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{{Short description|Variable stars which exhibit non-radial pulsations}}
'''Alpha Cygni variables''' are [[variable star]]s which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time other parts expand. They are [[supergiant]] stars of [[Stellar classification|spectral types]] B or A. Variations in brightness on the order of 0.1 [[apparent magnitude|magnitudes]] are associated with the pulsations, which often seem [[irregular variable|irregular]], due to [[Beat (acoustics)|beat]]ing of multiple pulsation periods. The pulsations typically have periods of several days to several weeks.

The prototype of these stars, [[Deneb]] (α Cygni), exhibits fluctuations in brightness between magnitudes +1.21 and +1.29. Small amplitude rapid variations have been known in many early supergiant stars, but they were not formally grouped into a class until the 4th edition of the General Catalogue of Variable Stars was published in 1985. It used the acronym ACYG for Alpha Cygni variable stars.<ref>{{cite journal|bibcode=1996yCat.2139....0K|title=VizieR Online Data Catalog: General Catalog of Variable Stars, 4th Ed. (GCVS4) (Kholopov+ 1988)|journal=VizieR On-Line Data Catalog: II/139B. Originally Published in: Moscow: Nauka Publishing House (1985–1988)|volume=2139|pages=0|last1=Kholopov|first1=P. N.|last2=Samus'|first2=N. N.|last3=Frolov|first3=M. S.|last4=Goranskij|first4=V. P.|last5=Gorynya|first5=N. A.|last6=Kireeva|first6=N. N.|last7=Kukarkina|first7=N. P.|last8=Kurochkin|first8=N. E.|last9=Medvedeva|first9=G. I.|last10=Perova|first10=N. B.|date=1996}}</ref> Many [[luminous blue variable]]s (LBVs) show Alpha Cygni-type variability during their quiescent (hot) phases, but the LBV classification is generally used in these cases.

A large number (32) were discovered by Christoffel Waelkens and colleagues analysing Hipparcos data in a 1998 study.<ref name="waelkens 1998"/>

==Pulsations==
The pulsations of Alpha Cygni Variable stars are not fully understood. They are not confined to a narrow range of temperatures and luminosities in the way that most pulsating stars are. Instead, most luminous A and B supergiants, and possibly also O and F stars, show some type of unpredictable small-scale pulsations. [[Adiabatic process|Nonadiabatic]] strange mode [[radial pulsations]] are predicted but only for the most luminous supergiants. Pulsations have also been modelled for less luminous supergiants by assuming they are low mass post-red supergiant stars, but most Alpha Cygni variables do not appear to have passed through the red supergiant stage.<ref name=saio>{{cite book|bibcode=2013ASPC..479...47S|arxiv = 1305.4728 |chapter = Strange-Mode Instability for Micro-Variations in Luminous Blue Variables |title = Progress in Physics of the Sun and Stars: A New Era in Helio- and Asteroseismology. Proceedings of a Fujihara Seminar held 25–29 November |series=Astronomical Society of the Pacific Conference Series|volume = 479 |pages = 47 |last1 = Saio |first1 = H. |last2 = Georgy |first2 = C. |last3 = Meynet |first3 = G. |date = 2013 }}</ref><ref name="SaioGeorgy2013"/>

The pulsations are likely induced by [[kappa mechanism]], caused by iron opacity variations, with strange modes producing the observed short periods for both radial and non-radial pulsations. Non-adiabatic [[G-mode pulsation|g-modes]] may produce longer period variations, but these have not been observed in Alpha Cygni variables.<ref name="Saio2011">{{cite journal|last1=Saio|first1=Hideyuki|title=Linear analyses for the stability of radial and non-radial oscillations of massive stars|journal=Monthly Notices of the Royal Astronomical Society|volume=412|issue=3|date=2011|pages=1814–1822|issn=0035-8711|doi=10.1111/j.1365-2966.2010.18019.x|doi-access=free |arxiv = 1011.4729 |bibcode = 2011MNRAS.412.1814S |s2cid=118552910}}</ref>

