imported>21.Andromedae: These values of 0.7 and 3.5 for Enif are not associated with the variance of the star's brightness, but rather with specific times when that star was as bright as magnitude 0.7 and as faint as magnitude 3.5

2023-12-18T14:29:51Z

These values of 0.7 and 3.5 for Enif are not associated with the variance of the star's brightness, but rather with specific times when that star was as bright as magnitude 0.7 and as faint as magnitude 3.5

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{{Short description|Type of variable star}}
A '''slow irregular variable''' (ascribed the [[GCVS]] types L, LB and LC) is a [[variable star|variable]] [[star]] that exhibit no or very poorly defined periodicity in their slowly changing light emissions. These stars have often been little-studied, and once more is learnt about them, they are reclassified into other categories such as [[semiregular variable]]s.

==Nomenclature==
Irregular variable stars were first given acronyms based on the letter "I": ''Ia'', ''Ib''. and ''Ic''.<ref name=kholopov/> These were later refined so that the I codes were used "nebular" or "rapidly irregular" variable stars such as T Tauri and Orion variables. The remaining irregular stars, cool slowly varying giants and supergiants of type Ib or Ic were reassigned to Lb and Lc.<ref name=mayall/> When the [[General Catalogue of Variable Stars]] standardised its acronyms to be all uppercase, the codes LB and LC were used.<ref name=gcvs_vartype/>

===Type Lb===
''Slow irregular variables of late spectral types ([[Stellar classification|K]], [[Stellar classification|M]], [[carbon star|C]], [[S-type star|S]]); as a rule, they are giants''<ref name=gcvs_vartype/>

The GCVS also claims to give this type to slow irregular red variables where the luminosity or spectral type is not known, although it also uses the type L for slow irregular red stars where the spectral type or luminosity is unclear. The K5 star [[CO Cygni]] is given as a representative example.<ref name=gcvs_vartype/>

===Type Lc===
''Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V''<ref name=gcvs_vartype/>

The M2 supergiant [[TZ Cassiopeiae]] is given as a representative example.<ref name=gcvs_vartype/>

