RXJ1313.2-3259, a missing link in CV evolution?

Abstract

We present low-state IUE spectroscopy of the ROSAT-discovered polar RXJ1313.2-3259. The SWP spectrum displays a broad Lyman alpha absorption profile, which can be fitted with a two-temperature model of a white dwarf of Twd=15000K with a hot spot of Tspot=34000K which covers f~0.01 of the white dwarf surface. The white dwarf temperature is atypically low for the long orbital period (4.18h) of RXJ1313.2-3259. This low temperature implies either that the system is a young CV in the process of switching on mass transfer or that it is an older CV found in a prolonged state of low accretion rate, much below that predicted by standard evolution theory. In the first case, we can put a lower limit on the life time as pre-CV of 10e8yrs. In the second case, the good agreement of the white dwarf temperature with that expected from compressional heating suggests that the system has experienced the current low accretion rate for an extended period >10e4yrs. A possible explanation for the low accretion rate is that RXJ1313.2-3259 is a hibernating post nova and observational tests are suggested.