1608.04753
The awakening of a classical nova from hibernation
Mroz, et al
Cataclysmic variable stars (CVs) are close binary systems consisting of a white dwarf (primary) that is accreting matter from a low-mass companion star (secondary). From time to time such systems undergo large-amplitude brightening. The most spectacular eruptions, over 1e4 times in brightness, occurring classical novae and are caused by a thermonuclear runaway on the surface of the WD. Such eruptions are thought to recur on timescales of 1e4-1e6 [yrs]. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than 1e-9 Msun/yr, the accretion becomes unstable and the matter is dumped onto the WD during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for 1e3-1e6 years, staring the hibernation phase. After that the nova awakes again - with accretion returning to the pre-eruption level and leading to a new nova explosion. The hibernation model predicts cyclical evolution of CVs through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around war novae Z Cam and AT Cnc, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Report long-term observations of the classical nova V1213 en (Nova Cen 2009) covering its pre- and post-eruption phases. Within the 6 years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is 2 orders of magnitude brighter than the pre-nova at minimum light with no trace of dwarf nova behavior, implying that the mass-transfer rate increased considerably as a result of the nova explosion.
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