7,713 research outputs found
Impact of the inelastic proton -- nucleus cross section on the prompt neutrino flux
The description of the inelastic proton -- nucleus cross section at very high
energies is still an open question. The current theoretical uncertainty has
direct impact on the predictions of the cosmic ray and neutrino physics
observables. In this paper we consider different models for the treatment of
, compare its predictions at ultrahigh cosmic ray energies
and estimate the prompt neutrino flux at the neutrino energies that have been
probed by the IceCube Observatory. We demonstrate that depending of the model
used to describe , the predictions for the prompt neutrino
flux can differ by a factor of order of three. Such result demonstrate the
importance of a precise measurement of the inelastic proton -- nucleus cross
section at high energies.Comment: 5 pages, 3 figures; v2: corrected the range of horizontal axis in
figure 1. Matches the version published in Eur. Phys. J.
Phase diagram of random lattice gases in the annealed limit
An analysis of the random lattice gas in the annealed limit is presented. The
statistical mechanics of disordered lattice systems is briefly reviewed. For
the case of the lattice gas with an arbitrary uniform interaction potential and
random short-range interactions the annealed limit is discussed in detail. By
identifying and extracting an entropy of mixing term, a correct physical
expression for the pressure is explicitly given. As an application, the
one-dimensional lattice gas with uniform long-range interactions and random
short-range interactions satisfying a bimodal annealed probability distribution
is discussed. The model is exactly solved and is shown to present interesting
behavior in the presence of competition between interactions, such as the
presence of three phase transitions at constant temperature and the occurrence
of triple and quadruple points.Comment: Final version to be published in the Journal of Chemical Physic
The "red shelf" of the Hb line in the Seyfert 1 galaxies RXS J01177+3637 and HS 0328+05
A few Seyfert 1s have a Hb profile with a red wing usually called the "red
shelf". The most popular interpretation of this feature is that it is due to
broad redshifted lines of Hb and [OIII]4959,5007; we have observed two Seyfert
1s displaying a "red shelf" and showed that in these two objects the main
contributor is most probably the HeI 4922,5016 lines having the velocity and
width of the broad Hb component. There is no evidence for the presence of a
broad redshifted component of Hb or [OIII] in any of these two objects.Comment: LaTeX file (uses AA vers. 5.1 class, enclosed), 8 pages, 9 figures.
Accepted for publication in Astronomy & Astrophysics. Also available at
http://www.obs-hp.fr/www/preprints.htm
The improved nuclear parton distributions
In this paper we propose an improvement of the EKS nuclear parton
distributions for the small x region of high energy processes, where the
perturbative high parton density effects cannot be disregarded. We analyze the
behavior of the ratios and and verify that at small x
they are strongly modified when compared to the EKS predictions. The
implications of our results for the heavy ion collisions in RHIC and LHC are
discussed.Comment: 16 pages, 2 figure
Miscellaneous observations of active galactic nuclei. II
We observed 37 AGN candidates and classified them on the basis of their
spectroscopic properties; three are confirmed QSOs, one is a BL Lac object,
nine are Seyfert 1 galaxies, four Seyfert 2s, while twenty are HII regions.Comment: LaTeX 2e, 15 pages (4 tables and 9 .eps figures included in text).
Uses L-AA 3.0, epsf.tex and psfig.sty (not included). Accepted to appear in
A&
A spectrophotometric atlas of Narrow-Line Seyfert 1 galaxies
We have compiled a list of 83 objects classified as Narrow-Line Seyfert 1
galaxies (NLS1s) or known to have a broad Balmer component narrower than 2000
km/s. Out of these, 19 turned out to have been spectroscopically misidentified
in previous studies; only 64 of the selected objects are genuine NLS1s. We have
spectroscopically observed 59 of them and tried to characterize their Narrow
and Broad-Line Regions (NLR and BLR) by fitting the emission-lines with
Gaussian and/or Lorentzian profiles. In most cases, the broad Balmer components
are well fitted by a single Lorentzian profile. This has consequences
concerning their FWHMs and line ratios: when the broad Balmer components are
fitted with a Lorentzian, most narrow line regions have line ratios typical of
Seyfert 2s while, when a Gaussian profile isused for fitting the broad Balmer
components, the line ratios are widely scattered in the usual diagnostic
diagrams (Veilleux & Osterbrock 1987). We find that, in general, the [O III]
lines have a relatively narrow Gaussian profile (~ 200-500 km/s FWHM) with
often, in addition, a second broad (~ 500-1800 km/s FWHM), blueshifted Gaussian
component. We do not confirm that the [O III] lines are weak in NLS1s. As
previously suggested, there is a continuous transition of all properties
between NLS1s and classical Broad-Line Seyfert 1 Galaxies (BLS1s) and the limit
of 2000 km/s used to separate the two species is arbitrary; R_4570, the ratio
of the Fe II to the H_beta fluxes, could be a physically more meaningful
parameter to distinguish them. (abridged abstract)Comment: LaTeX file, 24 pages, 15 figures, uses the new A&A macro (enclosed:
aa5.cls). Figs. 1-5 and 7 are bitmapped; non-bitmapped, high quality figures
are included in the .ps and .pdf versions of the paper, available at
http://www.obs-hp.fr/www/preprints.html. Accepted for publication in
Astronomy & Astrophysic
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