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H.E.S.S. discovers the first VHE gamma-ray Nova

Artist’s impression of the white dwarf and red giant binary system following the nova outburst. (Credits: DESY/H.E.S.S., Science Communication Lab)

In a publication in Science, the H.E.S.S. collaboration has for the first time described the time sequence of the acceleration process in a nova.
Novae are a source of high-energy particles and photons and RS Ophiuchi (RS Oph) is a recurrent nova system comprising a white dwarf and a companion red giant star. RS Ophiuchi exploded on August 8, 2021 and the H.E.S.S. telescopes were turned to the constellation in the night after the first sightings and promptly detected the explosion. The observations continued for more than one month, resulting in an exquisitely covered light-curve of the event.
The paper ‘Time-resolved hadronic particle acceleration in the recurrent nova RS Ophiuchi’ describes the spectral and temporal properties of the gamma-ray emission. They reveal that it takes longer to reach maximum brightness at the highest energies compared to less energetic light and offers insights that allow a more profound understanding of such explosions.

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