Z Cam stars: A particular response to a general phenomenon

We show that the disc instability model can reproduce all the observed properties of Z Cam stars if the energy equation includes heating of the outer disc by the mass-transfer stream impact and by tidal torques and if the mass-transfer rate from the secondary varies by about $30\%$ around the value...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2001-04, Vol.369 (3), p.925-931
Main Authors: Buat-Ménard, V., Hameury, J.-M., Lasota, J.-P.
Format: Article
Language:English
Subjects:
(stars:) binaries: close
(stars:) novae
accretion
accretion discs
Astrophysics
cataclysmic variables
Cosmology and Extra-Galactic Astrophysics
instabilities
Physics
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Summary:We show that the disc instability model can reproduce all the observed properties of Z Cam stars if the energy equation includes heating of the outer disc by the mass-transfer stream impact and by tidal torques and if the mass-transfer rate from the secondary varies by about $30\%$ around the value critical for stability. In particular the magnitude difference between outburst maxima and standstills corresponds to observations, all outbursts are of the inside-out type and can be divided into two classes: long (wide) and short (narrow) outbursts, as observed. Mass transfer rate fluctuations should occur in other dwarf novae but one can exclude variations similar to those observed in magnetic systems (AM Her's and some DQ Her's) and some nova-like systems (VY Scl's), in which $\dot{M}$ become very small during low states; these would produce mini-outbursts which, although detectable, have never been observed.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361:20010176