77,741 research outputs found
Planetary companions orbiting M giants HD 208527 and HD 220074
Aims. The purpose of the present study is to research the origin of planetary
companions by using a precise radial velocity (RV) survey.
Methods. The high-resolution spectroscopy of the fiber-fed Bohyunsan
Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy
Observatory (BOAO) is used from September 2008 to June 2012.
Results. We report the detection of two exoplanets in orbit around HD 208527
and HD 220074 exhibiting periodic variations in RV of 875.5 +/- 5.8 and 672.1
+/- 3.7 days. The RV variations are not apparently related to the surface
inhomogeneities and a Keplerian motion of the planetary companion is the most
likely explanation. Assuming possible stellar masses of 1.6 +/- 0.4 and 1.2 +/-
0.3 M_Sun, we obtain the minimum masses for the exoplanets of 9.9 +/- 1.7 and
11.1 +/- 1.8 M_Jup around HD 208527 and HD 220074 with an orbital semi-major
axis of 2.1 +/- 0.2 and 1.6 +/- 0.1 AU and an eccentricity of 0.08 and 0.14,
respectively. We also find that the previously known spectral classification of
HD 208527 and HD 220074 was in error: Our new estimation of stellar parameters
suggest that both HD 208527 and HD 220074 are M giants. Therefore, HD 208527
and HD 220074 are so far the first candidate M giants to harbor a planetary
companion.Comment: 7 pages, 9 figures, 4 tables, accepted for publisation in Astronomy &
Astrophysic
Pixelated Semantic Colorization
While many image colorization algorithms have recently shown the capability
of producing plausible color versions from gray-scale photographs, they still
suffer from limited semantic understanding. To address this shortcoming, we
propose to exploit pixelated object semantics to guide image colorization. The
rationale is that human beings perceive and distinguish colors based on the
semantic categories of objects. Starting from an autoregressive model, we
generate image color distributions, from which diverse colored results are
sampled. We propose two ways to incorporate object semantics into the
colorization model: through a pixelated semantic embedding and a pixelated
semantic generator. Specifically, the proposed convolutional neural network
includes two branches. One branch learns what the object is, while the other
branch learns the object colors. The network jointly optimizes a color
embedding loss, a semantic segmentation loss and a color generation loss, in an
end-to-end fashion. Experiments on PASCAL VOC2012 and COCO-stuff reveal that
our network, when trained with semantic segmentation labels, produces more
realistic and finer results compared to the colorization state-of-the-art
Intrinsic mechanism of phase locking in two-dimensional Josephson junction networks in presence of an external magnetic field
We present numerical simulations of the dynamics of two-dimensional Josephson
junction arrays to study the mechanism of mutual phase locking. We show that in
the presence of an external magnetic field two mechanisms are playing a role in
phase locking: feedback through the external load and internal coupling between
rows due to microwave currents induced by the field. We have found the
parameter values (junction capacitance, cell loop inductance, impedance of the
external load) for which the interplay of both these mechanisms leads to the
in-phase solution. The case of unshunted arrays is discussed as well.Comment: 13 pages, incl. 6 ps figures, Subm. to Europhysics Letter
Flavor changing t -> c l_1^- l_2^+ decay in the general two Higgs doublet model
We study the flavor changing t-> c l_1^- l_2^+ decay in the framework of the
general two Higgs doublet model, the so called model III. We predict the
branching ratio for l_1=\tau, l_2=\mu at the order of magnitude of BR \sim
10^{-8}.Comment: 12 Pages, 5 Figure
A scheme for demonstration of fractional statistics of anyons in an exactly solvable model
We propose a scheme to demonstrate fractional statistics of anyons in an
exactly solvable lattice model proposed by Kitaev that involves four-body
interactions. The required many-body ground state, as well as the anyon
excitations and their braiding operations, can be conveniently realized through
\textit{dynamic}laser manipulation of cold atoms in an optical lattice. Due to
the perfect localization of anyons in this model, we show that a quantum
circuit with only six qubits is enough for demonstration of the basic braiding
statistics of anyons. This opens up the immediate possibility of
proof-of-principle experiments with trapped ions, photons, or nuclear magnetic
resonance systems.Comment: 4 pages, 3 figure
Refactoring, reengineering and evolution: paths to Geant4 uncertainty quantification and performance improvement
Ongoing investigations for the improvement of Geant4 accuracy and
computational performance resulting by refactoring and reengineering parts of
the code are discussed. Issues in refactoring that are specific to the domain
of physics simulation are identified and their impact is elucidated.
