 狗国增二的位置（红圈）Location of θ2 Sagittarii (circled) | |
| 观测资料 历元 J2000.0 | |
|---|---|
| 星座 | 人马座 |
| 星官 | |
| 赤经 | 19h 59m 51.35684s[1] |
| 赤纬 | −34° 41′ 52.0797″[1] |
| 视星等（V） | +5.30[2] |
| 特性 | |
| 光谱分类 | A4/A5 IV[3] |
| U−B 色指数 | +0.06[2] |
| B−V 色指数 | +0.17[2] |
| 天体测定 | |
| 径向速度 (Rv) | −17.60[4] km/s |
| 自行 (μ) | 赤经：+108.23[1] mas/yr 赤纬：−69.51[1] mas/yr |
| 视差 (π) | 20.62 ± 0.28[1] mas |
| 距离 | 158 ± 2 ly (48.5 ± 0.7 pc) |
| 绝对星等 (MV) | +1.87[5] |
| 详细资料 | |
| 质量 | 1.93[6] M☉ |
| 表面重力 (log g) | 4.07±0.14[6] |
| 亮度 | 14[7] L☉ |
| 温度 | 8,113±276[6] K |
| 自转速度 (v sin i) | 45.2±0.5[8] km/s |
| 年龄 | 809[6] Myr |
| 其他命名 | |
| 参考数据库 | |
| SIMBAD | data |
狗国增二（人马座θ2）是黄道星座人马座中一颗单独的恒星 [10]。它的视星等为 +5.30等[2]，在足够黑暗的场所肉眼隐约可见。这颗恒星正以每秒17.60公里的径向速度朝向太阳接近[4]。根据从地球测得年周视差20.62mas的数值[1]，它与太阳的距离是158光年。
狗国增二光谱的类型是A4/A5IV[3]，估计它的年龄为8亿900万年[6]，是一颗演化至A型的次巨星。它被怀疑是一颗Am星，因为至少在1992年的观测周期上，经光度测量是颗变星[11]。估计它的质量是太阳的1.93倍[6]，辐射是太阳的14倍[7]，来自光球的有效温度是8,113K[6]。它自转的投影自转速度是每秒45.2公里[8]。
狗国增二有一对目视伴星。伴星B的视星等11.3等，在2000年的角距离为32.8弧秒，位置角165°；伴星C在1965年与B的距离为1.5弧秒，位置角104度[12]。但这两者与狗国增二都没有物理上的实质关系[10]。
参考资料
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F., Validation of the new Hipparcos reduction, Astronomy and Astrophysics, 2007, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752
, doi:10.1051/0004-6361:20078357.
- ↑ 2.0 2.1 2.2 2.3 Mendoza, E. E.; et al, UBVRI photometry of 225 AM stars, Astronomical Journal, June 1978, 83: 606–614, Bibcode:1978AJ.....83..606M, doi:10.1086/112242.
- ↑ 3.0 3.1 Houk, Nancy, Michigan catalogue of two-dimensional spectral types for the HD stars 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, 1979, Bibcode:1982mcts.book.....H.
- ↑ 4.0 4.1 Gontcharov, G. A., Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system, Astronomy Letters, November 2006, 32 (11): 759–771, Bibcode:2006AstL...32..759G, arXiv:1606.08053 , doi:10.1134/S1063773706110065.
- ↑ Anderson, E.; Francis, Ch., XHIP: An extended hipparcos compilation, Astronomy Letters, 2012, 38 (5): 331, Bibcode:2012AstL...38..331A, arXiv:1108.4971 , doi:10.1134/S1063773712050015.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 David, Trevor J.; Hillenbrand, Lynne A., The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets, The Astrophysical Journal, 2015, 804 (2): 146, Bibcode:2015ApJ...804..146D, arXiv:1501.03154 , doi:10.1088/0004-637X/804/2/146.
- ↑ 7.0 7.1 McDonald, I.; et al, Fundamental Parameters and Infrared Excesses of Hipparcos Stars, Monthly Notices of the Royal Astronomical Society, 2012, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037 , doi:10.1111/j.1365-2966.2012.21873.x.
- ↑ 8.0 8.1 Díaz, C. G.; et al, Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum, Astronomy & Astrophysics, July 2011, 531: A143, Bibcode:2011A&A...531A.143D, arXiv:1012.4858 , doi:10.1051/0004-6361/201016386.
- ↑ tet02 Sgr. SIMBAD. 斯特拉斯堡天文资料中心. [2017-07-07].
- ↑ 10.0 10.1 Eggleton, P. P.; Tokovinin, A. A., A catalogue of multiplicity among bright stellar systems, Monthly Notices of the Royal Astronomical Society, September 2008, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878 , doi:10.1111/j.1365-2966.2008.13596.x.
- ↑ Anders, G. J., Theta2 Sgr: Serendipitous Discovery of Variability in an Am Star?, Information Bulletin on Variable Stars, September 1992, 3768: 1, Bibcode:1992IBVS.3768....1A.
- ↑ Mason, B. D.; et al, The Washington Visual Double Star Catalog, 2014 [2015-07-22], Bibcode:2001AJ....122.3466M, doi:10.1086/323920 .