Observations of the SW Sextantis star BH Lyncis in a high state

We present time-resolved photometry and medium resolution (2 Angstrom) spectroscopy of the SW Sextantis star BH Lyncis obtained during a high state of the system. Previous detailed observations have been obtained only during low and intermediate states. In addition, we present the first International Ultraviolet Explorer low-resolution (6 Angstrom) spectrum of BH Lyn. A revised photometric ephemeris, HJD(min)=2,447,180.3366(2)+0.15587535(6)E, is derived based on new and previously published eclipse timings. The amplitude of the pre-eclipse hump in light curves of BH Lyn is shown to vary, suggesting that the degree to which the incoming accretion stream impacts the edge of the disk changes over time. We estimate system parameters using the V-band eclipse width and He II lambda 4686 emission-line radial velocity (i approximate to 79 degrees, q approximate to 0.45, M(WD)approximate to 0.7 M., M-2 approximate to 0.3 M., R-2 approximate to 0.4 R., a approximate to 1.2 R.). Doppler tomograms constructed for the prominent emission lines in BH Lyn show a lack of emission at the expected locations of the bright spot and accretion stream trajectories. The differences between the low and high states of BH Lyn are discussed, along with the possible origin of a significant amount of the emission-line flux in a wind from the disk and/or white dwarf primary star. Finally, a model involving the presence of vertically extended bulges in the accretion disk is introduced to explain the characteristic phase-dependent absorption feature found in emission lines of the SW Sex stars.