天鹅座α型变星

天鹅座α型变星是显示出非径向脉动的变星,意味著当恒星表面有些地方收缩时,而同时也有些地方是扩张的[1]。它们是光谱类型B或A的超巨星,亮度变化在0.1视星等,并与脉动相关联,而由于和多脉动周期的节拍相关联,因而通常是不规则变星。脉冲周期通常有几天到几个星期的周期。

这种变星的原型是天津四(天鹅座α),显示的亮度在1.21 和 +1.29 之间波动。众所周知很多在早期的超巨星都有小幅快速的变动,但之前它们未被归为一类,直到1985年的变星总表第四版才收录为变星的一种,缩写的字母为ACYG(Alpha Cygni variable stars)[2]。许多高光度蓝变星(LBVs)在它们平静(热)阶段显示出天鹅座α型变星的型态,但在这种情况下一般仍使用LBV的分类。

克里斯托费尔(Christoffel Waelkens)和他的同事在1998年的研究,分析依巴谷卫星的资料,发现了大量(32)此类变星[3]

脉动

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还不完全清楚天鹅座α型变星的脉动,它们并不限于窄幅的温度和光度脉动星的方式。可以是最明亮的A和B超巨星,也可能是O和F的恒星,显示某种不可预知的小规模(尺度)脉动类型。非绝热过程的奇怪模式迳向脉动只显现在最明亮的超巨星。通过假设它们是低质量的后红超巨星,低明亮的超巨星也有脉动模式,但多数的天鹅座α型变星似乎未显现经历过红巨星的阶段[4][5]

卖有可能诱发κ机制,造成铁不透明度的变化,产生观测上奇怪的短周期迳向和非迳向脉动方式。非绝热的G-模式可能会产生较长的周期变化,但这些均未在天鹅座α型变星上观测到[6]

列表

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银河系的

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名称 星座 发现 最大视星等 (mV)[7] 最小视星等 (mV)[7] 周期(天) 光谱类型 发光度 注解
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]  
半人马座ο2 半人马座 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] 天鹅座 Lee (1910)[14] 1m.21 1m.29 A2 Ia 196,000[15] 原型
天鹅座σ 天鹅座 Abt (1957)[16] 4m.19 4m.26 120.2 B9 Iab 39,000[17]  
双子座3 双子座 Waelkens et al. (1998)[3] 5m.75 13.70 B3 Ia 200,000[18]  
狮子座ρ 狮子座 Olsen (1974)[19] 3m.83 3m.9 3.4271 B1Iab 295,000[11]  
参宿七[5] 猎户座 Waelkens et al. (1998)[3] 0m.17 0m.22 2.0748 B8Ia 279,000[20]

218,000[21]

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

537,000[23]

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

其他星系

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名称 星系 发现 最大视星等 (mV) 最小视星等 (mV) 周期(天) 光谱类型 发光度 注解
LHA 115-S 18[24] SMC 13m.3 复杂的 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+    

参考资料

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