AR Scorpii

AR Scorpii (AR Sco) is a binary pulsar that consists of white dwarf and a red dwarf.[2] It is the first "white dwarf-pulsar" to be discovered.[3] The 3.56-hour period in AR Sco's light curve caused it to be misclassified as a Delta Scuti variable, but in 2016, this period was found to be the binary orbital period. In addition, the system shows very strong optical, ultraviolet, and radio pulsations originating from the red dwarf with a period of just 1.97 minutes, which is a beat period from the orbital rotation and the white dwarf spin.[2] These pulsations occur when a relativistic beam from the white dwarf sweeps across the red dwarf, which then reprocesses the beam into the observed electromagnetic energy. At present, the white dwarf is not accreting significantly, and the system is powered by the spin-down of the white dwarf.[3] The pulsar is about the same size as Earth.

AR Scorpii

Artist’s impression of AR Scorpii.
Observation data
Epoch 2000      Equinox 2000
Constellation Scorpius
Right ascension  16h 21m 47.28s[1]
Declination −22° 53′ 10.3″[1]
Characteristics
Evolutionary stage White dwarf
Evolutionary stage Main sequence
Spectral type M5[2]
Astrometry
Distance116 ± 16[2] pc
Details
White dwarf
Mass0.81 - 1.29[2] M☉
Rotation1.95[2] minutes
Red dwarf
Mass0.28 - 0.45[2] M☉
Other designations
AR Sco, 2MASS J16214728-2253102
Database references
SIMBADdata

AR Sco's unusual nature was first noticed by amateur astronomers.[4]

References
  1. Cutri, R. M.; et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
  2. Marsh, T. R.; et al. (2016). "A radio-pulsing white dwarf binary star". Nature. 537 (7620): 374–377. arXiv:1607.08265. Bibcode:2016Natur.537..374M. doi:10.1038/nature18620. PMID 27462808.
  3. Buckley, D. A. H.; Meintjes, P. J.; Potter, S. B.; Marsh, T. R.; Gänsicke, B. T. (2017-01-23). "Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii". Nature Astronomy. 1 (2): 0029. arXiv:1612.03185. Bibcode:2017NatAs...1E..29B. doi:10.1038/s41550-016-0029.
  4. Hambsch, Franz-Josef. "Amateurs Help Discover Pulsing White Dwarf". Sky and Telescope.


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