Program: GN-2023B-FT-204

We propose observations with the Gemini North Multi-Object Spectrograph of J1927+3411 (hereafter J1927), a, ultra-short period HW Vir binary. The 93.5 min orbital period of this presumably sdB+dM/BD binary puts it among the top ten shortest period systems known of its class, however only four of those systems are bright enough to obtain time-series spectroscopy with an integration time short enough to avoid smearing over the short eclipse durations. The Gemini observations we propose will provide measurements of the radial velocity semi-amplitude and atmospheric parameters of the sdB star in J1927, which will also allow us to infer the nature of the secondary companion. These Gemini observations will lead directly to a publication, as there already exists high S/N Zwicky Transient Facility photometry to complement the proposed spectroscopy. Fully characterizing the shortest-period HW Vir binaries is necessary for understanding their formation and will, more importantly, provide important boundary conditions for binary evolution involving common-envelope processes.