Examinando por Autor "Bayo, A."

Mostrando 1 - 7 de 7

Acceso Abierto
ALMA observations of the early stages of substellar formation in the Lupus 1 and 3 molecular clouds
(EDP Sciences, 2021-01-29) Santamaría Miranda, A.; De Gregorio Monsalvo, I.; Plunkett, A. L.; Huélamo, N.; López, Cristián; Ribas, Álvaro; Schreiber, M. R.; Muzic, K.; Palau, A.; Knee, L. B. G.; Bayo, A.; Comerón, F.; Hales, A.; Agencia Estatal de Investigación (AEI); Fundacao para a Ciencia e a Tecnologia (FCT); Consejo Nacional de Ciencia y Tecnología (CONACYT); Santamaría Miranda, A. [0000-0001-6267-2820]; De Gregorio Monsalvo, I. [0000-0003-4518-407X]; Plunkett, A. L. [0000-0002-9912-5705]; Huélamo, N. [0000-0002-2711-8143]; Ribas, Á. [0000-0003-3133-3580]; Schreiber, M. R. [0000-0003-3903-8009]; Muzic, K. [0000-0002-7989-2595]; Palau, A. [0000-0002-9569-9234]; Bayo, A. [0000-0001-7868-7031]; Comerón, F. [0000-0002-7838-2606]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The dominant mechanism leading to the formation of brown dwarfs (BDs) remains uncertain. While the census of Class II analogs in the substellar domain continues to grow, the most direct keys to formation, which are obtained from younger objects (pre-BD cores and proto-BDs), are limited by the very low number statistics available. Aims. We aim to identify and characterize a set of pre- and proto-BDs as well as Class II BDs in the Lupus 1 and 3 molecular clouds to test their formation mechanism. Methods. We performed ALMA band 6 (1.3 mm) continuum observations of a selection of 64 cores previously identified from AzTEC/ASTE data (1.1 mm), along with previously known Class II BDs in the Lupus 1 and 3 molecular clouds. Surveyed archival data in the optical and infrared were used to complement these observations. We expect these ALMA observations prove efficient in detecting the youngest sources in these regions, since they probe the frequency domain at which these sources emit most of their radiation. Results. We detected 19 sources from 15 ALMA fields. Considering all the pointings in our observing setup, the ALMA detection rate was ∼23% and the derived masses of the detected sources were between ∼0.18 and 124 MJup. We classified these sources according to their spectral energy distribution as 5 Class II sources, 2 new Class I/0 candidates, and 12 new possible pre-BD or deeply embedded protostellar candidates. We detected a promising candidate for a Class 0/I proto-BD source (ALMA J154229.778−334241.86) and inferred the disk dust mass of a bona fide Class II BD. The pre-BD cores might be the byproduct of an ongoing process of large-scale collapse. The Class II BD disks follow the correlation between disk mass and the mass of the central object that is observed at the low-mass stellar regime. Conclusions. We conclude that it is highly probable that the sources in the sample are formed as a scaled-down version of low-mass star formation, although disk fragmentation may be responsible for a considerable fraction of BDs.
