SU Ursae Majoris

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SU Ursae Majoris
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension  08h 12m 28.26946s[1]
Declination +62° 36′ 22.4280″[1]
Apparent magnitude (V) 10.8 – 14.96[2]
Variable type SU UMa[2]
Radial velocity (Rv)+27.0[3] km/s
Proper motion (μ) RA: +6.582[1] mas/yr
Dec.: −24.538[1] mas/yr
Parallax (π)4.5347 ± 0.0286[1] mas
Distance719 ± 5 ly
(221 ± 1 pc)
Absolute magnitude (MV)+5.1[4]
Period (P)0.076351±0.000043 d
Inclination (i)42[4]°
Periastron epoch (T)2,446,143.6672±0.0015 HJD
Semi-amplitude (K1)
59±7 km s–1 km/s
White dwarf
Mass0.8[6] M
Temperature28,000[6] K
Red dwarf
Mass0.105[7] M
Radius0.167[7] R
Other designations
AAVSO 0803+62, SU UMa, 2MASS J08122826+6236224[8]
Database references

SU Ursae Majoris, or SU UMa, is a close binary star in the northern circumpolar constellation of Ursa Major. It is a periodic cataclysmic variable that varies in magnitude from a peak of 10.8 down to a base of 14.96.[2] The distance to this system, as determined from its annual parallax shift of 4.53 mas,[1] is 719 light years. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.[3]

The variable nature of this star was discovered at the Moscow Observatory by Lidiya Tseraskaya (L. Ceraski) in 1908.[9] It was classified as a U Geminorum-type variable, or dwarf nova.[10] Observation since 1926 showed that this variable undergoes two different types of eruptions: a short maxima lasting around two days that ranged in brightess between 11.6–12.9 magnitude, and a longer maxima extending for 13 days that ranged between 10.4–11.8 magnitude. The later event came to be referred to as 'supermaxima'.[11] Similar dwarf novae of this class have since been discovered, and SU UMa is now the prototype for this sub-category of variable stars.[12]

This is a single-lined spectroscopic binary with an orbital period of 1.83 hours.[5] It consists of a white dwarf star that is acquiring matter from its close companion via an accretion disk. This disk is unstable and undergoes periodic outbursts which increase the luminosity of the system.[13] For SU UMa, the accretion rate from the companion is 9.8×10−13 M·yr−1.[14] X-ray emission has been detected in the vicinity of the white dwarf, which drops by a factor of four during outbursts. This emission is theorized to come from the boundary layer between the white dwarf and its accretion disk.[13]

See also[edit]


  1. ^ a b c d e f 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.
  2. ^ a b c Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  3. ^ a b Duflot, M.; et al. (December 1995). "Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Radial velocities: The Wilson-Evans-Batten catalogue". Astronomy and Astrophysics Supplement. 114: 269. Bibcode:1995A&AS..114..269D.
  4. ^ a b Patterson, Joseph (2011). "Distances and absolute magnitudes of dwarf novae: Murmurs of period bounce". Monthly Notices of the Royal Astronomical Society. 411 (4): 2695–2716. doi:10.1111/j.1365-2966.2010.17881.x.
  5. ^ a b Thorstensen, John R.; et al. (October 1986). "A Spectroscopic Study of the Cataclysmic Binary Star SU Ursae Majoris". Astrophysical Journal. 309: 721. Bibcode:1986ApJ...309..721T. doi:10.1086/164641.
  6. ^ a b Urban, Joel A; Sion, Edward M (2006). "The Dwarf Novae during Quiescence". The Astrophysical Journal. 642 (2): 1029–1041. arXiv:astro-ph/0602126. Bibcode:2006ApJ...642.1029U. doi:10.1086/501430.
  7. ^ a b Knigge, Christian; Sion, Edward M (2006). "The donor stars of cataclysmic variables". Monthly Notices of the Royal Astronomical Society. 373 (2): 484–502. arXiv:astro-ph/0609671. Bibcode:2006MNRAS.373..484K. doi:10.1111/j.1365-2966.2006.11096.x.
  8. ^ "SU UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 5, 2018.
  9. ^ Ceraski, W. (February 1908). "Une variable nouvelle 5.1908 Ursae majoris". Astronomische Nachrichten. 177 (11): 173. Bibcode:1908AN....177..173C. doi:10.1002/asna.19081771105.
  10. ^ Kraft, Robert P.; Luyten, Willem J. (October 1965). "Binary Stars among Cataclysmic Variables. VI. on the Mean Absolute Magnitude of U Geminorum Variables". The Astrophysical Journal. 142: 1041. Bibcode:1965ApJ...142.1041K. doi:10.1086/148374.
  11. ^ Isles, J. E. (1974). "SU UMa, 1926-54". Journal of the British Astronomical Association. 84: 365–373. Bibcode:1974JBAA...84..365I.
  12. ^ van Paradijs, J. (September 1983). "Superoutburst : a general phenomenon in dwarf novae". Astronomy and Astrophysics. 125: L16–L18. Bibcode:1983A&A...125L..16V.
  13. ^ a b Collins, David J.; Wheatley, Peter J. (March 2010). "X-ray observations of SU UMa throughout six outbursts". Monthly Notices of the Royal Astronomical Society. 402 (3): 1816–1823. Bibcode:2010MNRAS.402.1816C. doi:10.1111/j.1365-2966.2009.16009.x.
  14. ^ Zead, I.; et al. (April 2017). "Spectral and photometric behavior of SU UMa during quiescence and outburst states". New Astronomy. 52: 122–132. Bibcode:2017NewA...52..122Z. doi:10.1016/j.newast.2016.10.010.

Further reading[edit]