1,230 research outputs found
Radial velocities and metallicities from infrared Ca II triplet spectroscopy of open clusters II. Berkeley 23, King 1, NGC 559, NGC 6603 and NGC 7245
Context: Open clusters are key to studying the formation and evolution of the
Galactic disc. However, there is a deficiency of radial velocity and chemical
abundance determinations for open clusters in the literature. Aims: We intend
to increase the number of determinations of radial velocities and metallicities
from spectroscopy for open clusters. Methods: We acquired medium-resolution
spectra (R~8000) in the infrared region Ca II triplet lines (~8500 AA) for
several stars in five open clusters with the long-slit IDS spectrograph on the
2.5~m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain).
Radial velocities were obtained by cross-correlation fitting techniques. The
relationships available in the literature between the strength of infrared Ca
II lines and metallicity were also used to derive the metallicity for each
cluster. Results: We obtain = 48.6+/-3.4, -58.4+/-6.8, 26.0+/-4.3 and
-65.3+/-3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603 and NGC 7245,
respectively. We found [Fe/H] =-0.25+/-0.14 and -0.15+/-0.18 for NGC 559 and
NGC 7245, respectively. Berkeley 23 has a low metallicity, [Fe/H]
=-0.42+/-0.13, similar to other open clusters in the outskirts of the Galactic
disc. In contrast, we derived a high metallicity ([Fe/H] =+0.43+/-0.15) for NGC
6603, which places this system among the most metal rich known open clusters.
To our knowledge, this is the first determination of radial velocities and
metallicities from spectroscopy for these clusters, except NGC 6603, for which
radial velocities had been previously determined. We have also analysed ten
stars in the line of sight to King 1. Because of the large dispersion obtained
in both radial velocity and metallicity, we cannot be sure that we have sampled
true cluster members.Comment: 10 pages, 5 figures, accepted for publication in A&A (minor
modifications
New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach
We have calculated proper motions and re-evaluated the membership
probabilities of 810 stars in the area of two NGC objects, NGC 1817 and NGC
1807. We have obtained absolute proper motions from 25 plates in the reference
system of the Tycho-2 Catalogue. The plates have a maximum epoch difference of
81 years; and they were taken with the double astrograph at Zo-Se station of
Shanghai Observatory, which has an aperture of 40 cm and a plate scale of 30
arcsec/mm. The average proper motion precision is 1.55 mas/yr. These proper
motions are used to determine the membership probabilities of stars in the
region, based on there being only one very extended physical cluster: NGC 1817.
With that aim, we have applied and compared parametric and non-parametric
approaches to cluster/field segregation. We have obtained a list of 169
probable member stars.Comment: 11 pages, 8 figures, A&A in pres
A new eclipsing binary system with a pulsating component detected by CoRoT
We report the discovery of CoRoT 102980178 (R.A.= 06:50:12.10, Dec.=
-02:41:21.8, J2000) an Algol-type eclipsing binary system with a pulsating
component (oEA). It was identified using a publicly available 55 day long
monochromatic lightcurve from the CoRoT initial run dataset (exoplanet field).
Eleven consecutive 1.26m deep total primary and the equal number of 0.25m deep
secondary eclipses (at phase 0.50) were observed. The following light elements
for the primary eclipse were derived: HJD_MinI= 2454139.0680 + 5.0548d x E. The
lightcurve modeling leads to a semidetached configuration with the photometric
mass ratio q=0.2 and orbital inclination i=85 deg. The out-of-eclipse
lightcurve shows ellipsoidal variability and positive O'Connell effect as well
as clear 0.01m pulsations with the dominating frequency of 2.75 c/d. The
pulsations disappear during the primary eclipses, which indicates the primary
(more massive) component to be the pulsating star. Careful frequency analysis
reveals the second independent pulsation frequency of 0.21 c/d and numerous
combinations of these frequencies with the binary orbital frequency and its
harmonics. On the basis of the CoRoT lightcurve and ground based multicolor
photometry, we favor classification of the pulsating component as a gamma
Doradus type variable, however, classification as an SPB star cannot be
excluded.Comment: 16 pages, 7 figures, 3 tables, accepted to Communications in
Asteroseismolog
Hunting for open clusters in \textit{Gaia} DR2: the Galactic anticentre
The Gaia Data Release 2 (DR2) provided an unprecedented volume of precise
astrometric and excellent photometric data. In terms of data mining the Gaia
catalogue, machine learning methods have shown to be a powerful tool, for
instance in the search for unknown stellar structures. Particularly, supervised
and unsupervised learning methods combined together significantly improves the
detection rate of open clusters. We systematically scan Gaia DR2 in a region
covering the Galactic anticentre and the Perseus arm and
, with the goal of finding any open clusters that may
exist in this region, and fine tuning a previously proposed methodology
successfully applied to TGAS data, adapting it to different density regions.
