Precise Age For The Binary HD 21278 In The Young Alpha Persei Cluster

TL;DR

This study precisely measures the masses and age of the binary star HD 21278 in the young alpha Persei cluster, providing insights into stellar evolution and the white dwarf initial-final mass relation.

Contribution

It offers the first precise mass measurements of the binary components and refines the cluster's age, also revisiting white dwarf progenitors to challenge existing models.

Findings

Binary star masses: 5.381 and 3.353 solar masses.

Cluster age: approximately 49 million years.

White dwarf progenitor masses challenge current models.

Abstract

We present a study of the double-lined spectroscopic binary HD 21278 that contains one of the brightest main sequence stars in the young $\alpha$ Persei open cluster. We analyzed new spectra and reanalyzed archived spectra to measure precise new radial velocity curves for the binary. We also obtained interferometric data using the CHARA Array at Mount Wilson to measure the sky positions of the two stars and the inclination of the $\sim$ 2 milliarcsecond orbit. We determine that the two stars have masses of $5.381 \pm 0.084 M_{\odot}$ and $3.353 \pm 0.064 M_{\odot}$. From isochrone fits, we find the cluster's age to be $49 \pm 7$ Myr (using PARSEC models) or $49.5 \pm 6$ Myr (MIST models). Finally, we revisit the massive white dwarfs that are candidate escapees from the $\alpha$ Persei cluster to try to better characterize the massive end of the white dwarf initial-final mass relation. The implied progenitor masses challenge the idea that Chandrasekhar-mass white dwarfs are made by single stars with masses near $8 \msun$.