Sazuna/UAT_keywords huggingface dataset:
The Radiative Effects of Photochemical Hazes on the Atmospheric Circulation and Phase Curves of Sub-Neptunes. Measuring the atmospheric composition of hazy sub-Neptunes like GJ 1214b through transmission spectroscopy is difficult because of the degeneracy between mean molecular weight (MMW) and haziness. It has been proposed that phase-curve observations can break this degeneracy because of the relationship between MMW and phase-curve amplitude. However, photochemical hazes can strongly affect phase-curve amplitudes as well. We present a large set of general circulation model simulations of the sub-Neptune GJ 1214b that include photochemical hazes with varying atmospheric composition, haze opacity, and haze optical properties. In our simulations, photochemical hazes cause temperature changes of up to 200 K, producing thermal inversions and cooling deeper regions. This results in increased phase-curve amplitudes and adds a considerable scatter to the phase-curve amplitude─metallicity relationship. However, we find that if the haze production rate is high enough to significantly alter the phase curve, the secondary eclipse spectrum will exhibit either emission features or strongly muted absorption features. Thus, the combination of a white-light phase curve and a secondary eclipse spectrum can successfully distinguish between a hazy, lower-MMW and a clear, high-MMW scenario.

Keywords: Exoplanet atmospheric dynamics, Extrasolar gaseous planets, Extrasolar gaseous giant planets, Exoplanet atmospheres, Exoplanet atmospheric structure
The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations. Pulsar timing array observations have found evidence for an isotropic gravitational-wave background with the Hellings─Downs angular correlations between pulsar pairs. This interpretation hinges on the measured shape of the angular correlations, which is predominantly quadrupolar under general relativity. Here we explore a more flexible parameterization: we expand the angular correlations into a sum of Legendre polynomials and use a Bayesian analysis to constrain their coefficients with the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). When including Legendre polynomials with multipoles ℓ ≥ 2, we only find a significant signal in the quadrupole with an amplitude consistent with general relativity and nonzero at the ∼95% confidence level and a Bayes factor of 200. When we include multipoles ℓ ≤ 1, the Bayes factor evidence for quadrupole correlations decreases by more than an order of magnitude due to evidence for a monopolar signal at approximately 4 nHz, which has also been noted in previous analyses of the NANOGrav 15 yr data. Further work needs to be done in order to better characterize the properties of this monopolar signal and its effect on the evidence for quadrupolar angular correlations.

Keywords: Supermassive black holes, Millisecond pulsars, Gravitational wave astronomy, Gravitational waves, Radio pulsars
The Impact of Stellar Flares on the Atmospheric Escape of Exoplanets Orbiting M Stars. I. Insights from the AU Mic System. The X-ray and extreme ultraviolet (XUV) emission from M stars can drive the atmospheric escape on planets orbiting them. M stars are also known for their frequent emission of stellar flares, which will increase the high-energy flux received by their orbiting planets. To understand how stellar flares impact the primordial atmospheres of planets orbiting young M stars, we use UV spectroscopic data of flares from the Habitable Zones and M dwarf Activity across Time and Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems programs as a proxy for the XUV flare emission. Using the software package VPLanet, we simulate the young AU Mic planetary system composed of two Neptune-sized and one Earth-sized planet orbiting a 23 Myr old M1 star. Our findings show that the Earth-sized planet AU Mic d should be in the process of completely losing its atmosphere in the next couple million years, solely due to the quiescent emission, with flares not significantly contributing to its atmospheric escape, due to the small size of AU mic d and its close-in distance from the star. However, our results indicate that flares would play a crucial role for such planets farther away, in the habitable zone (i.e., 0.2935 au) of AU Mic-like stars during the post-saturation phase, accelerating the total atmospheric loss process by a few billion years. For planets between 0.365 au and the HZ outer edge, the additional XUV from flares is necessary to fully deplete primordial atmospheres, since the quiescent emission alone is insufficient.