Our methodology uses an unsupervised, density-based, clustering algorithm,
DBSCAN, that identifies overdensities in the five-dimensional astrometric
parameter space that may correspond
to physical clusters. The overdensities are separated into physical clusters
(open clusters) or random statistical clusters using an artificial neural
network to recognise the isochrone pattern that open clusters show in a colour
magnitude diagram. The method is able to recover more than 75% of the open
clusters confirmed in the search area. Moreover, we detected 53 open clusters
unknown previous to Gaia DR2, which represents an increase of more than 22%
with respect to the already catalogued clusters in this region. We find that
the census of nearby open clusters is not complete. Different machine learning
methodologies for a blind search of open clusters are complementary to each
other; no single method is able to detect 100% of the existing groups. Our
methodology has shown to be a reliable tool for the automatic detection of open
clusters, designed to be applied to the full Gaia DR2 catalogue.Comment: 8 pages, accepted by Astronomy and Astrophysics (A&A) the 14th May,
2019. Tables 1 and 2 available at the CD
A ring in a shell: the large-scale 6D structure of the Vela OB2 complex
The Vela OB2 association is a group of 10 Myr stars exhibiting a complex
spatial and kinematic substructure. The all-sky Gaia DR2 catalogue contains
proper motions, parallaxes (a proxy for distance) and photometry that allow us
to separate the various components of Vela OB2. We characterise the
distribution of the Vela OB2 stars on a large spatial scale, and study its
internal kinematics and dynamic history. We make use of Gaia DR2 astrometry and
published Gaia-ESO Survey data. We apply an unsupervised classification
algorithm to determine groups of stars with common proper motions and
parallaxes. We find that the association is made up of a number of small
groups, with a total current mass over 2330 Msun. The three-dimensional
distribution of these young stars trace the edge of the gas and dust structure
known as the IRAS Vela Shell across 180 pc and shows clear signs of expansion.
We propose a common history for Vela OB2 and the IRAS Vela Shell. The event
that caused the expansion of the shell happened before the Vela OB2 stars
formed, imprinted the expansion in the gas the stars formed from, and most
likely triggered star formation.Comment: Accepted by A&A (02 November 2018), 13 pages, 9+2 figure
Earthmoving construction automation with military applications: Past, present and future
© ISARC 2018 - 35th International Symposium on Automation and Robotics in Construction and International AEC/FM Hackathon: The Future of Building Things. All rights reserved. Amongst increasing innovations in frontier engineering sciences, the advancements in Robotic and Autonomous Systems (RAS) has brought about a new horizon in construction applications. There is evidence of the increasing interest in RAS technologies in the civil construction sector being reflected in construction efforts of many military forces. In particular, Army or ground-based forces are frequently called upon to conduct construction tasks as part of military operations, tasks which could be partially or fully aided by the employment of RAS technologies. Along with recent advances in the Internet of Things (IoT) and cyber-physical system infrastructure, it is essential to examine the current maturity, technical feasibility, and affordability, as well as the challenges and future directions of the adoption and application of RAS to military construction. This paper presents a comprehensive survey and provides a contemporary and industry-independent overview on the state-of-the-art of earthmoving construction automation used in defence, spanning current world’s best practice through to that which is predicted over the coming years
Self-Perceptions, Self-Worth and Sport Participation in Adolescents
The purpose of this study was to study the associations between specific self-perceptions and global self-worth with different frequency levels of sport participation among Spanish boys and girls adolescents. Students (457 boys and 460 girls) completed the Self Perception Profile for Children (Harter, 1985) and items assessing sport engagement from The Health Behavior in School Children Questionnaire (Wold, 1995). Results showed that some specific dimensions of self-perception were related to different frequency of sport participation whereas overall judgments of self-worth did not. Specifically, for boys and girls, higher levels of sport participation were positively associated to Athletic Competence, and for boys were also associated with Physical Appearance and Social Acceptance. The potential implications of domain specific socialisation processes on the configuration of self-perceptions are highlighted.</jats:p
