Have Any LISA Verification Binaries Been Found?

Abstract Some electromagnetically observed ultracompact binaries will be strong gravitational wave sources for space-based detectors like the Laser Interferometer Space Antenna (LISA). These sources have historically been referred to as “verification binaries” under the assumption that they will be exploited to assess mission performance. This paper quantitatively interrogates that scenario by considering targeted analyses of known galactic sources in the context of a full simulation of the galactic gravitational wave foreground. We find that the analysis of the best currently known LISA binaries, even making maximal use of the available information about the sources, is susceptible to ambiguity or biases when not simultaneously fitting to the rest of the galactic population. While galactic binaries discovered electromagnetically in advance of, or during, the LISA survey are highly valuable multimessenger systems, the need for a global treatment of the galactic gravitational wave foreground calls into question whether or not they are the best sources for data characterization.