7,802 research outputs found
The PROUST radar
The Stratosphere-Troposphere (ST) radar called PROUST works at 935 MHz using the same klystron and antenna as the coherent-scatter radar. The use of this equipment for ST work has required some important modifications of the transmitting system and the development of receiving, data processing and acquisition (1984,1985) equipment. The modifications are discussed
The PROUST radar: First results
Two campaigns took place in 1984 with the PROUST Radar operating in a bistatic mode, the transmitting antenna pointing at the vertical and the receiving one, 1 deg. off the vertical axis. The antenna beam intersection covers an altitude range between 3 and 9 km. The first of these campaigns are analyzed. The results analyzed show the capability of the PROUST Radar to measure the turbulent parameters and study the turbulence-wave interaction. In its present configuration (bistatic mode and 600 m vertical resolution), it has been necessary to make some assumptions that are known not to be truly fulfilled: homogeneous turbulence and constant vertical wind intensity over a 600-m thickness. It is clear that a more detailed study of the interaction between wave and turbulence will be possible with the next version of PROUST Radar (30-m altitude resolution and monostatic mode) that will soon be achieved
The optical-ultraviolet continuum of Seyfert 2 galaxies
This paper aims to understand the continuum of Seyfert 2 galaxies. By fitting
the single galaxies in the sample of Heckman et al. (1995) with composite
models (shock+ photoionization from the active center), we show that five main
components characterize the SED of the continuum. Shocks play an important role
since they produce a high temperature zone where soft X-rays are emitted.
We show that in the optical-UV range, the slope of the NLR emission
reproduces the observed values, and may be the main component of the
featureless continuum. The presence of star forming regions cannot be excluded
in the circumnuclear region of various Seyfert galaxies. An attempt is made to
find their fingerprints in the observed AGN spectra. Finally, it is
demonstrated that multi-cloud models are necessary to interpret the spectra of
single objects, even in the global investigation of a sample of galaxies.Comment: 26 pages, LaTeX (including 5 Tables) + 17 PostScript figures. To
appear in "The Astrophysical Journal
A Second Luminous Blue Variable in the Quintuplet Cluster
H and K band moderate resolution and 4 m high resolution spectra have
been obtained for FMM#362, a bright star in the Quintuplet Cluster near the
Galactic Center. The spectral features in these bands closely match those of
the Pistol Star, a luminous blue variable and one of the most luminous stars
known. The new spectra and previously-obtained photometry imply a very high
luminosity for FMM#362, L \Lsun, and a temperature of 10,000 -
13,000 K. Based on its luminosity, temperature, photometric variability, and
similarities to the Pistol Star, we conclude that FMM#362 is a luminous blue
variable.Comment: Accepted for publication in The Astrophysical Journal Letters, 4
PostScript figures, 2 table
Recent star formation in the inner Galactic Bulge seen by ISOGAL. I - Classification of bright mid-IR sources in a test field
Context: The stellar populations in the central region of the Galaxy are
poorly known because of the high visual extinction and very great source
density in this direction.
Aims: To use recent infrared surveys for studying the dusty stellar objects
in this region.
Methods: We analyse the content of a 20x20 arcmin^2 field centred at
(l,b)=(-0.27,-0.06) observed at 7 and 15 microns as part of the ISOGAL survey.
These ISO observations are more than an order of magnitude better in
sensitivity and spatial resolution than the IRAS observations. The sources are
cross-associated with other catalogues to identify various types of objects. We
then derive criteria to distinguish young objects from post-main sequence
stars.
Results: We find that a sample of about 50 young stellar objects and
ultra-compact HII regions emerges, out of a population of evolved AGB stars. We
demonstrate that the sources colours and spatial extents, as they appear in the
ISOGAL catalogue, possibly complemented with MSX photometry at 21 microns, can
be used to determine whether the ISOGAL sources brighter than 300 mJy at 15
microns (or [15] < 4.5 mag) are young objects or late-type evolved stars.Comment: 15 pages, 12 figures. Accepted for publication in Astronomy and
Astrophysic
As indicações geográficas como estratégia mercadológica para vinhos.
