1,303 research outputs found
ΠΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΌΠ΅ΡΠΎΠ΄Π° Π²ΠΎΠ»Π½ΠΎΠ²ΠΎΠΉ ΡΠΎΠΌΠΎΠ³ΡΠ°ΡΠΈΠΈ Π΄Π»Ρ ΠΎΠ±ΡΠ°Π±ΠΎΡΠΊΠΈ Π΄Π°Π½Π½ΡΡ ΠΌΠ°Π»ΠΎΠ³Π»ΡΠ±ΠΈΠ½Π½ΠΎΠΉ ΡΠ΅ΠΉΡΠΌΠΎΡΠ°Π·Π²Π΅Π΄ΠΊΠΈ
An Investigation of the Large-scale Variability of the Apparently Single Wolf-Rayet Star WR 1
In recent years, much studies have focused on determining the origin of the
large-scale line-profile and/or photometric patterns of variability displayed
by some apparently single Wolf-Rayet stars, with the existence of an unseen
(collapsed?) companion or of spatially extended wind structures as potential
candidates. We present observations of WR 1 which highlight the unusual
character of the variations in this object. Our narrowband photometric
observations reveal a gradual increase of the stellar continuum flux amounting
to Delta v = 0.09 mag followed by a decline on about the same timescale (3-4
days). Only marginal evidence for variability is found during the 11 following
nights.
Strong, daily line-profile variations are also observed but they cannot be
easily linked to the photometric variations.
Similarly to the continuum flux variations, coherent time-dependent changes
are observed in 1996 in the centroid, equivalent width, and skewness of He II
4686. Despite the generally coherent nature of the variations, we do not find
evidence in our data for the periods claimed in previous studies. While the
issue of a cyclical pattern of variability in WR 1 is still controversial, it
is clear that this object might constitute in the future a cornerstone for our
understanding of the mechanisms leading to the formation of largely anisotropic
outflows in Wolf-Rayet stars.Comment: 11 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Nuclear star cluster formation in energy-space
In a virialized stellar system, the mean-square velocity is a direct tracer
of the energy per unit mass of the system. Here, we exploit this to estimate
and compare root-mean-square velocities for a large sample of nuclear star
clusters and their host (late- or early-type) galaxies. Traditional
observables, such as the radial surface brightness and second-order velocity
moment profiles, are subject to short-term variations due to individual
episodes of matter infall and/or star formation. The total mass, energy and
angular momentum, on the other hand, are approximately conserved. Thus, the
total energy and angular momentum more directly probe the formation of galaxies
and their nuclear star clusters, by offering access to more fundamental
properties of the nuclear cluster-galaxy system than traditional observables.
We find that there is a strong correlation, in fact a near equality, between
the root-mean-square velocity of a nuclear star cluster and that of its host.
Thus, the energy per unit mass of a nuclear star cluster is always comparable
to that of its host galaxy. We interpret this as evidence that nuclear star
clusters do not form independently of their host galaxies, but rather that
their formation and subsequent evolution are coupled. We discuss how our
results can potentially be used to offer a clear and observationally testable
prediction to distinguish between the different nuclear star cluster formation
scenarios, and/or quantify their relative contributions.Comment: 12 pages, 3 figures, 4 tables; accepted for publication in MNRA
ΠΠΊΠΎΠ»ΠΎΠ³ΠΈΡ Π² ΠΆΠΈΠ·Π½ΠΈ ΡΠΎΠ²ΡΠ΅ΠΌΠ΅Π½Π½ΡΡ ΡΠΏΠΎΡΡΡΠΌΠ΅Π½ΠΎΠ²
ΠΡΠ½ΠΎΠ²Π½ΡΠΌ ΡΠ²ΠΎΠΉΡΡΠ²ΠΎΠΌ ΡΠΊΠΎΠ»ΠΎΠ³ΠΈΠΈ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ° ΡΠ²Π»ΡΠ΅ΡΡΡ Π΅Π΅ Π΅ΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎΠ΅ ΡΠΎΡΡΠΎΡΠ½ΠΈΠ΅, ΠΊΠΎΡΠΎΡΠΎΠ΅ ΠΎΡΡΠ°ΠΆΠ°Π΅Ρ ΠΈΠ½Π΄ΠΈΠ²ΠΈΠ΄ΡΠ°Π»ΡΠ½ΠΎ ΠΏΡΠΈΡΠΏΠΎΡΠΎΠ±ΠΈΡΠ΅Π»ΡΠ½ΡΠ΅ ΡΠ΅Π°ΠΊΡΠΈΠΈ ΠΊΠ°ΠΆΠ΄ΠΎΠ³ΠΎ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ° Π² ΠΎΠ±ΡΠ΅ΡΡΠ²Π΅ ΠΈ ΡΠΏΠΎΡΠΎΠ±Π½ΠΎΡΡΡ Π΅Π³ΠΎ Π½Π°ΠΈΠ±ΠΎΠ»Π΅Π΅ ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎ ΠΎΡΡΡΠ΅ΡΡΠ²Π»ΡΡΡ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎ-Π±ΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΡΡ ΡΡΠ½ΠΊΡΠΈΡ Π² ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Π½ΡΡ
ΡΡΠ»ΠΎΠ²ΠΈΡΡ
