Examinando por Autor "Bayo, A."

Mostrando 1 - 4 de 4

Acceso Abierto
Exocomets: A spectroscopic survey
(EDP Sciences, 2020-07-01) Rebollido, I.; Eiroa, C.; Montesinos, B.; Maldonado, J.; Villaver, E.; Absil, O.; Bayo, A.; Canovas, H.; Carmona, A.; Chen, Ch.; Ertel, E.; Henning, T.; Iglesias, D. P.; Launhardt, R.; Liseau, R.; Meeus, G.; Moór, A.; Mora, A.; Olofsson, J.; Rauw, G.; Rivière Marichalar, P.; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Ministerio de Economía y Competitividad (MINECO); 0000-0002-4388-6417; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around β Pic in the early 1980s, only ∼20 stars have been reported to host exocomet-like events. Aims. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. Methods. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the Ca II K&H and Na I D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. Results. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the Ca II and/or Na I lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the Ca II K line are similar to those observed in β Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger v sin i is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.
Acceso Abierto
Lithium-rotation connection in the newly discovered young stellar stream Psc–Eri (Meingast 1)
(EDP Sciences, 2020-03-31) Arancibia Silva, J.; Bouvier, J.; Bayo, A.; Galli, P. A. B.; Brandner, W.; Bouy, H.; Barrado, D.; Agencia Estatal de Investigación (AEI); Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); European Research Council (ERC); Agence Nationale de la Recherche (ANR); Barrado, D. [0000-0002-5971-9242]; Galli, P. [0000-0003-2271-9297]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. As a fragile element, lithium is a sensitive probe of physical processes occurring in stellar interiors. Aims. We aim to investigate the relationship between lithium abundance and rotation rate in low-mass members of the newly discovered 125 Myr-old Psc–Eri stellar stream. Methods. We obtained high-resolution optical spectra and measured the equivalent width of the 607.8 nm LiI line for 40 members of the Psc–Eri stream, whose rotational periods have been previously derived. Results. We show that a tight correlation exists between the lithium content and rotation rate among the late-G to early-K-type stars of the Psc–Eri stream. Fast rotators are systematically Li rich, while slow rotators are Li depleted. This trend mimics that previously reported for the similar age Pleiades cluster. Conclusions. The lithium-rotation connection thus seems to be universal over a restricted effective temperature range for low-mass stars at or close to the zero-age main sequence, and does not depend on environmental conditions.
Acceso Abierto
Lithium-rotation connection in the newly discovered young stellar stream Psc-Eri (Meingast 1) (Corrigendum)
(EDP Sciences, 2020-08-07) Arrancibia Silva, J.; Bouvier, J.; Bayo, A.; Galli, P. A. B.; Brandner, W.; Bouy, H.; Barrado, D.; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); Agencia Estatal de Investigación (AEI); European Research Council (ERC); Agence Nationale de la Recherche (ANR); Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Navascues Barrado, D. [0000-0002-5971-9242]; Galli, P. [0000-0003-2271-9297]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. As a fragile element, lithium is a sensitive probe of physical processes occurring in stellar interiors. Aims. We aim to investigate the relationship between lithium abundance and rotation rate in low-mass members of the newly discovered 125 Myr-old Psc–Eri stellar stream. Methods. We obtained high-resolution optical spectra and measured the equivalent width of the 607.8 nm LiI line for 40 members of the Psc–Eri stream, whose rotational periods have been previously derived. Results. We show that a tight correlation exists between the lithium content and rotation rate among the late-G to early-K-type stars of the Psc–Eri stream. Fast rotators are systematically Li rich, while slow rotators are Li depleted. This trend mimics that previously reported for the similar age Pleiades cluster. Conclusions. The lithium-rotation connection thus seems to be universal over a restricted effective temperature range for low-mass stars at or close to the zero-age main sequence, and does not depend on environmental conditions.
Acceso Abierto
The Gaia -ESO Survey: A new approach to chemically characterising young open clusters: I. Stellar parameters, and iron-peak, α -, and proton-capture elements
(EDP Sciences, 2020-01-31) Baratella, M.; D´Orazi, V.; Carraro, G.; Desidera, S.; Randich, S.; Magrini, L.; Adibekyan, V.; Smiljanic, R.; Spina, L.; Tsantaki, M.; Tautvaisilenè, G.; Sousa, S. G.; Jofre, P.; Jiménez Esteban, F. M.; Delgado Mena, E.; Martell, S.; Van der Swaelmen, M.; Roccatagliata, V.; Gilmore, G.; Alfaro, Emilio J.; Bayo, A.; Bensby, T.; Bragaglia, A.; Franciosini, E.; Gonneau, A.; Heiter, U.; Hourihane, A.; Jeffries, R. D.; Koposov, S. E.; Morbidelli, L.; Prisinzano, L.; Sacco, G.; Sbordone, L.; Worley, Christopher; Zaggia, S.; Lewis, J.; European Commission (EC); Leverhulme Trust; Fundacao para a Ciencia e a Tecnologia (FCT); Agencia Estatal de Investigación (AEI); Jeffries, R. D. [0000-0001-5668-1288]; Magrini, L. [0000-0003-4486-6802]; Mena, E. D. [0000-0003-4434-2195]; Smiljanic, R. [0000-0003-0942-7855]; Koposov, S. [0000-0003-2644-135X]; Carraro, G. [0000-0002-0155-9434]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Open clusters are recognised as excellent tracers of Galactic thin-disc properties. At variance with intermediate-age and old open clusters, for which a significant number of studies is now available, clusters younger than ≲ 150 Myr have been mostly overlooked in terms of their chemical composition until recently (with few exceptions). On the other hand, previous investigations seem to indicate an anomalous behaviour of young clusters, which includes (but is not limited to) slightly sub-solar iron (Fe) abundances and extreme, unexpectedly high barium (Ba) enhancements. Aims. In a series of papers, we plan to expand our understanding of this topic and investigate whether these chemical peculiarities are instead related to abundance analysis techniques. Methods. We present a new determination of the atmospheric parameters for 23 dwarf stars observed by the Gaia-ESO survey in five young open clusters (τ < 150 Myr) and one star-forming region (NGC 2264). We exploit a new method based on titanium (Ti) lines to derive the spectroscopic surface gravity, and most importantly, the microturbulence parameter. A combination of Ti and Fe lines is used to obtain effective temperatures. We also infer the abundances of Fe » I, Fe » II, Ti » I, Ti » II, Na » I, Mg » I, Al » I, Si » I, Ca » I, Cr » I, and Ni » I. Results. Our findings are in fair agreement with Gaia-ESO iDR5 results for effective temperatures and surface gravities, but suggest that for very young stars, the microturbulence parameter is over-estimated when Fe lines are employed. This affects the derived chemical composition and causes the metal content of very young clusters to be under-estimated. Conclusions. Our clusters display a metallicity [Fe/H] between +0.04 ± 0.01 and +0.12 ± 0.02; they are not more metal poor than the Sun. Although based on a relatively small sample size, our explorative study suggests that we may not need to call for ad hoc explanations to reconcile the chemical composition of young open clusters with Galactic chemical evolution models. © ESO 2020.