A Gemini Snapshot Survey for Double Degenerates

TL;DR

This study reports the discovery and characterization of four double degenerate binary systems with short orbital periods from a Gemini survey of low-mass white dwarf candidates, enhancing understanding of white dwarf binary populations.

Contribution

The paper presents new short-period double white dwarf systems identified through a targeted radial-velocity survey, refining their orbital parameters and analyzing period distributions.

Findings

Four double degenerate systems with periods from 53 min to 7 hours identified.

The median period decreases with lower white dwarf mass.

No significant correlation between orbital period and white dwarf mass found.

Abstract

We present the results from a Gemini snapshot radial-velocity survey of 44 low-mass white dwarf candidates selected from the Sloan Digital Sky Survey spectroscopy. To find sub-hour orbital period binary systems, our time-series spectroscopy had cadences of 2 to 8 min over a period of 20-30 min. Through follow-up observations at Gemini and the MMT, we identify four double degenerate binary systems with periods ranging from 53 min to 7 h. The shortest period system, SDSS J123549.88+154319.3, was recently identified as a subhour period detached binary by Breedt and collaborators. Here we refine the orbital and physical parameters of this system. High-speed and time domain survey photometry observations do not reveal eclipses or other photometric effects in any of our targets. We compare the period distribution of these four systems with the orbital period distribution of known double white dwarfs; the median period decreases from 0.64 to 0.24 d for $M=0.3-0.5 M_{\odot}$ to $M<0.3 M_{\odot}$ white dwarfs. However, we do not find a statistically significant correlation between the orbital period and white dwarf mass.