SU Ursae Majoris

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.[3] The distance to this system, as determined from its annual parallax shift of 4.53 mas,[2] is 719 light-years. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.[4]

SU Ursae Majoris

A visual band light curve for the April 1989 superoutburst of SU Ursae Majoris, adapted from Udalski et al. (1990)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 12m 28.26946s[2]
Declination +62° 36′ 22.4280″[2]
Apparent magnitude (V) 10.8–14.96[3]
Characteristics
Variable type SU UMa[3]
Astrometry
Radial velocity (Rv)+27.0[4] km/s
Proper motion (μ) RA: +6.582[2] mas/yr
Dec.: −24.538[2] mas/yr
Parallax (π)4.5347 ± 0.0286 mas[2]
Distance719 ± 5 ly
(221 ± 1 pc)
Absolute magnitude (MV)+5.1[5]
Orbit[6]
Period (P)0.076351±0.000043 d
Inclination (i)42[5]°
Periastron epoch (T)2,446,143.6672±0.0015 HJD
Semi-amplitude (K1)
(primary)		59±7 km s–1 km/s
Details
White dwarf
Mass0.8[7] M☉
Temperature28,000[7] K
Red dwarf
Mass0.105[8] M☉
Radius0.167[8] R☉
Other designations
AAVSO 0803+62, SU UMa, 2MASS J08122826+6236224[9]
Database references
SIMBADdata

The variable nature of this star was discovered at the Moscow Observatory by Lidiya Tseraskaya (L. Ceraski) in 1908.[10] It was classified as a U Geminorum-type variable, or dwarf nova.[11] Observation since 1926 showed that this variable undergoes two different types of eruptions: a short maxima lasting around two days that ranged in brightness 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'.[12] Similar dwarf novae of this class have since been discovered, and SU UMa is now the prototype for this sub-category of variable stars.[13]

This is a single-lined spectroscopic binary with an orbital period of 1.83 hours.[6] 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.[14] For SU UMa, the accretion rate from the companion is 9.8×10−13 M☉·yr−1.[15] 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.[14]

See also

References
  1. Udalski, A. (July 1990). "SU Ursae Majoris: The Perfect Prototype of SU UMa Subclass of Dwarf Novae". The Astronomical Journal. 100: 226. Bibcode:1990AJ....100..226U. doi:10.1086/115508. Retrieved 22 April 2022.
  2. 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.
  3. 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. S2CID 125853869.
  4. 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.
  5. 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. Bibcode:2011MNRAS.411.2695P. doi:10.1111/j.1365-2966.2010.17881.x.
  6. 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.
  7. 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. S2CID 1434460.
  8. 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. S2CID 2616606.
  9. "SU UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 5, 2018.
  10. 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.
  11. 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.
  12. Isles, J. E. (1974). "SU UMa, 1926-54". Journal of the British Astronomical Association. 84: 365–373. Bibcode:1974JBAA...84..365I.
  13. van Paradijs, J. (September 1983). "Superoutburst : a general phenomenon in dwarf novae". Astronomy and Astrophysics. 125: L16–L18. Bibcode:1983A&A...125L..16V.
  14. 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. arXiv:0911.2711. Bibcode:2010MNRAS.402.1816C. doi:10.1111/j.1365-2966.2009.16009.x. S2CID 118649844.
  15. 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
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