Keywords: M dwarf stars, Extrasolar rocky planets, Exoplanets, Extreme ultraviolet astronomy, Ultraviolet spectroscopy, M stars, Exoplanet astronomy, Stellar flares, Star-planet interactions, Habitable zone, Exoplanet atmospheres, Exoplanet atmospheric evolution
JWST Observations of the Ring Nebula (NGC 6720). III. A Dusty Disk around Its Central Star. The planetary nebula NGC 6720, also known as the "Ring Nebula," is one of the most iconic examples of nearby planetary nebulae whose morphologies present a challenge to our theoretical understanding of the processes that govern the deaths of most stars in the Universe that evolve on a Hubble time. We present new imaging with JWST of the central star of this planetary nebula (CSPN) and its close vicinity, in the near-to-mid-IR wavelength range. We find the presence of a dust cloud around the CSPN, both from the spectral energy distribution at wavelengths ≳5 μm as well as from radially extended emission in the 7.7, 10, and 11.3 μm images. From the modeling of these data, we infer that the CSPN has a luminosity of 310 L⊙ and is surrounded by a dust cloud with a size of ∼2600 au, consisting of relatively small amorphous silicate dust grains (radius ∼0.01 μm) with a total mass of 1.9 × 10‑6 M⊕. However, our best-fit model shows a significant lack of extended emission at 7.7 μm—we show that such emission can arise from a smaller (7.3 × 10‑7 M⊕) but uncertain mass of (stochastically heated) ionized polycyclic aromatic hydrocarbon (PAHs). However, the same energetic radiation also rapidly destroys PAH molecules, suggesting that these are most likely being continuously replenished, via the outgassing of cometary bodies and/or the collisional grinding of planetesimals. We also find significant photometric variability of the central source that could be due to the presence of a close dwarf companion of mass ≤0.1 M⊙.

Keywords: Silicate grains, Polycyclic aromatic hydrocarbons, Light curves, Post-asymptotic giant branch, Ultraviolet spectroscopy, Stellar mass loss, Infrared astronomy, James Webb Space Telescope, Planetary nebulae, Planetesimals, Circumstellar dust, Gaia
Exact Nonlinear Decomposition of Ideal-MHD Waves Using Eigenenergies. III. Gravity, Generalized Inhomogeneous Quasi-linear Partial Differential Equations, Mode Conversion, and Numerical Implementation. Precise tracking and measurement of the energy carried by the individual magnetohydrodynamic (MHD) modes has important implications and utility in both astrophysical and laboratory plasmas. Previously, this was only achievable in limited linear MHD cases in the β ≪ 1 or β ≫ 1 regimes. In a series of papers, of which this is the third, we introduced the Eigenenergy Decomposition Method (or EEDM) and derived exact analytical expressions for the modal energy components—called eigenenergies—of nonlinear 3D disturbances governed by the homogeneous ideal MHD equations. Here we extend the method to inhomogeneous ideal MHD by introducing a source term accounting for gravity, and we provide detailed guidelines for applying the decomposition scheme to any general inhomogeneous quasi-linear partial differential equations that possess a globally conserved quantity, beyond the realm of MHD. Furthermore, we show that the eigenenergies can be used to locate and measure nonlinear mode conversions, which is an additional feature of the method. Finally, we provide well-categorized context for the application of the method to simulations and discuss the possible numerical inaccuracies that may inevitably arise owing to discretization. This paper provides a more mature description of the method and its interpretation and is recommended as the starting point for readers unfamiliar with the method.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar physics, Solar coronal waves, Alfven waves, Magnetohydrodynamical simulations
Evolution of Alfvén Waves in the Solar Wind. II. Broadband Driver. The propagation of azimuthal Alfvén waves and their interaction with the solar wind are investigated using a 2.5D magnetohydrodynamic model that incorporates the effects of optically thin radiation, as well as collisional and collisionless thermal conduction. The background plasma forms a dipole field that is extended into a helmet streamer by the solar wind, with slow wind near the equator and fast wind at mid- and high latitudes. Alfvénic wave trains, localized at random heliographic latitudes, are launched from the coronal base with a moderate amplitude of 9 km s‑1 across a wide range of frequencies. Experiments with 100 and 200 events are carried out, resulting in the formation of a cavity where the waves are trapped. The cavity expands or contracts based on the dominant driver period, with longer-period waves setting up larger cavities. A distinctive feature of the cavity is the formation of large-amplitude backward waves that provide an additional push to the solar wind plasma at mid- and high latitudes through the ponderomotive force. We find that episodic and localized wave trains are more efficient at heating and accelerating solar wind plasma compared to continuous monochromatic waves uniformly launched from all heliographic latitudes. Increasing the number of wave events results in enhanced acceleration and heating of the solar wind plasma, as well as suppression of plasmoid breakup events in the equatorial plasma sheet.

