التفاصيل البيبلوغرافية
| العنوان: |
Rotational broadening and conservation of angular momentum in post-extreme horizontal branch stars. |
| المؤلفون: |
Fontaine, G.1 (AUTHOR) fontaine@astro.umontreal.ca, Latour, M.2 (AUTHOR) marilyn.latour@fau.de |
| المصدر: |
Astronomy & Astrophysics / Astronomie et Astrophysique. May2018, Vol. 613, p1-N.PAG. 4p. |
| مصطلحات موضوعية: |
*HORIZONTAL branch stars, *ANGULAR momentum (Nuclear physics), *STELLAR rotation, *STELLAR evolution, *DWARF stars |
| مستخلص: |
We show that the recent realization that isolated post-extreme horizontal branch (post-EHB) stars are generally characterized by rotational broadening with values of Vrot sin i between 25 and 30 km s-1 can be explained as a natural consequence of the conservation of angular momentum from the previous He-core burning phase on the EHB. The progenitors of these evolved objects, the EHB stars, are known to be slow rotators with an average value of Vrot sin i of ~7:7 km s-1. This implies significant spin-up between the EHB and post- EHB phases. Using representative evolutionary models of hot subdwarf stars, we demonstrate that angular momentum conservation in uniformly rotating structures (rigid-body rotation) boosts that value of the projected equatorial rotation speed by a factor ~3:6 by the time the model has reached the region of the surface gravity-effective temperature plane where the newly-studied post-EHB objects are found. This is exactly what is needed to account for their observed atmospheric broadening. We note that the decrease of the moment of inertia causing the spin-up is mostly due to the redistribution of matter that produces more centrally-condensed structures in the post-EHB phase of evolution, not to the decrease of the radius per se. [ABSTRACT FROM AUTHOR] |
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