Examinando por Autor "Barrado, David"

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  • Miniatura
    Publicación
    A rich population of free-floating planets in the Upper Scorpius young stellar association
    (Springer Nature, 2021-12-22) Miret Roig, Nuria; Bouy, Hervé; Raymond, Sean N.; Tamura, Motohide; Bertin, Emmanuel; Barrado, David; Olivares Romero, Javier; Galli, P. A. B.; Cuillandre, Jean-Charles; Sarro Baro, Luis Manuel; Berihuete, Ángel; Huelamo, Nuria; https://orcid.org/0000-0001-5292-0421; https://orcid.org/0000-0002-7084-487X; https://orcid.org/0000-0001-8974-0758; https://orcid.org/0000-0002-6510-0681; https://orcid.org/0000-0002-3602-3664; https://orcid.org/0000-0002-5971-9242; https://orcid.org/0000-0003-2271-9297; https://orcid.org/0000-0002-3263-8645; https://orcid.org/0000-0002-8589-4423; https://orcid.org/0000-0002-2711-8143
    Free-floating planets (FFPs) are planetary-mass objects that are not bound to host stars. First discovered in the 1990s, their nature and origin are still largely unconstrained because of a lack of large homogeneous samples enabling a statistical analysis of their properties. To date, most FFPs have been discovered using indirect methods; micro-lensing surveys have proven particularly successful to detect these objects down to a few Earth masses1, 2. However, the ephemeral nature of micro-lensing events prevents any follow-up observations and individual characterisation. Several studies have identified FFPs in young stellar clusters3, 4 and the Galactic field5 but their samples are small or heterogeneous in age and origin. Here we report the discovery of between 70 and 170 FFPs (depending on the assumed age) in the region encompassing Upper Scorpius (USC) and Ophiuchus (Oph), the closest young OB association to the Sun. It is the largest homogeneous sample of nearly coeval FFPs discovered to date. We found an excess of FFPs by a factor of up to seven compared to core-collapse models predictions6–8, demonstrating that other formation mechanisms may be at work. We estimate that ejection from planetary systems might have a contribution comparable to that of core-collapse in the formation of FFPs. Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10 Myr of a system’s life.
  • Miniatura
    Publicación
    Ultracool dwarfs in Gaia DR3
    (EDP Sciences, 2023-01-26) Sarro Baro, Luis Manuel; Berihuete, Ángel; Smart, R. L.; Reylé, Céline; Barrado, David; Garcia Torres, Miguel; Cooper, W. J.; Jones, H. R. A.; Marocco, Federico; Creevey, Orlagh; Sordo, Rosanna; Bailer Jones, C. A. L.; Montegriffo, P.; Ruth Carballo; Andrae, Rene; Fouesneau, Morgan; Lanzafame, Alessandro; Pailler, Fred; Thévenin, F.; Lobel, A.; Delchambre, L.; Korn, Andreas J.; Recio Blanco, Alejandra; Schultheis, M.; Angeli, Francesca De; Brouillet, Nathalie; Casamiquela, Laia; Contursi, Gabriele; Laverny, P. de; Garcia Lario, Pedro; Kordopatis, G.; Lebreton, Y.; Livanou, E.; Lorca, Alejandro; Palicio, Pedro Alonso; Slezak Oreshina, I.; Contursi, Gabriele; Ulla, A.; Zhao, He; https://orcid.org/0000-0002-8589-4423; https://orcid.org/0000-0002-4424-4766; https://orcid.org/0000-0003-2258-2403; https://orcid.org/0000-0002-5971-9242; https://orcid.org/0000-0002-6867-7080; https://orcid.org/0000-0003-3501-8967; https://orcid.org/0000-0003-0433-3665; https://orcid.org/0000-0001-7519-1700; https://orcid.org/0000-0003-1853-6631; https://orcid.org/0000-0003-4979-0659; https://orcid.org/0000-0001-5013-5948; https://orcid.org/0000-0001-7412-2498; https://orcid.org/0000-0001-8006-6365; https://orcid.org/0000-0001-9256-5516; https://orcid.org/0000-0002-2697-3607; https://orcid.org/0000-0002-6855-2050; https://orcid.org/0000-0001-5030-019X; https://orcid.org/0000-0003-2559-408X; https://orcid.org/0000-0002-3881-6756; https://orcid.org/0000-0002-6590-1657; https://orcid.org/0000-0003-1879-0488; https://orcid.org/0000-0002-3274-7024; https://orcid.org/0000-0001-5238-8674; https://orcid.org/0000-0001-5370-1511; https://orcid.org/0000-0002-2817-4104; https://orcid.org/0000-0003-4039-8212; https://orcid.org/0000-0002-9035-3920; https://orcid.org/0000-0002-7985-250X; https://orcid.org/0000-0002-7432-8709; https://orcid.org/0000-0001-5370-1511; https://orcid.org/0000-0003-2645-6869
    Context. Previous Gaia data releases offered the opportunity to uncover ultracool dwarfs (UCDs) through astrometric, rather than purely photometric, selection. The most recent, the third data release (DR3), offers in addition the opportunity to use low-resolution spectra to refine and widen the selection. Aims. In this work we use the Gaia DR3 set of UCD candidates and complement the Gaia spectrophotometry with additional photometry in order to characterise the global properties of the set. This includes the inference of the distances, their locus in the Gaia colour-absolute magnitude diagram, and the (biased through selection) luminosity function at the faint end of the main sequence. We study the overall changes in the Gaia RP spectra as a function of spectral type. We study the UCDs in binary systems, we attempt to identify low-mass members of nearby young associations, star-forming regions, and clusters, and we analyse their variability properties. Methods. We used a forward model and the Bayesian inference framework to produce posterior probabilities for the distribution parameters and a calibration of the colour index as a function of the absolute magnitude in the form of a Gaussian process. Additionally, we applied the hierarchical mode association clustering (HMAC) unsupervised classification algorithm for the detection and characterisation of overdensities in the space of celestial coordinates, projected velocities, and parallaxes. Results. We detect 57 young, kinematically homogeneous groups, some of which are identified as well-known star-forming regions, associations, and clusters of different ages. We find that the primary members of the 880 binary systems with a UCD belong to the thin and thick disc components of the Milky Way. We identify 1109 variable UCDs using the variability tables in the Gaia archive, 728 of which belong to the star-forming regions defined by HMAC. We define two groups of variable UCDs with extreme bright or faint outliers. Conclusions. The set of sources identified as UCDs in the Gaia archive contains a wealth of information that will require focused follow-up studies and observations. It will help advance our understanding of the nature of the faint end of the main sequence and the stellar-substellar transition.