SW Ursae Majoris

SW Ursae Majoris

Light curves for SW Ursae Majoris, adapted from Robinson et al. (1987)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 36m 42.749s[2]
Declination +53° 28′ 37.98″[2]
Apparent magnitude (V) 9.7 to 16.5[3]
Characteristics
Variable type U Gem[3]
Astrometry
Proper motion (μ) RA: −28.713 mas/yr[2]
Dec.: 5.928 mas/yr[2]
Parallax (π)6.2002 ± 0.0602 mas[2]
Distance526 ± 5 ly
(161 ± 2 pc)
Absolute magnitude (MV)+4.9 (at maximum)[4]
Details
White dwarf
Mass0.61+0.06
−0.04[5] M☉
Radius0.0129+0.0009
−0.0010[5] R☉
Surface gravity (log g)8.01+0.11
−0.09[5] cgs
Temperature13,854+189
−131[5] K
donor
Mass0.1[6] M☉
Luminosity0.001[6] L☉
Other designations
SW UMa, 2MASS J08364276+5328378[7]
Database references
SIMBADdata

SW Ursae Majoris is a cataclysmic binary star system in the northern circumpolar constellation of Ursa Major, abbreviated SW UMa. During quiescence it has an apparent visual magnitude of 16.5–17, which is too faint to be visible to the naked eye.[8] Based on parallax measurements, it is located at a distance of approximately 526 light years from the Sun.[2]

The variable nature of this object was noted by L. Tseraskaya in 1909 when it increased in brightness to 10th magnitude.[9][10] It was determined to be a U Geminorum star, indicating this is a binary star system.[11] A short orbital period of 81.8 minutes was determined by A. W. Shafter and associates in 1986.[12] The same year, E. L. Robinson and associates detected superhumps with a period of 84.0 minutes.[1] Large amplitude quasi-periodic oscillations were observed by T. Kato and associates in 1992, which is a property of SU UMa-type dwarf novae.[13]

When the system is in a quiet period, it displays a periodicity of 15.9 minutes and has a marginal emission of soft X-rays. This is likely the rotation period of the white dwarf, and the system resembles an intermediate polar with a strongly-magnetized white dwarf as the accreting component.[8] It undergoes outbursts that vary in brightness and duration.[14] During quiescence, it is estimated that about 70% of the bolometric luminosity of the system is produced by the white dwarf, with almost all the rest produced by the accretion disk.[15]

  1. ^ a b Cite error: The named reference Robinson_et_al_1987 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference patterson2011 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference Pala_et_al_2022 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference povich2004 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Soejima_et_al_2009 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Ceranski_1909 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Hornby_1975 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Wellmann_1952 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Shafter_et_al_1986 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Kato_et_al_1992 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Howell_et_al_1995 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference urban2006 was invoked but never defined (see the help page).