Rapid Oscillations in Cataclysmic Variables. XVI. DW Cancri

Abstract

We report photometry and spectroscopy of the nova-like variable DW Cancri. The spectra show the usual broad H and He emission lines, with an excitation and continuum slope characteristic of a moderately high accretion rate. A radial-velocity search yields strong detections at two periods, 86.1015(3) minutes and 38.58377(6) minutes. We interpret these as respectively the orbital period Porb of the binary, and the spin period Pspin of a magnetic white dwarf. The light curve also shows the spin period, plus an additional strong signal at 69.9133(10) minutes, which coincides with the difference frequency 1/Pspin-1/Porb. These periods are stable over the 1 year baseline of measurement. This triply-periodic structure mimics the behavior of several well-credentialed members of the ``DQ Herculis'' (intermediate polar) class of cataclysmic variables. DQ Her membership is also suggested by the mysteriously strong sideband signal (at νspin-νorb), attesting to a strong pulsed flux at X-ray/EUV/UV wavelengths. DW Cnc is a new member of this class, and would be an excellent target for extended observation at these wavelengths.