Five Dwarf Novae with Orbital Periods Below Two Hours

Abstract

We give mean spectra and report orbital periods Porb based on radial velocities taken near minimum light for five dwarf novae, all of which prove to have Porb less than 2 hr. The stars and their periods are KX Aql, 0.06035(3) d; FT Cam, 0.07492(8) d; PU CMa, 0.05669(4) d; V660 Her, 0.07826(8) d;, and DM Lyr, 0.06546(6). The emission lines in KX Aql are notably strong and broad, and the other stars' spectra appear generally typical for short-period dwarf novae. We observed FT Cam, PU CMa, and DM Lyr on more than one observing run and constrain their periods accordingly. Differential time-series photometry of FT Cam shows strong flickering but rules out deep eclipses. Although dwarf novae in this period range generally show the superhumps and superoutbursts characteristic of the SU UMa subclass of dwarf novae, none of these objects have well-observed superhumps.