Bayesian Ages for Early-Type Stars from Isochrones Including Rotation, and a Possible Old Age for the Hyades

TL;DR

This paper introduces a Bayesian method combining stellar evolution models with rotation to accurately determine ages of early-type stars, revealing an older age for the Hyades cluster than previously estimated.

Contribution

It develops a Bayesian framework that integrates rotating stellar models and synthetic magnitudes to improve age estimates of early-type stars and clusters.

Findings

Good agreement with known young clusters like Pleiades and Beta Pictoris.

Derived an older age for the Hyades cluster (~750 Myr).

Provided a web tool for community use.

Abstract

We combine recently computed models of stellar evolution using a new treatment of rotation with a Bayesian statistical framework to constrain the ages and other properties of early-type stars. We find good agreement for early-type stars and clusters with known young ages, including beta Pictoris, the Pleiades, and the Ursa Majoris Moving Group. However, we derive a substantially older age for the Hyades open cluster (750+/-100 Myr compared to 625+/-50 Myr). This older age results from both the increase in main-sequence lifetime with stellar rotation and from the fact that rotating models near the main-sequence turnoff are more luminous, overlapping with slightly more massive (and shorter-lived) nonrotating ones. Our method uses a large grid of nonrotating models to interpolate between a much sparser rotating grid, and also includes a detailed calculation of synthetic magnitudes as a function of orientation. We provide a web interface at www.bayesianstellarparameters.info where the results of our analysis may be downloaded for individual early-type (B-V<~0.25) Hipparcos stars. The web interface accepts user-supplied parameters for a Gaussian metallicity prior and returns posterior probability distributions on mass, age, and orientation.