Spectroscopic view on the outburst activity of the symbiotic binary AG Draconis

Abstract

Variations of the emission lines in the spectrum of the yellow symbiotic star AG Dra have been studied for over 14 years (1997 - 2011), using more than 500 spectra obtained on the 1.5-metre telescope at Tartu Observatory, Estonia. The time interval covered includes the major (cool) outburst of AG Dra that started in 2006. Main findings can be summarized as follows: (i) cool and hot outbursts of AG Dra can be distinguished from the variations of optical emission lines; (ii) the Raman scattered emission line of O VI at $\lambda 6825$ almost disappeared during the cool outburst; (iii) lower excitation emission lines did not change significantly during the cool outburst, but they vary in hot outbursts and also follow orbital motion; (iv) similarity of variations in AG Dra to those in the prototypical symbiotic star Z And allows to suggest that a "combination nova" model proposed for the latter object might also be responsible for the outburst behaviour of AG Dra.

Accepted to MNRAS

References in corpus (7)

• Recent photometry of symbiotic stars - XII
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• Discovery of true, likely and possible symbiotic stars in the dwarf spheroidal NGC 205
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• Raman Scattered Ne VII$\lambda$973 at 4881 Å in the Symbiotic Star V1016 Cygni
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• DeGaPe 35: Amateur discovery of a new southern symbiotic star
• Stellar Wind Accretion and Raman Scattered O VI Features in the Symbiotic Star AG Draconis
• A Monte Carlo Study of Flux Ratios of Raman Scattered O~VI Features at 6825 Å and 7082 Å in Symbiotic Stars
• The emergence of a neutral wind region in the orbital plane of symbiotic binaries during their outbursts
• Spectrum of the Yellow Symbiotic Star LT Delphini before, during, and after the 2017 Outburst
• Photometry of Symbiotic Stars - XIV