The Ultramassive White Dwarfs of the Alpha Persei Cluster

TL;DR

This study identifies and confirms three ultramassive white dwarfs as escapees from the Alpha Persei cluster, revealing the existence of the most massive white dwarfs associated with a cluster and providing insights into their progenitors.

Contribution

First identification of ultramassive white dwarf escapees from a young cluster using Gaia data, expanding understanding of white dwarf mass limits and progenitor stars.

Findings

Three white dwarf escapees confirmed as young and massive

One white dwarf has a mass of about 1.20 solar masses

White dwarf progenitors include stars up to 8.5 solar masses

Abstract

We searched through the entire Gaia EDR3 candidate white dwarf catalogue for stars with proper motions and positions that are consistent with the stars having escaped from the Alpha Persei cluster within the past 81~Myr, the age of the cluster. In this search we found five candidate white dwarf escapees from Alpha Persei and obtained spectra for all five. We confirm that three are massive white dwarfs sufficiently young to have originated in the cluster. All three are more massive than any white dwarf previously associated with a cluster using Gaia astrometry, and possess some of the most massive progenitors. In particular, the white dwarf Gaia~EDR3~4395978097863572, which lies within 25~pc of the cluster centre, has a mass of about 1.20 solar masses and evolved from an 8.5 solar-mass star, pushing the upper limit for white dwarf formation from a single massive star, while still leaving a substantial gap between the resulting white dwarf mass and the Chandrasekhar mass.