Alpha2 Canum Venaticorum variable

An Alpha² Canum Venaticorum variable (or α² CVn variable) is a type of variable star. These stars are chemically peculiar main sequence stars of spectral class B8p to A7p. They have strong magnetic fields and strong silicon, strontium, or chromium spectral lines. Their brightness typically varies by 0.01 to 0.1 magnitudes over the course of 0.5 to 160 days.^[1]

A light curve for α² Canum Venaticorum, plotted from *TESS* data^[2]

In addition to their intensities, the intensities and profiles of the spectral lines of α² CVn variables also vary, as do their magnetic fields. The periods of these variations are all equal and are believed to equal the period of rotation of the star. It is thought that they are caused by an inhomogeneous distribution of metals in the atmospheres of these stars, so that the surface of the star varies in brightness from point to point.^[3]

The type-star which this class is named after is α² Canum Venaticorum, a star in the binary system of Cor Caroli, which is in the northern constellation of Canes Venatici. Its brightness fluctuates by 0.14 magnitudes with a period of 5.47 days.^[4]

Examples

List of Alpha² Canum Venaticorum Variables^[5]
Designation (name)	Constellation	Discovery	Apparent magnitude (Maximum)	Apparent magnitude (Minimum)	Range of magnitude	Spectral type	Comment
(α² Canum Venaticorum) Cor Caroli	Canes Venatici		2.84	2.98	0.14	A0Vp(Si-Cr-Eu)	Prototype
(ε UMa) Alioth	Ursa Major		1.76		0.02	A1III-IVp kB9(Cr-Eu)	Brightest Member
α Dor	Dorado		3.26	3.30	0.04	B9IIIp(Si)	One of the hottest; binary
α Psc (Alrescha)	Pisces		3.82	3.83	0.01	A2IVp(Sr)	Binary
β Hydrae A	Hydra	1834	4.67	4.71	0.04	B8.5IIIp(Si)	Hottest member;binary
HD 187474	Sagittarius		5.28	5.34	0.06	A0 EuCrSr	Long 6.4 year period;binary

References

^ Variability types, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line August 20, 2008.
^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
^ pp. 83–85, Variable Stars, Michel Petit, foreword by Paolo Maffei, tr. from French by W. J. Duffin, Chichester, UK: John Wiley & Sons, 1987, ISBN 0-471-90920-3.
^ alf 2 CVn , database entry, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line August 20, 2008.
^ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.

Variable stars

Pulsating

Cepheids and cepheid-like	Type I (Classical cepheids, Delta Scuti) Type II (BL Herculis, W Virginis, RV Tauri) RR Lyrae Rapidly oscillating Ap SX Phoenicis
Blue-white with early spectra	Alpha Cygni Beta Cephei Slowly pulsating B-type PV Telescopii Blue large-amplitude pulsator
Long-period	Mira Semiregular Slow irregular
Other	Gamma Doradus Solar-like oscillations White dwarf

Eruptive

Protostar and PMS	Herbig Ae/Be Orion FU Orionis T Tauri
Giants and supergiants	Luminous blue variable R Coronae Borealis (DY Persei) Yellow hypergiant
Eruptive binary	Double periodic FS Canis Majoris RS Canum Venaticorum
Other	Flare Gamma Cassiopeiae Lambda Eridani Wolf–Rayet

Cataclysmic

Rotating

Non-spherical	Rotating ellipsoidal
Stellar spots	BY Draconis FK Comae Berenices
Magnetic fields	α² Canum Venaticorum Pulsar SX Arietis

Eclipsing

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Examples

References

Alpha² Canum Venaticorum variable