天鵝座α型變星

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天鵝座α型變星是顯示出非徑向脈動的變星,意味著當恆星表面有些地方收縮時,而同時也有些地方是擴張的[1]。它們是光譜類型B或A的超巨星,亮度變化在0.1視星等,並與脈動相關聯,而由於和多脈動週期的節拍相關聯,因而通常是不規則變星。脈衝週期通常有幾天到幾個星期的周期。

這種變星的原型是天津四(天鵝座α),顯示的亮度在1.21 和 +1.29 之間波動。眾所周知很多在早期的超巨星都有小幅快速的變動,但之前它們未被歸為一類,直到1985年的變星總表第四版才收錄為變星的一種,縮寫的字母為ACYG(Alpha Cygni variable stars)[2]。許多高光度藍變星(LBVs)在它們平靜(熱)階段顯示出天鵝座α型變星的型態,但在這種情況下一般仍使用LBV的分類。

克裡斯托費爾(Christoffel Waelkens)和他的同事在1998年的研究,分析依巴谷衛星的資料,發現了大量(32)此類變星[3]

脈動[编辑]

還不完全清楚天鵝座α型變星的脈動,它們並不限於窄幅的溫度和光度脈動星的方式。可以是最明亮的A和B超巨星,也可能是O和F的恆星,顯示某種不可預知的小規模(尺度)脈動類型。非絕熱過程的奇怪模式逕向脈動只顯現在最明亮的超巨星。通過假設它們是低質量的後紅超巨星,低明亮的超巨星也有脈動模式,但多數的天鵝座α型變星似乎未顯現經歷過紅巨星的階段[4][5]

賣有可能誘發κ機制,造成鐵不透明度的變化,產生觀測上奇怪的短週期逕向和非逕向脈動方式。非絕熱的G-模式可能會產生較長的週期變化,但這些均未在天鵝座α型變星上觀測到[6]

列表[编辑]

銀河系的[编辑]

名稱 星座 發現 最大視星等 (mV)[7] 最小視星等 (mV)[7] 週期(天) 光譜類型 發光度 註解
CE Cam (HD 21389) 鹿豹座 Percy & Welsh (1983)[8] 4m.54 A0Iab 63,000[9]  
CS Cam 鹿豹座 4m.259 B9Ia  
大犬座η(Aludra) 大犬座 Kazarovets et al. (1999)[10] 2m.38 2m.48 4.70433 B5Ia 105,000[9]  
大犬座ο2 大犬座 Waelkens et al. (1998)[3] 2m.98 3m.04 24.44 B3Ia 219,000[11]  
仙后座κ 仙后座 Percy & Welsh (1983)[8] 4m.12 4m.21 2.64690 B1Ia 331,000[11]  
半人馬座ο2 半人馬座 5m.12 5m.22 46.3 A2Ia 136,000[12]  
仙王座ν 仙王座 Percy & Welsh (1983)[8] 4m.25 4m.35 A2 Iab 254,000[9]  
南十字座DL 南十字座 Waelkens et al. (1998)[3] 6m.24 6m.28 2.8778 B1.5Ia 242,000[13]  
天津四[5] 天鵝座 Lee (1910)[14] 1m.21 1m.29 A2 Ia 196,000[15] 原型
天鵝座σ 天鵝座 Abt (1957)[16] 4m.19 4m.26 120.2 B9 Iab 39,000[17]  
雙子座3 雙子座 Waelkens et al. (1998)[3] 5m.75 13.70 B3 Ia 200,000[18]  
獅子座ρ 獅子座 Olsen (1974)[19] 3m.83 3m.9 3.4271 B1Iab 295,000[11]  
參宿四[5] 獵戶座 Waelkens et al. (1998)[3] 0m.17 0m.22 2.0748 B8Ia 279,000[20]

218,000[21]

Brightest member
ε Ori(Alnilam) 獵戶座 Cousins (1960)[22] 1m.64 1m.74 2.0748 B0.5Iabea 275,000[11]

537,000[23]

 
獵戶座χ2(Rigel) 獵戶座 Waelkens et al. (1998)[3] 4m.68 4m.72 2.8682 B2Ia 446,000[11]  

其他星系[编辑]

名稱 星系 發現 最大視星等 (mV) 最小視星等 (mV) 週期(天) 光譜類型 發光度 註解
LHA 115-S 18[24] SMC 13m.3 複雜的 B[e]sg   可能是LBV
HDE 268835[24] LMC 10m.60 10m.68 >100 B8p    
HD 37974[24] LMC 10m.92 11m.00 400 B0.5Ia+    

參考資料[编辑]

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