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.
Contents
1 Nomenclature
1.1 Type Lb
1.2 Type Lc
2 List
3 Other irregular variables
4 References
5 External links
Nomenclature
Irregular variable stars were first given acronyms based on the letter "I": Ia, Ib. and Ic.[1] 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.[2] When the General Catalogue of Variable Stars standardised its acronyms to be all uppercase, the codes LB and LC were used.[3]
Type Lb
Slow irregular variables of late spectral types (K, M, C, S); as a rule, they are giants[3]
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.[3]
Type Lc
Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V[3]
The M2 supergiant TZ Cassiopeiae is given as a representative example.[3]
List
Designation (name) | Constellation | Discovery | Apparent magnitude (Maximum)[5] | Apparent magnitude (Minimum)[5] | Range of magnitude | Spectral type | Subtype | Comment |
|---|---|---|---|---|---|---|---|---|
U Antliae | Antlia | | 8m.1 (p) | 9m.7 (p) | 7000160000000000000♠1.6 | N:v | Lb | |
Beta Pegasi | Pegasus | Schmidt, 1847 | 2m.31 | 2m.74 | 6999430000000000000♠0.43 | M2.3 II-III | Lb | |
Epsilon Pegasi (Enif) | Pegasus | 0m.7 | 3m.5 | 7000280000000099999♠2.8 | K2 Ib | Lc | | |
TX Piscium | Pisces | | 4m.79 | 5m.20 | 6999420000000000000♠0.42 | C5 III | Lb | |
| Alpha Scorpii (Antares) | Scorpius | | 0m.88 | 1m.16 | 6999280000000000000♠0.28 | M1.5 Iab-b | Lc | |
| Alpha Tauri (Aldebaran) | Taurus | | 0m.75 | 0m.95 | 6999200000000000000♠0.20 | K5 III | Lb | |
Mu Geminorum | Gemini | | 2m.75 | 3m.02 | 6999280000000000000♠0.28 | M3 III | Lb | |
BE Camelopardalis | Camelopardalis | | 4m.35 | 4m.48 | 6999130000000000000♠0.13 | M2 II | Lc | |
Tau4 Eridani | Eridanus | | 3m.57 | 3m.72 | 6999150000000000000♠0.15 | M3 III | Lb | |
13 Boötis | Bootes | | 5m.29 | 5m.38 | 6998900000000000000♠0.09 | M2 IIIab | Lb | |
Psi Virginis | Virgo | | 4m.73 | 4m.96 | 6999230000000000000♠0.23 | M3 III | Lb | |
V854 Arae | Ara | | 5m.84 | 5m.99 | 6999120000000000000♠0.12 | M1.5 III | Lb | |
62 Sagittarii | Sagittarius | | 4m.45 | 4m.62 | 6999170000000000000♠0.17 | M4 III | Lb | |
TX Piscium | Pisces | | 4m.79 | 5m.20 | 6999410009999900000♠0.41 | C5 III | Lb | |
CQ Camelopardalis | Camelopardalis | | 5m.15 | 5m.27 | 6999120000000000000♠0.12 | M0 II | Lc | |
Pi Aurigae | Auriga | | 4m.24 | 4m.34 | 6999100000000000000♠0.10 | M3.5 II | Lc | |
NO Aurigae | Auriga | | 6m.06 | 6m.44 | 6999579990000000000♠0.58 | M2 Iab | Lc | |
Omicron1 Canis Majoris | Canis Major | | 3m.78 | 3m.99 | 6999210000000000000♠0.21 | M2.5 Iab | Lc | |
Sigma Canis Majoris | Canis Major | | 3m.43 | 3m.51 | 6998800000000000000♠0.08 | M1.5 Iab | Lc | |
NS Puppis | Puppis | | 4m.4 | 4m.5 | 6999100000000000000♠0.1 | K3 Ib | Lc | |
Lambda Velorum | Vela | | 2m.14 | 2m.30 | 6999160000000000000♠0.16 | K4 Ib-IIa | Lc | |
V337 Carinae | Carina | | 3m.36 | 3m.44 | 6998800000000000000♠0.08 | K3 II | Lc | |
GZ Velorum | Vela | | 3m.43 | 3m.81 | 6999380000000000000♠0.38 | K3 II | Lc | |
RX Telescopii | Telescopium | | 6m.6 | 7m.4 | 6999800000000000000♠0.8 | M3 Iab | Lc | |
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:[4]
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.[4]
References
^ Kholopov, P. N. (1959). "A Revised List of T-Associations and Their Members". Soviet Astronomy. 3: 291. Bibcode:1959SvA.....3..291K..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"""""""'""'"}.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
^ 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.
^ abcde "GCVS Variability Types". Retrieved 2016-09-04.
^ abc 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.
^ ab (visual magnitude, unless marked (B) (= blue) or (p) (= photographic))
External links
Classifying variable stars - Astronomical Society of South Australia
Why observe variable stars - British Astronomical Association
Variable stars | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Pulsating |
| ||||||||
| Eruptive |
| ||||||||
| Cataclysmic |
| ||||||||
| Rotating |
| ||||||||
| Eclipsing |
| ||||||||
 Star portal | |||||||||
