Slow irregular variable
A slow irregular variable (ascribed the GCVS types L, LB and LC) is a 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 variables.
Nomenclature
Irregular variable stars were first given acronyms based on the letter "I": Ia, Ib. and Ic.[2] 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.[3] When the General Catalogue of Variable Stars standardised its acronyms to be all uppercase, the codes LB and LC were used.[4]
Type Lb
Slow irregular variables of late spectral types (K, M, C, S); as a rule, they are giants[4]
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.[4]
Type Lc
Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V[4]
The M2 supergiant TZ Cassiopeiae is given as a representative example.[4]
List
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| Designation (name) | Constellation | Discovery | Apparent magnitude (Maximum)[a] | Apparent magnitude (Minimum)[a] | Range of magnitude | Spectral type | Subtype | Comment |
|---|---|---|---|---|---|---|---|---|
| U Antliae | Antlia | Template:Ntsh8m.1 (p) | Template:Ntsh9m.7 (p) | Script error: No such module "Number table sorting". | N:v | Lb | ||
| Beta Pegasi | Pegasus | Schmidt, 1847 | Template:Ntsh2m.31 | Template:Ntsh2m.74 | Script error: No such module "Number table sorting". | M2.3 II-III | Lb | |
| Epsilon Pegasi (Enif) | Pegasus | Template:Ntsh2m.37 | Template:Ntsh2m.45 | Script error: No such module "Number table sorting". | K2 Ib | Lc | ||
| TX Piscium | Pisces | Template:Ntsh4m.79 | Template:Ntsh5m.20 | Script error: No such module "Number table sorting". | C5 III | Lb | ||
| Alpha Scorpii (Antares) | Scorpius | Template:Ntsh0m.88 | Template:Ntsh1m.16 | Script error: No such module "Number table sorting". | M1.5 Iab-b | Lc | ||
| Alpha Tauri (Aldebaran) | Taurus | Template:Ntsh0m.75 | Template:Ntsh0m.95 | Script error: No such module "Number table sorting". | K5 III | Lb | ||
| Mu Geminorum | Gemini | Template:Ntsh2m.75 | Template:Ntsh3m.02 | Script error: No such module "Number table sorting". | M3 III | Lb | ||
| BE Camelopardalis | Camelopardalis | Template:Ntsh4m.35 | Template:Ntsh4m.48 | Script error: No such module "Number table sorting". | M2 II | Lc | ||
| Tau4 Eridani | Eridanus | Template:Ntsh3m.57 | Template:Ntsh3m.72 | Script error: No such module "Number table sorting". | M3 III | Lb | ||
| 13 Boötis | Bootes | Template:Ntsh5m.29 | Template:Ntsh5m.38 | Script error: No such module "Number table sorting". | M2 IIIab | Lb | ||
| Psi Virginis | Virgo | Template:Ntsh4m.73 | Template:Ntsh4m.96 | Script error: No such module "Number table sorting". | M3 III | Lb | ||
| V854 Arae | Ara | Template:Ntsh5m.84 | Template:Ntsh5m.99 | Script error: No such module "Number table sorting". | M1.5 III | Lb | ||
| 62 Sagittarii | Sagittarius | Template:Ntsh4m.45 | Template:Ntsh4m.62 | Script error: No such module "Number table sorting". | M4 III | Lb | ||
| CQ Camelopardalis | Camelopardalis | Template:Ntsh5m.15 | Template:Ntsh5m.27 | Script error: No such module "Number table sorting". | M0 II | Lc | ||
| Pi Aurigae | Auriga | Template:Ntsh4m.24 | Template:Ntsh4m.34 | Script error: No such module "Number table sorting". | M3.5 II | Lc | ||
| NO Aurigae | Auriga | Template:Ntsh6m.06 | Template:Ntsh6m.44 | Script error: No such module "Number table sorting". | M2 Iab | Lc | ||
| Omicron1 Canis Majoris | Canis Major | Template:Ntsh3m.78 | Template:Ntsh3m.99 | Script error: No such module "Number table sorting". | M2.5 Iab | Lc | ||
| Sigma Canis Majoris | Canis Major | Template:Ntsh3m.43 | Template:Ntsh3m.51 | Script error: No such module "Number table sorting". | M1.5 Iab | Lc | ||
| NS Puppis | Puppis | Template:Ntsh4m.4 | Template:Ntsh4m.5 | Script error: No such module "Number table sorting". | K3 Ib | Lc | ||
| Lambda Velorum | Vela | Template:Ntsh2m.14 | Template:Ntsh2m.30 | Script error: No such module "Number table sorting". | K4 Ib-IIa | Lc | ||
| V337 Carinae | Carina | Template:Ntsh3m.36 | Template:Ntsh3m.44 | Script error: No such module "Number table sorting". | K3 II | Lc | ||
| GZ Velorum | Vela | Template:Ntsh3m.43 | Template:Ntsh3m.81 | Script error: No such module "Number table sorting". | K3 II | Lc | ||
| RX Telescopii | Telescopium | Template:Ntsh6m.6 | Template:Ntsh7m.4 | Script error: No such module "Number table sorting". | M3 Iab | Lc | ||
| 45 G. Volantis | Volans | Template:Ntsh5m.89 | Template:Ntsh5m.90 | Script error: No such module "Number table sorting". | M1III | Lb | ||
| AF Columbae | Columba | Perryman et al., 1997 | Template:Ntsh5m.60 | Template:Ntsh5m.71 | Script error: No such module "Number table sorting". | M2 II/III | Lb |
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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 variables:[5]
- γ Cassiopeiae variables, eruptive shell stars
- Orion variables, pre-main-sequence stars, including T Tauri stars and YY Orionis stars
- 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 or cataclysmic variable are highly unpredictable.[5]
References
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- ^ Page Module:Citation/CS1/styles.css has no content."Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
- ^ Page Module:Citation/CS1/styles.css has no content.Kholopov, P. N. (1959). "A Revised List of T-Associations and Their Members". Soviet Astronomy. 3: 291. Bibcode:1959SvA.....3..291K.
- ^ Page Module:Citation/CS1/styles.css has no content.Mayall, Margaret W. (1964). "Variable Star Notes- from the XII General Assembly, I.A.U.; 043274 X Camelopardalis". Journal of the Royal Astronomical Society of Canada. 58: 283. Bibcode:1964JRASC..58..283M.
- ^ a b c d e Page Module:Citation/CS1/styles.css has no content."GCVS Variability Types". Retrieved 2016-09-04.
- ^ a b c Page Module:Citation/CS1/styles.css has no content.Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S.
External links
- Classifying variable stars - Astronomical Society of South Australia
- Why observe variable stars - British Astronomical Association
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