1,705 research outputs found
Swift/UVOT Photometry of the Planetary Nebula WeBo 1: Unmasking A Faint Hot Companion Star
We present an analysis of over 150 ks of data on the planetary nebula WeBo 1
(PN G135.6+01.0) obtained with the Swift Ultraviolet Optical Telescope (UVOT).
The central object of this nebula has previously been described as a late-type
K giant barium star with a possible hot companion, most likely a young
pre-white dwarf. UVOT photometry shows that while the optical photometry is
consistent with a large cool object, the near-ultraviolet (UV) photometry shows
far more UV flux than could be produced by any late-type object. Using model
stellar atmospheres and a comparison to UVOT photometry for the pre-white dwarf
PG 1159-035, we find that the companion has a temperature of at least 40,000 K
and a radius of, at most, 0.056 R_sun. While the temperature and radius are
consistent with a hot compact stellar remnant, they are lower and larger,
respectively, than expected for a typical young pre-white dwarf. This likely
indicates a deficiency in the assumed UV extinction curve. We find that higher
temperatures more consistent with expectations for a pre-white dwarf can be
derived if the foreground dust has a strong "blue bump" at 2175 AA and a lower
R_V. Our results demonstrate the ability of Swift to both uncover and
characterize hot hidden companion stars and to constrain the UV extinction
properties of foreground dust based solely on UVOT photometry.Comment: 26 pages, 9 figure, accepted to Astronomical Journa
Culture and rapport promotion in service encounters: protecting the ties that bind
The present study aimed at investigating possible cultural effects on the perceived importance of interactional concerns in service encounters. Individual values were examined to establish an explanatory framework for any effects that might emerge. Hong Kong Chinese and Filipinos participated in the present study by rating the importance of 12 interactional concerns in five hypothetical scenarios involving service provision. “Rapport promotion” was the only consistent factor of interactional concerns to emerge from the five scenarios in each of the two cultural groups. The dimensions of individual values, labeled “Conservation” and “Self-Transcendence” by Schwartz (1992), significantly predicted a respondent’s level of rapport promotion across all scenarios, with self-transcendence partially unpackaging the cultural difference that emerged in one of the service scenarios. We use these results to support a model of communication in service provision that predicts communication concerns as arising from cultural socialization for personal characteristics and situational features of the encounter, leading to the petitioner’s being more dependent on the good will of the service provider
AN EXAMINATION OF MULTIPLE OPTIMIZATION APPROACHES TO THE SCHEDULING OF MULTI-PERIOD MIXED-BTU NATURAL GAS PRODUCTS
As worldwide production and consumption of natural gas increase, so does the importance of maximizing profit when trading this commodity in a highly competitive market. Decisions regarding the buying, storing and selling of natural gas are difficult in the face of high volatility of prices and uncertain demand. With the introduction of alternative sources of fuels with lower levels of methane, the primary component of natural gas, these decisions become more complicated. This is an issue faced by investors as well as operational planners of industrial and commercial consumers of natural gas where incorrect planning decisions can be costly.A great deal of research in the academic and commercial arenas has been accomplished regarding the problem of optimizing the scheduling of injection and withdrawal of this commodity. While various commercial products have been in use for years and research on new approaches continues, one aspect of the problem that has received less attention is that of combining gases of different heat contents. This study examines multiple approaches to maximizing profits by optimally scheduling the purchase and storage of two gas products of different energy densities and the sales of the same in combination with a product that is a blend of the two. The result provides an initial basis for planners to improve decision making and minimize the cost of natural gas consumed.This multi-product multi-period finite (twelve-month) horizon product-mix problem is NP-Hard. The first approach developed is a Branch and Bound (B&B) technique combined with a linear program (LP) solver. Heuristics are applied to limit the expansion the trinomial tree generated. In the second approach, a stochastic search algorithm-linear programming hybrid (SS-LP) is developed. The third approach implemented is a pure random search (PRS). To make each technique computationally tractable, constraints on the units of product moved in each transaction are implemented.Then, using numerical data, the three approaches are tested, analyzed and compared statistically and graphically along with computer performance information. The best approach provides a tool for optimizing profits and offers planners an advantage over approaches that are solely history-based
La boîte à outils géotechniques de demain: EN 1997-1: 202x Règles générales
This paper describes the development of the final Project Team (PT) draft of the next generation
of Eurocode 7 Part 1 (EN 1997-1:202x). The use of Nationally Determined Parameters and the drive for ease-of-use is highlighted. Key changes from the previous version of EN 1997-1 are explained, including the introduction of the Geotechnical Design Model; revision of the Geotechnical Categories and their application; the implementation of Consequence Classes and Geotechnical Complexity Classes in achieving the reliability required by the Eurocodes; elaboration on the use of numerical methods within Eurocode 7; the treatment of rock on an equal basis with soil; and greater emphasis on the Observational Method.Postprint (published version
Tracing the Filamentary Structure of the Galaxy Distribution at z~0.8
