PG 1159星,通常也称为前简并星[1],是一颗大气层的不足够,而中心正在转变成为行星状星云和高热白矮星恒星。这些恒星非常热,表面温度在75,000K至200,000K[2],并且特征是大气层只有少量的的吸收谱线;它们的表面重力介于104和106m/s2。有些PG 1159星还在进行氦融合[3], § 2.1.1, 2.1.2, Table 2.。PG 1159星是依据它们的原型,PG 1159-035命名的,这颗恒星是在帕洛马绿色巡天调查紫外线过量时发现的天体 [4],是被发现的第一颗PG 1159星。

人们认为PG 1159星的大气层之所以奇怪是因为已经流失了,在它们进入渐近巨星分支之后,它们只留下氦融合的核心。结果是,PG 1159星的大气层混合了其前身AGB形态时的氢和氦燃烧壳层的物质[3], §1.他们认为最终将流失质量、变冷,和成为DO白矮星[2][5], §4.

有些PG 1159恒星非常明亮。由于在本身内部的引力波在非径向方向上的脉动,使它们的光度有着轻微的变化(5-10%)。它们同时有多种振动模式,典型的周期在300至3,000秒[6][7], Table 1.。 第一颗知道的这一种恒星也是PG 1159-35,在1979年发现这种变化[8],并且在1985年将这种变化标示为室女座GW [9],因此也称为室女座GW星,并将之作为原型,同时这一类型还可以分为 DOVPNNV[7], § 1.1;[10]

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参考资料

  1. ^ Jaschek & Jaschek: CARBON C. [2010-11-29]. (原始内容存档于2011-02-27). 
  2. ^ 2.0 2.1 Observational constraints on the evolutionary connection between PG 1159 stars and DO white dwarfs页面存档备份,存于互联网档案馆), S. D. Huegelmeyer, S. Dreizler, K. Werner, J. Krzesinski, A. Nitta, and S. J. Kleinman. arXiv:astro-ph/0610746.
  3. ^ 3.0 3.1 The Elemental Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars页面存档备份,存于互联网档案馆), Klaus Werner and Falk Herwig, Publications of the Astronomical Society of the Pacific 118, #840 (February 2006), pp. 183–204
  4. ^ The Palomar-Green catalog of ultraviolet-excess stellar objects页面存档备份,存于互联网档案馆), R. F. Green, M. Schmidt, and J. Liebert, Astrophysical Journal Supplement 61 (June 1986), pp. 305–352. CDS ID II/207页面存档备份,存于互联网档案馆).
  5. ^ Determination of Mass-Loss Rates of PG 1159 Stars from Far-Ultraviolet Spectroscopy, Lars Koesterke and Klaus Werner, Astrophysical Journal 500 (June 1998), pp. L55–L59.
  6. ^ Asteroseismology of white dwarf stars, D. E. Winget, Journal of Physics: Condensed Matter 10, #49 (December 14, 1998), pp. 11247–11261. DOI 10.1088/0953-8984/10/49/014.
  7. ^ 7.0 7.1 Mapping the Instability Domains of GW Vir Stars in the Effective Temperature-Surface Gravity Diagram页面存档备份,存于互联网档案馆), Quirion, P.-O., Fontaine, G., Brassard, P., Astrophysical Journal Supplement Series 171 (2007), pp. 219–248.
  8. ^ PG1159-035: A new, hot, non-DA pulsating degenerate, J. T. McGraw, S. G. Starrfield, J. Liebert, and R. F. Green, pp. 377–381 in White Dwarfs and Variable Degenerate Stars, IAU Colloquium #53, ed. H. M. van Horn and V. Weidemann, Rochester: University of Rochester Press, 1979.
  9. ^ The 67th Name-List of Variable Stars, P. N. Kholopov, N. N. Samus, E. V. Kazarovets, and N. B. Perova, Information Bulletin on Variable Stars, #2681, March 8, 1985.
  10. ^ §1, Detection of non-radial g-mode pulsations in the newly discovered PG 1159 star HE 1429-1209页面存档备份,存于互联网档案馆), T. Nagel and K. Werner, Astronomy and Astrophysics 426 (2004), pp. L45–L48.