9,913 research outputs found
Simulations of the relativistic parsec-scale jet in 3C273
We present a hydrodynamical 3D simulation of the relativistic jet in 3C273,
in comparison to previous linear perturbation analysis of Kelvin-Helmholtz
instability developing in the jet. Our aim is to assess advantages and
limitations of both analytical and numerical approaches and to identify spatial
and temporal scales on which the linear regime of Kelvin-Helmholtz instability
can be applied in studies of morphology and kinematics of parsec-scale jets.Comment: 4 pages, 3 figures; to be published in Proceedings of the workshop
"Multiband Approach to AGN", held on Sep.30-Oct.2 in Bonn. Publication:
Memorie della Societa Astronomica Italiana, v. 26, No.1 (2005). Reduced
figure resolution! Version with original figures is availavble at
http://www.mpifr-bonn.mpg.de/bonn04/proceedings/perucho.pd
Orbital X-Ray Variability of the Microquasar LS 5039
The properties of the orbit and the donor star in the high mass X-ray binary
microquasar LS 5039 indicate that accretion processes should mainly occur via a
radiatively driven wind. In such a scenario, significant X-ray variability
would be expected due to the eccentricity of the orbit. The source has been
observed at X-rays by several missions, although with a poor coverage that
prevents to reach any conclusion about orbital variability. Therefore, we
conducted RossiXTE observations of the microquasar system LS 5039 covering a
full orbital period of 4 days. Individual observations are well fitted with an
absorbed power-law plus a Gaussian at 6.7 keV, to account for iron line
emission that is probably a diffuse background feature. In addition, we have
taken into account that the continuum is also affected by significant diffuse
background contamination. Our results show moderate power-law flux variations
on timescales of days, as well as the presence of miniflares on shorter
timescales. The new orbital ephemeris of the system recently obtained by
Casares et al. have allowed us to show, for the first time, that an increase of
emission is seen close to the periastron passage, as expected in an accretion
scenario. Moreover, the detected orbital variability is a factor of ~4 smaller
than the one expected by using a simple wind accretion model, and we suggest
that an accretion disk around the compact object could be responsible for this
discrepancy. On the other hand, significant changes in the photon index are
also observed clearly anti-correlated with the flux variations. We interpret
the overall X-ray spectral characteristics of LS 5039 in the context of X-ray
radiation produced by inverse Compton and/or synchrotron processes in the jet
of this microquasar.Comment: published in Astrophysical Journal, submission format (real number of
pages: 7, 4 figures
Experimental results on adiabatic coupling into SOI photonic crystal coupled-cavity waveguides
Agire nello Spirito. Sullâesperienza morale della vita spirituale. [Reseña]
Reseña de Paolo MIRABELLA, Agire nello Spirito.
Sullâesperienza morale della vita spirituale,
Cittadella Editrice («Questioni di
etica teologica»), Assisi 2003, 232 pp.,
15 x 21, ISBN 88-308-0757-5
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