Contact binary

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Artist's rendering of the massive contact binary star VFTS 352, located in the Large Magellanic Cloud An artist's impression of the hottest and most massive touching double star.jpg
Artist's rendering of the massive contact binary star VFTS 352, located in the Large Magellanic Cloud

In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontact binary. [1] [2] The term "contact binary" was introduced by astronomer Gerard Kuiper in 1941. [3] Almost all known contact binary systems are eclipsing binaries; [4] eclipsing contact binaries are known as W Ursae Majoris variables, after their archetype star, W Ursae Majoris. [5]

In a contact binary, both stars have filled their Roche lobes, allowing the more massive primary component to transfer both mass and luminosity to the secondary member. As a result, the components in a contact binary often have similar effective temperatures and luminosities, regardless of their respective masses. The rate of energy transfer between the components is dependent on their mass ratio and luminosity ratio. In cases where the stars are in geometric contact but the thermal contact is poor, there can exist wide differences between their respective temperatures. [6]

Contact binaries are not to be confused with common envelopes. Whereas the configuration of two touching stars in a contact binary has a typical lifetime of millions to billions of years, the common envelope is a dynamically unstable phase in binary evolution that either expels the stellar envelope or merges the binary in a timescale of months to years. [7]

See also

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W Ursae Majoris is the variable star designation for a binary star system in the northern constellation of Ursa Major. It has an apparent visual magnitude of about 7.9, which is too faint to be seen with the naked eye. However, it can be viewed with a small telescope. Parallax measurements place it at a distance of roughly 169 light years (52 parsecs) from Earth.

<span class="mw-page-title-main">Dubhe</span> Binary star in the constellation Ursa Major

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<span class="mw-page-title-main">Merak (star)</span> Star in the constellation Ursa Major

Merak, also called Beta Ursae Majoris, is a star in the northern constellation of Ursa Major.

<span class="mw-page-title-main">W Ursae Majoris variable</span>

A W Ursae Majoris variable, also known as a low mass contact binary, is a type of eclipsing binary variable star. These stars are close binaries of spectral types F, G, or K that share a common envelope of material and are thus in contact with one another. They are termed contact binaries because the two stars touch and transfer mass and energy through the connecting neck, although astronomer Robert E. Wilson argues that the term "overcontact" is more appropriate.

Theta Ursae Majoris is a suspected spectroscopic binary star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.17, placing it among the brighter members of this constellation. The distance to this star has been measured directly using the parallax method, yielding an estimated value of 43.96 light-years.

Kappa Ursae Majoris is a binary star in the constellation of Ursa Major. With a combined apparent magnitude of +3.60, the system is approximately 358 light-years from Earth.

<span class="mw-page-title-main">44 Boötis</span> Triple star system in the constellation Boötes

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<span class="mw-page-title-main">UW Canis Majoris</span> Beta Lyrae variable star in the constellation Canis Major

UW Canis Majoris is a star in the constellation Canis Major. It is classified as a Beta Lyrae eclipsing contact binary and given the variable star designation UW Canis Majoris. Its brightness varies from magnitude +4.84 to +5.33 with a period of 4.39 days. Bode had initially labelled it as Tau2 Canis Majoris, but this designation had been dropped by Gould and subsequent authors.

<span class="mw-page-title-main">S Antliae</span> Star in the constellation Antlia

S Antliae is a W Ursae Majoris-type eclipsing binary star in Antlia.

<span class="mw-page-title-main">Y Sextantis</span> Variable star in the constellation Sextans

Y Sextantis, abbreviated as Y Sex, is a variable star system in the equatorial constellation of Sextans. The system is invisible to the naked eye with a mean apparent visual magnitude of 9.88. It is located roughly at 1,300 light years from the Sun based on parallax.

<span class="mw-page-title-main">RR Centauri</span> Star in the constellation Centaurus

RR Centauri is a variable star of apparent magnitude maximum +7.29. It is located in the constellation of Centaurus, approximately 320 light years distant from the solar system.

<span class="mw-page-title-main">65 Ursae Majoris</span> Star system in the constellation Ursa Major

65 Ursae Majoris, abbreviated as 65 UMa, is a star system in the constellation of Ursa Major. With a combined apparent magnitude of about 6.5, it is at the limit of human eyesight and is just barely visible to the naked eye in ideal conditions. It is about 760 light years away from Earth.

<span class="mw-page-title-main">V752 Centauri</span> Star in the constellation Centaurus

V752 Centauri is multiple star system and variable star in the constellation of Centaurus. An eclipsing binary, its apparent magnitude has a maximum of 9.10, dimming to 9.66 during primary eclipse and 9.61 during secondary eclipse. Its variability was discovered by Howard Bond in 1970. From parallax measurements by the Gaia spacecraft, the system is located at a distance of 410 light-years from Earth.

