3.16 Instituto de Astrofísica

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Browsing 3.16 Instituto de Astrofísica by Author "Chanamé, Julio"

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    An experiment in near field cosmology: A search for the Magellanic Wake
    (2024) Cavieres Carrera, Manuel Antonio; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    The infall of the Magellanic Cloud system into the Milky Way halo hasstrong effects on the distribution of the stars and dark matter in the outerhalo of our Galaxy. In particular, N-body simulations predict a large-scaledensity asymmetry that spans the northern Galactic hemisphere (known as thecollective response), along with a localized overdensity (the Wake) that trailsthe LMC’s orbit. In this study, we collected wide-field deep near-infrared andoptical photometry from the VISTA and DECam instruments in four fieldsalong the expected position of the Magellanic Wake, covering most of thedensity range predicted to be found in the outer halo, as predicted by numericalmodels. This data allows us to select a clean sample of halo stars that reachthe oldest main sequence turn-off (MSTO) up to 100 kpc, with ∼ 400 stellarsources further than 60 kpc, on two separate tracers, near main sequence turnoff stars and red giant branch. We found that the Magellanic Wake overdensityis present in our data with a relative overdensity of 3.07 ± 0.7. Comparisonof the radial density profiles of near-MSTO stars with simulations of the MilkyWay/LMC interaction is best fitted by a massive LMC model with a total massof 2.5 × 10^11M⊙. This work provides the first unambiguous detection of thewake with consistent densities between two tracers.
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    Discovery and characterization of exoplanets in the TESS full frame images
    (2022) Rojas Henríquez, Felipe Ignacio; Jordán Colzani, Andrés Cristóbal; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    En los últimos años la cantidad de exoplanetas ha ido en aumento. Hoy conocemos más de 5000 y este numero seguirá creciendo gracias a misiones como TESS, que monitorea constantemente estrellas cercanas desde el espacio. No obstante, de todos estos planetas descubiertos, menos de 1000 tienen mediciones de su masa y radio con una precisión del 20% o mejor. Conocer estos parámetros con precisión nos da una idea inicial de su composición y por ende, de cómo pudo haber sido su proceso de formación. Además, se conocen muy pocos planetas gigantes con órbitas con períodos superior a los 10 días. Este tipo de planetas (Gigantes Tibios) despiertan la pregunta de cómo es que se encuentran tan cerca de la estrella que orbitan. Al mismo tiempo, estos conservan posibles rastros de su evolución dinámica en sus órbitas, a diferencia de planetas con órbitas más pequeñas. El objetivo de este proyecto es implementar un sistema de procesamiento de las imágenes de la misión TESS y búsqueda de planetas gigantes tibios, en el marco de la colaboración WINE, dedicada al estudio de estos planetas. De los candidatos a planeta encontrados, se realizó el seguimiento, confirmación y caracterización de un Neptuno (TOI-883 b) y un sub-Saturno (TOI-899 b), que orbitan estrellas muy parecidas al Sol con períodos de 10 y 12 días, respectivamente.
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    Hierarchical triple systems in Gaia
    (2022) Moraga Mejías, Víctor; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    Investigación enfocada en la búsqueda de sistemas triples jerárquicos de estrellas en la Vía Láctea. Se usó como punto de partida una muestra de 224 sistemas de un catálogo de binarias anchas, los cuales fueron estudiados para determinar su real multiplicidad. Mediante una campaña de observaciones de espectroscopia, se determinaron nuevas velocidades radiales para 116 de estos sistemas. Al comparar con mediciones en la literatura existente, se encontraron 74 estrellas cuya variación en velocidad indica la presencia de un sistema espectroscópico no detectado hasta la fecha.
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    New constraints for the initial-to-final mass relation of white dwarfs
    (2020) Barrientos Laurence, Manuel Hernán; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    We present observational constraints for the initial-to-final mass relation (IFMR) derived from 11 white dwarfs (WDs) in wide binaries (WBs) that contain a turnoff/subgiant primary. Because the components of old-enough WBs are coeval to a good approximation, the age of the WD progenitor (and hence its mass) can be determined from the study of its wide companion. However, previous works that used wide binaries to constrain the IFMR suffered from large uncertainties in the initial masses because their MS primaries are difficult to age-date with good precision. Our more careful selection of wide binaries with evolved primaries avoids this problem by restricting to a region of parameter space where isochrone ages are significantly easier to determine with precision. We selected a sample of wide binary systems with adequate characteristics for our program by matching existing catalogs of WDs with the Gaia astrometric surveys. Having introduced the use of wide subgiant-WD binaries, the study of the IFMR of WDs is not limited anymore by the precision in initial mass, but now the pressure is on final mass, i.e., the mass of the WD today. Our results indicate a non-negligible spread in WD final masses within this initial-mass range. As already noted, improved determinations of the masses of the WDs in this regime would be important for settling this question.
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    The consistency of chemical clocks among coeval stars
    (2021) Espinoza Rojas, Francisca; Chanamé, Julio; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    The abundance ratios of some chemical species have been found to correlate with stellar age, leading to the possibility of using measurements of abundances in stellar atmospheres as age indicators thanks to the Galactic chemical evolution. These chemical clocks have been calibrated with solar-twins, open clusters and red giants, however, how effective they are in identifying coeval systems has not been tested for populations that sample a broader parameter space. In that sense, wide binary systems are the perfect objects to assess the applications of chemical clocks, because their components have a common origin and are separated by great distances, so they should not interact with each other, and their abundances and ages are expected to be consistent. In this thesis, I determined the abundances of a sample of 5 wide binaries and collected data for other 31 systems from the literature in order to test the applicability of chemical clocks. I found that wide binaries have more consistent abundances than random pairs. I also found that chemical clocks are even more consistent among the components of wide binaries than their [X/Fe] ratios. Not only that, but the special case of the pair HIP 34426/HIP 34407 would indicate that chemical clocks are consistent for coeval stars even when their abundances are not. Finally, given the evidence that chemical clocks trace information about stellar birthplaces and chemical evolution, I briefly studied their benefits for chemical tagging by using them to reconstruct a sample of 3 open clusters, and found that chemical clocks do not improve the identification of the cluster’s members, but could be used for decontamination. Despite this, the results are limited by the age range of the sample, and there is still much work that could be done to better evaluate this idea and find more applications for chemical clocks.