New Ultracool Companions to Nearby White Dwarfs

TL;DR

This study identified 51 new ultracool companions to nearby white dwarfs using multi-method searches, confirmed some with spectroscopy, and found others with infrared excess, providing valuable benchmarks for ultracool dwarf characterization.

Contribution

The paper reports the discovery and confirmation of new ultracool companions to white dwarfs, including spectroscopic validation and infrared excess analysis, expanding the known sample for future studies.

Findings

51 new candidate ultracool companions identified

4 companions confirmed via near-infrared spectroscopy

Infrared excess suggests additional low-mass companions or disks

Abstract

We conducted a search for new ultracool companions to nearby white dwarfs using multiple methods, including the analysis of colors and examination of images in both the optical and the infrared. Through this process, we identified fifty-one previously unrecognized systems with candidate ultracool companions. Thirty-one of these systems are resolved in at least one catalog, and all but six are confirmed as co-moving companions via common proper motion and consistent parallax measurements (when available). We have followed up four co-moving companions with near-infrared spectroscopy and confirm their ultracool nature. The remaining twenty candidates are unresolved, but show clear signs of infrared excess which is most likely due to the presence of a cold, low-mass companion or a dusty circumstellar disk. Three of these unresolved systems have existing optical spectra that clearly show the presence of a cool stellar companion to the white dwarf primary via spectral decomposition. These new discoveries, along with our age estimates for the primary white dwarfs, will serve as valuable benchmark systems for future characterization of ultracool dwarfs.