Earth and Planetary Astrophysics (astro-ph.EP)

Abstract: A tau-Herculid meteor outburst or even a storm was predicted by several models to occur around 5~UT on 31~May, 2022 as a consequence of the break-up of comet 73P/Schwassmann-Wachmann 3 in 1995. The multi-instrument and multi-station experiment was carried-out within the Czech Republic to cover possible earlier activity of the shower between 21 and 1 UT on 30/31 May. Multi-station observations using video and photographic cameras were used for calculation of the atmospheric trajectories and heliocentric orbits of the meteors. Their arrival times are used for determination of the shower activity profile. Physical properties of the meteoroids are evaluated using various criteria based on meteor heights. Evolution of spectra of three meteors are studied as well. This annual but poor meteor shower was active for the whole night many hours before the predicted peak. A comparison with dynamical models shows that a mix of older material ejected after 1900 and fresh particles originating from the 1995 comet fragmentation event was observed. Radiant positions of both groups of meteors were identified and found to be in good agreement with simulated radiants. Meteoroids with masses between 10 mg and 10 kg were recorded. The mass distribution index was slightly higher than 2. A study of the physical properties shows that the tau-Herculid meteoroids belong to the most fragile particles observed ever, especially among higher masses of meteoroids. Exceptionally bright bolide observed during the dawn represents a challenge for the dynamical simulations as it is necessary to explain how to transfer a half metre body to the vicinity of the Earth at the same time as millimetre sized particles.

Abstract: Jupiter's deep abundances help to constrain the formation history of the planet and the environment of the protoplanetary nebula. Juno recently measured Jupiter's deep oxygen abundance near the equator to be 2.2$_{-2.1}^{+3.9}$ times the protosolar value (2$\sigma$ uncertainties). Even if the nominal value is supersolar, subsolar abundances cannot be ruled out. Here we use a state-of-the-art one-dimensional thermochemical and diffusion model with updated chemistry to constrain the deep oxygen abundance with upper tropospheric CO observations. We find a value of 0.3$_{-0.2}^{+0.5}$ times the protosolar value. This result suggests that Jupiter could have a carbon-rich envelope that accreted in a region where the protosolar nebula was depleted in water. However, our model can also reproduce a solar/supersolar water abundance if vertical mixing is reduced in a radiative layer where the deep oxygen abundance is obtained. More precise measurements of the deep water abundance are needed to discriminate between these two scenarios and understand Jupiter's internal structure and evolution.

Abstract: Mean motion resonances (MMR) are a frequent phenomenon among extrasolar planetary systems. Current observations indicate that many systems have planets that are close to or inside the 2:1 MMR, when the orbital period of one of the planets is twice the other. Analytical models to describe this particular MMR can only be reduced to integrable approximations in a few specific cases. While there are successful approaches to the study of this MMR in the case of very elliptic and/or very inclined orbits using semi-analytical or semi-numerical methods, these may not be enough to completely understand the resonant dynamics. In this work, we propose to apply a well-established numerical method to assess the global portrait of the resonant dynamics, which consists in constructing dynamical maps. Combining these maps with the results from a semi-analytical method, helps to better understand the underlying dynamics of the 2:1 MMR, and to identify the behaviors that can be expected in different regions of the phase space and for different values of the model parameters. We verify that the family of stable resonant equilibria bifurcate from symmetric to asymmetric librations, depending on the mass ratio and eccentricities of the resonant planets pair. This introduces new structures in the phase space, that turns the classical V-shape of the MMR, in the semi-major axis vs. eccentricity space, into a sand clock shape. We construct dynamical maps for three extrasolar planetary systems, TOI-216, HD27894, and K2-24, and discuss their phase space structure and their stability in the light of the orbital fits available in the literature.

Abstract: Stellar obliquity, the angle between a planet's orbital axis and its host star's spin axis, traces the formation and evolution of a planetary system. In transiting exoplanet observations, only the sky-projected stellar obliquity can be measured, but this can be de-projected using an estimate of the stellar obliquity. In this paper, we introduce a flexible, hierarchical Bayesian framework that can be used to infer the stellar obliquity distribution solely from sky-projected stellar obliquities, including stellar inclination measurements when available. We demonstrate that while a constraint on the stellar inclination is crucial for measuring the obliquity of an individual system, it is not required for robust determination of the population-level stellar obliquity distribution. In practice, the constraints on the stellar obliquity distribution are mainly driven by the sky-projected stellar obliquities. When applying the framework to all systems with measured sky-projected stellar obliquity, which are mostly Hot Jupiter systems, we find that the inferred population-level obliquity distribution is unimodal and peaked at zero degrees. The misaligned systems have nearly isotropic stellar obliquities with no strong clustering near 90 degrees. The diverse range of stellar obliquities prefers dynamic mechanisms, such as planet-planet scattering after a convergent disk migration, which could produce both prograde and retrograde orbits of close-in planets with no strong inclination concentrations other than 0 degrees.