RS Canum Venaticorum is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

system in the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Canes Venatici. It serves as the prototype to the class of RS Canum Venaticorum variables. The peak apparent visual magnitude of this system is below the level needed to observe it with the naked eye. It is located at a distance of approximately 443

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Sun based on

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

, but is drifting closer with a net

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of −14 km/s.

Olin J. Eggen Olin Jeuck Eggen (July 9, 1919 – October 2, 1998) was an American astronomer. Biography Olin Jeuck Eggen was born to Olin Eggen and Bertha Clare Jeuck in the village of Orfordville in Rock County, Wisconsin. Both of his parents were of Norw ...

(1991) included this system as a member of the

IC 2391 IC 2391 (also known as the Omicron Velorum Cluster or Caldwell 85) is an open cluster in the constellation Vela. The Persian astronomer Al Sufi may have first described it about 964. It was found by Abbe Lacaille and cataloged as Lac II 5. Th ...

supercluster, but it was later excluded.

Variability

The variable nature of RS Canum Venaticorum was discovered by the Russian astronomer Lidiya Tseraskaya in 1914. It is a detached binary in a close, circular orbit with a period of 4.8 days. The orbital plane is inclined by an angle of 85.55° to the line of sight from the Earth, causing this to be viewed from Earth as an eclipsing binary. Some of the brightness variations are caused by large spots on the surface of the star. Similar variable stars are known as RS Canum Venaticorum variables. Some RS Canum Venaticorum variables, including this star, also undergo eclipses. The primary eclipse minimum decreases the visual brightness of the system by 1.21 magnitudes, while the secondary minimum decreases it by 0.26 magnitudes. The exact magnitudes vary somewhat due to the inherent variability of the secondary. The General Catalogue of Variable Stars lists magnitude 8.19 for the secondary minimum and 9.14 for the primary minimum.

Components

The primary component is a relatively inactive F-type main-sequence star with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of F5V. It has 2.1 times the

radius of the Sun Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.9 ...

with a projected rotational velocity of about 11 km/s. That rate is slower than expected if the rotation of the star were locked with its orbital period. It has an estimated age of 2.5 billion years. The secondary component is a magnetically active K-type subgiant star with a class of K2 IV. It has 4.3 times the Sun's radius and a relatively high rotation rate with a projected rotational velocity of 42 km/s. This rapid spin was likely driven by interaction with the primary, and it generates the surface magnetic activity that makes the star variable. As with the Sun, it is undergoing differential rotation. Lower temperature

starspots Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in gene ...

cover a significant fraction of the secondary's surface, causing light variation as the star rotates. These are found at several active latitudes on the star below 70°, and appear to migrate at the rate of 0.1° per day. The total amount of spots varies in intensity with a cycle of , ranging from 17% to 37% coverage of the surface. The luminosity also varies slightly (0.01) due to proximity and reflection from the primary star.

X-ray emission Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays. Several types of astrophysical objects emit X-rays. They include galaxy clusters, black holes in active galactic nuclei (AGN), ...

has been detected from this star with a luminosity of . It has also been detected in the radio band.

Variability

Components

References

Further reading