Colloquium on 7 April 2016
Active phases and flickering in symbiotic stars.


Title: Active phases and flickering in symbiotic stars.
Speaker: Krystian Ilkiewicz (Nicolaus Copernicus Astronomical Center)
Date: Thursday, 7 April 2016
Time: 11:00 - 12:00
Venue: SAAO Auditorium


Symbiotic stars are close binaries consisting of a late-type giant transferring material  to a much hotter compact companion. Some of them are known to  exhibit  active phases, characterized by apparent increases in the hot component temperature and appearance of flickering, i.e. changes of the observed flux on time-scale of minutes. Throughout the years UV observations allowed authors to excluded geometrical and orbitally related nature of this phenomenon, while indicating connection to a mass transfer variability. I present optical and X-ray observations of one of the symbiotic systems, T CrB, that helped determine the nature of both active phases and flickering in symbiotic stars.  In particular, the X-ray observations indicate that the flickering originates in the boundary zone between the accretion disc and the white dwarf. The X-ray radiation from the boundary zone is then reprocessed by thick accretion disc or a nebula into UV radiation.

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