Issue |
A&A
Volume 422, Number 3, August II 2004
|
|
---|---|---|
Page(s) | 1039 - 1043 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20040402 | |
Published online | 16 July 2004 |
The absence of jets in cataclysmic variable stars *
1
Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel e-mail: soker@physics.technion.ac.il
2
Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France e-mail: lasota@iap.fr
Received:
7
March
2004
Accepted:
20
April
2004
We show that the recently developed thermal model which
successfully describes how jets are launched by young stellar
objects, when applied to system containing disk-accreting white
dwarfs naturally explain the otherwise surprising absence of jets
in cataclysmic variable stars. Our main argument uses the crucial
element of the thermal model, namely that the accreted material is
strongly shocked due to large gradients of physical quantities in
the boundary layer, and then cools on a time scale longer than its
ejection time from the disk. In our scenario the magnetic fields
are weak, and serve only to recollimate the outflow at large
distances from the source, or to initiate the shock, but not as a
jet-driving agent. Using two criteria in that model, for the shock
formation and for the ejection of mass, we find the mass accretion
rate above which jets could be blown from accretion disks around
young stellar objects and white dwarfs. We find that these
accretion mass rates are and
for young stellar objects and white dwarfs respectively.
Considering the uncertainties of the model, these limits could
overestimate the critical value by a factor of ∼10.
Key words: accretion, accretion disks / ISM: jets and outflows / stars: winds, outflows / stars: novae, cataclysmic variables
© ESO, 2004
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