FUSE, RXTE, EUVE and Optical Observations of the Asynchronous Polar BY Cam

The magnetic cataclysmic variable BY Cam is one of only a few known asynchronous systems, with slightly different spin and orbital periods giving a beat period of 14 days. It also exhibits peculiar line ratios with strong NV and weak CIV so that NV/CIV is about 30 times larger than is typical for Polars. In January, 2000, we obtained simultaneous FUSE, RXTE, EUVE and optical spectra and photometry during a high state of accretion. The RXTE data are fit with a 20 keV bremsstrahlung source while the EUVE gives an upper limit on the EUV flux. The FUSE flux distribution joins smoothly to past IUE data. After strong airglow lines are removed, broad emission lines of OVI, HeII, NIII are present while CIII is conspicuously weak. In comparison to AM Her, the OVI/CIV ratio in BY Cam is weaker while the NV/OVI ratio is stronger and there is no evidence of the narrow component in OVI evident in AM Her. Simple ionization models cannot reproduce the line ratios, so non-solar abundances (with N overabundant and C underabundant) may be operating. Doppler tomograms of the optical spectra indicate an origin of the Balmer emission near the secondary while the HeII emission is near the white dwarf. This work was partially supported by NASA grant NAG5-8981 to PS.