ΠΈ Π² ΠΊΠΎΠ½ΠΊΡΠ΅ΡΠ½ΠΎΠΉ ΠΌΠ΅ΡΡΠ½ΠΎΡΡΠΈ. ΠΠ»Ρ ΠΊΠ°ΠΆΠ΄ΠΎΠ³ΠΎ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ° ΠΊΠ°ΡΠ΅ΡΡΠ²ΠΎ ΠΏΠΎΠΏΡΠ»ΡΡΠΈΠΎΠ½Π½ΠΎΠ³ΠΎ Π·Π΄ΠΎΡΠΎΠ²ΡΡ ΠΎΡΡΠ°ΠΆΠ°Π΅ΡΡΡ ΡΡΠ΅ΠΏΠ΅Π½ΡΡ Π²Π΅ΡΠΎΡΡΠ½ΠΎΡΡΠΈ Π½Π° ΠΏΡΠΎΡΡΠΆΠ΅Π½ΠΈΠΈ Π²ΡΠ΅ΠΉ ΠΆΠΈΠ·Π½ΠΈ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ°, Π° ΡΠ°ΠΊΠΆΠ΅ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·ΡΠ΅Ρ Π΅Π³ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ ΠΈ ΠΆΠΈΠ·Π½Π΅Π½Π½ΡΠ΅ ΠΏΠΎΠ·ΠΈΡΠΈΠΈ ΠΊΠ°ΠΊ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΎΡΠ³Π°Π½ΠΈΠ·ΠΌΠ° Π² ΡΠ΅Π»ΠΎΠΌ
Properties of the Chandra Sources in M81
The Chandra X-ray Observatory obtained a 50-ks observation of the central
region of M81 using the ACIS-S in imaging mode. The global properties of the 97
x-ray sources detected in the inner 8.3x8.3 arcmin field of M81 are examined.
Roughly half the sources are concentrated within the central bulge. The
remainder are distributed throughout the disk with the brightest disk sources
lying preferentially along spiral arms. The average hardness ratios of both
bulge and disk sources are consistent with power law spectra of index Gamma~1.6
indicative of a population of x-ray binaries. A group of much softer sources
are also present. The background source-subtracted logN-logS distribution of
the disk follows a power law of index ~ -0.5 with no change in slope over three
decades in flux. The logN-logS distribution of the bulge follows a similar
shape but with a steeper slope above ~4.0e+37 ergs/s. There is unresolved x-ray
flux from the bulge with a radial profile similar to that of the bulge sources.
This unresolved flux is softer than the average of the bulge sources and
extrapolating the bulge logN-logS distribution towards weaker sources can only
account for 20% of the unresolved flux. No strong time variability was observed
for any source with the exception of one bright, soft source.Comment: 5 pages, 3 color PS figures, to appear in ApJ
Local height probabilities in a composite Andrews-Baxter-Forrester model
We study the local height probabilities in a composite height model, derived
from the restricted solid-on-solid model introduced by Andrews, Baxter and
Forrester, and their connection with conformal field theory characters. The
obtained conformal field theories also describe the critical behavior of the
model at two different critical points. In addition, at criticality, the model
is equivalent to a one-dimensional chain of anyons, subject to competing two-
and three-body interactions. The anyonic-chain interpretation provided the
original motivation to introduce the composite height model, and by obtaining
the critical behaviour of the composite height model, the critical behaviour of
the anyonic chains is established as well. Depending on the overall sign of the
hamiltonian, this critical behaviour is described by a diagonal coset-model,
generalizing the minimal models for one sign, and by Fateev-Zamolodchikov
parafermions for the other.Comment: 34 pages, 5 figures; v2: expanded introduction, references added and
other minor change
Collaborative Deep Learning for Recommender Systems
Collaborative filtering (CF) is a successful approach commonly used by many
recommender systems. Conventional CF-based methods use the ratings given to
items by users as the sole source of information for learning to make
recommendation. However, the ratings are often very sparse in many
applications, causing CF-based methods to degrade significantly in their
recommendation performance. To address this sparsity problem, auxiliary
information such as item content information may be utilized. Collaborative
topic regression (CTR) is an appealing recent method taking this approach which
tightly couples the two components that learn from two different sources of
information. Nevertheless, the latent representation learned by CTR may not be
very effective when the auxiliary information is very sparse. To address this
problem, we generalize recent advances in deep learning from i.i.d. input to
non-i.i.d. (CF-based) input and propose in this paper a hierarchical Bayesian
model called collaborative deep learning (CDL), which jointly performs deep
representation learning for the content information and collaborative filtering
