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Volume 315 - The Golden Age of Cataclysmic Variables and Related Objects IV (GOLDEN 2017) - Cataclysmic Variables
The long-term activity of dwarf novae and soft X-ray transients
V. Simon
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Pre-published on: 2018 May 23
Published on: 2018 September 13
Abstract
We show the activity of dwarf novae (DNe) and soft X-ray transients (SXTs) which were observed to undergo series of relatively frequent outbursts. The length of the recurrence time of these events, $T_{\rm C}$, is usually less than a year (at most about 4 years). We show that the energy output (e.g. fluence) sometimes largely differs even for the neighboring outbursts both of DNe and SXTs. This energy output is related to the fraction of the disk mass, accreted during an outburst, but this difference of the energy output does not influence the length of $T_{\rm C}$ in a given object. The length of $T_{\rm C}$ in a given DN or SXT is variable, but the occurrence of these outbursts is not dramatically irregular in most cases. The long-term trends can be clearly resolved in the O--C diagrams of $T_{\rm C}$ but they show only small epoch-to-epoch fluctuations. In DNe, the disk zone where the outburst starts can change even in a given binary for the individual outbursts. The decaying branch of the outburst is governed by propagation of cooling front and the observations show that this part of the light curve reproduces well for the ensemble of outbursts in a given DN. As for SXTs, the final phase of the decay in the 1.5--12\,keV band reproduces well for the individual outbursts while the preceding phase can vary for the individual events. We also show an analogy of the Z\,Cam-type behavior in an SXT (transitions between the segments of a hot thermally stable (in standstills) and unstable disk (outbursts)).
DOI: https://doi.org/10.22323/1.315.0035
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