347 research outputs found
Gaia FGK Benchmark Stars and their reference parameters
In this article we summarise on-going work on the so-called Gaia FGK
Benchmark Stars. This work consists of the determination of their atmospheric
parameters and of the construction of a high-resolution spectral library. The
definition of such a set of reference stars has become crucial in the current
era of large spectroscopic surveys. Only with homogeneous and well documented
stellar parameters can one exploit these surveys consistently and understand
the structure and history of the Milky Way and therefore other of galaxies in
the Universe.Comment: to appear in ASI Conference Series, 2014, Vol. 10 for the Workshop of
Spectral Libraries held in Lyon, Oct. 201
Test de la technique de marquage chimique avec des amas ouverts
Context. Stars are born together from giant molecular clouds and, if weassume that they were chemically homogeneous and well-mixed, we expect them toshare the same chemical composition.Most of the stellar aggregates are disrupted while orbiting the Galaxy and thedynamic information is lost, thus the only possibility to reconstruct the stellarformation history is to analyze the chemical abundances that we observe today.Aims. The chemical tagging technique aims to recover disrupted stellarclusters based merely on their chemical composition. We evaluate the viability of thistechnique to recover conatal stars that are not gravitationally bound anymore.Methods. We built a high-quality stellar spectra library to facilitate theassessment of spectral analyses. We developed our own spectral analysisframework, named iSpec, capable of homogeneizing stellar spectra and derivingatmospheric parameters/chemical abundances. Finally, we compiled stellar spectrafrom 32 Open Clusters, homogeneously derived atmospheric parameters and 17abundance species, and applied machine learning algorithms to group the starsbased on their chemical composition. This approach allows us to evaluate theviability of the chemical tagging technique.Results. We found that stars in different evolutionary stages havedistinguished chemical patterns may be due to NLTE effects, atomic diffusion, mixingand correlations from atmospheric parameter determinations. When separating starsper evolutionary stage, we observed a high degree of overlapping among OpenCluster’s chemical signatures, making it difficult to recover conatal aggregates byapplying the chemical tagging technique.Contexte. Les étoiles naissent ensemble dans des nuages moléculaires géants. Si nous faisons l’hypothèse qu’ils étaient à l’origine chimiquement homogènes et bien mélangés, nous nous attendrions à ce que les étoiles issues d’un même nuage aient la même composition chimique. La plupart des groupes d’étoiles sont perturbés lors de leur évolution dans la galaxie et l’information dynamique est perdue. Ainsi la seule possibilité que nous ayons de reconstruire l’histoire de la formation stellaire est d’analyser les abondances chimiques que l’on observe aujourd’hui.But. La technique de marquage chimique a pour but de retrouver les amas d’étoiles dissociés en se basant uniquement sur leur composition chimique. Nous évaluons la viabilité de cette technique pour retrouver les étoiles qui sont nées dans un même amas mais qui ne sont plus gravitationnellement liées.Méthodes. Nous avons créé une librairie de spectres stellaires de haute qualité afin de faciliter l’évaluation des analyses spectrales. Nous avons développé notre propre outil d’analyse spectrale, nommée iSpec, capable d’homogénéiser les spectres stellaires venant de tous types d’instruments et de dériver les paramètres atmosphériques et les abondances chimiques. Finalement, nous avons compilé des spectres stellaires d’étoiles de 32 amas ouverts, nous avons dérivé de façon homogène les paramètres atmosphériques et les abondances de 17 espèces, et nous avons utilisé des algorithmes d’apprentissage automatique pour grouper les étoiles en se basant sur leur composition chimique.Résultats. Nous avons trouvé que les étoiles à des étapes d’évolution différentes ont des motifs chimiques distincts qui peuvent être dus à des effets NLTE,de diffusion atomique, de mélange et de corrélation à partir des déterminations de paramètres atmosphériques. Quand nous séparons les étoiles suivant leur stade d’évolution, nous observons qu’il y a un important degré de recouvrement dans la détermination des signatures chimiques des amas ouverts. Ceci rend difficile de retrouver les groupes d’étoiles nées ensemble en utilisant la technique de marquage chimique
On the influence of equilibrium tides on transit-timing variations of close-in super-Earths. I. Application to single-planet systems and the case of K2-265 b
In this work, we investigate the influence of planetary tidal interactions on
the transit-timing variations of short-period low-mass rocky exoplanets. For
such purpose, we employ the recently-developed creep tide theory to compute
tidally-induced TTVs. We implement the creep tide in the recently-developed
Posidonius N-body code, thus allowing for a high-precision evolution of the
coupled spin-orbit dynamics of planetary systems. As a working example for the
analyses of tidally-induced TTVs, we apply our version of the code to the
K2-265 b planet. We analyse the dependence of tidally-induced TTVs with the
planetary rotation rate, uniform viscosity coefficient and eccentricity. Our
results show that the tidally-induced TTVs are more significant in the case
where the planet is trapped in non-synchronous spin-orbit resonances, in
particular the 3/2 and 2/1 spin-orbit resonant states. An analysis of the TTVs
induced separately by apsidal precession and tidally-induced orbital decay has
allowed for the conclusion that the latter effect is much more efficient at
causing high-amplitude TTVs than the former effect by 2 - 3 orders of
magnitude. We compare our findings for the tidally-induced TTVs obtained with
Posidonius with analytical formulations for the transit timings used in
previous works, and verified that the results for the TTVs coming from
Posidonius are in excellent agreement with the analytical formulations. These
results show that the new version of Posidonius containing the creep tide
theory implementation can be used to study more complex cases in the future.
