319 research outputs found
KIC 9821622: An interesting lithium-rich giant in the Kepler field
We report the discovery of a new exceptional young lithium-rich giant, KIC
9821622, in the \textit{Kepler} field that exhibits an unusually large
enhancement of , Fe-peak, and \textit{r}-process elements. From
high-resolution spectra obtained with GRACES at Gemini North, we derived
fundamental parameters and detailed chemical abundances of 23 elements from
equivalent widths and synthesis analysis. By combining atmospheric stellar
parameters with available asteroseismic data, we obtained the stellar mass,
radius, and age. The data analysis reveals that KIC 9821622 is a Li-rich
(A(Li) = 1.80 0.2) intermediate-mass giant star ( = 1.64
) located at the red giant branch near the luminosity bump. We find
unexpectedly elevated abundances of Fe-peak and \textit{r}-process elements. In
addition, as previously reported, we find that this is a young star (2.37 Gyr)
with unusually high abundances of -elements ([/Fe] = 0.31). The
evolutionary status of KIC 9821622 suggests that its Li-rich nature is the
result of internal fresh Li that is synthesized through the Cameron-Fowler
mechanism near the luminosity bump. However, its peculiar enhancement of
, Fe-peak, and \textit{r}-process elements opens the possibility of
external contamination by material enriched by a supernova explosion. Although
it is less likely, planet accretion cannot be ruled out.Comment: Letter, 6 pages, 3 figures, Accepted for publication in A&A. - Some
language editing include
Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
Aims. To explore the possible chemical signature of planet formation in the
binary system HAT-P-4, by studying abundance vs condensation temperature Tc
trends. The star HAT-P-4 hosts a planet detected by transits while its stellar
companion does not have any detected planet. We also study the Lithium content,
which could shed light on the problem of Li depletion in exoplanet host stars.
Conclusions. The exoplanet host star HAT-P-4 is found to be ~0.1 dex more metal
rich than its companion, which is one of the highest differences in metallicity
observed in similar systems. This could have important implications for
chemical tagging studies, disentangling groups of stars with a common origin.
We rule out a possible peculiar composition for each star as lambda Boo, delta
Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements
relative to volatile when compared to its stellar companion. Notably, the
Lithium abundance in HAT-P-4 is greater than in its companion by ~0.3 dex,
which is contrary to the model that explains the Lithium depletion by the
presence of planets. We propose a scenario where, at the time of planet
formation, the star HAT-P-4 locked the inner refractory material in
planetesimals and rocky planets, and formed the outer gas giant planet at a
greater distance. The refractories were then accreted onto the star, possibly
due to the migration of the giant planet. This explains the higher metallicity,
the higher Lithium content, and the negative Tc trend detected. A similar
scenario was recently proposed for the solar twin star HIP 68468, which is in
some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ~ 10
Mearth locked in refractory material in order to reproduce the observed Tc
trends and metallicity.Comment: 5 pages, 6 figures, A&A Letters accepte
News territorials configurations in the southwestern edge of the City of San Juan as a result of implementing housing policies
En la expansión urbana dispersa hacia el sur-oeste de la Ciudad de San Juan sin un plan integrado de desarrollo y sobre espacios tradicionalmente dedicados a la agricultura intensiva, se destaca por un lado la construcción, desde el año 2005, de barrios con viviendas de interés social, destinados a población socialmente vulnerable erradicada de asentamientos irregulares y por otro, el mejoramiento habitacional a grupos con niveles de ingresos medio - bajos.
El objetivo del presente artículo es mostrar las nuevas configuraciones producidas a raíz de la implementación de la política pública de vivienda.
Se realizaron sucesivos relevamientos del área de estudio a fin de corroborar las progresivas transformaciones territoriales, complementándose con análisis de bases
de datos censales provistos por el Instituto Provincial de la Vivienda.
Los resultados muestran la conformación de territorios de borde en los que la producción del uso de suelo residencial es progresiva, lo cual hace prever a mediano plazo una tendencia al cambio de uso del suelo rural a urbano o su transformación en urbanizable.
Las nuevas configuraciones territoriales tienen al Estado como actor principal, pero el abordaje sectorial si bien permite el acceso a la vivienda digna, acentúa los problemas de movilidad intraurbana, disponibilidad de equipamientos e infraestructura y provisión de servicios, situaciones que podrían ser evitadas si se lograra integrar las políticas habitacionales con estrategias de desarrollo y ordenamiento territorial, orientadas hacia
el crecimiento urbano sostenible.In the urban sprawl towards the southwest of the City of San Juan- without an integrated approach development and spaces traditionally devoted to intensive agriculture it stands out
on the one hand the construction from year 2005 of neighborhoods with social interest housing, intended for socially vulnerable population eradicated from irregular settlements and on the other housing improvement for groups with levels of lower middle income.
The objectives of this paper is to show the new configurations produced the wake of the
implementation housing policy.
Successive surveys were done of the study area to corroborate the progressive territorial
transformations complemented through analysis of census databases and provided by the
Provincial Housing Institute.
The results show the conformation of edge of territories where the production of residential land use is progressive, which seems to indicate a medium term trend change of use of
rural soil to urban or to urbanize
The new territorial configurations have the state as the main actor, but the sectorial approacheven though allows access to decent housing, accentuates the problems o intra-urban mobility availability of equipment and infrastructure and provision of services, situations that could be avoided if it were possible integrate housing policies with
development strategies and spatial planning, geared towards sustainable urban growth.Fil: Jofré, R. del Carmen.
