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A radio-pulsing white dwarf binary star
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(2016) A radio-pulsing white dwarf binary star. Nature, 537 . pp. 374-377. doi:10.1038/nature18620 ISSN 0028-0836.
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Official URL: http://dx.doi.org/10.1038/nature18620
Abstract
White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive1. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line2 and X-ray3 emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic4. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star5, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco’s optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 107-year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf’s spin, they mainly originate from the cool star. AR Sco’s broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf’s magnetosphere.
Item Type: | Journal Article | ||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||
Library of Congress Subject Headings (LCSH): | White dwarf stars, X-ray astronomy, Radio astronomy | ||||||||||
Journal or Publication Title: | Nature | ||||||||||
Publisher: | Nature Publishing | ||||||||||
ISSN: | 0028-0836 | ||||||||||
Official Date: | 15 September 2016 | ||||||||||
Dates: |
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Volume: | 537 | ||||||||||
Page Range: | pp. 374-377 | ||||||||||
DOI: | 10.1038/nature18620 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||||
Date of first compliant deposit: | 24 August 2016 | ||||||||||
Date of first compliant Open Access: | 27 January 2017 | ||||||||||
Funder: | Science and Technology Facilities Council (Great Britain) (STFC), European Research Council (ERC), Fondo Nacional de Desarrollo Científico y Tecnológico (Chile) (FONDECYT), Chile. Ministerio de Economía, Samnakngān Kō̜ngthun Sanapsanun Kānwičhai [Thailand Research Fund], Thailand. Samnakngān Khana Kammakān Wičhai hǣng Chāt [National Research Council of Thailand] | ||||||||||
Grant number: | ST/L000733, ST/M001350/1 (STFC), 320964, 647208 (ERC), 3140585, 1141269 (FONDECYT), Millenium 9 Nucleus RC130007 (Chile), MRG5680152, R2559B034 (Thailand) |
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