== List ==

=== Galactic ===
{| class="wikitable sortable" style="font-size:90%;"
|- style="background:#efefef;"
! style="width:10%;"|'''Designation (name)'''
! style="width:10%;"|'''Constellation'''
! style="width:15%;"|'''Discovery'''
! style="width:10%;"|''Maximum [[Apparent magnitude]]'' (mV)<ref name="gcvs"/>
! style="width:10%;"|''Minimum [[Apparent magnitude]]'' (mV)<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.|date=2009|display-authors=etal}}</ref>
! style="width:15%;"|'''Period''' (days)
! style="width:10%;"|'''Spectral class'''
! style="width:10%;"|'''Luminosity'''
! style="width:10%;"|'''Comment'''
|-
| [[HD 21389|CE Cam (HD 21389)]]
| [[Camelopardalis]]
| Percy & Welsh (1983)<ref name="PercyWelch1983"/>
| 4m.54
|
|
| A0Iab
| 63,000<ref name=an331_4_349/>
|  
|-
| [[CS Camelopardalis|CS Cam]]
| [[Camelopardalis]]
| Rufener (1982)<ref name=rufener>{{cite journal|bibcode=1982A&AS...48..503R|title=List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry|journal=Astronomy and Astrophysics Supplement Series|volume=48|pages=503|last1=Rufener|first1=F.|last2=Bartholdi|first2=P.|year=1982}}</ref>
| 4m.259
|
|
| B9Ia
| 75,900<ref name=mcerlean>{{cite journal|bibcode=1999A&A...349..553M|title=Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions|journal=Astronomy and Astrophysics|volume=349|pages=553|last1=McErlean|first1=N. D.|last2=Lennon|first2=D. J.|last3=Dufton|first3=P. L.|year=1999}}</ref>
|  
|-
| [[Eta Canis Majoris|η CMa (Aludra)]]
| [[Canis Major]]
| Kazarovets et al. (1999)<ref>{{cite journal|bibcode=1999IBVS.4659....1K|title=The 74th Special Name-list of Variable Stars|journal=Information Bulletin on Variable Stars|volume=4659|pages=1|last1=Kazarovets|first1=E. V.|last2=Samus|first2=N. N.|last3=Durlevich|first3=O. V.|last4=Frolov|first4=M. S.|last5=Antipin|first5=S. V.|last6=Kireeva|first6=N. N.|last7=Pastukhova|first7=E. N.|date=1999}}</ref>
| 2m.38
| 2m.48
| 4.70433
| B5Ia
| 105,000<ref name=an331_4_349>{{citation | last1=Hohle | first1=M. M. | last2=Neuhäuser | first2=R. | last3=Schutz | first3=B. F. | title=Masses and luminosities of O- and B-type stars and red supergiants | journal=Astronomische Nachrichten | volume=331 | issue=4 | page=349 |date=April 2010 | doi=10.1002/asna.200911355 | bibcode=2010AN....331..349H |arxiv = 1003.2335 | s2cid=111387483 }}</ref>
|  
|-
| [[Omicron2 Canis Majoris|ο2 CMa]]
| [[Canis Major]]
| Waelkens et al. (1998)<ref name="waelkens 1998"/>
| 2m.98
| 3m.04
| 24.44
| B3Ia
| 219,000<ref name=crowther/>
|  
|-
| [[Kappa Cassiopeiae|κ Cas]]
| [[Cassiopeia (constellation)|Cassiopeia]]
| Percy & Welsh (1983)<ref name="PercyWelch1983"/>
| 4m.12
| 4m.21
| 2.64690
| B1Ia
| 331,000<ref name=crowther/>
|  
|-
| [[6 Cassiopeiae|6 Cas]]
| [[Cassiopeia (constellation)|Cassiopeia]]
| Abt (1957)<ref name="Abt1957">{{cite journal|last1=Abt|first1=Helmut A.|title=The Variability of Supergiants.|journal=The Astrophysical Journal|volume=126|date=1957|pages=138|issn=0004-637X|doi=10.1086/146379|bibcode = 1957ApJ...126..138A }}</ref>
| 5m.34
| 5m.45
| 30
| B2 Ia+
| 200,000<ref name=achmad>{{cite journal|bibcode=1997A&A...320..196A|title=Radiation driven wind models for A, F and G supergiants|journal=Astronomy and Astrophysics|volume=320|pages=196|last1=Achmad|first1=L.|last2=Lamers|first2=H. J. G. L. M.|last3=Pasquini|first3=L.|year=1997}}</ref>
| Hypergiant
|-
| [[Omicron2 Centauri|ο2 Cen]]
| [[Centaurus]]
|
| 5m.12
| 5m.22
| 46.3
| A2Ia
