The Symbiotic Stars

TL;DR

Symbiotic stars are binary systems with white dwarfs accreting from red giants, exhibiting diverse behaviors and evolving through complex processes, with recent discoveries revealing a larger, optically-quiet population and new physical phenomena.

Contribution

This paper provides a comprehensive review of symbiotic stars, highlighting their types, behaviors, and the latest understanding of their complex accretion and evolution processes.

Findings

Identification of a larger, optically-quiet symbiotic star population

Revelation of complex 3D geometries and shock phenomena in accretion flows

Unified evolution scheme connecting different symbiotic star types

Abstract

Any white dwarf or neutron star that accretes enough material from a red giant companion, such that this interaction can be detected at some wavelength, is currently termed Symbiotic Star (typical P(orb)=2-3 years). In the majority of ~400 known systems, the WD burns nuclearly at its surface the accreted material, and the resulting high temperature (T(eff)=10(^5)~K) and luminosity (L(hot)=10(^3)-10(^4) Lsun) allow ionization of a large fraction of the cool giant's wind, making such symbiotic stars easily recognizable through the whole Galaxy and across the Local Group. X-ray observations are now revealing the existence of a parallel (and larger ?) population of optically-quiet, accreting-only symbiotic stars. Accretion flows and disks, ionization fronts and shock, complex 3D geometries and new evolution channels are gaining relevance and are reshaping our understanding of symbiotic stars. We review the different types of symbiotic stars currently in the family and their variegated outburst behaviors through an unified evolution scheme connecting them all.