Dog Type RS Variable

Variables of the type RS Hounds Dogs ( RS Canum Venaticorum , RS CVn ) are eruptive variable stars. This type includes close binary systems with H and K Ca II emission in the spectrum , the components of which exhibit increased chromospheric activity, causing a quasiperiodic variability of their brightness with a period close to the period of revolution and a variable amplitude, usually reaching 0.2 ^m .

The first to isolate these variables in a separate class was Otto Struve in 1946. In 1974, American astronomer Oliver DS (Oliver DS) defined a set of visual characteristics of variables such as RS Hounds of Dogs and 1976 the American astronomer Hall (Hall), based on them, divided these systems into five groups). ^[1] :

• I. Periodic systems. The circulation period is from 1 to 14 days. A hotter component of spectral class F or G and luminosity class V or IV. The spectral lines of Ca II H and K are clearly pronounced, while the components do not overshadow each other.
• II. Short-period systems. The circulation period is less than 1 day. A hotter component of spectral class F or G and luminosity class V or IV. The spectral lines of Ca II H and K are present in the spectrum of one or both components.
• III. Long-period systems. The circulation period is more than 14 days. One of the components of the spectral class G or K and the luminosity class II, III or IV. The spectral lines of Ca II H and K are clearly pronounced, while the components do not overshadow each other.
• IV. Flashing stars. The hotter component of the spectral class is dKe or dMe, the spectral lines of Ca II Н and К are clearly expressed in its spectrum ,
• V. Type T Taurus systems. The hotter component is the white dwarf . The colder component belongs to the spectral class G or K, the spectral lines of Ca II Н and К are clearly expressed in its spectrum ,

The light curve variables of the RS type of the Hounds of Dogs demonstrate a quasiperiodic structure. There is a plateau on the curve. In 1979, American astronomers Eaton and Hall proposed the simplest mechanism of plateau formation - “star spots”, that is, cold large areas on the surface of a star by analogy with sunspots . Similar spots are now detected by indirect methods in many stars ^[2] .

Chromospheric activity is detected by the presence of the Ca II H and K spectral lines , as well as by the Ballmer or Hα series . By analogy with the Sun, it can be assumed that this activity is associated with powerful magnetic fields and spots on the surface of the star.

Some variables such as RS Hounds of the Dogs are sources of x-ray and radio emission. Radio emission is not related to surface temperature and can serve as an indicator of powerful magnetic fields. X-ray emission L _x >> 10 ²⁴ watts. Such powerful radiation, by analogy with the Sun , can be interpreted as evidence of a very hot corona : T ~ 10 ⁷ K.