山案座W

**山案座W（W Mensae）**
觀測資料; 曆元 J2000.0
星座	山案座
星官
赤經	05h 26m 24.516s
赤緯	-71° 11′ 11.79″
視星等（V）	13.90 (13.4pg - <18.3pg)
特性
光谱分类	F5Ipec
视星等 (R)	13.700
视星等 (J)	13.032
视星等 (H)	12.831
视星等 (K)	12.296
U−B 色指数	−0.24
B−V 色指数	+0.45
J−H 色指数	0.201
J−K 色指数	0.736
变星类型	R CrB
天体测定
徑向速度 (Rv)	+260 km/s
距离	~168,000 ly ; (~51,500 pc)
绝对星等 (MV)	−4.8
詳細資料
半徑	61 R☉
表面重力 (log g)	0.5
亮度	7,700 L☉
溫度	6,700 K
其他命名
	W Mensae、HV 966、RMC 102、2MASS J05262451-7111117、 AAVSO 0527-71、OGLE LMC-RCB-13
參考資料庫
SIMBAD	资料

山案座W （W Men）是在南天山案座大麥哲倫星系內一顆不尋常的黃超巨星。它是一顆北冕座R型變星，光度會週期性的降低好幾個星等。

山案座W位於鄰近的大麥哲倫星系南邊缺乏金屬的邊緣地區，距離地球很遠^[2]。儘管它有很高的亮度，但它最亮時的視星等只有+13.8^m^[4]，對小望遠鏡來說是太黯淡了。依據計算得知它的半徑是太陽的61倍^[2]。

山案座W的變異性質是威廉·雅各·盧伊滕（英语：Willem Jacob Luyten）在1927年發現的^[8]。它屬於非常罕見的北冕座R型變星，這一類變星的光度偶爾會有非常大幅的下降，因此通常被稱為「逆新星」。山案座W的光度最低時的照相藍星等會低於+18.3等，以致於在當時的照相乾版上檢測不到^[9]。在長波的觀測下，亮度的下降並不明顯，因此認為恆星整體的亮度沒有太大的變化。這樣的變化是由塵埃引起的，是塵埃暫時遮擋了恆星。可見光的短波被吸收後，會以紅外線再輻射出來。許多北冕座R型變星顯示出小振幅的脈動，山案座W的脈動周期約為67天^[4]。

參考資料

^ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 ^1.6 ^1.7 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003). VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C. 2003, 2246. Bibcode:2003yCat.2246....0C.
^ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 ^2.6 Goldsmith, M. J.; Evans, A.; Albinson, J. S.; Bode, M. F. Effective temperatures of RCB stars. Monthly Notices of the Royal Astronomical Society. 1990, 245 (1): 119–29. Bibcode:1990MNRAS.245..119G. ISSN 0035-8711.
^ ^3.0 ^3.1 Milone, Luis A. Identification charts for southern R Coronae Borealis-stars. Astrophysics and Space Science. 1990, 172: 263. Bibcode:1990Ap&SS.172..263M. doi:10.1007/BF00643318.
^ ^4.0 ^4.1 ^4.2 Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. V. R Coronae Borealis Stars in the Large Magellanic Cloud. Acta Astronomica. 2009, 59: 335. Bibcode:2009AcA....59..335S. arXiv:0912.2097 .
^ Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Determination of Radial Velocities and their Applications. 1967, 30: 57. Bibcode:1967IAUS...30...57E.
^ Sherwood, Vicki E. Some Statistics of Southern R Coronae Borealis Variables (abstract). Variable Stars and Stellar Evolution; Proceedings of the Symposium. 1975, 67: 147. Bibcode:1975IAUS...67..147S.
^ ^7.0 ^7.1 Pollard, K. R.; Cottrell, P. L.; Lawson, W. A. An Abundance Analysis of R-Coronae Stars in the Galaxy and the Large Magellanic Cloud. Monthly Notices of the Royal Astronomical Society. 1994, 268 (2): 544. Bibcode:1994MNRAS.268..544P. doi:10.1093/mnras/268.2.544.
^ Luyten, W. J. A New Irregular Variable of the R Coronae Type. Harvard College Observatory Bulletin. 1927, 846 (846): 31–33. Bibcode:1927BHarO.846...33L. 1927BHarO.846...33L.
^ Milone, L. A. A Note on V CrA and W Men. Information Bulletin on Variable Stars. 1975, 989: 1. Bibcode:1975IBVS..989....1M.

[2mass-1] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 ^1.6 ^1.7 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003). VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C. 2003, 2246. Bibcode:2003yCat.2246....0C.

[Goldsmith-2] 2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 ^2.6 Goldsmith, M. J.; Evans, A.; Albinson, J. S.; Bode, M. F. Effective temperatures of RCB stars. Monthly Notices of the Royal Astronomical Society. 1990, 245 (1): 119–29. Bibcode:1990MNRAS.245..119G. ISSN 0035-8711.

[milone-3] 3.0 ^3.1 Milone, Luis A. Identification charts for southern R Coronae Borealis-stars. Astrophysics and Space Science. 1990, 172: 263. Bibcode:1990Ap&SS.172..263M. doi:10.1007/BF00643318.

[ogle-4] 4.0 ^4.1 ^4.2 Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. V. R Coronae Borealis Stars in the Large Magellanic Cloud. Acta Astronomica. 2009, 59: 335. Bibcode:2009AcA....59..335S. arXiv:0912.2097 .

[5] Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Determination of Radial Velocities and their Applications. 1967, 30: 57. Bibcode:1967IAUS...30...57E.

[sherwood-6] Sherwood, Vicki E. Some Statistics of Southern R Coronae Borealis Variables (abstract). Variable Stars and Stellar Evolution; Proceedings of the Symposium. 1975, 67: 147. Bibcode:1975IAUS...67..147S.

[pollard-7] 7.0 ^7.1 Pollard, K. R.; Cottrell, P. L.; Lawson, W. A. An Abundance Analysis of R-Coronae Stars in the Galaxy and the Large Magellanic Cloud. Monthly Notices of the Royal Astronomical Society. 1994, 268 (2): 544. Bibcode:1994MNRAS.268..544P. doi:10.1093/mnras/268.2.544.

[8] Luyten, W. J. A New Irregular Variable of the R Coronae Type. Harvard College Observatory Bulletin. 1927, 846 (846): 31–33. Bibcode:1927BHarO.846...33L. 1927BHarO.846...33L.

[9] Milone, L. A. A Note on V CrA and W Men. Information Bulletin on Variable Stars. 1975, 989: 1. Bibcode:1975IBVS..989....1M.

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山案座W

參考資料

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