| 136,000<ref name="Kaufer 1996">{{cite journal|author=Kaufer, A.|author2=Stahl, O.|author3=Wolf, B.|author4=Gaeng, T.|author5=Gummersbach, C. A.|author6=Kovacs, J.|author7=Mandel, H.|author8=Szeifert, T.|date=1996|title=Long-term spectroscopic monitoring of BA-type supergiants. I. Halpha_ line-profile variability.|journal=Astronomy and Astrophysics|volume=305|pages=887–901 | bibcode=1996A&A...305..887K}}</ref>
|  
|-
| [[Nu Cephei|ν Cep]]
| [[Cepheus (constellation)|Cepheus]]
| Percy & Welsh (1983)<ref name="PercyWelch1983">{{cite journal|last1=Percy|first1=J. R.|last2=Welch|first2=D. L.|title=Photometric variability of B- and A-type supergiants|journal=Publications of the Astronomical Society of the Pacific|volume=95|date=1983|pages=491|issn=0004-6280|doi=10.1086/131198|bibcode = 1983PASP...95..491P |doi-access=free}}</ref>
| 4m.25
| 4m.35
|
| A2 Iab
| 254,000<ref name=an331_4_349/>
|  
|-
| [[DL Crucis|DL Cru]]
| [[Crux]]
| Waelkens et al. (1998)<ref name="waelkens 1998"/>
| 6m.24
| 6m.28
| 2.8778
| B1.5Ia
| 242,000<ref name=lamers1995>{{cite journal|last1=Lamers|first1=Henny J. G. L. M.|last2=Snow|first2=Theodore P.|last3=Lindholm|first3=Douglas M.|title=Terminal Velocities and the Bistability of Stellar Winds|journal=The Astrophysical Journal|volume=455|date=1995|pages=269|issn=0004-637X|doi=10.1086/176575|bibcode = 1995ApJ...455..269L }}</ref>
|  
|-
| [[Deneb]]<ref name="SaioGeorgy2013">{{cite journal|last1=Saio|first1=H.|last2=Georgy|first2=C.|last3=Meynet|first3=G.|title=Evolution of blue supergiants and Cygni variables: puzzling CNO surface abundances|journal=Monthly Notices of the Royal Astronomical Society|volume=433|issue=2|date=2013|pages=1246–1257|bibcode=2013MNRAS.433.1246S|doi=10.1093/mnras/stt796|doi-access=free |arxiv = 1305.2474 }}</ref>
| [[Cygnus (constellation)|Cygnus]]
| Lee (1910)<ref name="Lee1910">{{cite journal|last1=Lee|first1=O. J.|title=Four stars having variable radial velocities.|journal=The Astrophysical Journal|volume=31|date=1910|pages=176|issn=0004-637X|doi=10.1086/141741|bibcode = 1910ApJ....31..176L }}</ref>
| 1m.21
| 1m.29
|
| A2 Ia
| 196,000<ref name=schiller>
{{cite journal
|last1=Schiller |first1=F.
|last2=Przybilla |first2=N.
|date=2008
|title=Quantitative spectroscopy of Deneb
|journal=[[Astronomy & Astrophysics]]
|volume=479 |issue=3 |pages=849–858
|arxiv=0712.0040
|bibcode=2008A&A...479..849S
|doi=10.1051/0004-6361:20078590
|s2cid=119225384
}}</ref>
| Prototype
|-
| [[Sigma Cygni|σ Cyg]]
| [[Cygnus (constellation)|Cygnus]]
| Abt (1957)<ref name="Abt1957"/>
| 4m.19
| 4m.26
| 120.2
| B9 Iab
| 39,000<ref name="MarkovaPuls2008">{{cite journal|last1=Markova|first1=N.|last2=Puls|first2=J.|title=Bright OB stars in the Galaxy|journal=Astronomy and Astrophysics|volume=478|issue=3|date=2008|pages=823–842|issn=0004-6361|doi=10.1051/0004-6361:20077919|arxiv = 0711.1110 |bibcode = 2008A&A...478..823M |s2cid=14510634}}</ref>
|  
|-
| [[55 Cygni|55 Cyg]]
| [[Cygnus (constellation)|Cygnus]]
| Hill et al. (1976)<ref name=hill>{{cite journal|bibcode=1979IBVS.1581....1K|title=64th Name-List of Variable Stars|journal=Information Bulletin on Variable Stars|volume=1581|pages=1|last1=Kholopov|first1=P. N.|last2=Kukarkina|first2=N. P.|last3=Perova|first3=N. B.|year=1979}}</ref>
| 4m.81
| 4m.87
|
| B2.5 Ia
| ~400,000<ref name=kraus>{{cite journal|bibcode=2015A&A...581A..75K|arxiv=1507.01846|title=Interplay between pulsations and mass loss in the blue supergiant 55 Cygnus = HD 198 478|journal=Astronomy & Astrophysics|volume=581|pages=A75|last1=Kraus|first1=M.|last2=Haucke|first2=M.|last3=Cidale|first3=L. S.|last4=Venero|first4=R. O. J.|last5=Nickeler|first5=D. H.|last6=Németh|first6=P.|last7=Niemczura|first7=E.|last8=Tomić|first8=S.|last9=Aret|first9=A.|last10=Kubát|first10=J.|last11=Kubátová|first11=B.|last12=Oksala|first12=M. E.|last13=Curé|first13=M.|last14=Kamiński|first14=K.|last15=Dimitrov|first15=W.|last16=Fagas|first16=M.|last17=Polińska|first17=M.|year=2015|doi=10.1051/0004-6361/201425383|s2cid=55392478}}</ref>
