Found 4 talks width keyword white dwarfs
Rotation plays an important role in the life of stars and offers a potential diagnostic to infer their ages and that of their planets. This idea is known as gyrochronology, and if properly calibrated, its applications to Galactic, stellar, and exoplanetary astrophysics would be far-reaching. Nevertheless, while potentially fruitful over a wide range of ages and masses, recent results have raised concerns regarding gyrochronology’s applicability. In this talk, I will present the opportunities that the Gaia astrometry has opened to address these issues. First, regarding rotation’s classical calibrators, I will illustrate the impact that removing the non-member contamination has on the rotational sequences of open clusters. Second, I will present a novel method that tests the state-of-the-art gyrochronology relations in under-explore domains using wide binary stars. Finally, I will discuss the prospects for expanding the existing rotational constraints in unprecedented regimes using data from the TESS mission.
The new generation of spectrometers designed for extreme precision radial velocities enable correspondingly precise stellar spectroscopy. It is now fruitful to theoretically explore what the information content would be if stellar spectra could be studied with spectral resolutions of a million or more, and to deduce what signatures remain at lower resolutions. Hydrodynamic models of stellar photospheres predict how line profiles shapes, asymmetries, and convective wavelength shifts vary from disk center to limb. Corresponding high-resolution spectroscopy across spatially resolved stellar disks is now practical using differential observations during exoplanet transits, thus enabling the testing of such models. A most demanding task is to understand and to model spectral microvariability toward the radial-velocity detection of also low-mass planets in Earth-like orbits around solar-type stars. Observations of the Sun-as-a-star with extreme precision spectrometers now permit searches for spectral-line modulations on the level of a part in a thousand or less, feasible to test against hydrodynamic models of various solar features.
Planetary systems have been found systematically orbiting main sequence stars and red giants. But the detection of planets per se during the white dwarf phase has been more elusive with only 3 systems. We have, however, ample indirect evidence of the existence of planetary debris around these systems in the form of material acreted onto the white dwarf, disks and even planetesimals. In this talk, I will review how we can put the pieces together: how we can reconcile what we see in white dwarfs with what we can infer regarding the evolution of planetary systems from the main sequence phase.
The formation and evolution of planets in general is closely linked to the life of their host star. What happens to the planetary systems at the end stages of the life cycle of their star has been one of the questions that have received attention from a theoretical point of view but has had a lack of real life examples to study. Among more than 4000 known exoplanets to date only a few of these objects have been found orbiting around pulsars, but so far we have found nothing that resembles what our own solar system will be like long after the Sun leaves the main sequence.
In this talk we will discuss the recent announcement by A. Vanderburg et al. of a giant planet candidate detected by the transit method orbiting around a white dwarf. The candidate was discovered using data from the space-based NASA mission TESS and confirmed using GTC, Spitzer, and other ground-based facilities. We will talk about the role that GTC played in this discovery, the peculiarity of this candidate system, and the possibility of detecting atmospheres in rocky planets orbiting around white dwarfs.
Zoom link: https://rediris.zoom.us/j/95796802777
Youtube link: https://youtu.be/TX5KfTeJNAM
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- Globular clusters as tracers of the Milky Way assembly historyDr. Davide MassariThursday October 5, 2023 - 10:30 GMT+1 (Aula)
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