天弁二盾牌座δ)是在南天盾牌座的一颗巨星视星等4.72等[4],是在这个小且没有特征星座的第五亮星。分析依巴谷卫星任务期间测量的视差,这颗恒星与地球的距离大约是202光年(62秒差距[1]。天弁二是盾牌座δ变星的原型,这种变星来自体积胀缩造成光度的高振幅大约都在0.15星等左右。这颗恒星特有的化学丰度与Am星相似[8]

天弁二(盾牌座δ)

天弁二的位置(中心)。
观测资料
历元 J2000
星座 盾牌座
星官
赤经 18h 42m 16.422137s[1]
赤纬 −09° 03′ 09.19206″[1]
视星等(V) 4.60 - 4.79[2]
特性
光谱分类F2 IIIp[3]
U−B 色指数+0.16[4][2]
B−V 色指数+0.35[4]
变星类型盾牌座δ
天体测定
径向速度 (Rv)−44.8[5] km/s
自行 (μ) 赤经:9.21[1] mas/yr
赤纬:0.82[1] mas/yr
视差 (π)16.11 ± 0.31[1] mas
距离202 ± 4 ly
(62 ± 1 pc)
绝对星等 (MV)0.72±0.04[6]
详细资料
质量2.23+0.06
−0.05
[7] M
表面重力 (log g)3.5[8]
温度7000[8] K
金属量 [Fe/H]0.41[6] dex
自转速度 (v sin i)25.5[8] km/s
年龄0.7±0.1[6] Gyr
其他命名
盾牌座2、BD−09° 4796, FK5 1486、HD 172748、HIP 91726、HR 7020、 SAO 142515。[9]
参考数据库
SIMBAD资料

在1900年,天文学家威廉·华莱士·坎贝尔(William Wallace Campbell)和威廉·哈蒙德·赖特英语William Hammond Wright使用利克天文台的米尔斯光谱仪确定该恒星的径向速度会变化[10]。在1935年,测量出光度以0.19377日(4.65小时)的周期有着0.2等(在+4.60至+4.79之间变化)的振幅,并证实这种变化是内在的,而不是光谱联星造成的结果[11]。在1938年,发现了次要的周期,并提出脉动理论来模拟这种变异[12]。之后对天弁二的观测表明,它是在多重离散的径向和非径向模式下脉动。模式最强的频率是59.731μHz,其次是61.936μHz,依此类推,现在共建模了八种不同的频率模式[13]

这颗恒星在银道坐标系空间速度[U, V, W] = [–42, –17, –1] km·s−1。它以离心率0.11的轨道绕行银河系,最接近银河中心的距离是22.31 kly(6.84 kpc),最远的距离是27.59 kly(8.46 kpc)[6]。如果天弁二维持现在的运动和光度,它将以10光年的距离内经过太阳系附近[14],并且在西元11500001330000 CE成为天空中最亮的恒星,视星等为-1.84,比天狼星现在的-1.46还要明亮[15]

天弁二有二颗光学伴星。第一颗距离15.2角秒,视星等+12.2。第二颗距离53角秒,视星等+9.2[16]

佛兰斯蒂德没有将天弁二标示在盾牌座,而是将它与其它几颗星纳入天鹰座,并在星表中标记为天鹰座2拜耳名称的盾牌座δ是由古德命名的[17]

参考资料

  1. ^ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F., Validation of the new Hipparcos reduction, Astronomy and Astrophysics, November 2007, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 , doi:10.1051/0004-6361:20078357 
  2. ^ 2.0 2.1 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. 
  3. ^ Cowley, Anne; Fraquelli, Dorothy, MK Spectral Types for Some Bright F Stars, Publications of the Astronomical Society of the Pacific, February 1974, 86 (509): 7, Bibcode:1974PASP...86...70C, doi:10.1086/129562 
  4. ^ 4.0 4.1 4.2 Johnson, H. L.; et al. UBVRIJKL photometry of the bright stars. Communications of the Lunar and Planetary Laboratory. 1966, 4 (99): 99. Bibcode:1966CoLPL...4...99J. 
  5. ^ Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Batten, Alan Henry; Heard, John Frederick (编). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. June 20–24, 1966. Bibcode:1967IAUS...30...57E. 
  6. ^ 6.0 6.1 6.2 6.3 Holmberg, J.; Nordström, B.; Andersen, J., The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics, Astronomy and Astrophysics, July 2009, 501 (3): 941–947, Bibcode:2009A&A...501..941H, arXiv:0811.3982 , doi:10.1051/0004-6361/200811191 
  7. ^ Nordström, B.; et al, The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs, Astronomy and Astrophysics, May 2004, 418: 989–1019, Bibcode:2004A&A...418..989N, arXiv:astro-ph/0405198 , doi:10.1051/0004-6361:20035959 
  8. ^ 8.0 8.1 8.2 8.3 Yushchenko, A.; et al. The chemical composition of δ Scuti. Monthly Notices of the Royal Astronomical Society. May 2005, 359 (55): 865–873. Bibcode:2005MNRAS.359..865Y. doi:10.1111/j.1365-2966.2005.08921.x. 
  9. ^ del Sct – Variable star of delta Sct type. SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. [2009-10-23]. (原始内容存档于2020-11-05). 
  10. ^ Campbell, W. W.; Wright, W. H. A list of nine stars whose velocities in the line of sight are variable. Astrophysical Journal. 1900, 12: 254–257. Bibcode:1900ApJ....12..254C. doi:10.1086/140765.  Listed as 2 Scuti on p. 256.
  11. ^ Colacevich, A. On the variable radial velocity of δ Scuti. Publications of the Astronomical Society of the Pacific. August 1935, 47 (278): 231–232. Bibcode:1935PASP...47..231C. doi:10.1086/124599. 
  12. ^ Sterne, T. E. The Secondary Variation of δ Scuti. Astrophysical Journal. March 1938, 87: 133–150. Bibcode:1938ApJ....87..133S. doi:10.1086/143913. 
  13. ^ Templeton, Matthew R.; et al. A New Pulsation Spectrum and Asteroseismology of delta Scuti. The Astronomical Journal. October 1997, 114: 1592–1601. Bibcode:1997AJ....114.1592T. doi:10.1086/118590. 
  14. ^ García-Sánchez, J.; et al, Stellar encounters with the solar system, Astronomy and Astrophysics, 2001, 379 (2): 634–659, Bibcode:2001A&A...379..634G, doi:10.1051/0004-6361:20011330 
  15. ^ Sky and Telescope, April 1998 (p60), based on computations from Hipparcos mission data.
  16. ^ Burnham, Robert. Burnham's celestial handbook: an observer's guide to the universe beyond the solar system 3. Courier Dover Publications. 1978: 1746. ISBN 0-486-23673-0. 
  17. ^ Wagman, M. Flamsteed's Missing Stars. Journal for the History of Astronomy, Vol.18, NO. 3/AUG, P.209, 1987. August 1987, 18: 212. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305. 

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