Browsing by Author "Ribas, Alvaro"

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    Binary-induced spiral arms inside the disc cavity of AB Aurigae
    (2020) Poblete, Pedro P.; Calcino, Josh; Cuello, Nicolas; Macias, Enrique; Ribas, Alvaro; Price, Daniel J.; Cuadra, Jorge; Pinte, Christophe
    In this work we demonstrate that the inner spiral structure observed in AB Aurigae can be created by a binary star orbiting inside the dust cavity. We find that a companion with a mass-ratio of 0.25, semimajor axis of 40 au, eccentricity of 0.5, and inclination of 90 degrees produces gaseous spirals closely matching the ones observed in (CO)-C-12 (2-1) line emission. Based on dust dynamics in circumbinary discs (Poblete, Cuello & Cuadra 2019), we constrain the inclination of the binary with respect to the circumbinary disc to range between 60 degrees and 90 degrees. We predict that the stellar companion is located roughly 0.18 arcsec from the central star towards the east-southeast, above the plane of the disc. Should this companion be detected in the near future, our model indicates that it should be moving away from the primary star at a rate of 6 mas yr(-1) on the plane of the sky. Since our companion is inclined, we also predict that the spiral structure will appear to change with time, and not simply corotate with the companion.
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    Clustering Properties of Intermediate and High-mass Young Stellar Objects
    (2023) Vioque, Miguel; Cavieres, Manuel; Gonzalez, Michelangelo Pantaleoni; Ribas, Alvaro; Oudmaijer, Rene D.; Mendigutia, Ignacio; Kilian, Lena; Canovas, Hector; Kuhn, Michael A.
    We have selected 337 intermediate- and high-mass young stellar objects (YSOs; 1.5-20 M-circle dot) well-characterized with spectroscopy. By means of the clustering algorithm HDBSCAN, we study their clustering and association properties in the Gaia DR3 catalog as a function of stellar mass. We find that the lower-mass YSOs (1.5-4 M-circle dot) have clustering rates of 55%-60% in Gaia astrometric space, a percentage similar to that found in the T Tauri regime. However, intermediate-mass YSOs in the range 4-10 M-circle dot show a decreasing clustering rate with stellar mass, down to 27%. We find tentative evidence suggesting that massive YSOs (>10 M-circle dot) often (yet not always) appear clustered. We put forward the idea that most massive YSOs form via a mechanism that demands many low-mass stars around them. However, intermediate-mass YSOs form in a classical core-collapse T Tauri way, yet they do not appear often in the clusters around massive YSOs. We also find that intermediate- and high-mass YSOs become less clustered with decreasing disk emission and accretion rate. This points toward an evolution with time. For those sources that appear clustered, no major correlation is found between their stellar properties and the cluster sizes, number of cluster members, cluster densities, or distance to cluster centers. In doing this analysis, we report the identification of 55 new clusters. We tabulated all of the derived cluster parameters for the considered intermediate- and high-mass YSOs.