Keywords: Solar physics
Predicting Solar Flares Using a Convolutional Neural Network with Extreme-ultraviolet Images. Solar flares, as one of the most intense solar eruptive activities, can bring a destructive impact on the near-Earth space environment and technological infrastructure. Therefore, accurate and real-time forecast of the occurrence of flares is essential to reduce the potential damage to space facilities and navigation systems. Several types of flare forecasting methods have been proposed, e.g., the statistical methods, numerical methods, traditional machine learning, and the recently developed deep leaning. In this paper, we apply one of the deep learning methods, the convolutional neural network ResNet-18, to the tricolor (94, 193, and 304 Å) full-disk extreme-ultraviolet images observed by the Solar Dynamics Observatory Atmospheric Imaging Assembly from 2012 to 2022 with 5 × 24 × 365 × 11 images and 10026 flares ≥ C-class in total to build a solar flare forecasting model to predict whether a flare ≥ C-class would occur within the next m hr (m = 6, 12, 24, 48, and 72). The values of most performance evaluation metrics scores are over 0.8, with some even exceeding 0.9. The main advantage of this model lies in that it can effectively leverage the historical and spatial information of the source active regions as well as the interaction information from the surrounding active regions or other structures. This information, which cannot be provided by the data from a single active region alone, is demonstrated to be crucial in predicting solar flares. The results show that our prediction model performs well in both short-term and long-term forecasting.

Keywords: Solar activity, Solar physics, Solar flares
Influence of Planetary Rotation on Supersonic Flow of Lava Planets: A Two-dimensional Horizontal Model Analysis. The study of lava planets has attracted significant attention recently because of their close proximity to their host stars, which enhances their detectability for atmospheric characterization. Previous studies showed that the atmospheric flow becomes supersonic if the atmosphere is dominated by rocky vapor evaporated from the magma ocean around the substellar point. These studies often assumed an axisymmetric flow about the axis from the substellar point to the antistellar point but ignored the effect of planetary rotation. However, since the spin rate of lava planets can be rather fast due to their close-in orbits, the aforementioned symmetry may be broken, and significant asymmetric flow is expected. Here, we introduce a two-dimensional framework to explore the influence of planetary rotation on the atmospheric dynamics of these lava planets for the first time, and assess the sensitivity and range of application of our model. Starting from the established one-dimensional axisymmetric atmospheric solution, we obtain the governing equation for the asymmetric flow by expanding with respect to 1/Ro (Ro denotes Rossby number and exceeds unity for typical lava planets). The asymmetric component of supersonic flow is pivotal for future research on the observation of these atmospheres, flow patterns of the magma ocean currents driven by atmospheric winds, and deformation of the planetary shape over long timescales.

Keywords: Exoplanets, Exoplanet evolution, Exoplanet surfaces, Perturbation methods, Exoplanet atmospheres
Impact of Magnetohydrodynamic Disk Wind on Early Evolutionary Stage of Protoplanetary Disk and Dust Growth. We perform one-dimensional protoplanetary disk evolution calculations to investigate the impact of the magnetohydrodynamic (MHD) disk wind on disk evolution and dust particle growth. To examine the effect of the MHD disk wind, we compare calculations with and without it. In disk evolution calculations, episodic accretion events (or outbursts) occur repeatedly, as reported in previous studies, regardless of the presence of the MHD disk wind. However, the time interval between outbursts is shorter in cases with the MHD disk wind than in those without it. For the dust particle growth, during the infall phase, there is no significant difference between cases with and without the MHD disk wind, and the dust particles grow to approximately 1–10 cm. Inside the H2O snow line, the maximum dust particle size is limited by the collisional fragmentation of the dust particles. Outside the snow line, the maximum dust particle size is primarily determined by radial drift. After the infall phase, when the MHD disk wind is considered, the disk temperature decreases noticeably, and the snow line migrates inward. As a result, the dust particles can grow beyond 10 cm. Therefore, we find that the MHD disk wind plays a crucial role in dust growth and planet formation after the infall phase.

