735 research outputs found
High Mass Triple Systems: The Classical Cepheid Y Car
We have obtained an HST STIS ultraviolet high dispersion Echelle mode
spectrum the binary companion of the double mode classical Cepheid Y Car. The
velocity measured for the hot companion from this spectrum is very different
from reasonable predictions for binary motion, implying that the companion is
itself a short period binary. The measured velocity changed by 7 km/ s during
the 4 days between two segments of the observation confirming this
interpretation. We summarize "binary" Cepheids which are in fact members of
triple system and find at least 44% are triples. The summary of information on
Cepheids with orbits makes it likely that the fraction is under-estimated.Comment: accepted by A
Saliency Benchmarking Made Easy: Separating Models, Maps and Metrics
Dozens of new models on fixation prediction are published every year and
compared on open benchmarks such as MIT300 and LSUN. However, progress in the
field can be difficult to judge because models are compared using a variety of
inconsistent metrics. Here we show that no single saliency map can perform well
under all metrics. Instead, we propose a principled approach to solve the
benchmarking problem by separating the notions of saliency models, maps and
metrics. Inspired by Bayesian decision theory, we define a saliency model to be
a probabilistic model of fixation density prediction and a saliency map to be a
metric-specific prediction derived from the model density which maximizes the
expected performance on that metric given the model density. We derive these
optimal saliency maps for the most commonly used saliency metrics (AUC, sAUC,
NSS, CC, SIM, KL-Div) and show that they can be computed analytically or
approximated with high precision. We show that this leads to consistent
rankings in all metrics and avoids the penalties of using one saliency map for
all metrics. Our method allows researchers to have their model compete on many
different metrics with state-of-the-art in those metrics: "good" models will
perform well in all metrics.Comment: published at ECCV 201
Neutron dark-field imaging of hydrogen-fatigued pressure vessel steel
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Classical Cepheid Pulsation Models. III. The Predictable Scenario
Within the current uncertainties in the treatment of the coupling between
pulsation and convection, limiting amplitude, nonlinear, convective models
appear the only viable approach for providing theoretical predictions about the
intrinsic properties of radial pulsators. In this paper we present the results
of a comprehensive set of Cepheid models computed within such theoretical
framework for selected assumptions on their original chemical composition.Comment: 24 pages, 1 latex file containing 6 tables, 10 postscript figures,
accepted for publication on Ap
Line profile variations in classical Cepheids. Evidence for non-radial pulsations?
We have investigated line profiles in a large sample of Cepheid spectra, and
found four stars that show unusual (for Cepheids) line profile structure (bumps
or/and asymmetries). The profiles can be phase dependent but the behavior
persists over many cycles. The asymmetries are unlikely to be due to the
spectroscopic binarity of these stars or the specific velocity field in their
atmospheres caused by shock waves. As a preliminary hypothesis, we suggest that
the observed features on the line profiles in the spectra of X Sgr, V1334 Cyg,
EV Sct and BG Cru can be caused by the non-radial oscillations. It is possible
that these non-radial oscillations are connected to resonances between the
radial modes (3.2, 7.5 or 10.0 days).Comment: Accepted by A&
Calibrating the Cepheid Period-Luminosity relation from the infrared surface brightness technique I. The p-factor, the Milky Way relations, and a universal K-band relation
We determine Period-Luminosity relations for Milky Way Cepheids in the
optical and near-IR bands. These relations can be used directly as reference
for extra-galactic distance determination to Cepheid populations with solar
metallicity, and they form the basis for a direct comparison with relations
obtained in exactly the same manner for stars in the Magellanic Clouds,
presented in an accompanying paper. In that paper we show that the metallicity
effect is very small and consistent with a null effect, particularly in the
near-IR bands, and we combine here all 111 Cepheids from the Milky Way, the LMC
and SMC to form a best relation. We employ the near-IR surface brightness
(IRSB) method to determine direct distances to the individual Cepheids after we
have recalibrated the projection factor using the recent parallax measurements
to ten Galactic Cepheids and the constraint that Cepheid distances to the LMC
should be independent of pulsation period. We confirm our earlier finding that
the projection factor for converting radial velocity to pulsational velocity
depends quite steeply on pulsation period, p=1.550-0.186*log(P) in disagrement
with recent theoretical predictions. We delineate the Cepheid PL relation using
111 Cepheids with direct distances from the IRSB analysis. The relations are by
construction in agreement with the recent HST parallax distances to Cepheids
and slopes are in excellent agreement with the slopes of apparent magnitudes
versus period observed in the LMC.Comment: Accepted for publication by Astronomy and Astrophysics. 15 pages, 11
figure
Heavy Quarkonium Physics
This report is the result of the collaboration and research effort of the
Quarkonium Working Group over the last three years. It provides a comprehensive
overview of the state of the art in heavy-quarkonium theory and experiment,
covering quarkonium spectroscopy, decay, and production, the determination of
QCD parameters from quarkonium observables, quarkonia in media, and the effects
on quarkonia of physics beyond the Standard Model. An introduction to common
theoretical and experimental tools is included. Future opportunities for
research in quarkonium physics are also discussed.Comment: xviii + 487 pages, 260 figures. The full text is also available at
the Quarkonium Working Group web page: http://www.qwg.to.infn.i
Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP
Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are
used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~
events. Spin correlations are favoured by data, and found to agree with the
Standard Model predictions. In addition, correlations between the W-boson decay
planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events.
Decay-plane correlations, consistent with zero and with the Standard Model
predictions, are measured
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