475 research outputs found
Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*
Context. The discovery of pulsations in low-mass stars opens an opportunity
for probing their interiors and to determine their evolution, by employing the
tools of asteroseismology. Aims. We aim to analyze high-speed photometry of
SDSSJ145847.02070754.46 and SDSSJ173001.94070600.25 and discover
brightness variabilities. In order to locate these stars in the diagram we fit optical spectra (SDSS) with synthetic non-magnetic
spectra derived from model atmospheres. Methods. To carry out this study, we
used the photometric data obtained by us for these stars with the 2.15m
telescope at CASLEO, Argentina. We analyzed their light curves and we apply the
Discrete Fourier Transform to determine the pulsation frequencies. Finally, we
compare both stars in the diagram, with known two
pre-white dwarfs, seven pulsating pre-ELM white dwarf stars, Scuti and
SX Phe stars. Results. We report the discovery of pulsations in
SDSSJ145847.02070754.46 and SDSSJ173001.94070600.25. We determine their
effective temperature and surface gravity to be = 7 972 200
K, = 4.25 0.5 and = 7 925 200 K, =
4.25 0.5, respectively. With these parameters these new pulsating
low-mass stars can be identified with either ELM white dwarfs (with ~ 0.17 Mo)
or more massive SX Phe stars. We identified pulsation periods of 3 278.7 and 1
633.9 s for SDSSJ145847.02070754.46 and a pulsation period of 3 367.1 s for
SDSSJ173001.94070600.25. These two new objects together with those of Maxted
et al. (2013, 2014) indicate the possible existence of a new instability domain
towards the late stages of evolution of low-mass white dwarf stars, although
their identification with SX Phe stars cannot be discarded.Comment: 5 pages, 5 figures, 1 table, accepted for publication in A&A
Asteroseismology of the heartbeat star KIC 5006817
This paper summarizes the project work on asteroseismology at the ERASMUS+
GATE 2020 Summer school on space satellite data. The aim was to do a global
asteroseismic analysis of KIC 5006817 and quantify its stellar properties using
the high-quality, state of the art space missions data. We employed the
aperture photometry to analyze the data from the Kepler space telescope and the
Transiting Exoplanet Survey Satellite (TESS). Using the lightkurve Python
package, we have derived the asteroseismic parameters and calculated the
stellar parameters using the scaling relations. Our analysis of KIC 5006817
confirmed its classification as a heartbeat binary. The rich oscillation
spectrum facilitate estimating power excess () at
145.500.50 Hz and large frequency separation () to be
11.630.10 Hz. Our results showed that the primary component is a
low-luminosity, red-giant branch star with a mass, radius, surface gravity, and
luminosity of 1.530.07 M, 5.910.12 R, 3.080.01
dex, and 19.660.73 L, respectively. The orbital period of the
system is 94.830.05 d.Comment: 13 pages, 4 figures, 2 tables; Based on the project work at ERASMUS+
GATE 2020 Summer school; To be published in Contrib. Astron. Obs. Skalnat\'e
Ples
NAUTILUS-DTU10 MW Floating Offshore Wind Turbine at Gulf of Maine: Public numerical models of an actively ballasted semisubmersible
This study presents two numerical multiphysics models of the NAUTILUS-10 floating support structure mounting the DTU10 MW Reference Wind Turbine at Gulf of Maine site, and analyses its dynamics. With the site conditions and the FAST model of the onshore turbine as the starting point, the floating support structure: tower, floating substructure with its corresponding active ballast system and station keeping system, was designed by NAUTILUS. The numerical models were developed and the onshore DTU wind energy controller was tuned to avoid the resonance of the operating FOWT by TECNALIA, in the framework of H2020 LIFES50+ project. This concept and its subsystems are fully characterised throughout this paper and implemented in opensource code, FAST v8.16. Here, the mooring dynamics are solved using MoorDyn, and the hydrodynamic properties are computed using HydroDyn. Viscous effects, not captured by radiation-diffraction theory, are modelled using two different approaches: (1) through linear and quadratic additional hydrodynamic damping matrices and (2) by means of Morison elements. A set of simulations (such as, decay, wind only and broadband irregular waves tests) were carried out with system identification purposes and to analyse the differences between the two models presented. Then, a set of simulations in stochastic wind and waves were carried out to characterise the global response of the FOWT.European Union Horizon2020
