Back مغلف مشترك Arabic Estrella binària amb embolcall comú Catalan Common Envelope German Binaire à enveloppe commune French 共通外層 Japanese 공통외층 Korean Sampul sepunya Malay Envelope comum Portuguese Система с общей оболочкой Russian Зорі зі спільною оболонкою Ukrainian

Common envelope

Key stages in a common envelope phase. Top: A star fills its Roche lobe. Middle: The companion is engulfed; the core and companion spiral towards one another inside a common envelope. Bottom: The envelope is ejected or the two stars merge.

In astronomy, a common envelope (CE) is gas that contains a binary star system.[1] The gas does not rotate at the same rate as the embedded binary system. A system with such a configuration is said to be in a common envelope phase or undergoing common envelope evolution.

During a common envelope phase the embedded binary system is subject to drag forces from the envelope which cause the separation of the two stars to decrease. The phase ends either when the envelope is ejected to leave the binary system with much smaller orbital separation, or when the two stars become sufficiently close to merge and form a single star. A common envelope phase is short-lived relative to the lifetime of the stars involved.

Evolution through a common envelope phase with ejection of the envelope can lead to the formation of a binary system composed of a compact object with a close companion. Cataclysmic variables, X-ray binaries and systems of close double white dwarfs or neutron stars are examples of systems of this type which can be explained as having undergone common envelope evolution. In all these examples there is a compact remnant (a white dwarf, neutron star or black hole) which must have been the core of a star which was much larger than the current orbital separation. If these systems have undergone common envelope evolution then their present close separation is explained. Short-period systems containing compact objects are sources of gravitational waves and Type Ia supernovae.

Predictions of the outcome of common envelope evolution are uncertain.[2][3][4]

A common envelope is sometimes confused with a contact binary. In a common envelope binary system the envelope does not generally rotate at the same rate as the embedded binary system; thus it is not constrained by the equipotential surface passing through the L2 Lagrangian point.[1] In a contact binary system the shared envelope rotates with the binary system and fills an equipotential surface.[5]

  1. ^ a b Paczyński, B. (1976). "Common Envelope Binaries". In Eggleton, P.; Mitton, S.; Whelan, J. (eds.). Structure and Evolution of Close Binary Systems. IAU Symposium No. 73. Dordrecht: D. Reidel. pp. 75–80. Bibcode:1976IAUS...73...75P.
  2. ^ Iben, I.; Livio, M. (1993). "Common envelopes in binary star evolution". Publications of the Astronomical Society of the Pacific. 105: 1373–1406. Bibcode:1993PASP..105.1373I. doi:10.1086/133321.
  3. ^ Taam, R. E.; Sandquist, E. L. (2000). "Common Envelope Evolution of Massive Binary Stars". Annual Review of Astronomy and Astrophysics. 38: 113–141. Bibcode:2000ARA&A..38..113T. doi:10.1146/annurev.astro.38.1.113.
  4. ^ Ivanova, N.; Justham, S.; Chen, X.; De Marco, O.; Fryer, C. L.; Gaburov, E.; Ge, H.; Glebbeek, E.; Han, Z.; Li, X. D.; Lu, G.; Podsiadlowski, P.; Potter, A.; Soker, N.; Taam, R.; Tauris, T. M.; van den Heuvel, E. P. J.; Webbink, R. F. (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.
  5. ^ Eggleton, P. (2006). Evolutionary Processes in Binary and Multiple Stars. Cambridge: Cambridge University Press. ISBN 978-0521855570.

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