AR Scorpii

AR Scorpii (AR Sco) is a binary pulsar that consists of a white dwarf and a red dwarf.[3] It is located close to the ecliptic plane in the constellation Scorpius. Parallax measurements made by Gaia put the system at a distance of about 380 light-years (120 parsecs).[4]

A broadband optical light curve for AR Scorpii, plotted from Kepler data[6]
AR Scorpii

Artist’s impression of AR Scorpii.
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 16h 21m 47.28s[1]
Declination −22° 53′ 10.3″[1]
Characteristics
Apparent magnitude (G) 13.6 - 16.9[2]
Evolutionary stage White dwarf
Evolutionary stage Main sequence
Spectral type M5[3]
Astrometry
Proper motion (μ) RA: 9.707[4] mas/yr
Dec.: −51.469[4] mas/yr
Parallax (π)8.4918 ± 0.0408 mas[4]
Distance384 ± 2 ly
(117.8 ± 0.6 pc)
Details
White dwarf
Mass0.8[5] M☉
Radius0.01[5] R☉
Rotation1.95[3] minutes
Red dwarf
Mass0.28 - 0.45[3] M☉
Other designations
AR Sco, 2MASS J16214728-2253102
Database references
SIMBADdata

AR Scorpii is the first "white dwarf-pulsar" to be discovered.[7] Its unusual nature was first noticed by amateur astronomers.[8] The 3.56-hour period in AR Scorpii'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.[3] 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. Although the white dwarf shows evidence of accretion in the past, at present it is not accreting significantly, and the system is powered by the spin-down of the white dwarf.[7][5] The white dwarf's rotation will slow down on a timescale of 107 years.[5] It has a radius of about 7×103 km,[5] about the same size as Earth.

See also
  • AE Aquarii-Another white dwarf pulsar with weaker evidence.
  • PSR J1944-4410-the second confirmed white dwarf pulsar as of 2023[9][10][11]


References
  1. Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  2. "AR Scorpii". International Variable Star Index. AAVSO. Retrieved 2023-03-13.
  3. 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. S2CID 4451512.
  4. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  5. Singh, K. K.; Meintjes, P. J.; Yadav, K. K. (2021). "Properties of white dwarf in the binary system AR Scorpii and its observed features". Modern Physics Letters A. 36 (13). arXiv:2103.11602. Bibcode:2021MPLA...3650096S. doi:10.1142/S0217732321500966. S2CID 232307204.
  6. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  7. 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. S2CID 15683792.
  8. Hambsch, Franz-Josef (15 August 2016). "Amateurs Help Discover Pulsing White Dwarf". Sky and Telescope.
  9. Pelisoli, Ingrid; Marsh, T. R.; Buckley, David A. H.; Heywood, I.; Potter, Stephen B.; Schwope, Axel; Brink, Jaco; Standke, Annie; Woudt, P. A.; Parsons, S. G.; Green, M. J.; Kepler, S. O.; Munday, James; Romero, A. D.; Breedt, E. (2023-06-15). "A 5.3-min-period pulsing white dwarf in a binary detected from radio to X-rays". Nature Astronomy. 7 (8): 931–942. arXiv:2306.09272. doi:10.1038/s41550-023-01995-x. ISSN 2397-3366. S2CID 259164753.
  10. Gamillo, Elizabeth (2023-06-21). "Second-ever elusive white dwarf pulsar spotted | Astronomy.com". Astronomy Magazine. Retrieved 2023-07-15.
  11. Lewis, Evan (23 June 2023). "The Only Known White Dwarf Pulsar Just Got a Little Sibling". Astrobites.
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