The Oldest Cataclysmic Variables

Angular momentum loss grinds cataclysmic variables down to very short period onrelatively short timescales (13 Gyr); then they should bounce at Porbvirgul80 minand begin evolving back to longer period. Since the Galaxy is 10 Gyr old, theseperiod bouncers should now be extremely numerous. Unfortunately, none have yetbeen securely identified. We believe we have finally identified a few of thesestars (5), based on their very low mass ratios. These stars are a newlyrecognized class of CV, and 110 keV Xrays appear to be a major part (abouthalf) of their accretion luminosity budget. XMM observations would clarify theorigin of the Xrays and probe physical conditions in the accreting gas, donatedby a star which has been stripped down to 0.020.04 solar masses. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]