Vfrdtyky

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.^[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

List of Slow Irregular Variables^[4]
Designation (name)	Constellation	Discovery	Apparent magnitude (Maximum)^[5]	Apparent magnitude (Minimum)^[5]	Range of magnitude	Spectral type	Subtype
U Antliae	Antlia		8^m.1 (p)	9^m.7 (p)	7000160000000000000♠1.6	N:v	Lb
Beta Pegasi	Pegasus	Schmidt, 1847	2^m.31	2^m.74	6999430000000000000♠0.43	M2.3 II-III	Lb
Epsilon Pegasi (Enif)	Pegasus		0^m.7	3^m.5	7000280000000099999♠2.8	K2 Ib	Lc
TX Piscium	Pisces		4^m.79	5^m.20	6999420000000000000♠0.42	C5 III	Lb
Alpha Scorpii (Antares)	Scorpius		0^m.88	1^m.16	6999280000000000000♠0.28	M1.5 Iab-b	Lc
Alpha Tauri (Aldebaran)	Taurus		0^m.75	0^m.95	6999200000000000000♠0.20	K5 III	Lb
Mu Geminorum	Gemini		2^m.75	3^m.02	6999280000000000000♠0.28	M3 III	Lb
BE Camelopardalis	Camelopardalis		4^m.35	4^m.48	6999130000000000000♠0.13	M2 II	Lc
Tau⁴ Eridani	Eridanus		3^m.57	3^m.72	6999150000000000000♠0.15	M3 III	Lb
13 Boötis	Bootes		5^m.29	5^m.38	6998900000000000000♠0.09	M2 IIIab	Lb
Psi Virginis	Virgo		4^m.73	4^m.96	6999230000000000000♠0.23	M3 III	Lb
V854 Arae	Ara		5^m.84	5^m.99	6999120000000000000♠0.12	M1.5 III	Lb
62 Sagittarii	Sagittarius		4^m.45	4^m.62	6999170000000000000♠0.17	M4 III	Lb
TX Piscium	Pisces		4^m.79	5^m.20	6999410009999900000♠0.41	C5 III	Lb
CQ Camelopardalis	Camelopardalis		5^m.15	5^m.27	6999120000000000000♠0.12	M0 II	Lc
Pi Aurigae	Auriga		4^m.24	4^m.34	6999100000000000000♠0.10	M3.5 II	Lc
NO Aurigae	Auriga		6^m.06	6^m.44	6999579990000000000♠0.58	M2 Iab	Lc
Omicron1 Canis Majoris	Canis Major		3^m.78	3^m.99	6999210000000000000♠0.21	M2.5 Iab	Lc
Sigma Canis Majoris	Canis Major		3^m.43	3^m.51	6998800000000000000♠0.08	M1.5 Iab	Lc
NS Puppis	Puppis		4^m.4	4^m.5	6999100000000000000♠0.1	K3 Ib	Lc
Lambda Velorum	Vela		2^m.14	2^m.30	6999160000000000000♠0.16	K4 Ib-IIa	Lc
V337 Carinae	Carina		3^m.36	3^m.44	6998800000000000000♠0.08	K3 II	Lc
GZ Velorum	Vela		3^m.43	3^m.81	6999380000000000000♠0.38	K3 II	Lc
RX Telescopii	Telescopium		6^m.6	7^m.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.

^ ^a^b^c^d^e "GCVS Variability Types". Retrieved 2016-09-04.

^ ^a^b^c 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.

^ ^a^b (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

[kholopov-1] 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-2] 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.

[gcvs_vartype-3] "GCVS Variability Types". Retrieved 2016-09-04.

[gcvs-4] 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.

[ReferenceA-5] (visual magnitude, unless marked (B) (= blue) or (p) (= photographic))

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Vfrdtyky

Slow irregular variable

Contents

Nomenclature

Type Lb

Type Lc

List

Other irregular variables

References

External links

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