For instance, the code can be used to study multiplanetary systems, in which
case planet-planet gravitational perturbations must be taken into account
additionally to tidal interactions to obtain the TTVs.Comment: 12 pages, 9 figures. Accepted with minor revisions in Astronomy and
Astrophysics (A&A
Ground-based photometry of the 21-day Neptune HD106315c
Space-based transit surveys such as K2 and TESS allow the detection of small
transiting planets with orbital periods beyond 10 days. Few of these warm
Neptunes are currently known around stars bright enough to allow for detailed
follow-up observations dedicated to their atmospheric characterization. The
21-day period and 3.95 planet HD106315c has been discovered based on
the observation of two of its transits by K2. We have observed HD106315 using
the 1.2m Euler telescope equipped with the EulerCam camera on two instances to
confirm the transit using broad band photometry and refine the planetary
period. Based on two observed transits of HD106315c, we detect its 1 mmag
transit and obtain a precise measurement of the planetary ephemerids, which are
critical for planning further follow-up observations. We have used the attained
precision together with the predicted yield from the TESS mission to evaluate
the potential for ground-based confirmation of Neptune-sized planets found by
TESS. We find that 1-meter-class telescopes on the ground equipped with precise
photometers could substantially contribute to the follow-up of 162 TESS
candidates orbiting stars with magnitudes of . Out of these, 74
planets orbit stars with and 12 planets orbit , which
makes these candidates high-priority objects for atmospheric characterization
with high-end instrumentation.Comment: Published in A&A letters, 4 pages, 3 figure
Towards an MDE-based approach to test entity reconciliation applications
The management of large volumes of data has given rise to significant challenges to the entity reconciliation problem (which refers to combining data from different sources for a unified vision) due to the fact that the data are becoming more unstructured, unclean and incomplete, need to be more linked, etc. Testing the applications that implement the entity reconciliation problem is crucial to ensure both the correctness of the reconciliation process and the quality of the reconciled data. In this paper, we present a first approach, based on MDE, which allows the creation of test models for the integration testing of entity reconciliation applications.Ministerio de Ciencia y TecnologÃa TIN2013-46928-C3-1-RMinisterio de Ciencia y TecnologÃa TIN2013-46928-C3-3-RMinisterio de Ciencia y TecnologÃa TIN2015-71938-REDTPrincipado de Asturias GRUPIN14-00
Early Integration Testing for Entity Reconciliation in the Context of Heterogeneous Data Sources
Entity reconciliation (ER) aims to combine data from
different sources for a unified vision. The management of large
volumes of data has given rise to significant challenges to the ER
problem due to facts such as data becoming more unstructured, unclean,
and incomplete or the existence of many datasets that store
information about the same topic. Testing the applications that implement
the ER problem is crucial to ensure both the correctness
of the reconciliation process and the quality of the reconciled data.
This paper presents an approach based on model-driven engineering
that allows the creation of test models for the early integration
testing of ER applications, contributing in three main aspects: the
description of the elements of the proposed framework, the definition
of the testing model, and the validation of the proposal
through two real-world case studies. This validation verifies that
the early integration testing of the ER application is capable of
detecting a series of deficiencies, which a priori are not known and
that will help to improve the final result that the ER application
offers.Ministerio de Ciencia y TecnologÃa TIN2013-46928-C3-1-RMinisterio de Ciencia y TecnologÃa TIN2013-46928-C3-3-RMinisterio de Ciencia y TecnologÃa TIN2016-76956-C3-1-RMinisterio de Ciencia y TecnologÃa TIN2016-76956-C3-2-RMinisterio de Ciencia y TecnologÃa TIN2015-71938-RED
New ADS Functionality for the Curator
In this paper we provide an update concerning the operations of the NASA
Astrophysics Data System (ADS), its services and user interface, and the
content currently indexed in its database. As the primary information system
used by researchers in Astronomy, the ADS aims to provide a comprehensive index
of all scholarly resources appearing in the literature. With the current effort
in our community to support data and software citations, we discuss what steps
the ADS is taking to provide the needed infrastructure in collaboration with
publishers and data providers. A new API provides access to the ADS search
interface, metrics, and libraries allowing users to programmatically automate
discovery and curation tasks. The new ADS interface supports a greater
integration of content and services with a variety of partners, including ORCID
claiming, indexing of SIMBAD objects, and article graphics from a variety of
publishers. Finally, we highlight how librarians can facilitate the ingest of
gray literature that they curate into our system.Comment: Submitted to the Proceedings of Library and Information Services in
Astronomy VIII, Strasbourg, Franc
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