for the ratings (feedback) matrix. Extensive experiments on three real-world
datasets from different domains show that CDL can significantly advance the
state of the art
Effect of H on the crystalline and magnetic structures of the YCo3-H(D) system. I. YCo3 from neutron powder diffraction and first-principles calculations
This paper reports investigations into the influence of hydrogen on the magnetic properties of the YCo3-H
system. We report results on the magnetic structure and magnetic transitions of YCo3 using a combination of
neutron powder diffraction measurements and first-principles full potential augmented plane wave + local
orbital calculations under the generalized gradient approximation. The ferromagnetic and ferrimagnetic structures
are examined on an equal footing. However, we identify that, no matter which structure is used as the
starting point, the neutron diffraction data always refines down to the ferrimagnetic structure with the Co2
atoms having antiparallel spins. In the ab initio calculations, the inclusion of spin-orbit coupling is found to be
important in the prediction of the correct magnetic ground state. Here, the results suggest that, for zero external
field and sufficiently low temperatures, the spin arrangement of YCo3 is ferrimagnetic rather than ferromagnetic
as previously believed. The fixed spin moment calculation technique has been employed to understand
the two successive field-induced magnetic transitions observed in previous magnetization measurements under
increasing ultrahigh magnetic fields. We find that the magnetic transitions start from the ferrimagnetic phase
οΏ½0.61οΏ½B/CoοΏ½ and terminate with the ferromagnetic phase οΏ½1.16οΏ½B/CoοΏ½, while the spin on the Co2 atoms
progressively changes from antiparallel ferrimagnetic to paramagnetic and then to ferromagnetic. Our neutron
diffraction measurements, ab initio calculations, and the high field magnetization measurements are thus
entirely self-consistent
Π‘ΠΎΠ²ΡΠ΅ΠΌΠ΅Π½Π½ΠΎΠ΅ ΡΠΎΡΡΠΎΡΠ½ΠΈΠ΅ ΠΈ ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Ρ ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΠΠΠ’ Π’ΠΎΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ
Π ΡΠ°Π±ΠΎΡΠ΅ Π΄Π°Π½Π° Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠ° ΡΠ΅ΡΠΈ ΠΎΡΠΎΠ±ΠΎ ΠΎΡ
ΡΠ°Π½ΡΠ΅ΠΌΡΡ
ΠΏΡΠΈΡΠΎΠ΄Π½ΡΡ
ΡΠ΅ΡΡΠΈΡΠΎΡΠΈΠΉ Π’ΠΎΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ, Π΅Π΅ ΡΠΎΠ»ΠΈ Π² ΠΏΠΎΠ΄Π΄Π΅ΡΠΆΠ°Π½ΠΈΠΈ ΡΠΊΠΎΠ»ΠΎΠ³ΠΎ-Ρ
ΠΎΠ·ΡΠΉΡΡΠ²Π΅Π½Π½ΠΎΠ³ΠΎ Π±Π°Π»Π°Π½ΡΠ° ΠΎΠ±Π»Π°ΡΡΠΈ. ΠΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Ρ ΡΡΠ°ΠΏΡ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΠ΅ΡΠΈ ΠΠΠΠ’. ΠΠ°Π½ Π°Π½Π°Π»ΠΈΠ· Π³Π΅ΠΎΠ³ΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ°Π·Π½ΠΎΠΎΠ±ΡΠ°Π·ΠΈΡ ΡΠ΅ΡΠΈ ΠΠΠΠ’ ΠΈ ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π½ΠΎΡΡΠΈ Π΅Π΅ Π² Π°Π΄ΠΌΠΈΠ½ΠΈΡΡΡΠ°ΡΠΈΠ²Π½ΡΡ
ΡΠ°ΠΉΠΎΠ½Π°Ρ
ΠΎΠ±Π»Π°ΡΡΠΈ. ΠΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Π° ΡΠΎΠ»Ρ ΡΠ΅ΡΠΈ ΠΠΠΠ’ Π² ΡΠΎΡ
ΡΠ°Π½Π΅Π½ΠΈΠΈ ΡΠ΅Π΄ΠΊΠΈΡ
ΠΈ ΠΈΡΡΠ΅Π·Π°ΡΡΠΈΡ
Π²ΠΈΠ΄ΠΎΠ² ΡΠ°ΡΡΠ΅Π½ΠΈΠΉ ΠΈ ΠΆΠΈΠ²ΠΎΡΠ½ΡΡ
. Π Π°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π° ΠΈ ΡΠ΅Π°Π»ΠΈΠ·ΠΎΠ²Π°Π½Π° ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΠΎΠΉ ΠΎΡΠ΅Π½ΠΊΠΈ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ ΡΠ΅ΡΠΈ ΠΠΠΠ’. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Ρ ΠΏΡΡΠΈ Π΅Π΅ ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΈ ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ.In work the characteristic of the network of specially protected natural territories of the Tomsk region, its role in maintaining ecological and economic balance of the region. The stages of forming a network of protected areas. The analysis of the geographic diversity of the PA network and its representation in the administrative districts of the region. Defined the role of the network of protected areas in the conservation of rare and endangered species of plants and animals. Developed and implemented a methodology of comprehensive evaluation of the effectiveness of the PA network. The proposed ways of its development and optimization
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