Searching for White Dwarf Candidates Formed Through Binary evolution in Star Clusters

TL;DR

This paper identifies white dwarf candidates in star clusters using Gaia data, highlighting those likely formed through binary evolution, and confirms their properties with spectroscopic observations, providing insights into exotic WD formation.

Contribution

It introduces a method to identify binary-evolved white dwarfs in star clusters using Gaia astrometry and spectroscopic follow-up, revealing their magnetic and rotational characteristics.

Findings

Identified 244 white dwarf candidates likely formed via binary evolution.

Spectroscopy revealed some WDs with strong magnetic fields and rapid rotation.

Supports the binary evolution origin for a significant subset of cluster WDs.

Abstract

White dwarfs (WDs), the evolutionary endpoints of most stars, can form through both single-star and binary channels. While single-star evolutionary models enable reliable WD age estimates, binary evolution introduces interactions that can accelerate WD formation and result in a variety of exotic WDs, which may exhibit strong magnetic fields, rapid rotation, or even serve as potential gravitational wave sources. Such systems offer valuable insights into magnetic field generation, angular momentum evolution, and compact object physics. Star clusters, with their approximately coeval populations, allow precise age determination of member WDs. If a WD's total age derived from single-star evolution exceeds that of its host cluster, it likely indicates a binary origin. In this study, we use \textit{Gaia} 5D astrometry to identify 439 WD candidates in 117 open clusters, with 244 likely formed via binary evolution. We discuss the possibility of dynamical ejection for WDs meeting only 2D (proper motion space) membership criteria. Spectroscopic observations further reveal a subset with strong magnetic fields and rapid rotation, supporting their binary evolutionary origin.