Keywords: Star formation, Protoplanetary disks
Possibility of Using 3.3 μm Polycyclic Aromatic Hydrocarbon Luminosity as a Molecular Gas Mass Estimator. We present CO(1–0) observations of 50 star-forming galaxies at 0.01 &lt; z &lt; 0.35, for which 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission flux or its upper limit is available. A scaling relation between 3.3 μm PAH luminosity and CO(1–0) luminosity is established covering ∼2 orders of magnitude in total IR luminosity and CO luminosity, with a scatter of ∼0.23 dex:   =   +(‑1.10 ± 0.70). The slope is near unity, allowing the use of a single value of   =‑1.09 ± 0.36 [L⊙/(K km s‑1 pc2)] in the conversion between 3.3 μm PAH and CO luminosities. The variation in the   ratio is not dependent on the galaxy properties, including total IR luminosity, stellar mass, and star formation rate excess. The total gas mass, estimated using the dust-to-gas ratio and dust mass, is correlated with 3.3 μm PAH luminosity, in line with the prescription using αCO = 0.8–4.5 covering both normal star-forming galaxies and starburst galaxies. Active galactic nucleus (AGN)-dominated galaxies tend to have a lower   than non-AGN galaxies, which needs to be investigated further with an increased sample size. The established L3.3–  correlation is expected to be applicable to wide-field near-infrared spectrophotometric surveys that allow the detection of 3.3 μm emission from numerous low-redshift galaxies.

Keywords: Starburst galaxies, Molecular gas, Polycyclic aromatic hydrocarbons, Star formation, Ultraluminous infrared galaxies, Galaxies, Luminous infrared galaxies
Limits of Solar Flare Forecasting Models and New Deep Learning Approach. Reliable forecasting models are necessary to mitigate the risks posed by solar flares to human technology. This study introduces a novel deep learning forecasting approach while emphasizing the need for performance evaluation methods tailored to better highlight current models' limitations. In particular, we show that models reaching state-of-the-art performance with traditional metrics have similar explanatory power to no-skill persistence models and notably struggle to forecast change in activity significantly better than random guesses. We also discuss shortcomings in traditional evaluation metrics like the True Skill Statistic (TSS), which we show to be mathematically dependent on the class balance for specific models. We introduce patch-distributed CNNs, which allow us to perform full-disk forecasts while providing event probabilities in solar subregions and position predictions. This new framework offers similar information to active region (AR)-based forecasting models while bypassing the problem of unrecorded and misattributed flares that are detrimental to machine learning training. As a result, the model also operates independently of prior feature extraction and AR detection, thus offering promising operational utility with minimal external dependencies. Finally, a method is proposed for constructing balanced and independent cross-validation folds for full-disk models. Models combining Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly EUV images as inputs show improved performance compared to employing SDO/HMI photospheric magnetograms, with a TSS of 0.74 for the C+ model and 0.62 for the M+ model. *V1 preprint released on 2024 February, V2 released on 2024 May 15 on ESS Open Archive 10.22541/essoar.170688972.24631782/v3.