|  
|-
| [[3 Geminorum|3 Gem]]
| [[Gemini (constellation)|Gemini]]
| Waelkens et al. (1998)<ref name="waelkens 1998"/>
| 5m.75
|
| 13.70
| B3 Ia
| 200,000<ref>{{cite journal|bibcode=1999A&A...350..970K|arxiv = astro-ph/9910449 |title = The wind momentum-luminosity relationship of galactic A- and B-supergiants |journal = Astronomy and Astrophysics |volume = 350 |pages = 970 |last1 = Kudritzki |first1 = R. P. |last2 = Puls |first2 = J. |last3 = Lennon |first3 = D. J. |last4 = Venn |first4 = K. A. |last5 = Reetz |first5 = J. |last6 = Najarro |first6 = F. |last7 = McCarthy |first7 = J. K. |last8 = Herrero |first8 = A. |date = 1999 }}</ref>
|  
|-
| [[Rho Leonis|ρ Leo]]
| [[Leo (constellation)|Leo]]
| Olsen (1974)<ref name=olsen>{{cite journal|bibcode=1974IBVS..925....1O|title=Variable Stars among the Four-Colour (uvby) Standard Stars|journal=Information Bulletin on Variable Stars|volume=925|pages=1|last1=Olsen|first1=E. H.|date=1974}}</ref>
| 3m.83
| 3m.9
| 3.4271
| B1Iab
| 295,000<ref name=crowther/>
|  
|-
| [[Rigel|β Ori (Rigel)]]<ref name="SaioGeorgy2013"/>
| [[Orion (constellation)|Orion]]
| Waelkens et al. (1998)<ref name="waelkens 1998">{{cite journal|author=Waelkens, C.|author2=Aerts, C.|author3=Kestens, E.|author4=Grenon, M.|author5=Eyer, L.|date=1998|title=Study of an unbiased sample of B stars observed with Hipparcos: the discovery of a large amount of new slowly pulsating B star|journal=Astronomy and Astrophysics|volume=330|pages=215–21|bibcode=1998A&A...330..215W}}</ref>
| 0m.17
| 0m.22
|
| B8Ia
| 279,000<ref name="Chesneau 2014"/> 
218,000<ref name=aaa445_3_1099/>
| Brightest member
|-
| [[Alnilam|ε Ori (Alnilam)]]
| [[Orion (constellation)|Orion]]
| Cousins (1960)<ref name=cousins>{{cite journal|bibcode=1960MNSSA..19...56C|title=New Bright Variable Stars|journal=Monthly Notes of the Astronomical Society of Southern Africa|volume=19|pages=56|last1=Cousins|first1=A. W. J.|date=1960}}</ref>
| 1m.64
| 1m.74
|
| B0.5Iabea
| 275,000<ref name=crowther/> 
537,000<ref name="Searle 2008">{{cite journal|author=Searle, S. C.|author2=Prinja, R. K.|author3=Massa, D.|author4=Ryans, R.|date=2008|title=Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters|journal=Astronomy and Astrophysics|volume=481|issue=3|pages=777–97|doi=10.1051/0004-6361:20077125 |bibcode=2008A&A...481..777S |arxiv = 0801.4289 |s2cid=1552752}}</ref>
|  
|-
| [[Chi2 Orionis|χ2 Ori]]
| [[Orion (constellation)|Orion]]
| Waelkens et al. (1998)<ref name="waelkens 1998"/>
| 4m.68
| 4m.72
| 2.8682
| B2Ia
| 446,000<ref name=crowther>{{Cite journal | last1 = Crowther | first1 = P. A. | last2 = Lennon | first2 = D. J. | last3 = Walborn | first3 = N. R. | title = Physical parameters and wind properties of galactic early B supergiants | doi = 10.1051/0004-6361:20053685 | journal = Astronomy and Astrophysics | volume = 446 | issue = 1 | pages = 279–293 | date = 2006 |arxiv = astro-ph/0509436 |bibcode = 2006A&A...446..279C | s2cid = 18815761 }}</ref>
|  
|-
| [[9 Persei|9 Per]]
| [[Perseus (constellation)|Perseus]]
| Abt (1957)<ref name="Abt1957"/>
| 5m.15
| 5m.25
|
| A2 Ia
| 141,000<ref name=verdugo>{{cite journal|bibcode=1999A&A...346..819V|title=Understanding A-type supergiants. II. Atmospheric parameters and rotational velocities of Galactic A-type supergiants|journal=Astronomy and Astrophysics|volume=346|pages=819|last1=Verdugo|first1=E.|last2=Talavera|first2=A.|last3=Gómez De Castro|first3=A. I.|year=1999}}</ref>
|  
|}

