Activity and Kinematics of White Dwarf-M Dwarf Binaries from the SUPERBLINK Proper Motion Survey

TL;DR

This study analyzes the activity and motion of white dwarf-M dwarf binary systems from the SUPERBLINK survey, revealing higher activity levels in binaries compared to single M dwarfs and insights into their kinematic properties.

Contribution

It introduces a new UV-optical-IR color criterion for identifying WD+dM binaries and provides detailed activity and kinematic analysis of these systems, including many new discoveries.

Findings

Higher activity fraction in WD+dM binaries than single M dwarfs at certain spectral types.

Binary systems show a large vertical velocity dispersion, indicating a dynamically hotter population.

Inactive M dwarfs in binaries exhibit signs of older stellar populations.

Abstract

We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV-optical-IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use H$\alpha$ chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population.