The absence of jets in cataclysmic variable stars

Abstract

Abstract. 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 arė M(YSO) > ∼ 10 −7 M yr −1 andṀ(WD) > ∼ 10 −6 M yr −1 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.

A Transient Radio Jet in an Erupting Dwarf Nova

“…In this case the jet emission of SS Cyg, especially during the optical plateau, may correspond to the highest accreting states in XRBs and not to the hard state. For such high accretion rates jet launching for CVs has been suggested by (5).…”

Effects of a solid surface on jet formation around neutron stars

“…These are created by an overestimated density inside the rotating torus. Further simulations need to show whether this scenario still works at lower rates and will have to fix the value of a critical accretion rate, as stated in the analytic model by Soker & Lasota (2004).…”

Cataclysmic variables: New frontiers in multi-wavelength research

“…However, evidence of collimated jets in CVs have until recently been notoriously elusive (e.g. [21]). Triple Hα emission lines have been observed in the RN T Pyx, but this source is similar to SSSs in the sense that hydrogen burning is still taking place on the WD surface as part of a slow nova outburst, even though its accretion rate is lower than in SSSs [22].…”