Algol variable
Algol variables or Algol-type binaries are a class of
When the cooler component passes in front of the hotter one, part of the latter's light is blocked, and the total brightness of the binary, as viewed from Earth, temporarily decreases. This is the primary minimum of the binary. Total brightness may also decrease, but less so, when the hotter component passes in front of the cooler one; this is the secondary minimum.[2]
The
Component stars of Algol binary systems have a
Generally the amplitudes of the brightness variations are of the order of one magnitude, the largest variation known being 3.4 magnitudes (V342 Aquilae). The components may have any spectral type, though in most cases the brighter component is found to have a B, A, F, or G class.
Algol itself, the prototype of this type of variable star, Bayer designation Beta Persei, first had its variability recorded in 1667 by Geminiano Montanari. The mechanism for its being variable was first correctly explained by John Goodricke in 1782.
Many thousands of Algol binaries are now known: the latest edition of the General Catalogue of Variable Stars (2003) lists 3,554 of them (9% of all variable stars).
Designation (name) | Constellation | Discovery | Apparent magnitude (Maximum)[nb 1] | Apparent magnitude (Minimum)[nb 2] | Range of magnitude | Period | Subtype | Spectral types (eclipsing components) |
Comment |
---|---|---|---|---|---|---|---|---|---|
ε Aur | Auriga | J.H. Fritsch, 1821 | 2m.92 | 3m.83 | 0.91 | 27.08 years | GS | F0 Iab + ~ B5V | |
U Cep | Cepheus | 6m.75 | 9m.24 | 2.49 | 2.49305 d | ||||
R CMa | Canis Major | 5m.70 | 6m.34 | 0.64 | 1.13594 d | SD | triple system | ||
S Cnc | Cancer | Hind, 1848 | 8m.29 | 10m.25 | 1.96 | 9.48455 d | DS | ||
α CrB (Alphecca or Gemma) | Corona Borealis | 2m.21 (B) | 2m.32 (B) | 0.11 | 17.35991 d | DM | A0V + G5V | ||
U CrB | Corona Borealis | 7m.66 | 8m.79 | 1.13 | 3.45220 d | SD | |||
u Her (68 Her) | Hercules | 4m.69 | 5m.37 | 0.68 | 2.05103 d | SD | |||
VW Hya | Hydra | 10m.5 | 14m.1 | 3.6 | 2.69642 d | SD | |||
δ Ori (Mintaka) | Orion | John Herschel, 1834 | 2m.14 | 2m.26 | 0.12 | 5.73248 d | DM | O9.5 II + B0.5III | |
VV Ori | Orion | 5m.31 | 5m.66 | 0.35 | 1.48538 d | KE | |||
β Per (Algol) | Perseus | Geminiano Montanari, 1669 | 2m.12 | 3m.39 | 1.27 | 2.86730 d | SD | B8V + K0IV | prototype, triple system |
ζ Phe | Phoenix | 3m.91 | 4m.42 | 0.51 | 1.66977 d | DM | B6 V + B9 V | probable quadruple system | |
U Sge | Sagitta | 6m.45 | 9m.28 | 2.83 | 3.38062 d | SD | |||
λ Tau | Taurus | Baxendell, 1848 | 3m.37 | 3m.91 | 0.54 | 3.95295 d | DM | B3 V + A4 IV | triple system |
δ Vel | Vela | Otero, Fieseler, 2000 | 1m.96 | 2m.39 | 0.43 | 45.15 d | DM | A2 IV + A4 V | triple, probable quintuple system |
TX Leonis | Leo | Meyer, Ernst-Joachim, 1933 | 5m.66 | 5m.75 | 0.09 | 2.445 d | DM | A2V | triple system |
BL Tel | Telescopium | Luyten, 1935 | 7m.09 | 8m.08 | 0.99 | 778 d | GS | F4Ib+M | one component may be variable |
- DM = A detached main-sequence system. Both components are main-sequence stars and neither fills their inner Roche lobe
- DS = A detached system with a subgiant. The subgiant does not fill its inner critical surface
- GS = A system with one or both giant and supergiant components; one of the components may be a main sequence star
- KE = A contact system of early (O-A) spectral type, both components being close in size to their inner critical surfaces.
- SD = A semidetached system. One star fills its Roche lobe.
References
- ^ "GCVS Variability Types". General Catalogue of Variable Stars. Retrieved 2022-05-15.
- S2CID 119308241.
- doi:10.1086/170967.
Further reading
- Eclipsing Binary Stars, D. Bruton (Stephen F. Austin State University)