A 150 MG magnetic white dwarf in the cataclysmic variable RX J1554.2+2721

We report the detection of Zeeman-split Lyalpha absorption pi and sigma(+) lines in the far-ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph (STIS) spectrum of the magnetic cataclysmic variable RX J1554.2 + 2721. Fitting the STIS data with magnetic white dwarf model spectra, we derive a field strength of B similar or equal to 144 MG and an effective temperature of 17,000 K less than or similar to T-eff less than or similar to 23,000 K. This measurement makes RX J1554.2 + 2721 only the third cataclysmic variable containing a white dwarf with a field exceeding 100 MG. Similar to the other high-field polar AR UMa, RX J1554.2 + 2721 is often found in a state of feeble mass transfer, which suggests that a considerable number of high-field polars may still remain undiscovered.