M31N 2008-12a Provides Unique Opportunity To Study Pre-supernova Activity

M31N 2008-12a (Credit: M. Darnley / LJMU/RAS)

An international team of astronomers has identified a ‘best candidate’ binary star system for type 1a supernova (SN1a). Located in the Andromeda galaxy (M31), M31N 2008-12a is a ‘recurrent nova‘ (see diagram) that was correctly predicted to erupt in October 2014–the accuracy of this prediction was made due to successive annual events, recorded since its initial discovery in 2008.

“We’ve never seen anything like this before,” says Dr Matt Darnley of the Astrophysics Research Institute, Liverpool John Moores University. “Here is a pair of stars [White Dwarf & main/post-main sequence] that release vast amounts of energy almost every year. The system is right on the cusp of total destruction, so we are getting a first look at how it is changing right before it erupts as a supernova.”

Nova mechanism: gas is pulled off Sun like star by the white dwarf companion causing occasional thermonuclear explosions. SN1a events are initiated once a critical (Chandrasekhar) limit is reached. Due to its regular outburst period M31N 2008-12a is believed to be close to supernova

Nova/SN1a mechanism: gas is pulled off a Sun-like star (accretion) by the binary system’s white dwarf companion, causing occasional thermonuclear explosions (novae). SN1a events are initiated once a critical (Chandrasekhar) limit is reached. Due to its regular outburst period, M31N 2008-12a is believed to be nearing supernova. (Credit: NASA)

The team used the combined abilities of the robotic Liverpool Telescope (Observatorio del Roque de los Muchachos, Spain) and NASA’s Swift gamma/X-ray facility to carry out their observations. This is the second year of their ongoing exploration programme, which should help provide deeper insights into accreting binary star systems and how novae events change and evolve on their journey towards eventual supernova.

Although the regularity of the observed nova activity suggests an SN1a is imminent, the team point out that we should not hold our breath: eventual destruction of the accreting white dwarf component could occur either tomorrow, or hundreds of thousands of years in the future”.

However, even confronted with this potentially large time window, Darnley and his team intend to carry on monitoring the system, as its predictable, metronomic like, behaviour provides a “unique laboratory for further detailed studies”.

The next nova event is predicted to occur later this year, autumn 2015.

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Paul Hattle

As a strong advocate for science and learning, I am a passionate supporter of the 'Campaign for Science and Engineering' (CaSE) Fellow of the 'Royal Astronomical Society' (RAS) Associate Member of the 'Institute of Physics' (IOP) & 'The Institute of Scientific and Technical Communicators' (ISTC)

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