Formation of a disk structure in the symbiotic binary AX Per during its 2007-10 precursor-type activity

TL;DR

This paper investigates the formation of a disk structure in the symbiotic binary AX Per during its 2007-10 active phase, revealing a connection between enhanced stellar wind and disk formation.

Contribution

It introduces the discovery of a warm, flared disk forming around the hot star during activity, linked to increased stellar wind, a novel insight into symbiotic star behavior.

Findings

Formation of a warm, flared disk during active phase

Enhanced hot star wind correlates with disk formation

Presence of a neutral, disk-like zone around the accretor

Abstract

AX Per is an eclipsing symbiotic binary. During active phases, deep narrow minima are observed in its light curve, and the ionization structure in the binary changes significantly. From 2007.5, AX Per entered a new active phase. It was connected with a significant enhancement of the hot star wind. Simultaneously, we identified a variable optically thick warm (Teff ~ 6000 K) source that contributes markedly to the composite spectrum. The source was located at the hot star's equator and has the form of a flared disk, whose outer rim simulates the warm photosphere. The formation of the neutral disk-like zone around the accretor during the active phase was connected with its enhanced wind. We suggested that this connection represents a common origin of the warm pseudophotospheres that are indicated during the active phases of symbiotic stars.