We study filamentary structure in the galaxy distribution at z ~ 0.8 using
data from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Redshift Survey
and its evolution to z ~ 0.1 using data from the Sloan Digital Sky Survey
(SDSS). We trace individual filaments for both surveys using the Smoothed
Hessian Major Axis Filament Finder, an algorithm which employs the Hessian
matrix of the galaxy density field to trace the filamentary structures in the
distribution of galaxies. We extract 33 subsamples from the SDSS data with a
geometry similar to that of DEEP2. We find that the filament length
distribution has not significantly changed since z ~ 0.8, as predicted in a
previous study using a \LamdaCDM cosmological N-body simulation. However, the
filament width distribution, which is sensitive to the non-linear growth of
structure, broadens and shifts to smaller widths for smoothing length scales of
5-10 Mpc/h from z ~ 0.8 to z ~ 0.1, in accord with N-body simulations.Comment: 10 pages, 8 figures, accepted for the publication in MNRA
Crawling the Cosmic Network: Identifying and Quantifying Filamentary Structure
We present the Smoothed Hessian Major Axis Filament Finder (SHMAFF), an
algorithm that uses the eigenvectors of the Hessian matrix of the smoothed
galaxy distribution to identify individual filamentary structures. Filaments
are traced along the Hessian eigenvector corresponding to the largest
eigenvalue, and are stopped when the axis orientation changes more rapidly than
a preset threshold. In both N-body simulations and the Sloan Digital Sky Survey
(SDSS) main galaxy redshift survey data, the resulting filament length
distributions are approximately exponential. In the SDSS galaxy distribution,
using smoothing lengths of 10 h^{-1} Mpc and 15 h^{-1} Mpc, we find filament
lengths per unit volume of 1.9x10^{-3} h^2 Mpc^{-2} and 7.6x10^{-4} h^2
Mpc^{-2}, respectively. The filament width distributions, which are much more
sensitive to non-linear growth, are also consistent between the real and mock
galaxy distributions using a standard cosmology. In SDSS, we find mean filament
widths of 5.5 h^{-1} Mpc and 8.4 h^{-1} Mpc on 10 h^{-1} Mpc and 15 h^{-1} Mpc
smoothing scales, with standard deviations of 1.1 h^{-1} Mpc and 1.4 h^{-1}
Mpc, respectively. Finally, the spatial distribution of filamentary structure
in simulations is very similar between z=3 and z=0 on smoothing scales as large
as 15 h^{-1} Mpc, suggesting that the outline of filamentary structure is
already in place at high redshift.Comment: 10 pages, 11 figures, accepted to MNRA
Crawling the Cosmic Network: Exploring the Morphology of Structure in the Galaxy Distribution
Although coherent large-scale structures such as filaments and walls are
apparent to the eye in galaxy redshift surveys, they have so far proven
difficult to characterize with computer algorithms. This paper presents a
procedure that uses the eigenvalues and eigenvectors of the Hessian matrix of
the galaxy density field to characterize the morphology of large-scale
structure. By analysing the smoothed density field and its Hessian matrix, we
can determine the types of structure - walls, filaments, or clumps - that
dominate the large-scale distribution of galaxies as a function of scale. We
have run the algorithm on mock galaxy distributions in a LCDM cosmological
N-body simulation and the observed galaxy distributions in the Sloan Digital
Sky Survey. The morphology of structure is similar between the two catalogues,
both being filament-dominated on 10-20 h^{-1} Mpc smoothing scales and
clump-dominated on 5 h^{-1} Mpc scales. There is evidence for walls in both
distributions, but walls are not the dominant structures on scales smaller than
~25 h^{-1} Mpc. Analysis of the simulation suggests that, on a given comoving
smoothing scale, structures evolve with time from walls to filaments to clumps,
where those found on smaller smoothing scales are further in this progression
at a given time.Comment: 37 pages, 14 figures. Accepted to MNRAS
Search full text options here 2 of 4 KMT-2021-BLG-0912Lb: a microlensing super Earth around a K-type star
Aims. The light curve of the microlensing event KMT-2021-BLG-0912 exhibits a very short anomaly relative to a single-lens single-source form. We investigate the light curve for the purpose of identifying the origin of the anomaly.
Methods. We model the light curve under various interpretations. From this, we find four solutions, in which three solutions are found under the assumption that the lens is composed of two masses (2L1S models), and the other solution is found under the assumption that the source is comprised of binary stars (1L2S model). The 1L2S model is ruled out based on the contradiction that the faint source companion is bigger than its primary, and one of the 2L1S solutions is excluded from the combination of the poorer fit, blending constraint, and lower overall probability, leaving two surviving solutions with the planet/host mass ratios of q similar to 2.8 x 10(-5) and similar to 1.1 x 10(-5). A subtle central deviation supports the possibility of a tertiary lens component, either a binary companion to the host with a very large or small separation, or a second planet lying near the Einstein ring, but it is difficult to claim a secure detection due to the marginal improvement of the fit, lack of consistency among different data sets, and difficulty in uniquely specifying the nature of the tertiary component.
Results. With the observables of the event, it is estimated that the masses of the planet and host are similar to(6.9 M-circle plus, 0.75 M-circle dot) according to one solution and similar to(2.8 M-circle plus, 0.80 M-circle dot) according to the other, indicating that the planet is a super Earth around a K-type star, regardless of the solution. The fact that 16 (including the one reported in this work) out of 19 microlensing planets with M less than or similar to 10 M-circle plus were detected during the last 6 yr nicely demonstrates the importance of high-cadence global surveys in detecting very low-mass planets
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