Earth and Planetary Astrophysics (astro-ph.EP)

Abstract: The near-Earth asteroid, Kamo`oalewa (469219), is one of a small number of known quasi-satellites of Earth. Numerical simulations show that it transitions between quasi-satellite and horseshoe orbital states on centennial timescales, maintaining this dynamics over megayears. Its reflectance spectrum suggest a similarity to lunar silicates. Considering its Earth-like orbit and its physical resemblance to lunar surface materials, we explore the hypothesis that it might have originated as a debris-fragment from a meteoroidal impact with the lunar surface. We carry out numerical simulations of the dynamical evolution of particles launched from different locations on the lunar surface with a range of ejection velocities. As these ejecta escape the Earth-Moon environment and evolve into heliocentric orbits, we find that a small fraction of launch conditions yield outcomes that are compatible with Kamo`oalewa's dynamical behavior. The most favored conditions are launch velocities slightly above the escape velocity from the trailing lunar hemisphere.

Abstract: Understanding the temperature structure of protoplanetary disks is crucial for answering the fundamental question of when and where in the disks rocky planets like our own form. However, the thermal structure of the inner few au of the disks is poorly understood not only because of lack of observational constraints but also because of the uncertainty of accretion heating processes. Here, we propose thermal tomography of the inner regions of protoplanetary disks with the ngVLA and ALMA. The proposed approach is based on the assumption that the inner disk regions are optically thick at submillimeter wavelengths but are marginally optically thin at longer millimeter wavelengths. By combining high-resolution millimeter continuum images from the ngVLA with submillimeter images at comparable resolutions from ALMA, we will be able to reconstruct the radial and vertical structure of the inner few au disk regions. We demonstrate that the thermal tomography we propose can be used to constrain the efficiency of midplane accretion heating, a process that controls the timing of snow-line migration to the rocky planet-forming region, in the few au regions of protoplanetary disks at a distance of 140 pc.

Abstract: Current space-based missions, such as the Transiting Exoplanet Survey Satellite (TESS), provide a large database of light curves that must be analysed efficiently and systematically. In recent years, deep learning (DL) methods, particularly convolutional neural networks (CNN), have been used to classify transit signals of candidate exoplanets automatically. However, CNNs have some drawbacks; for example, they require many layers to capture dependencies on sequential data, such as light curves, making the network so large that it eventually becomes impractical. The self-attention mechanism is a DL technique that attempts to mimic the action of selectively focusing on some relevant things while ignoring others. Models, such as the Transformer architecture, were recently proposed for sequential data with successful results. Based on these successful models, we present a new architecture for the automatic classification of transit signals. Our proposed architecture is designed to capture the most significant features of a transit signal and stellar parameters through the self-attention mechanism. In addition to model prediction, we take advantage of attention map inspection, obtaining a more interpretable DL approach. Thus, we can identify the relevance of each element to differentiate a transit signal from false positives, simplifying the manual examination of candidates. We show that our architecture achieves competitive results concerning the CNNs applied for recognizing exoplanetary transit signals in data from the TESS telescope. Based on these results, we demonstrate that applying this state-of-the-art DL model to light curves can be a powerful technique for transit signal detection while offering a level of interpretability.

Abstract: Mean plane measurements of the Kuiper Belt from observational data are of interest for their potential to test dynamical models of the solar system. Recent measurements have yielded inconsistent results. Here we report a measurement of the Kuiper Belt's mean plane with a sample size more than twice as large as in previous measurements. The sample of interest is the non-resonant Kuiper belt objects, which we identify by using machine learning on the observed Kuiper Belt population whose orbits are well-determined. We estimate the measurement error with a Monte Carlo procedure. We find that the overall mean plane of the non-resonant Kuiper Belt (semimajor axis range 35-150 au) and also that of the classical Kuiper Belt (semimajor axis range 42-48 au) are both close to (within about 0.7 degrees) but distinguishable from the invariable plane of the solar system to greater than 99.7% confidence. When binning the sample into smaller semimajor axis bins, we find the measured mean plane mostly consistent with both the invariable plane and the theoretically expected Laplace surface forced by the known planets. Statistically significant discrepancies are found only in the semimajor axis ranges 40.3-42 au and 45-50 au; these ranges are in proximity to a secular resonance and Neptune's 2:1 mean motion resonance where the theory for the Laplace surface is likely to be inaccurate. These results do not support a previously reported anomalous warp at semimajor axes above 50 au.

Abstract: The extraordinary 2021 September-October outburst of Centaur 29P/Schwassmann-Wachmann 1 afforded an opportunity to test the composition of primitive Kuiper disk material at high sensitivity. We conducted nearly simultaneous multi-wavelength spectroscopic observations of 29P/Schwassmann-Wachmann 1 using iSHELL at the NASA Infrared Telescope Facility and nFLASH at the Atacama Pathfinder EXperiment (APEX) on 2021 October 6, with follow-up APEX/nFLASH observations on 2021 October 7 and 2022 April 3. This coordinated campaign between near-infrared and radio wavelengths enabled us to sample molecular emission from a wealth of coma molecules and to perform measurements that cannot be accomplished with either wavelength alone. We securely detected CO emission on all dates with both facilities, including velocity-resolved spectra of the CO (J=2-1) transition with APEX/nFLASH and multiple CO (v=1-0) rovibrational transitions with IRTF/iSHELL. We report rotational temperatures, coma kinematics, and production rates for CO and stringent (3-sigma) upper limits on abundance ratios relative to CO for CH4, C2H6, CH3OH, H2CO, CS, and OCS. Our upper limits for CS/CO and OCS/CO represent their first values in the literature for this Centaur. Upper limits for CH4, C2H6, CH3OH, and H2CO are the most stringent reported to date, and are most similar to values found in ultra CO-rich Oort cloud comet C/2016 R2 (PanSTARRS), which may have implications for how ices are preserved in cometary nuclei. We demonstrate the superb synergy of coordinated radio and near-infrared measurements, and advocate for future small body studies that jointly leverage the capabilities of each wavelength.