Post-AGB star

In today's world, Post-AGB star has become a topic of increasing interest. Over time, the importance of Post-AGB star has been consolidated in different areas, from people's personal lives to the global economy. The relevance of Post-AGB star has led to research being carried out and debates generated around this topic, in order to fully understand it and make informed decisions about it. In this article, we will explore different aspects related to Post-AGB star, from its origin to its implications today, with the aim of providing a comprehensive vision of this topic that has so much impact on society.

A post-AGB star (pAGB, abbreviation of post-asymptotic giant branch) is a type of luminous supergiant star of intermediate mass in a very late phase of stellar evolution. The post-AGB stage occurs after the asymptotic giant branch (AGB or second-ascent red giant) has ended. The stage sees the dying star, initially very cool and large, shrink and heat up.[1] The duration of the post-AGB stage varies based on the star's initial mass, and can range from 100,000 years for a solar-mass star to just over 1,000 years for more massive stars. The timescale gets slightly shorter with lower metallicity.[2]

Towards the end of this stage, post-AGB stars also tend to produce protoplanetary nebulae as they shed their outer layers, and this creates a large infrared excess and obscures the stars in visible light. After reaching an effective temperature of about 30,000 K, the star is able to ionise its surrounding nebula, producing a true planetary nebula.

Properties

Post-AGB stars span a large range of temperatures, as they are in the process of heating up from very cool temperatures (3,000 K or less) up to about 30,000 K. Technically, the post-AGB stage only ends when the star reaches its maximum temperature of 100-200,000 K,[2] but beyond 30,000 K, the star ionises the surrounding gas and would be considered a central star of a planetary nebula more often than a post-AGB star.

On the other hand, the luminosity of post-AGB stars is usually constant throughout the post-AGB stage, and slightly dependent on the star’s core mass, and getting slightly brighter with lower metallicity.[3][2]

Examples

Due to the dust usually obscuring them, many post-AGB stars are visually relatively dim. However there are still some post-AGB stars visible to the naked eye, the brightest of which is 89 Herculis.

Other examples include:

References

  1. ^ Habing, Harm (1997). Paresce, Francesco (ed.). AGB and POST-AGB STARS: an Overview. Science with the VLT Interferometer. Science with the VLT Interferometer. ESO Astrophysics Symposia. Berlin, Heidelberg: Springer. pp. 183–191. doi:10.1007/978-3-540-69398-7_23. ISBN 978-3-540-69398-7.
  2. ^ a b c Bertolami, Marcelo Miguel Miller (2016-04-01). "New models for the evolution of post-asymptotic giant branch stars and central stars of planetary nebulae". Astronomy & Astrophysics. 588: A25. arXiv:1410.1679. Bibcode:2016A&A...588A..25M. doi:10.1051/0004-6361/201526577. ISSN 0004-6361.
  3. ^ Vickers, Shane B.; Frew, David J.; Owers, Matt S.; Parker, Quentin A.; Bojičič, Ivan S. (2016). "Improving the distances of post-AGB objects in the Milky Way". Journal of Physics: Conference Series. 728 (7): 072013. Bibcode:2016JPhCS.728g2013V. doi:10.1088/1742-6596/728/7/072013. hdl:10722/237688. S2CID 126383516.