Browsing by Author "Cuello, Nicolas"

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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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    Dust trapping around Lagrangian points in protoplanetary disks
    (2020) Montesinos, Matias; Garrido-Deutelmoser, Juan; Olofsson, Johan; Giuppone, Cristian A.; Cuadra, Jorge; Bayo, Amelia; Sucerquia, Mario; Cuello, Nicolas
    Aims. Trojans are defined as objects that share the orbit of a planet at the stable Lagrangian points L-4 and L-5. In the Solar System, these bodies show a broad size distribution ranging from micrometer (mu m) to centimeter (cm) particles (Trojan dust) and up to kilometer (km) rocks (Trojan asteroids). It has also been theorized that earth-like Trojans may be formed in extra-solar systems. The Trojan formation mechanism is still under debate, especially theories involving the effects of dissipative forces from a viscous gaseous environment.
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    Flyby-induced misalignments in planet-hosting discs
    (2020) Nealon, Rebecca; Cuello, Nicolas; Alexander, Richard
    We now have several observational examples of misaligned broken protoplanetary discs, where the disc inner regions are strongly misaligned with respect to the outer disc. Current models suggest that this disc structure can be generated with an internal misaligned companion (stellar or planetary), but the occurrence rate of these currently unobserved companions remains unknown. Here we explore whether a strong misalignment between the inner and outer disc can be formed without such a companion. We consider a disc that has an existing gap - essentially separating the disc into two regions - and use a flyby to disturb the discs, leading to a misalignment. Despite considering the most optimistic parameters for this scenario, we find maximum misalignments between the inner and outer disc of similar to 45 degrees and that these misalignments are short-lived. We thus conclude that the currently observed misaligned discs must harbour internal, misaligned companions.
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    Long Live the Disk: Lifetimes of Protoplanetary Disks in Hierarchical Triple-star Systems and a Possible Explanation for HD 98800 B
    (2021) Paula Ronco, Maria; Guilera, Octavio M.; Cuadra, Jorge; Miller Bertolami, Marcelo M.; Cuello, Nicolas; Fontecilla, Camilo; Poblete, Pedro; Bayo, Amelia
    The gas dissipation from a protoplanetary disk is one of the key processes affecting planet formation, and it is widely accepted that it happens on timescales of a few million years for disks around single stars. In recent years, several protoplanetary disks have been discovered in multiple-star systems, and despite the complex environment in which they find themselves, some of them seem to be quite old, a situation that may favor planet formation. A clear example of this is the disk around HD 98800 B, a binary in a hierarchical quadruple stellar system, which at an similar to 10 Myr age seems to still be holding significant amounts of gas. Here we present a 1D+1D model to compute the vertical structure and gas evolution of circumbinary disks in hierarchical triple-star systems considering different stellar and disk parameters. We show that tidal torques due to the inner binary, together with the truncation of the disk due to the external companion, strongly reduce the viscous accretion and expansion of the disk. Even allowing viscous accretion by tidal streams, disks in these kind of environments can survive for more than 10 Myr, depending on their properties, with photoevaporation being the main gas dissipation mechanism. We particularly apply our model to the circumbinary disk around HD 98800 B and confirm that its longevity, along with the current nonexistence of a disk around the companion binary HD 98800 A, can be explained with our model and by this mechanism.
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    Planet formation and stability in polar circumbinary discs
    (2019) Cuello, Nicolas; Giuppone, Cristian A.
    Context. Dynamical studies suggest that most circumbinary discs (CBDs) should be coplanar (i.e. the rotation vectors of the binary and the disc should be aligned). However, some theoretical works show that under certain conditions a CBD can become polar, which means that its rotation vector is orthogonal with respect to the binary orbital plane. Interestingly, very recent observations show that polar CBDs exist in nature (e.g. HD 98800).
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    Ploonets: formation, evolution, and detectability of tidally detached exomoons
    (2019) Sucerquia, Mario; Alvarado-Montes, Jaime A.; Zuluaga, Jorge, I; Cuello, Nicolas; Giuppone, Cristian
    Close-in giant planets represent the most significant evidence of planetary migration. If large exomoons form around migrating giant planets which are more stable (e.g. those in the Solar system), what happens to these moons after migration is still under intense research. This paper explores the scenario where large regular exomoons escape after tidal interchange of angular momentum with its parent planet, becoming small planets by themselves. We name this hypothetical type of object a ploonet. By performing semi-analytical simulations of tidal interactions between a large moon with a close-in giant, and integrating numerically their orbits for several Myr, we found that in similar to 50 per cent of the cases a young ploonet may survive ejection from the planetary system, or collision with its parent planet and host star, being in principle detectable. Volatile-rich ploonets are dramatically affected by stellar radiation during both planetocentric and siderocentric orbital evolution, and their radius and mass change significantly due to the sublimation of most of their material during time-scales of hundreds of Myr. We estimate the photometric signatures that ploonets may produce if they transit the star during the phase of evaporation, and compare them with noisy light curves of known objects (Kronian stars and non-periodical dips in dusty light curves). Additionally, the typical transit timing variations (TTV) induced by the interaction of a ploonet with its planet are computed. We find that present and future photometric surveys' capabilities can detect these effects and distinguish them from those produced by other nearby planetary encounters.