=== Extragalactic ===
{| class="wikitable sortable" style="font-size:90%;"
|- style="background:#efefef;"
! style="width:10%;"|'''Designation (name)'''
! style="width:10%;"|'''Galaxy'''
! style="width:15%;"|'''Discovery'''
! style="width:10%;"|''Maximum [[Apparent magnitude]]'' (mV)
! style="width:10%;"|''Minimum [[Apparent magnitude]]'' (mV)
! style="width:15%;"|'''Period''' (days)
! style="width:10%;"|'''Spectral class'''
! style="width:10%;"|'''Luminosity'''
! style="width:10%;"|'''Comment'''
|-
| [[LHA 115-S 18]]<ref name="vanGenderenSterken2002"/>
| [[Small Magellanic Cloud|SMC]]
|
| 13m.3
|
| Complex
| B[e]sg
|  
| Possible LBV
|-
| [[HDE 268835]]<ref name="vanGenderenSterken2002"/>
| [[Large Magellanic Cloud|LMC]]
|
| 10m.60
| 10m.68
| >100
| B8p
|  
|  
|-
| [[HD 37974]]<ref name="vanGenderenSterken2002"/>
| [[Large Magellanic Cloud|LMC]]
|
| 10m.92
| 11m.00
| 400
| B0.5Ia+
|  
|  
|-
|[[HD 37836]]<ref>{{Cite journal |last1=Balona |first1=L A |last2=Handler |first2=G |last3=Chowdhury |first3=S |last4=Ozuyar |first4=D |last5=Engelbrecht |first5=C A |last6=Mirouh |first6=G M |last7=Wade |first7=G A |last8=David-Uraz |first8=A |last9=Cantiello |first9=M |date=2019-02-27 |title=Rotational modulation in TESS B stars |journal=Monthly Notices of the Royal Astronomical Society |volume=485 |issue=3 |pages=3457–3469 |doi=10.1093/mnras/stz586 |issn=0035-8711|doi-access=free |arxiv=1902.09470 }}</ref>
|[[Large Magellanic Cloud|LMC]]
|
|10m.55
|
|
|B0Iae
|
|LBV candidate
|}

