WHY SO MUCH SHELL BURNING ON THE WHITE DWARFS IN WIDE BINARIES?

ACCRETING WHITE DWARFS (WDS) IN WIDE BINARIES WITH RED-GIANT (RG) DONORS CONTAIN A POTENTIAL CLUE TO A HUGE QUESTION IN LOW-MASS BINARY STELLAR EVOLUTION: CAN ACCRETING WDS GROW IN MASS? A SURPRISINGLY LARGE NUMBER OF WDS IN SUCH BINARIES EXPERIENCE QUASI-STEADY SHELL BURNING WHICH IS ASSOCIATED WITH MASS RETENTION AND GROWTH. BUT THE CAUSE OF THE SHELL BURNING IS UNKNOWN. THE GOAL OF THE PROPOSED PROGRAM IS TO USE XMM OBSERVATIONS OF TWO RG+WD BINARIES WITH RECENT NOVA-LIKE ERUPTIONS TO TEST THE HYPOTHESIS THAT THE SHELL BURNING IS RESIDUAL BURNING FROM PRIOR THERMONUCLEAR RUNAWAYS THAT EJECTED RELATIVELY LITTLE MASS. CAO ET AL. RECENTLY CONFIRMED THAT RG+WD BINARIES PRODUCE AT LEAST SOME SNIA SO REVEALING HOW THEIR WDS CAN GAIN MASS HAS MAJOR IMPLICATIONS. SINCE IT REQUIRES X-RAY SPECTROSCOPY AND UNINTERRUPTED UV LIGHT CURVES THIS PROGRAM IS IDEAL FOR XMM.