Preliminary quantitative results are reported.Comment: To be published in the Proc. CHEP (Computing in High Energy Physics)
201
The Many Possible Interpretations of Microlensing Event OGLE-2002-BLG-055
Microlensing event OGLE-2002-BLG-055 is characterized by a smooth, slightly
asymmetric single-lens curve with an isolated, secure data point that is ~0.6
magnitudes brighter than neighboring points separated by a few days. It was
previously suggested that the single deviant data point and global asymmetry
were best explained by a planetary companion to the primary lens with mass
ratio log(q)=-3 to -2, and parallax effects induced by the motion of the Earth.
We revisit the interpretation of OGLE-2002-BLG-055, and show that the data can
be explained by wide variety of models. We find that the deviant data point can
be fit by a large number of qualitatively different binary-lens models whose
mass ratios range, at the ~3-sigma level, from log(q) ~ -4 to -1. This range is
consistent with a planet, brown dwarf, or M-dwarf companion for reasonable
primary masses of M> 0.8 M_sun. A subset of these binary-lens fits consist of a
family of continuously degenerate models whose mass ratios differ by an
order-of-magnitude, but whose light curves differ by <2% for the majority of
the perturbation. The deviant data point can also explained by a binary
companion to the source with secondary/primary flux ratio of ~1%. This model
has the added appeal that the global asymmetry is naturally explained by the
acceleration of the primary induced by the secondary. The binary-source model
yields a measurement of the Einstein ring radius projected on source plane of
\hat r_E=1.87 +/- 0.40 AU. OGLE-2002-BLG-055 is an extreme example that
illustrates the difficulties and degeneracies inherent in the interpretation of
weakly perturbed and/or poorly sampled microlensing light curves.Comment: 8 pages, 3 figures, 1 table. Minor changes. Accepted to ApJ, to
appear in the August 10, 2004 issue (v611
Detection of an exoplanet around the evolved K giant HD 66141
Aims. We have been carrying out a precise radial velocity (RV) survey for K
giants to search for and study the origin of the lowamplitude and long-periodic
RV variations.
Methods. We present high-resolution RV measurements of the K2 giant HD 66141
from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory
Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO).
Results. We find that the RV measurements for HD 66141 exhibit a periodic
variation of 480.5 +/- 0.5 days with a semi-amplitude of 146.2 +/- 2.7 m/s. The
Hipparcos photometry and bisector velocity span (BVS) do not show any obvious
correlations with RV variations. We find indeed 706.4 +/- 35.0 day variations
in equivalent width (EW) measurements of H_alpha line and 703.0 +/- 39.4 day
variations in a space-born measurements 1.25{\mu} flux of HD 66141 measured
during COBE/DIRBE experiment. We reveal that a mean value of long-period
variations is about 705 +/- 53 days and the origin is a rotation period of the
star and variability that is caused by surface inhomogeneities. For the 480 day
periods of RV variations an orbital motion is the most likely explanation.
Assuming a stellar mass of 1.1 +/- 0.1 M_Sun? for HD 66141, we obtain a minimum
mass for the planetary companion of 6.0 +/- 0.3 M_Jup with an orbital
semi-major axis of 1.2 +/- 0.1 AU and an eccentricity of 0.07 +/- 0.03.Comment: 7 pages, 10 figures, 3 tables, accepted for publisation in Astronomy
& Astrophysic
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