==List==
{{dynamic list}}
{| class="wikitable sortable" style="font-size:90%;"
|+ List of Slow Irregular Variables<ref name=gcvs/>
|- bgcolor="#efefef"
! width="15%"|'''Designation (name)'''
! width="10%"|'''Constellation'''
! width="15%"|'''Discovery'''
! width="8%"|''[[Apparent magnitude]]'' (Maximum)<ref name="ReferenceA"/>
! width="8%"|''[[Apparent magnitude]]'' (Minimum)<ref name="ReferenceA"/>
! width="8%"|''Range of magnitude''
! width="15%"|'''Spectral type'''
! width="6%"|'''Subtype'''
! width="15%"|'''Comment'''
|---
| [[U Antliae]]
| [[Antlia]]
|  
| {{ntsh|8.1}}8m.1 (p)
| {{ntsh|9.7}}9m.7 (p)
| {{nts|1.6}}
| N:v
| Lb
|  
|---
| [[Beta Pegasi]]
| [[Pegasus (constellation)|Pegasus]]
| [[Johann Friedrich Julius Schmidt|Schmidt]], 1847
| {{ntsh|2.31}}2m.31
| {{ntsh|2.74}}2m.74
| {{nts|0.43}}
| M2.3 II-III
| Lb
|  
|---
| [[Epsilon Pegasi]] (Enif)
| [[Pegasus (constellation)|Pegasus]]
|
| {{ntsh|2.37}}2m.37
| {{ntsh|2.45}}2m.45
| {{nts|0.07}}
| K2 Ib
| Lc
|  
|---
| [[TX Piscium]]
| [[Pisces (constellation)|Pisces]]
|  
| {{ntsh|4.79}}4m.79
| {{ntsh|5.20}}5m.20
| {{nts|0.42}}
| C5 III
| Lb
|  
|---
| Alpha Scorpii ([[Antares]])
| [[Scorpius]]
|  
| {{ntsh|0.88}}0m.88
| {{ntsh|1.16}}1m.16
| {{nts|0.28}}
| M1.5 Iab-b
| Lc
|  
|---
| Alpha Tauri ([[Aldebaran]])
| [[Taurus (constellation)|Taurus]]
|  
| {{ntsh|0.75}}0m.75
| {{ntsh|0.95}}0m.95
| {{nts|0.20}}
| K5 III
| Lb
|  
|---
| [[Mu Geminorum]]
| [[Gemini (constellation)|Gemini]]
|  
| {{ntsh|2.75}}2m.75
| {{ntsh|3.02}}3m.02
| {{nts|0.28}}
| M3 III
| Lb
|  
|---
| [[BE Camelopardalis]]
| [[Camelopardalis]]
|  
| {{ntsh|4.35}}4m.35
| {{ntsh|4.48}}4m.48
| {{nts|0.13}}
| M2 II
| Lc
|  
|---
| [[Tau4 Eridani|Tau4 Eridani]]
| [[Eridanus (constellation)|Eridanus]]
|  
| {{ntsh|3.57}}3m.57
| {{ntsh|3.72}}3m.72
| {{nts|0.15}}
| M3 III
| Lb
|  
|---
| [[13 Boötis]]
| [[Bootes]]
|  
| {{ntsh|5.29}}5m.29
| {{ntsh|5.38}}5m.38
| {{nts|0.09}}
| M2 IIIab
| Lb
|  
|---
| [[Psi Virginis]]
| [[Virgo (constellation)|Virgo]]
|  
| {{ntsh|4.73}}4m.73
| {{ntsh|4.96}}4m.96
| {{nts|0.23}}
| M3 III
| Lb
|  
|---
| [[HD 155035|V854 Arae]]
| [[Ara (constellation)|Ara]]
|  
| {{ntsh|5.87}}5m.84
| {{ntsh|5.99}}5m.99
| {{nts|0.12}}
| M1.5 III
| Lb
|  
|---
| [[62 Sagittarii]]
| [[Sagittarius (constellation)|Sagittarius]]
|  
| {{ntsh|4.45}}4m.45
| {{ntsh|4.62}}4m.62
| {{nts|0.17}}
| M4 III
| Lb
|  
|---
| [[CQ Camelopardalis]]
| [[Camelopardalis]]
|  
| {{ntsh|5.15}}5m.15
| {{ntsh|5.27}}5m.27
| {{nts|0.12}}
| M0 II
| Lc
|  
|---
| [[Pi Aurigae]]
| [[Auriga (constellation)|Auriga]]
|  
| {{ntsh|4.24}}4m.24
| {{ntsh|4.34}}4m.34
| {{nts|0.10}}
| M3.5 II
| Lc
|  
|---
| [[NO Aurigae]]
| [[Auriga (constellation)|Auriga]]
|  
| {{ntsh|6.06}}6m.06
| {{ntsh|6.44}}6m.44
| {{nts|0.58}}
| M2 Iab
| Lc
|  
|---
| [[Omicron1 Canis Majoris]]
| [[Canis Major]]
|  
| {{ntsh|3.78}}3m.78
| {{ntsh|3.99}}3m.99
| {{nts|0.21}}
| M2.5 Iab
| Lc
|  
|---
| [[Sigma Canis Majoris]]
| [[Canis Major]]
|  
| {{ntsh|3.43}}3m.43
| {{ntsh|3.51}}3m.51
| {{nts|0.08}}
| M1.5 Iab
| Lc
|  
|---
| [[NS Puppis]]
| [[Puppis]]
|  
| {{ntsh|4.4}}4m.4
| {{ntsh|4.5}}4m.5
| {{nts|0.1}}
| K3 Ib
| Lc
|  
|---
| [[Lambda Velorum]]
| [[Vela (constellation)|Vela]]
|  
| {{ntsh|2.14}}2m.14
| {{ntsh|2.30}}2m.30
| {{nts|0.16}}
| K4 Ib-IIa
| Lc
|  
|---
| [[V337 Carinae]]
| [[Carina (constellation)|Carina]]
|  
| {{ntsh|3.36}}3m.36
| {{ntsh|3.44}}3m.44
| {{nts|0.08}}
| K3 II
| Lc
|  
|---
| [[GZ Velorum]]
| [[Vela (constellation)|Vela]]
|  
| {{ntsh|3.43}}3m.43
| {{ntsh|3.81}}3m.81
| {{nts|0.38}}
| K3 II
| Lc
|  
|---
| [[RX Telescopii]]
| [[Telescopium]]
|  
| {{ntsh|6.6}}6m.6
| {{ntsh|7.4}}7m.4
| {{nts|0.8}}
| M3 Iab
| Lc
|  
|---
| [[HD 77887|45 G. Volantis]]
| [[Volans]]
|
| {{ntsh|5.89}}5m.89
| {{ntsh|5.9}}5m.90
| {{nts|0.01}}
| M1III
| Lb
|
|---
| [[AF Columbae]]
| [[Columba (constellation)|Columba]]
| Perryman et al., 1997
| {{ntsh|5.6}}5m.60
| {{ntsh|5.71}}5m.71
| {{nts|0.11}}
| M2 II/III
| Lb
|
|}