<span class="mw-page-title-main">TX Ursae Majoris</span> Eclipsing binary star system in the constellation of Ursa Major

TX Ursae Majoris is an eclipsing binary star system in the northern circumpolar constellation of Ursa Major. With a combined apparent visual magnitude of 6.97, the system is too faint to be readily viewed with the naked eye. The pair orbit each other with a period of 3.063 days in a circular orbit, with their orbital plane aligned close to the line of sight from the Earth. During the primary eclipse, the net brightness decreases by 1.74 magnitudes, while the secondary eclipse results in a drop of just 0.07 magnitude. TX UMa is located at a distance of approximately 780 light years from the Sun based on parallax measurements, but is drifting closer with a mean radial velocity of −13 km/s.

<span class="mw-page-title-main">UX Ursae Majoris</span> Variable star in the constellation Ursa Major

UX Ursae Majoris is an Algol type binary star system in the northern circumpolar constellation of Ursa Major. It is classified as a nova-like variable star similar to DQ Herculis, although no eruptions have been reported. Since its discovery in 1933, this system has been the subject of numerous studies attempting to determine its properties. The combined apparent visual magnitude of UX UMa ranges from 12.57 down to 14.15. The system is located at a distance of approximately 952 light years from the Sun based on parallax, and is drifting further away with a radial velocity of 112 km/s.

<span class="mw-page-title-main">VZ Piscium</span> Variable star in the constellation Pisces

VZ Piscium is a triple star system in the equatorial constellation of Pisces. it is located at a distance of 178 light years from the Sun based on parallax measurements, and has an apparent visual magnitude of about 10.3. This is an eclipsing binary system that undergoes shallow eclipses; the brightness decreases to magnitude 10.45 during the primary eclipse, then to magnitude 10.43 with the secondary eclipse, although as a contact binary the brightness varies continuously with no period of constant maximum brightness. The system is drifting closer with a radial velocity of approximately −4 km/s, and has a net heliocentric velocity of 144.1 km/s.

<span class="mw-page-title-main">VV Ursae Majoris</span> Variable star system in the constellation Ursa Major

VV Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major, abbreviated VV UMa. It is a variable star system with a brightness that cycles around an apparent visual magnitude of 10.19, making it too faint to be visible to the naked eye. The system is located at a distance of approximately 1,500 light years based on parallax measurements.

<span class="mw-page-title-main">AW Ursae Majoris</span> Variable star in the constellation Ursa Major

AW Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major, abbreviated AW UMa. It is an A-type W Ursae Majoris variable with an apparent visual magnitude of 6.83, which is near the lower limit of visibility to the naked eye. This is an eclipsing binary with the brightness dropping to magnitude 7.13 during the primary eclipse and to 7.08 with the secondary eclipse. Parallax measurements give a distance estimate of 221 light years from the Sun. It is drifting closer to the Sun with a radial velocity of approximately −17 km/s. The system has a high proper motion, traversing the celestial sphere at the rate of 0.216 arc second per annum.

<span class="mw-page-title-main">BE Ursae Majoris</span> Variable star in the constellation Ursa Major

BE Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major, abbreviated BE UMa. The two components are an unusual M-class dwarf star and a subdwarf O star, borderline white dwarf. It is classified as a detached Algol variable and ranges in brightness from an apparent visual magnitude of 14.8 down to 17.8. This is too faint to be visible to the naked eye. The distance to this system is approximately 4,600 light years based on parallax measurements.

<span class="mw-page-title-main">U Pegasi</span> Binary star in the constellation Pegasus

U Pegasi is a binary star system in the constellation of Pegasus, abbreviated U Peg. The pair form an eclipsing binary with a combined peak apparent visual magnitude of 9.23, which is far too faint to be visible to the naked eye. During the primary eclipse the magnitude decreases to 10.07, while the secondary eclipse only drops to magnitude 9.73. This system is located at a distance of approximately 596 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of around −28.5 km/s.

References

  1. ↑ Darling, David. "binary star". www.daviddarling.info. Retrieved 2019-05-06.
  2. ↑ Thompson, Michael J. (2006). An Introduction to Astrophysical Fluid Dynamics. London: Imperial College Press. pp. 51–53. ISBN   1-86094-615-1.
  3. ↑ Kuiper, Gerard P. (1941). "On the Interpretation of β Lyrae and Other Close Binaries". Astrophysical Journal. 93: 133. Bibcode:1941ApJ....93..133K. doi: 10.1086/144252 .
  4. ↑ Tassoul, Jean Louis; et al. (2000). Stellar Rotation. Cambridge, UK, New York: Cambridge University Press. p. 231. ISBN   0-521-77218-4.
  5. ↑ Mullaney, James (2005). Double and Multiple Stars and how to Observe Them. New York, London: Springer. p. 19. ISBN   1-85233-751-6.
  6. ↑ Csizmadia, Sz.; Klagyivik, P. (November 2004). "On the properties of contact binary stars". Astronomy and Astrophysics. 426 (3): 1001–1005. arXiv: astro-ph/0408049 . Bibcode:2004A&A...426.1001C. doi:10.1051/0004-6361:20040430.
  7. ↑ Ivanova, N.; et al. (2013). "Common envelope evolution: where we stand and how we can move forward". The Astronomy and Astrophysics Review. 21: 59. arXiv: 1209.4302 . Bibcode:2013A&ARv..21...59I. doi:10.1007/s00159-013-0059-2.
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