7,999 research outputs found
Soft-excess in ULX spectra: disc emission or wind absorption?
We assess the claim that Ultra-luminous X-ray sources (ULXs) host
intermediate-mass black holes (BH) by comparing the cool disc-blackbody model
with a range of other models, namelly a more complex physical model based on a
power-law component slightly modified at various energies by smeared
emission/absorption lines from highly-ionized gas. Our main conclusion is that
the presence of a soft excess, or a soft deficit, depends entirely on the
energy range to which we choose to fit the ``true'' power-law continuum; hence,
we argue that those components should not be taken as evidence for accretion
disc emission, nor used to infer BH masses. We speculate that bright ULXs could
be in a spectral state similar to (or an extension of) the steep-power-law
state of Galactic BH candidates, in which the disc is completely comptonized
and not directly detectable, and the power-law emission may be modified by the
surrounding, fast-moving, ionized gas.Comment: To appear in the proceedings of "The Multicoloured Landscape of
Compact Objects and their Explosive Progenitors: Theory vs. Observations",
Cefalu', Sicily, June 11-24, 2006 (AIP). Compilation needs specific AIP .clo,
.cls, .sty and .tex files (included along with the paper .tex file and
figures
Information-entropic analysis of Korteweg--de Vries solitons in the quark-gluon plasma
Solitary waves propagation of baryonic density perturbations, ruled by the
Korteweg--de Vries equation in a mean-field quark-gluon plasma model, are
investigated from the point of view of the theory of information. A recently
proposed continuous logarithmic measure of information, called configurational
entropy, is used to derive the soliton width, defining the pulse, for which the
informational content of the soliton spatial profile is more compressed, in the
Shannon's sense.Comment: 6 pages, 1 figur
Does magnetic pressure affect the ICM dynamics?
A possible discrepancy found in the determination of mass from gravitational
lensing data, and from X-rays observations, has been largely discussed in the
latest years (for instance, Miralda-Escude & Babul (1995)). Another important
discrepancy related to these data is that the dark matter is more centrally
condensed than the X-ray-emitting gas, and also with respect to the galaxy
distribution (Eyles et al. 1991). Could these discrepancies be consequence of
the standard description of the ICM, in which it is assumed hydrostatic
equilibrium maintained by thermal pressure? We follow the evolution of the ICM,
considering a term of magnetic pressure, aiming at answering the question
whether or not these discrepancies can be explained via non-thermal terms of
pressure. Our results suggest that the magnetic pressure could only affect the
dynamics of the ICM on scales as small as < 1kpc. Our models are constrained by
the observations of large and small scale fields and we are successful at
reproducing available data, for both Faraday rotation limits and inverse
Compton limits for the magnetic fields. In our calculations the radius (from
the cluster center) in which magnetic pressure reaches equipartition is smaller
than radii derived in previous works, as a consequence of the more realistic
treatment of the magnetic field geometry and the consideration of a sink term
in the cooling flow.Comment: 8 pages with 7 figures included. MNRAS accepted. Minor changes in the
section of discussions and conclusions. Also available at
http://www.iac.es/publicaciones/preprints.htm
Properties improvement of poly(o-methoxyaniline) based supercapacitors : experimental and theoretical behaviour study of self-doping effect
The support of this research by FAPESP (2011/10897-2, 2013/07296-2), CsF-PVE (99999.007708/2015-07), CAPES and CNPq is gratefully acknowledged. We also thank the University of Aberdeen for providing computational time on MaxwellPeer reviewedPostprin
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