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    Radiative Scale Height and Shadows in Protoplanetary Disks
    (2021) Montesinos, Matias; Cuello, Nicolas; Olofsson, Johan; Cuadra, Jorge; Bayo, Amelia; Bertrang, Gesa H. -M.; Perrot, Clement
    Planets form in young circumstellar disks called protoplanetary disks. However, it is still difficult to catch planet formation in situ. Nevertheless, from recent ALMA/SPHERE data, encouraging evidence of the direct and indirect presence of embedded planets has been identified in disks around young stars: co-moving point sources, gravitational perturbations, rings, cavities, and emission dips or shadows cast on disks. The interpretation of these observations needs a robust physical framework to deduce the complex disk geometry. In particular, protoplanetary disk models usually assume the gas pressure scale height given by the ratio of the sound speed over the azimuthal velocity H/r = c(s)/v(k). By doing so, radiative pressure fields are often ignored, which could lead to a misinterpretation of the real vertical structure of such disks. We follow the evolution of a gaseous disk with an embedded Jupiter-mass planet through hydrodynamical simulations, computing the disk scale height including radiative pressure, which was derived from a generalization of the stellar atmosphere theory. We focus on the vertical impact of the radiative pressure in the vicinity of circumplanetary disks, where temperatures can reach greater than or similar to 1000 K for an accreting planet and radiative forces can overcome gravitational forces from the planet. The radiation pressure effects create a vertical, optically thick column of gas and dust at the protoplanet location, casting a shadow in scattered light. This mechanism could explain the peculiar illumination patterns observed in some disks around young stars such as HD 169142 where a moving shadow has been detected or the extremely high aspect ratio H/r similar to 0.2 observed in systems like AB Aur and CT Cha.
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    Resolving the FU Orionis System with ALMA: Interacting Twin Disks?
    (2020) Perez, Sebastian; Hales, Antonio; Liu, Hauyu Baobab; Zhu, Zhaohuan; Casassus, Simon; Williams, Jonathan; Zurlo, Alice; Cuello, Nicolas; Cieza, Lucas; Principe, David
    FU Orionis objects are low-mass pre-main sequence stars characterized by dramatic outbursts several magnitudes in brightness. These outbursts are linked to episodic accretion events in which stars gain a significant portion of their mass. The physical processes behind these accretion events are not yet well understood. The archetypal FU Ori system, FU Orionis, is composed of two young stars with detected gas and dust emission. The continuum emitting regions have not been resolved until now. Here, we present 1.3 mm observations of the FU Ori binary system using the Atacama Large Millimeter/submillimeter Array. The disks are resolved at 40 mas resolution. Radiative transfer modeling shows that the emission from FU Ori north (primary) is consistent with a dust disk with a characteristic radius of similar to 11 au. The ratio between the major and minor axes shows that the inclination of the disk is similar to 37 degrees. FU Ori south is consistent with a dust disk of similar inclination and size. Assuming the binary orbit shares the same inclination angle as the disks, the deprojected distance between the north and south components is 06, i.e., similar to 250 au. Maps of (CO)-C-12 emission show a complex kinematic environment with signature disk rotation at the location of the northern component, and also (to a lesser extent) for FU Ori south. The revised disk geometry allows us to update FU Ori accretion models, yielding a stellar mass and mass accretion rate of FU Ori north of 0.6 M and 3.8 x 10(-5) M yr(-1), respectively.
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    Signatures of an eccentric disc cavity: Dust and gas in IRS 48
    (2019) Calcino, Josh; Price, Daniel J.; Pinte, Christophe; van der Marel, Nienke; Ragusa, Enrico; Dipierro, Giovanni; Cuello, Nicolas; Christiaens, Valentin
    We test the hypothesis that the disc cavity in the 'transition disc' Oph IRS 48 is carved by an unseen binary companion. We use 3D dust-gas smoothed-particle hydrodynamics simulations to demonstrate that marginally coupled dust grains concentrate in the gas overdensity that forms in the cavity around a low binary mass ratio binary. This produces high contrast ratio dust asymmetries at the cavity edge similar to those observed in the disc around IRS 48 and other transition discs. This structure was previously assumed to be a vortex. However, we show that the observed velocity map of IRS 48 displays a peculiar asymmetry that is not predicted by the vortex hypothesis. We show the unusual kinematics are naturally explained by the non-Keplerian flow of gas in an eccentric circumbinary cavity. We further show that perturbations observed in the isovelocity curves of IRS 48 may be explained as the product of the dynamical interaction between the companion and the disc. The presence of an similar to 0.4 M-circle dot companion at an similar to 10 au separation can qualitatively explain these observations. High spatial resolution line and continuum imaging should be able to confirm this hypothesis.
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    Size and density sorting of dust grains in SPH simulations of protoplanetary discs
    (OXFORD UNIV PRESS, 2017) Pignatale, F. C.; Gonzalez, J. F.; Cuello, Nicolas; Bourdon, Bernard; Fitoussi, Caroline
    The size and density of dust grains determine their response to gas drag in protoplanetary discs. Aerodynamical (size x density) sorting is one of the proposed mechanisms to explain the grain properties and chemical fractionation of chondrites. However, the efficiency of aerodynamical sorting and the location in the disc in which it could occur are still unknown. Although the effects of grain sizes and growth in discs have been widely studied, a simultaneous analysis including dust composition is missing. In this work, we present the dynamical evolution and growth of multicomponent dust in a protoplanetary disc using a 3D, two-fluid (gas+dust) smoothed particle hydrodynamics code. We find that the dust vertical settling is characterized by two phases: a density-driven phase that leads to a vertical chemical sorting of dust and a size-driven phase that enhances the amount of lighter material in the mid-plane. We also see an efficient radial chemical sorting of the dust at large scales. We find that dust particles are aerodynamically sorted in the inner disc. The disc becomes sub-solar in its Fe/Si ratio on the surface since the early stage of evolution but sub-solar Fe/Si can be also found in the outer disc-mid-plane at late stages. Aggregates in the disc mimic the physical and chemical properties of chondrites, suggesting that aerodynamical sorting played an important role in determining their final structure.