Las orientaciones de meta y los motivos de práctica deportiva en los jóvenes deportistas valencianos escolarizados
En este trabajo se analizan las relaciones entre las orientaciones de meta y los motivos de práctica deportiva en una muestra representativa de los adolescentes escolarizados valencianos. Contamos con 640 sujetos (232 chicas y 408 chicos) entre los 11 y los 18 años. Se les administró la versión castellana del TEOSQ (Duda, 1989; Balaguer, Castillo, y Tomás, 1996) y del HBSC (Wold, 1995;Balaguer, 1999). Los resultados muestran que los chicos y chicas con una alta orientación al ego enfatizan más los motivos de aprobación social y de demostración de capacidad para practicar deporte que los chicos y chicas con una baja orientación al ego. Los chicos y chicas con una alta orientación a la tarea consideran más importantes los motivos de afiliación para practicar deporte que los chicos y chicas con una baja orientación a la tarea. Finalmente los chicos con una alta orientación a la tarea consideran los motivos de salud más importantes que los chicos con una baja orientación a la tarea-In this study, we analyze the relationship between task and ego orientations and sport participation motivation among a representative sample of Valencian adolescents [N = 640 adolescents (232 girls and 408 boys); Age range = 11-18 years]. Participants completed a Spanish version of the TEOSQ (Duda, 1989; Balaguer, Castillo, & Tomás, 1996) and the HBSC (Wold, 1995; Balaguer, 1999). MANOVA indicated that high ego-oriented boys and girls emphasized achievement motives more than low ego-oriented boys and girls. High task-oriented boys and girls stressed social reasons for being involved in sport more than low task-oriented boys and girls. Finally, males high in task orientation were involved in sport more for purposes of enhancing health than low task-oriented males
Apoyo a la autonomÃa, satisfacción de las necesidades, motivación y bienestar en deportistas de competición : un análisis de la teorÃa de la autodeterminación
A model of the hypothesized motivational sequence among the autonomy support, basic needs, self determined motivation, self-esteem and life satisfaction was tested on the basis of the self-determination theory (Deci and Ryan, 1985, 2000). A multi-part questionnaire was administered to 301 athletes (171 females, 130 females; M Age= 24.1 + 4.7 years) who participated in a variety of sports. The robust method structural equation modelling analysis using maximum likelihood (LISREL 8.54) showed that athletes' perceptions of autonomy support from coaches predicted their satisfaction of the needs for autonomy and relatedness. These needs, along with perceived competence, predicted self-determined motivation, which in turn corresponded to greater self esteem and life satisfaction
uvby-Hbeta CCD photometry and membership segregation of the open cluster NGC 2548; Gaps in the Main Sequence of open clusters
Deep CCD photometry in the uvby-Hbeta intermediate-band system is presented
for the cluster NGC 2548 (M 48). A complete membership analysis based on
astrometric and photometric criteria is applied. The photometric analysis of a
selected sample of stars yields a reddening value of E(b-y)=0.06\pm0.03, a
distance modulus of V_0-M_V=9.3\pm0.5 (725 pc) and a metallicity of [Fe/H]=
-0.24\pm0.27. Through isochrone fitting we find an age of log t = 8.6\pm0.1
(400 Myr). Our optical photometry and JHK from 2MASS are combined to derive
effective temperatures of cluster member stars. The effective temperature
distribution along the main sequence of the cluster shows several gaps. A test
to study the significance of these gaps in the main sequence of the HR diagram
has been applied. The method is also applied to several other open clusters
(Pleiades, Hyades, NGC 1817 and M 67) to construct a sequence of metallicities
and ages. The comparison of the results of each cluster gives four gaps with
high significance (one of them, centred at 4900 K, has not been previously
reported).Comment: 11 pages, 8 figures, A&A in press. Corrected typos on Table
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