Incorrect variable star

Irregular variable stars are a type of variable stars whose brightness variations vary according to a non-periodic law. There are 2 types of incorrect variables: eruptive and pulsating.

Eruptive variables are divided into 3 classes:

• I - irregular variables, the features of the brightness change and the spectral classes of which are unknown. A very heterogeneous group of objects, which in turn is divided into 2 subclasses:
  • IA - incorrect variables of early ( OA ) spectral classes .
  • IB - incorrect variables of intermediate (FG) and late (KM) spectral classes .

• Orion variables . Wrong eruptive variables associated with light and dark diffuse nebulae or observed in areas of such nebulae. The limits of brightness can reach several values. If a star exhibits rapid changes in brightness (up to 1 ^m in l-10 days), the type symbol is followed by the symbol S ( INS ). They are divided into the following subtypes:
  • INA - Orion variables of the early spectral classes BA-A or Ae.
  • INB - Orion variables of intermediate and late spectral classes FM or Fe-Me.
  • INT - Orion variables of type T Taurus
  • IN (YY) - In the spectra of some orion variables ( YY Orion ), dark components are observed on the long-wave side of the emission lines, which indicates the incidence of matter on the surface of the star.

If the connection with the nebula is invisible, the letter N in the type symbol may be omitted - IT.

• IS are fast irregular variables that are not explicitly associated with diffuse nebulae and show brightness changes of 0.5-1.0 ^m over several hours or days. There is no sharp boundary between fast irregular and orion variables . If a fast irregularity is observed in the region of the diffuse nebula , it refers to the orion variables and is indicated by the symbol INS.
  • ISA - Fast Irregular Early Spectral Classes BA or Ae.
  • ISB - fast irregular intermediate and late spectral classes of FM or Fe-Me.

Pulsating irregular variables , also called slow irregular variables, are variable stars ( giants or supergiants ) whose brightness changes are devoid of any signs of periodicity or periodicity is weakly expressed, occurring only occasionally. LB - giants and LC - supergiants are designated ^[1] .