Astronomy:AR Scorpii

From HandWiki
Short description: Binary pulsar system in the constellation Scorpius
AR Scorpii
Observation data
Equinox J2000.0]] (ICRS)
Constellation Scorpius
Right ascension  16h 21m 47.28s[1]
Declination −22° 53′ 10.3″[1]
Apparent magnitude (G) 13.6 - 16.9[2]
Evolutionary stage White dwarf
Evolutionary stage Main sequence
Spectral type M5[3]
Proper motion (μ) RA: 9.707[4] mas/yr
Dec.: −51.469[4] mas/yr
Parallax (π)8.4918 ± 0.0408[4] mas
Distance384 ± 2 ly
(117.8 ± 0.6 pc)
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

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 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]


  1. 1.0 1.1 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E. et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues 2246: II/246. Bibcode2003yCat.2246....0C. 
  2. "AR Scorpii". AAVSO. 
  3. 3.0 3.1 3.2 3.3 3.4 Marsh, T. R. (2016). "A radio-pulsing white dwarf binary star". Nature 537 (7620): 374–377. doi:10.1038/nature18620. PMID 27462808. Bibcode2016Natur.537..374M. 
  4. 4.0 4.1 4.2 4.3 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  5. 5.0 5.1 5.2 5.3 5.4 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). doi:10.1142/S0217732321500966. Bibcode2021MPLA...3650096S. 
  6. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. 
  7. 7.0 7.1 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. doi:10.1038/s41550-016-0029. Bibcode2017NatAs...1E..29B. 
  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 et al. (2023-06-15). "A 5.3-min-period pulsing white dwarf in a binary detected from radio to X-rays" (in en). Nature Astronomy 7 (8): 931–942. doi:10.1038/s41550-023-01995-x. ISSN 2397-3366. Bibcode2023NatAs...7..931P. 
  10. Gamillo, Elizabeth (2023-06-21). "Second-ever elusive white dwarf pulsar spotted |" (in en-US). 
  11. Lewis, Evan (23 June 2023). "The Only Known White Dwarf Pulsar Just Got a Little Sibling".