A search for white dwarfs in the Galactic plane: the field and the open cluster population

TL;DR

This study systematically searches for white dwarfs in the Galactic plane using VST Hα survey data, confirming candidates and identifying potential cluster members to better understand stellar evolution and mass-loss processes.

Contribution

It demonstrates the effectiveness of combining photometric surveys with spectroscopy to identify white dwarfs in open clusters and estimates progenitor properties for these cluster members.

Findings

Confirmed 17 white dwarf candidates spectroscopically.

Identified 5 likely cluster members among the candidates.

Discovered the most massive known cluster white dwarf in NGC 3532.

Abstract

We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope (VST) H$\alpha$ Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compared our findings to those for other cluster white dwarfs. A white dwarf in NGC 3532 is the most massive known cluster member (1.13 M$_{\odot}$), likely with an oxygen-neon core, for which we estimate an $8.8_{-4.3}^{+1.2}$ M$_{\odot}$ progenitor, close to the mass-divide between white dwarf and neutron star progenitors. A cluster member in Ruprecht 131 is a magnetic white dwarf, whose progenitor mass exceeded 2-3 M$_{\odot}$. We stress that wider searches, and improved cluster distances and ages derived from data of the ESA Gaia mission, will advance the understanding of the mass-loss processes for low- to intermediate-mass stars.