The peculiar outburst activity of the symbiotic binary AG Draconis

TL;DR

AG Draconis exhibits unusual hot outburst activity after a long quiescent period, with recent minor outbursts differing from typical behavior, providing new insights into its complex symbiotic interactions.

Contribution

This study documents the unprecedented hot outburst activity of AG Dra after a prolonged quiescence, highlighting its peculiarity compared to historical behavior.

Findings

Recent outbursts are of hot type, unlike typical cool outbursts.

AG Dra's activity pattern is unusual in its 130-year observational history.

The system shows a series of minor outbursts following a long flat quiescent phase.

Abstract

AG Draconis is a strongly interacting binary system which manifests characteristic symbiotic activity of alternating quiescent and active stages. The latter ones consist of the series of individual outbursts repeating at about a one-year interval. After seven years of flat quiescence following the 2006-2008 major outbursts, in the late spring of 2015, the symbiotic system AG Dra started to become brighter again toward what appeared to be a new minor outburst. The current outburst activity of AG Dra was confirmed by the following three outbursts in April 2016, May 2017 and April 2018. The photometric and spectroscopic observations suggest that all these outbursts are of the hot type. Such behaviour is considerably peculiar in almost 130-year history of observing of this object, because the major outbursts at the beginning of active stages are typically cool ones. In the present work, the current peculiar activity of the symbiotic binary AG Dra is described in detail.