PG0027+260 - AN EXAMPLE OF A CLASS OF CATACLYSMIC BINARIES WITH MYSTERIOUS, BUT CONSISTENT, BEHAVIOR

We report extensive optical observations which show this object to be an eclipsing novalike variable with an orbital period of 3.51 hr (0.1463533 +/- 8 x 10(-7) d). It displays several unexplained phenomena which are remarkably similar to three other novalikes (SW Sex, DW UMa, and V1315 Aql); we call these the SW Sex stars. All these objects are eclipsing novalikes with periods between 3 and 4 hr. In all, He II lambda-4686 is about half the strength of H-beta; in none is significant circular polarization seen. The Balmer emission velocities generally lag grossly behind the phase expected for the white dwarf; in PG0027 + 260, the lag is 76-degrees. Finally, all display transient absorption events at a range of phases opposite the eclipse. The new features seen in PG0027 + 260 are as follows. (1) There is transient absorption in the metal lines as well as the Balmer and He I lines. (2) The eclipse is only partial and highly variable in depth. We model the eclipse, and show that while the mean eclipse light curve is easy to match, there is no simple explanation for the variable depth. We argue that the behavior of these objects is so similar that it cannot be considered abnormal, and that they are due for a serious modeling effort.