Slow irregular variable

Last updated December 19, 2023

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)	1.6	N:v	Lb
Beta Pegasi	Pegasus	Schmidt, 1847	2^m.31	2^m.74	0.43	M2.3 II-III	Lb
Epsilon Pegasi (Enif)	Pegasus		2^m.37	2^m.45	0.07	K2 Ib	Lc
TX Piscium	Pisces		4^m.79	5^m.20	0.42	C5 III	Lb
Alpha Scorpii (Antares)	Scorpius		0^m.88	1^m.16	0.28	M1.5 Iab-b	Lc
Alpha Tauri (Aldebaran)	Taurus		0^m.75	0^m.95	0.20	K5 III	Lb
Mu Geminorum	Gemini		2^m.75	3^m.02	0.28	M3 III	Lb
BE Camelopardalis	Camelopardalis		4^m.35	4^m.48	0.13	M2 II	Lc
Tau⁴ Eridani	Eridanus		3^m.57	3^m.72	0.15	M3 III	Lb
13 Boötis	Bootes		5^m.29	5^m.38	0.09	M2 IIIab	Lb
Psi Virginis	Virgo		4^m.73	4^m.96	0.23	M3 III	Lb
V854 Arae	Ara		5^m.84	5^m.99	0.12	M1.5 III	Lb
62 Sagittarii	Sagittarius		4^m.45	4^m.62	0.17	M4 III	Lb
CQ Camelopardalis	Camelopardalis		5^m.15	5^m.27	0.12	M0 II	Lc
Pi Aurigae	Auriga		4^m.24	4^m.34	0.10	M3.5 II	Lc
NO Aurigae	Auriga		6^m.06	6^m.44	0.58	M2 Iab	Lc
Omicron1 Canis Majoris	Canis Major		3^m.78	3^m.99	0.21	M2.5 Iab	Lc
Sigma Canis Majoris	Canis Major		3^m.43	3^m.51	0.08	M1.5 Iab	Lc
NS Puppis	Puppis		4^m.4	4^m.5	0.1	K3 Ib	Lc
Lambda Velorum	Vela		2^m.14	2^m.30	0.16	K4 Ib-IIa	Lc
V337 Carinae	Carina		3^m.36	3^m.44	0.08	K3 II	Lc
GZ Velorum	Vela		3^m.43	3^m.81	0.38	K3 II	Lc
RX Telescopii	Telescopium		6^m.6	7^m.4	0.8	M3 Iab	Lc
45 G. Volantis	Volans		5^m.89	5^m.90	0.01	M1III	Lb
AF Columbae	Columba	Perryman et al., 1997	5^m.60	5^m.71	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 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]

Related Research Articles

The descriptive term long-period variable star refers to various groups of cool luminous pulsating variable stars. It is frequently abbreviated to LPV.

A Gamma Cassiopeiae variable is a type of variable star, named for its prototype γ Cassiopeiae.

An Orion variable is a variable star which exhibits irregular and eruptive variations in its luminosity and is typically associated with diffuse nebulae. It is thought that these are young stars which will later become regular, non-variable stars on the zero-age main sequence. Brightness fluctuations can be as much as several magnitudes.

119 Tauri is a red supergiant star in the constellation Taurus. It is a semiregular variable and its angular diameter has been measured at about 10 mas.

NO Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.

6 Cassiopeiae is a white hypergiant in the constellation Cassiopeia, and a small-amplitude variable star.

<span class="mw-page-title-main">RT Carinae</span> Star in the constellation Carina

RT Carinae, also known as CD-58 3538, is a variable star in the Carina Nebula in the constellation Carina. It has a mean apparent magnitude of +8.55.

55 Cygni is a blue supergiant star in the constellation Cygnus. It is thought to be a member of the Cygnus OB7 stellar association at about 2,700 light years.

5 Lacertae is a spectroscopic binary in the constellation Lacerta. Its apparent magnitude is 4.36.

13 Monocerotis is a class A0 Ib star in the constellation Monoceros. Its apparent magnitude is 4.5 and it is approximately 780 parsecs (2,500 ly) away.

9 Pegasi is a supergiant star in the constellation Pegasus. Its apparent magnitude is 4.35.

QU Normae, also known as HR 6131, is a blue supergiant star in the constellation Norma. It is also a variable star, thought to be an α Cyg variable.

3 Geminorum is a blue supergiant star in the constellation Gemini. It is a small amplitude pulsating variable and a close double star, with a mean combined apparent visual magnitude of about 5.7.

<span class="mw-page-title-main">Y Lyncis</span> Variable star in the constellation Lynx

Y Lyncis is a semiregular variable star in the constellation Lynx. It is an asymptotic giant branch star of spectral type M6S, with a luminosity class of Ib, indicating a supergiant luminosity. It is around 1,160 light years away.

HV 11423 is a red supergiant star in the Small Magellanic Cloud. It is about 200,000 light-years away towards the constellation of Tucana.

<span class="mw-page-title-main">V419 Cephei</span> Star in the constellation Cepheus

V419 Cephei is an irregular variable star in the constellation of Cepheus with an apparent magnitude that varies between 6.54 and 6.89.

BI Cygni(BI Cyg, IRC +40408, BD+36 4025) is a red supergiant in the constellation Cygnus. It is an irregular variable star with a maximum brightness of magnitude 8.4 and a minimum of magnitude 9.9. It is considered a member of the stellar Cygnus OB1 association, its distance is around 2,600 parsecs (8,500 ly) of the Solar System. It is less than a degree south of another variable red supergiant, BC Cygni.

<span class="mw-page-title-main">V528 Carinae</span> Star in the constellation Carina

V528 Carinae is a variable star in the constellation Carina.

BO Carinae, also known as HD 93420, is an irregular variable star in the constellation Carina.

DU Crucis is a red supergiant and slow irregular variable star in the open cluster NGC 4755, which is also known as the Kappa (κ) Crucis Cluster or Jewel Box Cluster.

References

↑ Kholopov, P. N. (1959). "A Revised List of T-Associations and Their Members". Soviet Astronomy. 3: 291. Bibcode:1959SvA.....3..291K.
↑ 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.
1 2 3 4 5 "GCVS Variability Types" . Retrieved 2016-09-04.
1 2 3 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.
1 2 (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

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[kholopov-1] Kholopov, P. N. (1959). "A Revised List of T-Associations and Their Members". Soviet Astronomy. 3: 291. Bibcode:1959SvA.....3..291K.

[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] 1 2 3 4 5 "GCVS Variability Types" . Retrieved 2016-09-04.

[gcvs-4] 1 2 3 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] 1 2 (visual magnitude, unless marked (B) (= blue) or (p) (= photographic))

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