85,923 research outputs found
The faint 2005 hard state outburst of Aquila X-1 seen by INTEGRAL and RXTE
We report on the spectral analysis of RXTE and INTEGRAL data of the 2005
April outburst of the transient Atoll source Aql X-1. Although this outburst is
one of the faintest ever detected for this source in the soft X-rays
(RXTE/ASM), one of our INTEGRAL observations, taken close to the soft X-ray
peak, shows that the source flux was quite high, with a 20-200 keV flux of 2.05
x 10^-9 erg cm^-2 s^-1. On this occasion we detect the source up to 150 keV for
the first time. We compare and discuss the similarity of the source behavior
with that of black hole transients especially XTE J1550-564.Comment: 4 pages 2 figures, Accepted for publication in A&A as a RESEARCH NOT
Hidden starburst in Seyfert 1 Galaxies
We report the detection of the 3.3 mu Polycyclic Aromatic Hydrocarbon (PAH)
feature in two Seyfert 1 galaxies - NGC 3227 and Mrk 766, and one QSO - Mrk
478, observed with SpeX at IRTF at a spectral resolution not previously
attained for this type of objects. Except for NGC 3227, this is the first time
that the 3.3 mu PAH emission is detected in Mrk 766 and Mrk 478. The widths of
the emission, reported also for the first time, are rather similar, ranging
from 450 A to 550 A. The luminosity of the 3.3 mu PAH emission measured in the
QSO Mrk 478 places it at a level similar of that found in starburst and
infrared luminous galaxies and implies that this object is having a vigorous
burst of star formation. The spatial resolution of the spectra allows us to
constrain the location of the star-forming region to the inner 1 Kpc for the
QSO and 150 pc for the Seyferts. Our results support the idea that these
objects resides in molecular gas-rich galaxies and that their observed infrared
excess is primarily due to star formation, as previously indicated by CO and
H_2 observations. We also report, for Mrk 1239, the presence of a broad
emission feature centred at 3.43 mu, not previosly detected in an extragalactic
object and whose origin is not yet clear.Comment: 5 pages, 1 figure. Accepted to MNRAS pink page
Double fluctuations on the attractive Hubbard model: ladder approximation
We explore, for the first time, the effect of double fluctuations on both the
diagonal and off-diagonal self-energy. We use the T-Matrix equations below
, developed recently by the Z\"urich group (M.H. Pedersen et al) for the
local pair attraction Hamiltonian. Here, we include as well the effect of
fluctuations on the order parameter (beyond the BCS solution) up to second
order in . This is equivalent to approximating the effective interaction
by in the off-diagonal self-energy. For , , and , we find four peaks both for the diagonal,
, and off-diagonal, ,
spectral functions. These peaks are not symmetric in pairs as previously found.
In addition: (a) in , the far left peak has a
vanishing small weight; (b) in the far left and
far right peaks have very small weights. The physical picture is, then, that
the pair physics in the normal phase () is still valid below .
However, the condensation of the e-h pairs produces an additional gap around
the chemical potential as in BCS, in other words, superconductivity opens a gap
in the lower branch of a Hubbard-type-I solution.Comment: LaTeX, 7 pages. 8 figures available on request. To appear in Z.
Physik
Nature of Decoupling in the Mixed Phase of Extremely Type-II Layered Superconductors
The uniformly frustrated layered XY model is analyzed in its Villain form. A
decouple pancake vortex liquid phase is identified. It is bounded by both
first-order and second-order decoupling lines in the magnetic field versus
temperature plane. These transitions, respectively, can account for the
flux-lattice melting and for the flux-lattice depinning observed in the mixed
phase of clean high-temperature superconductors.Comment: 11 pages of PLAIN TeX, 1 postscript figure, published version, many
change
Use of Multiple Methods: An Examination of Constraints Effecting Ethnic Minority Visitor Use of National Parks and Management Implications
Understanding outdoor recreation participation and national park visitation by members of ethnic minority groups has been a particular focus of outdoor recreation researchers for the past twenty years. Attracting ethnic minorities, and understanding their recreation needs and interests, demands a multi-faceted approach and sustained commitment not only by the U.S. National Park Service (NPS) but by other resource management agencies as well
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