Does millennia-long hibernation await star system after brilliant nova explosion?

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Artists impression of a classical nova explosion(Credit: Krzysztof Ulaczyk / Warsaw University Observatory)

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A new study is shedding light on a type of binary star system theorized to transition into a state of hibernation lasting thousands of years following powerful nova explosion events. The team focused their attention on a known white dwarf star orbiting closely with a low-mass companion star in the system V1213 Centauri (or Nova Centauri 2009). Star systems such as Nova Centauri 2009, which are the site of some of the brightest explosions known to take place in our galaxy, are known as a classical novae.

Over time, the white dwarf component of a classical novae siphons hydrogen-rich gas away from its companion star, and transfers the matter to its surface. This process continues until the white dwarf hits a point of critical mass, after which a dramatic thermonuclear nova eruption is inevitable.

These explosions cause the white dwarfs upon which they occur to brighten by a factor of several thousand. Nova explosions, though dramatic and powerful, are not to be mistaken with supernova events, which often mark the death of a stellar body.

It is thought that white dwarfs in classic nova systems experience multiple nova explosions with an interval of anywhere between thousands to millions of years. It is possible that, several decades after a nova explosion, that the white dwarf component of a binary system could go into a state of hibernation, during which time it would transfer barely any matter from its companion star. This is known as the hibernation theory.

Image displaying the location of Nova Centauri 2009 in the sky above the Warsaw Telescope, Chile. The top panels display the progression of the nova lifecycle leading up to, and after the May 2009 explosion(Credit: Krzysztof Ulaczyk / Warsaw University Observatory)

The long-term observations made using the 1.3 m (4.3 ft) Warsaw Telescope located at the Las Campanas Observatory, Chile, appear to support this theory. Images collected by the telescope between 2003 – 2016 seemingly display direct evidence of a transfer of stellar material prior to the nova explosion, which took place on May 8, 2009, and a significant brightening of the system following the event.

The increase in Nova Centauri 2009's luminosity hints that the white dwarf had increased the rate at which it was feeding off its companion star, seemingly as a direct result of the nova event. The behavior is in line with predictions made under the hibernation model for classical novae systems.

If Nova Centauri 2009 is indeed following the path described under the hibernation theory, it is likely that, over the next decade, that the system's luminosity will gradually fade as the mass transfer rate declines. It is possible that following this period of activity, Nova Centauri 2009 could slip into a hibernation lasting thousands of years. Upon awakening, the star would experience another nova event, thus beginning the cycle anew.

The team believes that its research will provide a solid basis for extensive follow-up observations that could support, or throw in to question, standing theories on the evolution of these classical novae systems.

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