Universidad Nacional de San JuanFil: Sarracina, Andrea E..
Universidad Nacional de San Jua
Metalicidad de estrellas con exoplanetas y discos de polvo
We present an uniform comparison among three different kind of objects: cool-Jupiter exoplanet host-stars, stars with dust disks and exoplanet host-stars with dust disks. The goal of this contribution was to determine why stellar objects originally surrounded by planetesimals evolve to different final configurations, from stars with planets to stars with debris disks.Realizamos una comparación uniforme de las metalicidades de tres grupos de objetos diferentes: estrellas con planetas del tipo Júpiter frío, estrellas con discos de polvo y estrellas que poseen tanto planetas como discos de polvo. El objetivo de esta contribución fue el de indagar sobre los motivos por los cuales objetos estelares que originalmente son circundados por planetesimales, evolucionan hacia configuraciones finales distintas, que van desde estrellas con compañeras de masa planetaria hasta estrellas rodeadas por discos de partículas sólidas.Fil: Petrucci, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Cientiâficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; ArgentinaFil: Jofré, E.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
High-contrast imaging of HD 29992 and HD 196385 with GPI
Based on high contrast images obtained with the Gemini Planet Imager (GPI),
we report the discovery of two point-like sources at angular separations of
and from the stars HD 29992 and HD 196385. A
combined analysis of the new GPI observations and images from the literature
indicates that the source close to HD 29992 could be a companion to the star.
Concerning HD 196385, the small number of contaminants () suggests
that the detected source may be gravitationally bound to the star. For both
systems, we discarded the presence of other potential companions with
M at . From stellar model atmospheres and
low-resolution GPI spectra, we derive masses of - M
for these sources. Using a Markov-chain Monte Carlo approach, we performed a
joint fit of the new astrometry measurements and published radial velocity data
to characterize the possible orbits. For HD 196385B, the median dynamic mass is
in agreement with that derived from model atmospheres, whilst for HD 29992B,
the orbital fit favors masses close to the brown dwarf regime(
M). HD 29992 and HD 196385 might be two new binary systems with
M-type stellar companions. However, new high angular resolution images would
help to definitively confirm whether the detected sources are gravitationally
bound to their respective stars, and permit tighter constraints on the orbital
parameters of both systems
ζ1 + ζ2 Reticuli binary system: a puzzling chromospheric activity pattern
We perform, for the first time, a detailed long-term activity study of the binary system ζ Ret. We use all available HARPS spectra obtained between the years 2003 and 2016. We build a time series of the Mount Wilson S index for both stars, then we analyse these series by using Lomb-Scargle periodograms. The components ζ1 Ret and ζ2 Ret that belong to this binary system are physically very similar to each other and also similar to our Sun, which makes it a remarkable system. We detect in the solar-analogue star ζ2 Ret a long-term activity cycle with a period of ?10 yr, similar to the solar one (?11 yr). It is worthwhile to mention that this object satisfies previous criteria for a flat star and for a cycling star simultaneously. Another interesting feature of this binary system is a high ?0.220 dex difference between the average log (R^´ }_HK) activity levels of both stars. Our study clearly shows that ζ1 Ret is significantly more active than ζ2 Ret. In addition, ζ1 Ret shows an erratic variability in its stellar activity. In this work, we explore different scenarios trying to explain this rare behaviour in a pair of coeval stars, which could help to explain the difference in this and other binary systems. From these results, we also warn that for the development of activity-age calibrations (which commonly use binary systems and/or stellar clusters as calibrators) the whole history of activity available for the stars involved should be taken into account.Fil: Flores, M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Buccino, Andrea Paola. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Jaque Arancibia, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: González, J F. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Nuñez, N E. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Jofré, E. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentin
Stellar parameters and chemical abundances of 223 evolved stars with and without planets
We present fundamental stellar parameters and chemical abundances for a
sample of 86 evolved stars with planets and for a control sample of 137 stars
without planets. The analysis was based on both high S/N and resolution echelle
spectra. The goals of this work are i) to investigate chemical differences
between stars with and without planets; ii) to explore potential differences
between the properties of the planets around giants and subgiants; and iii) to
search for possible correlations between these properties and the chemical
abundances of their host stars. In agreement with previous studies, we find
that subgiants with planets are, on average, more metal-rich than subgiants
without planets by ~ 0.16 dex. The [Fe/H] distribution of giants with planets
is centered at slightly subsolar metallicities and there is no metallicity
enhancement relative to the [Fe/H] distribution of giants without planets.
Furthermore, contrary to recent results, we do not find any clear difference
between the metallicity distributions of stars with and without planets for
giants with M > 1.5 Msun. With regard to the other chemical elements, the
analysis of the [X/Fe] distributions shows differences between giants with and
without planets for some elements, particularly V, Co, and Ba. Analyzing the
planet properties, some interesting trends might be emerging: i) multi-planet
systems around evolved stars show a slight metallicity enhancement compared
with single-planet systems; ii) planets with a 0.5 AU orbit
subgiants with [Fe/H] > 0 and giants hosting planets with a 1 AU
have [Fe/H] < 0; iii) higher-mass planets tend to orbit more metal-poor giants
with M < 1.5 Msun, whereas planets around subgiants seem to follow the
planet-mass metallicity trend observed on dwarf hosts; iv) planets orbiting
giants show lower orbital eccentricities than those orbiting subgiants and
dwarfs.Comment: 49 pages, 31 figures, Accepted for publication in A&A, abstract
shortened - corrected references, typos, acknowledgements include
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