programme under the agreement H2020-LCE-2014-1-640741, LIFES50+ projec
SÍNDROME DE BURNOUT, SATISFACCIÓN LABORAL Y RELACIONES INTERPERSONALES EN PROFESORES DE UNA INSTITUCIÓN EDUCATIVA DE AREQUIPA
En la presente investigación, se valoran las relaciones entre el síndrome de burnout, la satisfacción laboral y las relaciones interpersonales en un grupo de profesores de la ciudad de Arequipa. Para ello, se evaluó a 46 profesores de una institución educativa privada de esta ciudad, con el inventario de Burnout de Maslach, la Escala de Satisfacción Laboral de Warr, Cook y Wall, y la escala de Satisfacción de las Relaciones Interpersonales en el Trabajo. Todos estos instrumentos cuentan con propiedades psicométricas adecuadas para la ciudad de Arequipa. Los resultados indican que existen relaciones negativas y moderadas entre la satisfacción laboral y el síndrome de burnout, pero no con las relaciones interpersonales. No se encontraron diferencias significativas en función del sexo o el cargo de los profesores, y la satisfacción laboral intrínseca tuvo un efecto predictivo significativo y negativo sobre el síndrome de burnout
Spectral classification and HR diagram of pre-main sequence stars in NGC6530
Mechanisms involved in the star formation process and in particular the
duration of the different phases of the cloud contraction are not yet fully
understood. Photometric data alone suggest that objects coexist in the young
cluster NGC6530 with ages from ~1 Myr up to 10 Myrs. We want to derive accurate
stellar parameters and, in particular, stellar ages to be able to constrain a
possible age spread in the star-forming region NGC6530. We used low-resolution
spectra taken with VIMOS@VLT and literature spectra of standard stars to derive
spectral types of a subsample of 94 candidate members of this cluster. We
assign spectral types to 86 of the 88 confirmed cluster members and derive
individual reddenings. Our data are better fitted by the anomalous reddening
law with R=5. We confirm the presence of strong differential
reddening in this region. We derive fundamental stellar parameters, such as
effective temperatures, photospheric colors, luminosities, masses, and ages for
78 members, while for the remaining 8 YSOs we cannot determine the interstellar
absorption, since they are likely accretors, and their V-I colors are bluer
than their intrinsic colors. The cluster members studied in this work have
masses between 0.4 and 4 M and ages between 1-2 Myrs and 6-7 Myrs. We
find that the SE region is the most recent site of star formation, while the
older YSOs are loosely clustered in the N and W regions. The presence of two
distint generations of YSOs with different spatial distribution allows us to
conclude that in this region there is an age spread of ~6-7 Myrs. This is
consistent with the scenario of sequential star formation suggested in
literature.Comment: 23 pages, 16 Postscript figures, 5 tables. Accepted for publication
in Astronomy and Astrophysic
Unveiling the evolutionary state of three B supergiant stars: PU Gem, CMa and CMa
We aim to combine asteroseismology, spectroscopy, and evolutionary models to
establish a comprehensive picture of the evolution of Galactic blue supergiant
stars (BSG). To start such an investigation, we selected three BSG candidates
for our analysis: HD 42087 (PU Gem), HD 52089 ( CMa) and HD 58350
( CMa). These stars show pulsations and were suspected to be in an
evolutionary stage either preceding or succeding the red supergiant (RSG)
stage.
For our analysis, we utilized the 2-min cadence TESS data to study the
photometric variability and obtained new spectroscopic observations at the
CASLEO observatory. We calculated CMFGEN non-LTE radiative transfer models and
derived stellar and wind parameters using the iterative spectral analysis
pipeline XTGRID. The spectral modeling was limited to changing only the
effective temperature, surface gravity, CNO abundances, and mass-loss rates.
Finally, we compared the derived metal abundances with predictions from Geneva
stellar evolution models. The frequency spectra of all three stars show either
stochastic oscillations, nonradial strange modes, or a rotational splitting.
