The Influence of the Accretion Disc Structure on X-ray Spectral States in Symbiotic Binaries

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Main Authors: Toalá, Jesús A., Vasquez-Torres, Diego A.
Format: Preprint
Published: 2025
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author Toalá, Jesús A.
Vasquez-Torres, Diego A.
author_facet Toalá, Jesús A.
Vasquez-Torres, Diego A.
contents Symbiotic stars are binary systems where a white dwarf (WD) accretes material from the wind of an evolved, late-type companion. X-ray-emitting symbiotic systems are classified into $α$, $β$, $δ$, and $β/δ$ types, attributed to distinct physical mechanisms such as thermonuclear burning, wind interactions, and accretion-driven boundary layers. We present synthetic X-ray spectra derived from hydrodynamics simulations using the PHANTOM code, coupled with radiative-transfer calculations from SKIRT. We reproduce all X-ray spectral types by exploring different density structure of the accretion disc, the viewing angle, the plasma temperature of the boundary layer, and/or the presence of extended emission. The synthetic X-ray spectra consist of both absorbed and reflected components. In systems with massive, high-column density discs and viewing angles close to edge-on, the reflected continuum can dominate the X-ray emission. This effect is less pronounced in systems with low-mass, lower-column density discs. We explore i) systems going from $δ$ to $β$ states, ii) $δ$-types that become $β/δ$ sources, iii) the variability of the three Fe emission lines in the 6.0-7.0 energy range, and iv) the possible physical processes behind the $α$ sources. The observations from iconic symbiotic systems are discussed in line of the present models. Our framework offers predictive power for future X-ray monitoring and provides a path toward connecting accretion disc physics with observed spectral states in symbiotic binaries with accreting WDs.
format Preprint
id arxiv_https___arxiv_org_abs_2510_12654
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Influence of the Accretion Disc Structure on X-ray Spectral States in Symbiotic Binaries
Toalá, Jesús A.
Vasquez-Torres, Diego A.
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
Symbiotic stars are binary systems where a white dwarf (WD) accretes material from the wind of an evolved, late-type companion. X-ray-emitting symbiotic systems are classified into $α$, $β$, $δ$, and $β/δ$ types, attributed to distinct physical mechanisms such as thermonuclear burning, wind interactions, and accretion-driven boundary layers. We present synthetic X-ray spectra derived from hydrodynamics simulations using the PHANTOM code, coupled with radiative-transfer calculations from SKIRT. We reproduce all X-ray spectral types by exploring different density structure of the accretion disc, the viewing angle, the plasma temperature of the boundary layer, and/or the presence of extended emission. The synthetic X-ray spectra consist of both absorbed and reflected components. In systems with massive, high-column density discs and viewing angles close to edge-on, the reflected continuum can dominate the X-ray emission. This effect is less pronounced in systems with low-mass, lower-column density discs. We explore i) systems going from $δ$ to $β$ states, ii) $δ$-types that become $β/δ$ sources, iii) the variability of the three Fe emission lines in the 6.0-7.0 energy range, and iv) the possible physical processes behind the $α$ sources. The observations from iconic symbiotic systems are discussed in line of the present models. Our framework offers predictive power for future X-ray monitoring and provides a path toward connecting accretion disc physics with observed spectral states in symbiotic binaries with accreting WDs.
title The Influence of the Accretion Disc Structure on X-ray Spectral States in Symbiotic Binaries
topic High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2510.12654