title: Binary orbits as the driver of γ-ray emission and mass ejection in classical novae.
abstract: Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel about 10(-4) solar masses of material at velocities exceeding 1,000 kilometres per second. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of thermonuclear energy, prolonged optically thick winds or binary interaction with the nova envelope. Classical novae are now routinely detected at gigaelectronvolt γ-ray wavelengths, suggesting that relativistic particles are accelerated by strong shocks in the ejecta. Here we report high-resolution radio imaging of the γ-ray-emitting nova V959 Mon. We find that its ejecta were shaped by the motion of the binary system: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of γ-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are γ-ray emitters.
authors.affiliation: Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Chomiuk
authors.affiliation: Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Linford
authors.affiliation: 1] Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala, Sweden [2] Joint Institute for VLBI in Europe, Postbus 2, NL-7990 AA Dwingeloo, The Netherlands [3] Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030 Shanghai, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: O'Brien
authors.affiliation: Joint Institute for VLBI in Europe, Postbus 2, NL-7990 AA Dwingeloo, The Netherlands.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Paragi
authors.affiliation: National Radio Astronomy Observatory, PO Box O, Socorro, New Mexico 87801, USA.
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Mioduszewski
authors.affiliation: Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Beswick
authors.affiliation: Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Cheung
authors.affiliation: 1] Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA [2] CRESST and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, Maryland 20771, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Mukai
authors.affiliation: School of Physics and Astronomy, University of Minnesota, 115 Church Street Southeast, Minneapolis, Minnesota 55455, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nelson
authors.affiliation: Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
authors.forename: Valério A R M
authors.initials: VA
authors.lastname: Ribeiro
authors.affiliation: 1] National Radio Astronomy Observatory, PO Box O, Socorro, New Mexico 87801, USA [2] National Research Council, Herzberg Astronomy and Astrophysics, 717 White Lake Road, PO Box 248, Penticton, British Columbia V2A 6J9, Canada.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Rupen
authors.affiliation: Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Sokoloski
authors.affiliation: Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Weston
authors.affiliation: Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Bode
authors.affiliation: Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston PR1 2HE, UK.
authors.forename: Stewart
authors.initials: S
authors.lastname: Eyres
authors.affiliation: Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
authors.forename: Nirupam
authors.initials: N
authors.lastname: Roy
authors.affiliation: Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, New Mexico 87131-0001, USA.
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Taylor