Examinando por Autor "Maldonado, R. F."

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Do instabilities in high-multiplicity systems explain the existence of close-in white dwarf planets?
(Oxford Academics: Oxford University Press, 2021-02-03) Maldonado, R. F.; Villaver, E.; Mustill, A. J.; Chávez, M.; Bertone, E.; Consejo Nacional de Ciencia y Tecnología (CONACYT); National Aeronautics and Space Administration (NASA); Agencia Estatal de Investigación (AEI); Swedish Research Council
We investigate the origin of close-in planets and related phenomena orbiting white dwarfs (WDs), which are thought to originate from orbits more distant from the star. We use the planetary architectures of the 75 multiple-planet systems (four, five, and six planets) detected orbiting main-sequence stars to build 750 dynamically analogous templates that we evolve to the WD phase. Our exploration of parameter space, although not exhaustive, is guided and restricted by observations and we find that the higher the multiplicity of the planetary system, the more likely it is to have a dynamical instability (losing planets, orbit crossing, and scattering), that eventually will send a planet (or small object) through a close periastron passage. Indeed, the fraction of unstable four- to six-planet simulations is comparable to the 25–50 per cent fraction of WDs having atmospheric pollution. Additionally, the onset of instability in the four- to six-planet configurations peaks in the first Gyr of the WD cooling time, decreasing thereafter. Planetary multiplicity is a natural condition to explain the presence of close-in planets to WDs, without having to invoke the specific architectures of the system or their migration through the von Zeipel–Lidov–Kozai effects from binary companions or their survival through the common envelope phase.
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Understanding the origin of white dwarf atmospheric pollution by dynamical simulations based on detected three-planet systems
(Oxford Academics: Oxford University Press, 2020-09-25) Maldonado, R. F.; Villaver, E.; Mustill, A. J.; Chavez, M.; Bertone, E.; Knut and Alice Wallenberg Foundation; Consejo Nacional de Ciencia y Tecnologia (CONACYT); Agencia Estatal de Investigación (AEI); Swedish Research Council (VR); Mustill, A. J. [0000-0002-2086-3642]; Bertone, E. [0000-0002-3751-0181]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Between 25 and 50 per cent of white dwarfs (WD) present atmospheric pollution by metals, mainly by rocky material, which has been detected as gas/dust discs, or in the form of photometric transits in some WDs. Planets might be responsible for scattering minor bodies that can reach stargazing orbits, where the tidal forces of the WD can disrupt them and enhance the chances of debris to fall on to the WD surface. The planet–planet scattering process can be triggered by the stellar mass-loss during the post main-sequence (MS) evolution of planetary systems. In this work, we continue the exploration of the dynamical instabilities that can lead to WD pollution. In a previous work, we explored two-planet systems found around MS stars and here we extend the study to three-planet system architectures. We evolved 135 detected three-planet systems orbiting MS stars to the WD phase by scaling their orbital architectures in a way that their dynamical properties are preserved using the N-body integrator package MERCURY. We find that 100 simulations (8.6 per cent⁠) are dynamically active (having planet losses, orbit crossing, and scattering) on the WD phase, where low-mass planets (1–100 M⊕) tend to have instabilities in Gyr time-scales, while high-mass planets (>100 M⊕) decrease the dynamical events more rapidly as the WD ages. Besides, 19 simulations (1.6 per cent⁠) were found to have planets crossing the Roche radius of the WD, where 9 of them had planet–star collisions. Our three-planet simulations have a slight increase in percentage of simulations that may contribute to the WD pollution than the previous study involving two-planet systems and have shown that planet–planet scattering is responsible of sending planets close to the WD, where they may collide directly to the WD, become tidally disrupted or circularize their orbits, hence producing pollution on the WD atmosphere.