Close stellar binary systems by grazing envelope evolution

Noam Soker*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

I suggest a spiral-in process in which a stellar companion grazes the envelope of a giant star while both the orbital separation and the giant radius shrink simultaneously, forming a close binary system. The binary system might be viewed as evolving in a constant state of "just entering a common envelope (CE) phase." In cases where this process takes place, it can be an alternative to CE evolution where the secondary star is immersed in the giant's envelope. Grazing envelope evolution (GEE) is made possible only if the companion manages to accrete mass at a high rate and launches jets that remove the outskirts of the giant envelope, hence preventing the formation of a CE. The high accretion rate is made possible by the accretion disk launching jets which efficiently carry the excess angular momentum and energy from the accreted mass. The orbital decay itself is caused by the gravitational interaction of the secondary star with the envelope inward of its orbit, i.e., dynamical friction (gravitational tide). Mass loss through the second Lagrangian point can carry additional angular momentum and envelope mass. The GEE lasts for tens to hundreds of years. The high accretion rate, with peaks lasting from months to years, might lead to a bright object referred to as the intermediate luminosity optical transient (Red Novae; Red Transients). A bipolar nebula and/or equatorial ring are formed around the binary remnant.

Original languageEnglish
Article number114 (5pp)
JournalAstrophysical Journal
Volume800
Issue number2
DOIs
StatePublished - 20 Feb 2015
Externally publishedYes

Keywords

  • binaries: close
  • stars: AGB and post-AGB
  • stars: winds outflows

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