ZTF J1901+5309: A 40.6-Minute Orbital Period Eclipsing Double White Dwarf System

Abstract

The Zwicky Transient Facility has begun to discover binary systems with orbital periods that are less than 1\,hr. Combined with dedicated follow-up systems, which allow for high-cadence photometry of these sources, systematic confirmation and characterization of these sources are now possible. Here, we report the discovery of ZTF J190125.42+530929.5, a 40.6\,min orbital period, eclipsing double white-dwarf binary. Both photometric and spectroscopic modeling confirm its nature, yielding an estimated inclination of $i=86.2_{-0.2}^{+0.6}\mathrm{degrees}$ and primary and secondary effective temperatures of ${\text{T}}_{\text{eff}}=28,000_{-500}^{+500}K$ and ${\text{T}}_{\text{eff}}=17,600_{-400}^{+400}K$ respectively. This system adds to a growing list of sources for future gravitational-wave detectors and contributes to the demographic analysis of double degenerates.