Acceso Abierto
Exocomets: A spectroscopic survey
(EDP Sciences, 2020-07-01) Rebollido, I.; Eiroa, C.; Montesinos Comino, 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, Gregor; 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
Search for associations containing young stars (SACY) VIII. An updated census of spectroscopic binary systems exhibiting hints of non-universal multiplicity among their associations
(EDP Sciences, 2021-01-19) Zúñiga Fernández, Sebastián; Bayo, A.; Elliott, P.; Zamora, C.; Corvalán, G.; Haubois, X.; Corral Santana, J. M.; Olofsson, J.; Huélamo, N.; Sterzik, M. F.; Torres, C. A. O.; Quast, G. R.; Melo, C. H. F.; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Danish National Research Foundation (DNRF); European Space Agency (ESA); National Aeronautics and Space Administration (NASA); Agencia Estatal de Investigación (AEI); Unidad de Excelencia Maria de Maeztu-Centro de Astrobiologia (INTA-CSIC), MDM-2017-0737
Context. Nearby young associations offer one of the best opportunities for a detailed study of the properties of young stellar and substellar objects thanks to their proximity (<200 pc) and age (∼5−150 Myr). Previous works have identified spectroscopic (<5 au) binaries, close (5−1000 au) visual binaries, and wide or extremely wide (1000−100 000 au) binaries in the young associations. In most of the previous analyses, single-lined spectroscopic binaries (SB1) were identified based on radial velocities variations. However, this apparent variation may also be caused by mechanisms unrelated to multiplicity. Aims. We seek to update the spectroscopy binary fraction of the Search for Associations Containing Young stars (SACY) sample, taking into consideration all possible biases in our identification of binary candidates, such as activity and rotation. Methods. Using high-resolution spectroscopic observations, we produced ∼1300 cross-correlation functions (CCFs) to disentangle the previously mentioned sources of contamination. The radial velocity values we obtained were cross-matched with the literature and then used to revise and update the spectroscopic binary (SB) fraction in each object of the SACY association. In order to better describe the CCF profile, we calculated a set of high-order cross-correlation features to determine the origin of the variations in radial velocities. Results. We identified 68 SB candidates from our sample of 410 objects. Our results hint that at the possibility that the youngest associations have a higher SB fraction. Specifically, we found sensitivity-corrected SB fractions of 22−11+15% for ϵ Cha, 31−14+16% for TW Hya and 32−8+9% for β Pictoris, in contrast to the five oldest associations we have sampled (∼35−125 Myr) which are ∼10% or lower. This result seems independent of the methodology used to asses membership to the associations. Conclusions. The new CCF analysis, radial velocity estimates, and SB candidates are particularly relevant for membership revision of targets in young stellar associations. These targets would be ideal candidates for follow-up campaigns using high-resolution techniques to confirm binarity, resolve orbits, and, ideally, calculate dynamical masses. Additionally, if the results on the SB fraction in the youngest associations were confirmed, it could hint at a non-universal multiplicity among SACY associations.
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, Giuseppe Germano; 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.
Acceso Abierto
The Gaia -ESO Survey: Calibrating the lithium-age relation with open clusters and associations: I. Cluster age range and initial membership selections
(EDP Sciences, 2020-11-05) Gutiérrez Albarrán, M. L.; Montes, D.; Gómez Garrido, M.; Tabernero, H. M.; González Hernández, J. I.; Marfil, E.; Frasca, A.; Lanzafame, A. C.; Klutsch, A.; Franciosini, E.; Randich, S.; Smiljanic, R.; Korn, A. J.; Gilmore, G.; Alfaro, Emilio J.; Baratella, M.; Bayo, A.; Bensby, T.; Bonito, R.; Carraro, G.; Delgado Mena, E.; Feltzing, S.; Gonneau, A.; Heiter, U.; Hourihane, A.; Jiménez Esteban, F. M.; Jofre, P.; Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Roccatagliata, V.; Sousa, S. G.; Van der Swaelmen, M.; Worley, Charlotte C.; Zaggia, S.; Ministerio de Economía y Competitividad (MINECO); European Commission (EC); Istituto Nazionale di Astrofisica (INAF); Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR); Agencia Estatal de Investigación (AEI); Fundação para a Ciência e a Tecnologia (FCT); Leverhulme Trust; 0000-0002-7569-3513; 0000-0002-7779-238X; 0000-0002-8087-4298; 0000-0002-0264-7356; 0000-0001-8907-4775; 0000-0002-0474-0896; 0000-0001-7869-3888; 0000-0003-3969-0232; 0000-0003-2438-0899; 0000-0003-0942-7855; 0000-0003-3978-1409; 0000-0001-9297-7748; 0000-0002-0155-9434; 0000-0002-3148-9836
Context. Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars, these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. Aims. We perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open clusters. Methods. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate members for each of the clusters in the sample by deriving radial velocity distributions and studying the position of the kinematic selections in the EW(Li)-versus-Teff plane to obtain lithium members. We used gravity indicators to discard field contaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made use of studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections. Results. We identified likely member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted a comparative study that allowed us to characterize the properties of these members as well as identify field contaminant stars, both lithium-rich giants and non-giant outliers. Conclusions. This work is the first step towards the calibration of the lithium-age relation and its dependence on other GES parameters. During this project we aim to use this relation to infer the ages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups of different ages. © ESO 2020.