77 research outputs found
Observer la transition Ă©nergĂ©tique « par le bas »: Lâexemple des acteurs du bassin minier de Provence
Cette contribution a Ă©galement mobilisĂ© Hubert Amarillo (LEST, Aix-Marseille UniversitĂ©-CNRS), Nassim Amrouche (IDEMEC, Aix-Marseille universitĂ©-CNRS) et Yaya BassĂšne (TELEMME, Aix-Marseille UniversitĂ©-CNRS).International audienceSâappuyant sur une recherche menĂ©e dans lâancien bassin minier de Provence, une Ă©quipe de chercheurs aborde lâenjeu de la transition Ă©nergĂ©tique par le prisme des acteurs ordinaires. Ils montrent le rĂŽle jouĂ© dans ce processus par les PME et les mĂ©nages, mais aussi par les collectivitĂ©s locales et les travailleurs du secteur de lâĂ©nergie
Mid-infrared Period-Luminosity Relations of RR Lyrae Stars Derived from the WISE Preliminary Data Release
Interstellar dust presents a significant challenge to extending
parallax-determined distances of optically observed pulsational variables to
larger volumes. Distance ladder work at mid-infrared wavebands, where dust
effects are negligible and metallicity correlations are minimized, have been
largely focused on few-epoch Cepheid studies. Here we present the first
determination of mid-infrared period-luminosity (PL) relations of RR Lyrae
stars from phase-resolved imaging using the preliminary data release of the
Wide-Field Infrared Survey Explorer (WISE). We present a novel statistical
framework to predict posterior distances of 76 well-observed RR Lyrae that uses
the optically constructed prior distance moduli while simultaneously imposing a
power-law PL relation to WISE-determined mean magnitudes. We find that the
absolute magnitude in the bluest WISE filter is M_W1 = (-0.421+-0.014) -
(1.681+-0.147)*log(P/0.50118 day), with no evidence for a correlation with
metallicity. Combining the results from the three bluest WISE filters, we find
that a typical star in our sample has a distance measurement uncertainty of
0.97% (statistical) plus 1.17% (systematic). We do not fundamentalize the
periods of RRc stars to improve their fit to the relations. Taking the
Hipparcos-derived mean V-band magnitudes, we use the distance posteriors to
determine a new optical metallicity-luminosity relation which we present in
Section 5. The results of this analysis will soon be tested by HST parallax
measurements and, eventually, with the Gaia astrometric mission.Comment: 33 pages, 12 figures, 2 tables. Accepted for publication in ApJ, June
27th, 201
A Bayesian Approach to Calibrating Period-Luminosity Relations of RR Lyrae Stars in the Mid-Infrared
A Bayesian approach to calibrating period-luminosity (PL) relations has
substantial benefits over generic least-squares fits. In particular, the
Bayesian approach takes into account the full prior distribution of the model
parameters, such as the a priori distances, and refits these parameters as part
of the process of settling on the most highly-constrained final fit.
Additionally, the Bayesian approach can naturally ingest data from multiple
wavebands and simultaneously fit the parameters of PL relations for each
waveband in a procedure that constrains the parameter posterior distributions
so as to minimize the scatter of the final fits appropriately in all wavebands.
Here we describe the generalized approach to Bayesian model fitting and then
specialize to a detailed description of applying Bayesian linear model fitting
to the mid-infrared PL relations of RR Lyrae variable stars. For this example
application we quantify the improvement afforded by using a Bayesian model fit.
We also compare distances previously predicted in our example application to
recently published parallax distances measured with the Hubble Space Telescope
and find their agreement to be a vindication of our methodology. Our intent
with this article is to spread awareness of the benefits and applicability of
this Bayesian approach and encourage future PL relation investigations to
consider employing this powerful analysis method.Comment: 6 pages, 1 figure. Accepted for publication in Astrophysics & Space
Science. Following a presentation at the conference The Fundamental Cosmic
Distance Scale: State of the Art and the Gaia Perspective, Naples, May 201
Author Correction: A consensus-based transparency checklist.
An amendment to this paper has been published and can be accessed via a link at the top of the paper
Status and Prospects of Top-Quark Physics
The top quark is the heaviest elementary particle observed to date. Its large
mass of about 173 GeV/c^2 makes the top quark act differently than other
elementary fermions, as it decays before it hadronises, passing its spin
information on to its decay products. In addition, the top quark plays an
important role in higher-order loop corrections to standard model processes,
which makes the top quark mass a crucial parameter for precision tests of the
electroweak theory. The top quark is also a powerful probe for new phenomena
beyond the standard model. During the time of discovery at the Tevatron in 1995
only a few properties of the top quark could be measured. In recent years,
since the start of Tevatron Run II, the field of top-quark physics has changed
and entered a precision era. This report summarises the latest measurements and
studies of top-quark properties and gives prospects for future measurements at
the Large Hadron Collider (LHC).Comment: 76 pages, 35 figures, submitted to Progress in Particle and Nuclear
Physic
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
A consensus-based transparency checklist
We present a consensus-based checklist to improve and document the transparency of research reports in social and behavioural research. An accompanying online application allows users to complete the form and generate a report that they can submit with their manuscript or post to a public repository
Les Conseillers info énergie : petites mains incertaines des politiques énergétiques françaises
International audienceCet article examine la diffusion de lâ« Ă©conomie verte » Ă partir du mĂ©tier de Conseillers info Ă©nergie (CIE), crĂ©Ă© en 2002. Ces conseillers orientent les particuliers dans leur projet dâachat dâĂ©quipements dâĂ©nergie renouvelable ou de rĂ©novation Ă©nergĂ©tique de leur logement, afin de favoriser le « verdissement » du secteur de lâhabitat. Ă partir de lâhistoire et du positionnement de ce mĂ©tier, nous soutiendrons que lâĂ©conomie verte se trouve dans une incertitude vis-Ă -vis de son institutionnalisation
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