==Other irregular variables==
There are a number of other types of variable stars lacking clearly detectable periods, and which are sometimes referred to as [[irregular variable]]s:<ref name=gcvs/>
*[[γ Cassiopeiae variable]]s, eruptive [[shell star]]s
*[[Orion variable]]s, pre-main-sequence stars, including [[T Tauri star]]s and [[YY Orionis star]]s
*Rapid irregular variables, possibly similar to Orion variables with shorter period
*Poorly-defined irregular variable stars, of unknown type

In addition, many types of [[Eruptive variable|eruptive]] or [[cataclysmic variable]] are highly unpredictable.<ref name=gcvs/>

==References==
{{Reflist|refs=

<ref name="ReferenceA">''(visual magnitude, unless marked'' (B) ''(= blue) or'' (p) ''(= photographic))''</ref>

<ref name=kholopov>{{cite journal|bibcode=1959SvA.....3..291K|title=A Revised List of T-Associations and Their Members|journal=Soviet Astronomy|volume=3|pages=291|last1=Kholopov|first1=P. N.|year=1959}}</ref>

<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=02025|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009|display-authors=etal}}</ref>

<ref name=gcvs_vartype>{{cite web|url=http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt|access-date=2016-09-04|title=GCVS Variability Types}}</ref>

<ref name=mayall>{{cite journal|bibcode=1964JRASC..58..283M|title=Variable Star Notes- from the XII General Assembly, I.A.U.; 043274 X Camelopardalis|journal=Journal of the Royal Astronomical Society of Canada|volume=58|pages=283|last1=Mayall|first1=Margaret W.|year=1964}}</ref>

}}

==External links==
*[https://www.assa.org.au/sig/variables/classifications Classifying variable stars] - Astronomical Society of South Australia
*[http://www.britastro.org/vss/holland.pdf Why observe variable stars] - British Astronomical Association

{{Variable star topics}}

[[Category:Slow irregular variables|*]]

Slow irregular variable - Revision history

imported>21.Andromedae: These values ​​of 0.7 and 3.5 for Enif are not associated with the variance of the star's brightness, but rather with specific times when that star was as bright as magnitude 0.7 and as faint as magnitude 3.5

imported>21.Andromedae: These values of 0.7 and 3.5 for Enif are not associated with the variance of the star's brightness, but rather with specific times when that star was as bright as magnitude 0.7 and as faint as magnitude 3.5