Creation of neutral disks during outbursts of symbiotic binaries

TL;DR

This study models how enhanced stellar winds and rapid rotation during active phases of symbiotic binaries lead to the formation of transient neutral, disk-like zones around the hot star, explaining observed spectral features.

Contribution

It applies the wind compression model to symbiotic binaries to demonstrate the formation of neutral disks during active phases, a novel explanation for spectral observations.

Findings

Neutral disks form during active phases due to wind compression and rotation.

Such disks are transient and disappear during quiescent phases.

Enhanced wind mass loss rates are crucial for disk formation.

Abstract

Multiwavelength modelling of the spectral energy distribution of symbiotic binaries suggests that a neutral disk-like zone is created around the hot star near the orbital plane during active phases. Presumably, this is connected with the enhanced wind from the active hot star. To test this idea, we applied the wind compression model to active hot stars in symbiotic binaries, within which the wind particles are compressed more to the equatorial plane due to a fast rotation of the hot star. Accordingly, we calculated the ionization structure for such compressed wind and ionizing photons from the hot star. We found that the hot star wind, enhanced during active phases to \sim (10^-7 - 10^-6) M_sun yr^-1, and the rotational velocity of 100 - 350 km s^-1 at the star's equator lead to formation of a neutral disk-shaped zone. The presence of such disks is transient, being connected with the active phases of symbiotic binaries. During quiescent phases, such neutral disks cannot be created, because of insufficient mass loss rate.