==References==
{{reflist|refs=

<ref name="Chesneau 2014">{{cite journal|author=Chesneau, O.|author2=Kaufer, A.|author3=Stahl, O.|author4=Colvinter, C.|author5=Spang, A.|author6=Dessart, L.|author7=Prinja, R.|author8=Chini, R.|date=2014|title=The variable stellar wind of Rigel probed at high spatial and spectral resolution|journal=Astronomy & Astrophysics|volume=566|id=A125 |pages=18|doi=10.1051/0004-6361/201322894 |bibcode=2014A&A...566A.125C|arxiv = 1405.0907 |s2cid=118404460}}</ref>

<ref name=aaa445_3_1099>{{cite journal | display-authors=1 | last1=Przybilla | first1=N. | last2=Butler | first2=K. | last3=Becker | first3=S. R. | last4=Kudritzki | first4=R. P. | title=Quantitative spectroscopy of BA-type supergiants | journal=Astronomy and Astrophysics | volume=445 | issue=3 | pages=1099–1126 |date=January 2006 | doi=10.1051/0004-6361:20053832 | bibcode=2006A&A...445.1099P |arxiv = astro-ph/0509669 | s2cid=118953817 }}</ref>

<ref name="vanGenderenSterken2002">{{cite journal|last1=van Genderen|first1=A. M.|last2=Sterken|first2=C.|title=Light variations of massive stars (α Cyg variables)|journal=Astronomy and Astrophysics|volume=386|issue=3|date=2002|pages=926–935|bibcode=2002A&A...386..926V|doi=10.1051/0004-6361:20020360|doi-access=free}}</ref>

}}

==Sources==
*Samus N.N., Durlevich O.V., et al. ''Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.)''

{{Variable star topics}}

{{DEFAULTSORT:Alpha Cygni Variable}}
[[Category:Alpha Cygni variables|*]]

Alpha Cygni variable - Revision history

imported>Citation bot: Add: doi-access, authors 1-1. Removed URL that duplicated identifier. Removed parameters. Some additions/deletions were parameter name changes. | Use this bot. Report bugs. | Suggested by Headbomb | #UCB_toolbar