title: The awakening of a classical nova from hibernation.
abstract: Cataclysmic variable stars-novae, dwarf novae, and nova-likes-are close binary systems consisting of a white dwarf star (the primary) that is accreting matter from a low-mass companion star (the secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of ten thousand to a million years. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a billionth of a solar mass per year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate in the binary, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for a thousand to a million years, starting 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 cataclysmic variables through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around the dwarf novae Z Camelopardalis and AT Cancri, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Here we report long-term observations of the classical nova V1213 Cen (Nova Centauri 2009) covering its pre- and post-eruption phases and precisely documenting its evolution. Within the six years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is two orders of magnitude brighter than the pre-nova at minimum light with no trace of dwarf nova behaviour, implying that the mass-transfer rate increased considerably as a result of the nova explosion.
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Przemek
authors.initials: P
authors.lastname: Mróz
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Udalski
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Pietrukowicz
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Michał K
authors.initials: MK
authors.lastname: Szymański
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Igor
authors.initials: I
authors.lastname: Soszyński
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Wyrzykowski
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.|Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA.
authors.forename: Radosław
authors.initials: R
authors.lastname: Poleski
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Szymon
authors.initials: S
authors.lastname: Kozłowski
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Jan
authors.initials: J
authors.lastname: Skowron
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.|Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Ulaczyk
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Skowron
authors.affiliation: Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Pawlak