Recent X-Recent X-ray observations of the symbiotic star AG Peg: do they signify Colliding Stellar Winds?

TL;DR

Recent X-ray observations of AG Peg reveal variability and spectral characteristics suggesting that colliding stellar winds are unlikely the primary X-ray emission mechanism, with accretion processes possibly playing a significant role.

Contribution

This study provides new X-ray observations and analysis indicating a shift from colliding stellar winds to accretion as the main X-ray emission process in AG Peg.

Findings

X-ray variability on days scale observed in 2015.

Spectral analysis confirms AG Peg as a class β X-ray source.

Evidence suggests accretion processes may dominate X-ray emission.

Abstract

We present an analysis of recent X-ray observations of the symbiotic star AG Peg. The X-ray emission of AG Peg as observed with Swift in 2015 shows considerable variability on time scale of days as variability on shorter time scales might be present as well. Analysis of the X-ray spectra obtained in 2013 and 2015 confirms that AG Peg is an X-ray source of class $\beta$ of the X-ray sources amongst the symbiotic stars. The X-ray emission of AG Peg as observed with ROSAT (1993 June) might well originate from colliding stellar winds (CSW) in binary system. On the other hand, the characteristics of the X-ray emission of AG Peg in 2013 and 2015 (Swift) are hard to accommodate in the framework of the CSW picture. Analysis of the light curves in 2015 shows that the power spectrum of the X-ray variability in AG Peg resembles that of the flicker noise (or flickering) being typical for accretion processes in astronomical objects. This is a sign that CSWs did not play a key role for the X-ray emission from AG Peg in 2013-2015 and a different mechanism (probably accretion) is also getting into play.