Este texto tem como objetivo principal analisar, em termos de estratégia mercadológica, as indicações geográficas (IGs) como instrumento de agregação de valor para o agronegócio brasileiro. Além de analisar a evolução do conceito de indicações geográficas no Brasil, na França e em outros países, este trabalho discute os aspectos mercadológicos desse mecanismo da propriedade intelectual. A fim de ilustrar e sustentar a discussão, apresentam-se os resultados de um estudo das IGs, levando-se em conta a percepção das vinícolas brasileiras e de um nicho do mercado consumidor de vinhos do Distrito Federal, Brasil. Neste estudo, foi observado que as IGs são um fator de diferenciação mercadológica nesse nicho de mercado e, também, uma característica relevante que agrega valor aos vinho s. No mínimo 57% dos consumidores pesquisados estariam dispostos a pagar mais por vinhos que possuíssem uma IG. Por sua vez, as vinícolas brasileiras estão cientes da importância mercadológica das IGs, já que 83% das empresas pesquisadas têm tomado iniciativa com esse propósito. Exceto em alguns casos, observou-se o quão distintas são as percepções dos atores da cadeia pesquisada em relação aos fatores mercadológicos estudados, principalmente sobre a IG. Por fim, são tecidas considerações a respeito das indicações geográficas como uma oportunidade de agregação de valor para o agronegócio brasileiro, sugerindo-se que a construção de uma estratégia mercadológica baseada nas indicações geográficas, tendo como público-alvo consumidores que buscam qualidade superior, pode ser comercialmente positiva para determinados produtores e regiões do agronegócio nacional
The Nature of the Nuclear H2O Masers of NGC 1068: Reverberation and Evidence for a Rotating Disk Geometry
We report new (1995) Very Large Array observations and (1984 - 1999)
Effelsberg 100m monitoring observations of the 22 GHz H2O maser spectrum of the
Seyfert 2 galaxy NGC 1068. The sensitive VLA observations provide a
registration of the 22 GHz continuum emission and the location of the maser
spots with an accuracy of ~ 5 mas. Within the monitoring data, we find evidence
that the nuclear masers vary coherently on time-scales of months to years, much
more rapidly than the dynamical time-scale. We argue that the nuclear masers
are responding in reverberation to a central power source, presumably the
central engine. Between October and November 1997, we detected a simultaneous
flare of the blue-shifted and red-shifted satellite maser lines. Reverberation
in a rotating disk naturally explains the simultaneous flaring. There is also
evidence that near-infrared emission from dust grains associated with the maser
disk also responds to the central engine. We present a model in which an X-ray
flare results in both the loss of maser signal in 1990 and the peak of the
near-infrared light curve in 1994. In support of a rotating disk geometry for
the nuclear masers, we find no evidence for centripetal accelerations of the
redshifted nuclear masers; the limits are +/- 0.006 km/s/year, implying that
the masers are located within 2 degrees of the kinematic line-of-nodes. We also
searched for high velocity maser emission like that observed in NGC 4258. In
both VLA and Effelsberg spectra, we detect no high velocity lines between +/-
350 km/s to +/- 850 km/s relative to systemic, arguing that masers only lie
outside a radius of ~ 0.6 pc (1.9 light years) from the central engine
(assuming a distance of 14.4 Mpc).Comment: 62 pages, 19 figure
Stellar sources in the ISOGAL intermediate bulge fields
We present a study of ISOGAL sources in the "intermediate" galactic bulge
( 2, 1--4), observed by
ISOCAM at 7 and 15 . In combination with near-infrared (I, J, K) data of DENIS survey, complemented by 2MASS data, we discuss the nature of
the ISOGAL sources, their luminosities, the interstellar extinction and the
mass-loss rates. A large fraction of the 1464 detected sources at 15
are AGB stars above the RGB tip, a number of them show an excess in
([7]-[15]) and (K-[15]) colours, characteristic
of mass-loss. The latter, especially (K-[15]), provide
estimates of the mass-loss rates and show their distribution in the range
10 to 10 M/yr.Comment: 16 pages, accepted for publication in Astronomy and Astrophysic
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