E. Trussoni

Acceleration by synchrotron absorption and superluminal sources

A magnetized blob, containing relativistic electrons, can absorb, by the synchrotron process, low-frequency photons emitted by an underlying source. The momentum of the adsorbed photons can accelerate the blob to relativistic velocities. The final bulk Lorentz factor can be as large as required by observations of superluminal sources even if only the low-frequency part of the spectrum of a sub-Eddington central source is used for the acceleration process, and even if the blob contains an equal number of protons and electrons. This is mainly due to the large absorption cross section of the synchrotron process with respect to the electron scattering cross section, but partly because strongly aberrated photons are seen blueshifted in the rest frame of the blob and are less efficiently absorbed, reducing the importance of the braking force due to the radiation drag. 12 refs.

Kelvin–Helmholtz instabilities in radiating flows

The linear Kelvin–Helmholtz stability regime of two radiating fluids in relative motion is discussed. The study is carried out in plane geometry and in the vortex‐sheet approximation. Attention is focused on the effects of radiation losses on the instability pattern: it is found that the principal effect is the suppression of the cutoff at Mach number M=2√2, typical of the adiabatic Kelvin–Helmholtz mode; in particular radiation effects are small on the instability below the cutoff, while they become dominant above. Radiating fluids are also typically affected by thermal instability. In fact thermal modes are found also in the present case: they may have growth rates comparable to the Kelvin–Helmholtz instability above the cutoff.

BeppoSAX observation of Hercules A and MRC 0625-536

We present BeppoSAX observations of the two FR I type radio galaxies Hercules A (3C 348) and MRC 0625-536 in the energy range 0.2-200 keV. Data analysis shows that the X-ray flux from Hercules A is consistent with a diffuse thermal plasma emitting at

Radiative acceleration by synchrotron sources

T \approx 4

X-ray emission from galactic jets

-5 keV with a possible, but somewhat uncertain, contribution of a softer component at

Numerical simulations of supersonic directed flows in astrophysical plasmas

T \approx 3

BeppoSAX observations of low power radio galaxies: possible detection of obscured nuclei

keV. The non thermal emission from the active nucleus must be significantly smaller than the thermal one, and no indication of relevant core obscuration by a surrounding torus was detected. The flux from MRC 0625-536 originates from an extended region and has been fitted to a thermal law with

A kinematical study of R aquarii jet features

T \approx 5.7

Nonlinear Evolution of KH Instabilities in Stellar Jets and the Formation of Knots

keV and with a column density consistent with the galactic absorption. A spatially resolved spectral analysis does not show a relevant variation of the temperature and of the metallicity across the diffuse emission zone. A non thermal spectral component, related to the nuclear activity, may be present in the innermost region with some possible amount of local obscuration, contributing

Synchrotron Thermal Instabilities and Radio Filaments in the Lobes of Cygnus A

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