Irregular variable: Difference between revisions

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{{Short description|Type of variable star}}

An '''irregular variable''' is a type of [[variable star]] in which variations in brightness show no regular [[periodicity]]. There are two main sub-types of irregular variable - eruptive irregular variables and pulsating irregular variables.

{{Refimprove|date=December 2009}}

An '''irregular variable''' is a type of [[variable star]] in which variations in brightness show no regular [[Frequency|periodicity]]. There are two main sub-types of irregular variable -: eruptive irregular variables and pulsating irregular variables.

'''Eruptive''' irregular variables are divided into three categories:

Irregular eruptive variables are divided into three categories. Group I variables are split into subgroups IA (spectral types O to A) and IB (spectral types F through M). So-called IN (irregular nebulous) variables, indigenous to star-forming regions, may vary by several magnitudes with rapid changes of up to 1 magnitude in 1 to 10 days, are similarly divided by spectral type into subgroups INA and INB, but with the addition of another subgroup, INT, for T Tauri stars, or INT(YY) for YY Orionis stars. The third category of eruptive irregulars are the IS stars, which show rapid variations of 0.5 to 1 magnitude in a few hours or days; again, these come in subgroups ISA and ISB.

* Group I variables are split into subgroups IA (spectral types O to A) and IB (spectral types F through M).

Irregular pulsating giants or supergiants, all of late spectral types (K, M, C, or S), are classed as type L-LB for giants and LC for supergiants. How many of these are actually semi-regular variables that simply need more study, remains unclear.

Irregular* eruptive[[Orion variables]], areGCVS dividedtype into three categories. Group I variables are split into subgroups IAIN (spectral types O to A)irregular and IB (spectral types F through M). So-called IN (irregular nebulous) variables, indigenous to star-forming regions, may vary by several magnitudes with rapid changes of up to 1 magnitude in 1 to 10 days, are similarly divided by spectral type into subgroups INA and INB, but with the addition of another subgroup, INT, for [[T Tauri starsstar]]s, or INT(YY) for YY Orionis stars. The third category of eruptive irregulars are the IS stars, which show rapid variations of 0.5 to 1 magnitude in a few hours or days; again, these come in subgroups ISA and ISB.

* The third category of eruptive irregulars are the IS stars, which show rapid variations of 0.5 to 1 magnitude in a few hours or days; again, these come in subgroups ISA and ISB.

Irregular'''Pulsating''' pulsatingirregular giants or supergiants, called [[slow irregular variable]]s, are all of late spectral types (K, M, C, or S), areand classed as type L-LB for giants and LC for supergiants. How many of these are actually semi-regular variables that simply need more study, remains unclear.<ref>{{citation|title=Observing Variable Stars |author=Gerry Arlen Good|year= 2003|publisher=Springer Science|url= https://books.google.com/books?id=k9ViYKvKRz0C&q=%22Irregular+variable%22&pg=PA8|isbn=978-1-85233-498-7}}</ref>

== References ==

{{Reflist}}

[[Category:Irregular variables| ]]

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