內平二
（重定向自小獅座21）
小獅座21是在星座小獅座的一顆恆星。它的視星等大約是4.5等，黯淡的亮度使肉眼不易看見（參見波特爾暗空分類法）。由依巴谷衛星量測的視差估計，它距離地球大約92.1光年（28.2秒差距）[1]。它被認為是天狼星超級星團的一員[6]。
| 觀測資料 曆元 J2000 | |
|---|---|
| 星座 | 小獅座 |
| 星官 | |
| 赤經 | 10h 07m 25.76296s[1] |
| 赤緯 | +35° 14′ 40.8965″[1] |
| 視星等（V） | 4.47–4.52[2] |
| 特性 | |
| 光谱分类 | A7V[3] |
| U−B 色指数 | +0.08[4] |
| B−V 色指数 | +0.18[4] |
| 变星类型 | δ Sct[2] |
| 天体测定 | |
| 徑向速度 (Rv) | −11.40 ± 0.9[5] km/s |
| 自行 (μ) | 赤经：52.90[1] mas/yr 赤纬：0.62[1] mas/yr |
| 视差 (π) | 35.41 ± 0.18[1] mas |
| 距离 | 92.1 ± 0.5 ly (28.2 ± 0.1 pc) |
| 绝对星等 (MV) | +2.43[6] |
| 詳細資料 | |
| 質量 | 1.75[7] M☉ |
| 半徑 | 1.75[7] R☉ |
| 表面重力 (log g) | 4.07[8] |
| 亮度 | 9.91[7] L☉ |
| 溫度 | 7,839[8] K |
| 金属量 [Fe/H] | 0.03±0.08[7] dex |
| 自轉速度 (v sin i) | 155[9] km/s |
| 年齡 | 390[9] Myr 750[7] Myr |
| 其他命名 | |
| 參考資料庫 | |
| SIMBAD | 资料 |
小獅座21的旋轉速度相當快，它的投影旋轉速度估計為155公里/秒[9]，所以它的自轉至少得有那麼快。它被列為光譜類型A7V的的快速旋轉光譜標準星，而不是緩慢旋轉的標準星長蛇座2[11]。它也是盾牌座δ型變星，視星等在4.47至4.52之間變動[2]。
參考資料
- ^ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F.; et al. Validation of the new Hipparcos reduction. Astronomy and Astrophysics. 2007, 474 (2): 653–664 [2023-05-10]. Bibcode:2007A&A...474..653V. S2CID 18759600. arXiv:0708.1752
. doi:10.1051/0004-6361:20078357. （原始内容存档于2019-12-07）.
- ^ 2.0 2.1 2.2 Samus, N. N.; Durlevich, O. V.; et al. VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013). VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 2009, 1. Bibcode:2009yCat....102025S.
- ^ Johnson, H. L.; Morgan, W. W. Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas. The Astrophysical Journal. 1953, 117: 313. Bibcode:1953ApJ...117..313J. doi:10.1086/145697.
- ^ 4.0 4.1 Johnson, H. L. UBVRIJKL Photometry of the Bright Stars. Communications of the Lunar and Planetary Laboratory. 1966, 4: 99. Bibcode:1966CoLPL...4...99J.
- ^ Gontcharov, G. A. Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system. Astronomy Letters. 2006, 32 (11): 759–771. Bibcode:2006AstL...32..759G. S2CID 119231169. arXiv:1606.08053 . doi:10.1134/S1063773706110065.
- ^ 6.0 6.1 Eggen, Olin J., The Sirius Supercluster and Missing Mass near the Sun, The Astronomical Journal, August 1998, 116 (2): 782–788, Bibcode:1998AJ....116..782E, doi:10.1086/300465 .
- ^ 7.0 7.1 7.2 7.3 7.4 7.5 Gáspár, András; et al, The Correlation between Metallicity and Debris Disk Mass, The Astrophysical Journal, 2016, 826 (2): 171, Bibcode:2016ApJ...826..171G, S2CID 119241004, arXiv:1604.07403 , doi:10.3847/0004-637X/826/2/171.
- ^ 8.0 8.1 Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I. The Astronomical Journal. 2003, 126 (4): 2048. Bibcode:2003AJ....126.2048G. S2CID 119417105. arXiv:astro-ph/0308182 . doi:10.1086/378365.
- ^ 9.0 9.1 9.2 9.3 Rieke, G. H.; Su, K. Y. L.; Stansberry, J. A.; Trilling, D.; Bryden, G.; Muzerolle, J.; White, B.; Gorlova, N.; Young, E. T.; Beichman, C. A.; Stapelfeldt, K. R.; Hines, D. C. Decay of Planetary Debris Disks. The Astrophysical Journal. 2005, 620 (2): 1010. Bibcode:2005ApJ...620.1010R. CiteSeerX 10.1.1.579.8956 . S2CID 54676993. doi:10.1086/426937.
- ^ * 21 LMi. SIMBAD. 斯特拉斯堡天文資料中心.
- ^ Gray, R. O.; Garrison, R. F. The late A-type stars - Refined MK classification, confrontation with Stromgren photometry, and the effects of rotation. The Astrophysical Journal Supplement Series. 1989, 70: 623. Bibcode:1989ApJS...70..623G. doi:10.1086/191349.
