Toward a Spectroscopic Census of White Dwarfs Within 40 parsecs of the Sun

TL;DR

This study expands the nearby white dwarf census to 40 parsecs using proper motion data and spectroscopy, uncovering 193 new white dwarfs and providing detailed atmospheric parameters for a subset.

Contribution

It introduces a new method combining proper motion and color-magnitude criteria to identify white dwarfs within 40 parsecs, significantly increasing the known local sample.

Findings

Uncovered 193 new white dwarfs within 40 parsecs.

Identified 11 white dwarfs within 25 parsecs, including 5 within 20 parsecs.

Provided atmospheric parameters for 84 DA white dwarfs.

Abstract

We present the preliminary results of a survey aimed at significantly increasing the range and completeness of the local census of spectroscopically confirmed white dwarfs. The current census of nearby white dwarfs is reasonably complete only to about 20 parsecs of the Sun, a volume that includes around 130 white dwarfs, a sample too small for detailed statistical analyses. This census is largely based on follow-up investigations of stars with very large proper motions. We describe here the basis of a method that will lead to a catalog of white dwarfs within 40 parsecs of the Sun and north of the celestial equator, thus increasing by a factor of 8 the extent of the northern sky census. White dwarf candidates are identified from the SUPERBLINK proper motion database, allowing us to investigate stars down to a proper motion limit mu>40 mas yr-1, while minimizing the kinematic bias for nearby objects. The selection criteria and distance estimates are based on a combination of color-magnitude and reduced proper motion diagrams. Our follow-up spectroscopic observation campaign has so far uncovered 193 new white dwarfs, among which we identify 127 DA (including 9 DA+dM and 4 magnetic), 1 DB, 56 DC, 3 DQ, and 6 DZ stars. We perform a spectroscopic analysis on a subsample of 84 DAs, and provide their atmospheric parameters. In particular, we identify 11 new white dwarfs with spectroscopic distances within 25 pc of the Sun, including 5 candidates to the D<20 pc subset.