Beta Lyrae variables are a class of close binary stars. Their total brightness is variable because the two component stars orbit each other, and in this orbit one component periodically passes in front of the other one, thereby blocking its light. The two component stars of Beta Lyrae systems are quite heavy (several solar masses (M☉) each) and extended (giants or supergiants). They are so close, that their shapes are heavily distorted by mutual gravitation forces: the stars have ellipsoidal shapes, and there are extensive mass flows from one component to the other.
Beta Lyrae type eclipsing binary star. Heavier, whiter component is surrounded with a gas ring. Gas comes to teardrop shaped secondary component.
These mass flows occur because one of the stars, in the course of its evolution, has become a giant or supergiant. Such extended stars easily lose mass, just because they are so large: gravitation at their surface is weak, so gas easily escapes (the so-called stellar wind). In close binary systems such as beta Lyrae systems, a second effect reinforces this mass loss: when a giant star swells, it may reach its Roche limit, that is, a mathematical surface surrounding the two components of a binary star where matter may freely flow from one component to the other.
In binary stars the heaviest star generally is the first to evolve into a giant or supergiant. Calculations show that its mass loss then will become so large that in a comparatively very short time (less than half a million years) this star, that was once the heaviest, now becomes the lighter of the two components. Part of its mass is transferred to the companion star, the rest is lost in space.
The light curves of beta Lyrae variables are quite smooth: eclipses start and end so gradually that the exact moments are impossible to define. This occurs because the flow of mass between the components is so large that it envelopes the whole system in a common atmosphere. The amplitude of the brightness variations is in most cases less than one magnitude; the largest amplitude known is 2.3 magnitudes (V480 Lyrae).
The period of the brightness variations is very regular. It is determined by the revolution period of the binary - the time it takes for the two components to orbit once around each other. These periods are short, typically one or a few days. The shortest-known period is 0.29 days (QY Hydrae); the longest is 198.5 days (W Crucis). In beta Lyrae systems with periods longer than 100 days one of the components is generally a supergiant.
Beta Lyrae systems are sometimes[quantify] regarded[by whom?] as a subtype of the Algol variables; however, their light curves differ (the eclipses of Algol variables are much more sharply defined). On the other hand, beta Lyrae variables look somewhat like W Ursae Majoris variables; however, the latter are in general yet closer binaries (so-called contact binaries), and their component stars are mostly lighter than the beta Lyrae system components (about 1 M☉).
Nearly a thousand β Lyrae binaries are known: the latest edition of the General Catalogue of Variable Stars (2003) lists 835 of them (2.2% of all variable stars). Data for the ten brightest β Lyrae variables are given below. (See also the list of known variable stars.)
^"MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
January 01, 2023
beta, lyrae, variable, class, close, binary, stars, their, total, brightness, variable, because, component, stars, orbit, each, other, this, orbit, component, periodically, passes, front, other, thereby, blocking, light, component, stars, beta, lyrae, systems,. Beta Lyrae variables are a class of close binary stars Their total brightness is variable because the two component stars orbit each other and in this orbit one component periodically passes in front of the other one thereby blocking its light The two component stars of Beta Lyrae systems are quite heavy several solar masses M each and extended giants or supergiants They are so close that their shapes are heavily distorted by mutual gravitation forces the stars have ellipsoidal shapes and there are extensive mass flows from one component to the other Beta Lyrae type eclipsing binary star Heavier whiter component is surrounded with a gas ring Gas comes to teardrop shaped secondary component Contents 1 Mass flows 2 Light curves 3 Examples of b Lyrae stars 4 ReferencesMass flows EditThese mass flows occur because one of the stars in the course of its evolution has become a giant or supergiant Such extended stars easily lose mass just because they are so large gravitation at their surface is weak so gas easily escapes the so called stellar wind In close binary systems such as beta Lyrae systems a second effect reinforces this mass loss when a giant star swells it may reach its Roche limit that is a mathematical surface surrounding the two components of a binary star where matter may freely flow from one component to the other In binary stars the heaviest star generally is the first to evolve into a giant or supergiant Calculations show that its mass loss then will become so large that in a comparatively very short time less than half a million years this star that was once the heaviest now becomes the lighter of the two components Part of its mass is transferred to the companion star the rest is lost in space Light curves Edit A light curve for Beta Lyrae plotted from TESS data 1 The light curves of beta Lyrae variables are quite smooth eclipses start and end so gradually that the exact moments are impossible to define This occurs because the flow of mass between the components is so large that it envelopes the whole system in a common atmosphere The amplitude of the brightness variations is in most cases less than one magnitude the largest amplitude known is 2 3 magnitudes V480 Lyrae The period of the brightness variations is very regular It is determined by the revolution period of the binary the time it takes for the two components to orbit once around each other These periods are short typically one or a few days The shortest known period is 0 29 days QY Hydrae the longest is 198 5 days W Crucis In beta Lyrae systems with periods longer than 100 days one of the components is generally a supergiant Beta Lyrae systems are sometimes quantify regarded by whom as a subtype of the Algol variables however their light curves differ the eclipses of Algol variables are much more sharply defined On the other hand beta Lyrae variables look somewhat like W Ursae Majoris variables however the latter are in general yet closer binaries so called contact binaries and their component stars are mostly lighter than the beta Lyrae system components about 1 M Examples of b Lyrae stars EditThe prototype of the b Lyrae type variable stars is b Lyrae also called Sheliak Its variability was discovered in 1784 by John Goodricke Nearly a thousand b Lyrae binaries are known the latest edition of the General Catalogue of Variable Stars 2003 lists 835 of them 2 2 of all variable stars Data for the ten brightest b Lyrae variables are given below See also the list of known variable stars star type a period days maximummagnitude minimummagnitude spectrum distance lightyears z And EB GS RS 17 7695 3 92 4 14 K1II III 181DV Aqr EB 1 575529 5 89 6 25 A9V 280UW CMa EB KE 4 393407 4 84 5 33 O7Ia fp OB 3000t CMa EB 1 28 4 32 4 37 O9Ib 3000b Lyr prototype EB 12 913834 3 25 4 36 B8II IIIep 880TU Mus EB KE 1 3 8 17 8 75 O7 5V O9 5V 15500d Pic EB D 1 672541 4 65 4 90 B3III O9V 1700V Pup EB SD 1 4544859 4 35 4 92 B1Vp B3 1200PU Pup EB 2 57895 4 69 4 75 B9 550y Sgr EB GS 137 939 4 53 4 61 B8pI O9V or F2p 1700m1 Sco EB SD 1 44626907 2 94 3 22 B1 5V B6 5V 800p Sco EB 1 57 2 82 2 85 B1V B2V 460CX CMa EB 9 9 10 7 B5V EB Beta Lyrae variable GS at least one giant or supergiant component KE contact binary D detached binary SD semi detached binary RS RS Canum Venaticorum variableReferences Edit MAST Barbara A Mikulski Archive for Space Telescopes Space Telescope Science Institute Retrieved 8 December 2021 Retrieved from https en wikipedia org w index php title Beta Lyrae variable amp oldid 1101146168, wikipedia, wiki, book, books, library,