We conclude that the rather short sectoral observing windows of TESS prevent
establishing a reliable mode identification of low frequencies connected to
mass-loss variabilities. The spectral analysis confirmed gradual changes in the
mass-loss rates and the derived CNO abundances comply with the values reported
in the literature. We were able to achieve a quantitative match with stellar
evolution models for the stellar masses and luminosities. However, the
spectroscopic surface abundances turned out to be inconsistent with theoretical
predictions. The stars show N enrichment, typical for CNO cycle processed
material, but the abundance ratios do not reflect the associated levels of C
and O depletion.Comment: 29 pages, 18 figures, Accepted for publication in Galaxie
Hydrodynamic identification of NAUTILUS FOWT platform from small scale tests
A small-scale tank test campaign of the NAUTILUS offshore wind floating semisub-mersible platform was held at the Ifremer Deep Water Basin within the framework of the MaRINET 2 project. The support structure consists in four stabilized columns on a square pontoon supporting a generic 8-MW wind turbine. The tests were carried out at 1:36 Froude scale in parked conditions, and the mooring system was modelled as a set of aerial mooring springs providing a nonlinear stiffness. The hydrodynamic characterization of the floater from experimental data was tackled by using traditional techniques in naval architecture), as well as approaches derived from operational modal analysis in the frequency domain, such as the Sub Space Identification—Covariance (SSI-COV) method. The validity of this approach and its potential application to the identification of such kind of structures is discussed against the results of a more traditional technique based on the fitting of decay tests
Depresión de adultos mayores en residentes de un asilo y en un grupo de la comunidad en la ciudad de Toluca 2016
Objetivo: Analizar el grado de depresión en adultos mayores de dos grupos: residentes de un asilo en la ciudad de Toluca y el grupo semanal del DIF de la comunidad de San Mateo Tlachichilpan, municipio de Almoloya de Juárez. Material y Métodos: Es un estudio cuantitativo de tipo descriptivo y transversal, la muestra es probabilística por conveniencia integrado por 20 adultos mayores del asilo y 31 adultos mayores del programa comunitario del DIF municipal de Almoloya de Juárez. Se utilizó las escalas de Yesavage y de Beck, y se realizó su análisis estadístico a través del programa SSPS versión 22.0 en español. Resultados: Se utilizó un total de 51 instrumentos para la recolección de datos, 37.3% fueron hombres y 62.7% mujeres. La descripción del estado civil es: solteros 41%, casados 11.8% y viudos 47.1%, en la situación laboral 86.3% son desempleados. Se utilizó la escala de Yesavage: 66.7% sin depresión, 25.5% depresión leve y 7.8% depresión establecida. La escala de Beck normal o no depresión de 54.9%, depresión leve 39.2% y depresión moderada 5.9%. Conclusiones: El grado de depresión fue mayor en el asilo, en ambas valoraciones es mayor el grado de depresión en las personas que no reciben visitas, la depresión leve se presenta en ambos lugares. En la mayoría de los casos no se había integrado un diagnóstico de depresión.
Abstract
Objective: Analyze the degree of depression in older adults in two groups: residents of a nursing home in the city of Toluca and weekly group DIF community of San Mateo Tlachichilpan, municipality of Almoloya de Juarez. Materials and Methods: This research is quantitative descriptive approach and cross type, the sample was composed by convenience of 20 older adults and 31 elderly asylum Community program municipal DIF of Almoloya de Juarez. Yesavage scales and Beck were applied, statistical analysis was performed using the SSPS 22.0 program version in Spanish. Results: A total of 51 instruments for data collection, 37.3% were men and 62.7% were applied were women. The description of marital status is single 41%; married 11.8% and widowers 47.1% in the employment situation 86.3% are unemployed. Yesavage scale 25.5% 7.8% mild depression and depression set, Beck normal scale depression or 54.9%, 39.2% mild depression and moderate depression 5.9% was applied with a percentage of 66.7% without depression. Conclusions: The degree of depression was higher in the asylum in both assessments, the greater the degree of depression in people not receiving visits, mild depression occurs in both places, in most cases had not made a diagnosis of depression.
 
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