Keywords: Convolutional neural networks, Solar flares, Magnetogram
The UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Large Director's Discretionary Program with Hubble. I. Goals, Design, and Initial Results. Specifically selected to leverage the unique ultraviolet capabilities of the Hubble Space Telescope, the Hubble Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) is a Director's Discretionary program of approximately 1000 orbits—the largest ever executed—that produced a UV spectroscopic library of O and B stars in nearby low-metallicity galaxies and accreting low-mass stars in the Milky Way. Observations from ULLYSES combined with archival spectra uniformly sample the fundamental astrophysical parameter space for each mass regime, including spectral type, luminosity class, and metallicity for massive stars, and the mass, age, and disk accretion rate for low-mass stars. The ULLYSES spectral library of massive stars will be critical to characterize how massive stars evolve at different metallicities; to advance our understanding of the production of ionizing photons, and thus of galaxy evolution and the re-ionization of the Universe; and to provide the templates necessary for the synthesis of integrated stellar populations. The massive-star spectra are also transforming our understanding of the interstellar and circumgalactic media of low-metallicity galaxies. On the low-mass end, UV spectra of T Tauri stars contain a plethora of diagnostics of accretion, winds, and the warm disk surface. These diagnostics are crucial for evaluating disk evolution and provide important input to assess atmospheric escape of planets and to interpret powerful probes of disk chemistry, as observed with the Atacama Large Millimeter Array and the James Webb Space Telescope. In this paper, we motivate the design of the program, describe the observing strategy and target selection, and present initial results.

Keywords: B stars, O stars, Massive stars, Dwarf galaxies, Ultraviolet spectroscopy, Ultraviolet surveys, T Tauri stars, Star formation, Stellar accretion, Stellar accretion disks, Milky Way Galaxy
Modeling Triatomic Biosignatures: Ozone and Isotopomers. In this work, we present a new approach to produce spectroscopic constants and model first-principles synthetic spectra for all molecules of astrophysical interest. We have generalized our previous diatomic molecule simulation framework, employing transition-optimized shifted Hermite (TOSH) theory, thereby enabling the modeling of polyatomic rotational constants for molecules with three or more atoms. These capabilities are now provided by our new code Epimetheus. As a first validation of our approach, we confront our predictions and assess their accuracy against the well-studied triatomic molecule ozone 666 (16O3), in addition to eight of its potential isotopomers: ozone 668 (16O16O18O), 686 (16O18O16O), 667 (16O16O17O), 676 (16O17O16O), 688 (16O18O18O), 868 (18O16O18O), 888 (18O3), and 777 (17O3). We then assess the accuracy of these rotational constants using the Epimetheus data in our code Pandora, and generate synthetic molecular spectra. The ozone spectra presented here are purely infrared and not Raman. Epimetheus builds upon the work from our previous code Prometheus, which used the TOSH theory to account for anharmonicity for the fundamental ν = 0 → ν = 1 band, going further to now account for triatomic molecules. This is combined with thermal profile modeling for the rotational transitions. We have found that this extended method performs well, typically approximating the spectroscopic constants with errors of less than 2%. Some issues do arise depending on the symmetry group of the ozone isotopomer. From these spectroscopic constants and using our own spectral modeling code, we show that we can provide the data to produce appreciable molecular spectra, which are good approximations until high-resolution studies can be done.

Keywords: Biosignatures, Astrochemistry
SPYGLASS. VI. Feedback-driven Star Formation in the Circinus Complex. Young associations provide a record that traces the star formation process, and the youngest populations connect progenitor gas dynamics to the resulting stellar populations. We therefore conduct the first comprehensive overview of the Circinus Complex, an understudied and massive (∼1500 M⊙) region consisting of approximately 3100 recently formed stars alongside the Circinus Molecular Cloud. We find a clear age pattern in the contiguous central region (CirCe), where younger stars are found farther from the massive central cluster, and where the velocities are consistent with uniform expansion. By comparing this structure to an analogous STARFORGE simulation, we find that the age structure and dynamics of the association are consistent with star formation in two stages: the global collapse of the parent cloud that builds the 500M⊙ central cluster ASCC 79, followed by triggered star formation in a shell swept up after the first massive stars form. We also find that filaments with a range of distances from the central cluster can naturally produce multigenerational age sequences due to differences in feedback strength and exposure. Outlying populations show velocities consistent with formation independent from the CirCe region, but with similar enough velocities that they may be difficult to distinguish from one another later in their expansion. We therefore provide a new alternative view of sequential star formation that relies on feedback from a single central cluster rather than the multiple sequential generations that are traditionally invoked, while also providing insight into the star formation history of older populations.

Keywords: Stellar ages, Stellar kinematics, Star forming regions, Pre-main sequence stars, Star formation, Stellar associations