We summarize the behavior of AG Dra during the last 25 years, characterized by a sequence of 5 active phases (with 14 light maxima). Cool and hot outbursts are discussed. In general, during bursts the X-ray flux weakens or vanishes, which should be mostly due to an increase of the high energy opacity of the envelope, rather than to a decrease of the source temperature. An explanation is suggested for the different behavior of the He II Zanstra temperature during the two burst types, and the possibility is considered that during all the burst events AG Dra first passes through a hot phase, and that only in the strongest bursts it evolves towards the cool burst phase.
THE NON-STANDARD MULTIFREQUENCY BEHAVIOUR OF AG DRACONIS / R. F., Viotti; M., Friedjung; R., Gonzalez; Riestra, ; T., Iijima; F., Montagni; Rossi, Corinne. - STAMPA. - 16:(2007), pp. 20-22. (Intervento presentato al convegno Evolution ancd Chemistry ox Symbiotic stars and related objects tenutosi a Wierzba ( PL) nel 22-26 agosto 2006).
THE NON-STANDARD MULTIFREQUENCY BEHAVIOUR OF AG DRACONIS
ROSSI, Corinne
2007
Abstract
We summarize the behavior of AG Dra during the last 25 years, characterized by a sequence of 5 active phases (with 14 light maxima). Cool and hot outbursts are discussed. In general, during bursts the X-ray flux weakens or vanishes, which should be mostly due to an increase of the high energy opacity of the envelope, rather than to a decrease of the source temperature. An explanation is suggested for the different behavior of the He II Zanstra temperature during the two burst types, and the possibility is considered that during all the burst events AG Dra first passes through a hot phase, and that only in the strongest bursts it evolves towards the cool burst phase.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
