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，意味着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
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
银河系的
| 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
| 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.)
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