consistent with the possible rotational period of ~0.71 days recently reported based on magnetic field observations. Our updated evolutionary analysis explicitly incorporates rapid rotation, finding Vega to have a mass of 2.15+0.10_-0.15 Msun and an age 700-75+150 Myrs, substantially older than previous estimates with errors dominated by lingering metallicity uncertainties (Z=0.006+0.003-0.002).