Sazuna/UAT_keywords huggingface dataset:
Novae: An Important Source of Lithium in the Galaxy. The source of the Galactic lithium (Li) has long been a puzzle. With the discovery of Li in novae, extensive research has been conducted. However, there still exists a significant disparity between the observed abundance of Li in novae and the existing theoretical predictions. Using the Modules for Experiments in Stellar Astrophysics, we simulate the evolution of novae with element diffusion and appropriately increase the amount of 3He in the mixtures. Element diffusion enhances the transport efficiency between the nuclear reaction zone and the convective region on the surface of the white dwarf (WD) during nova eruptions, which results in more 7Be being transmitted to the WD surface and ultimately ejected. Compared to the previous predictions, the abundance of 7Be in novae simulated in our model significantly increases. The result is able to explain almost all observed novae. Using the method of population synthesis, we calculate Li yield in the Galaxy. We find that the Galactic occurrence rate of novae is about 130 yr‑1, and about 110 M ⊙ Li produced by nova eruption is ejected into the interstellar medium (ISM). About 73% of Li in the Galactic ISM originates from novae and approximately 15%–20% of the entire Galaxy. This means that novae are the important source of Li in the Galaxy.

Keywords: Binary stars, Nucleosynthesis, Chemical abundances, Novae, Recurrent novae, Galactic abundances
Repelling Planet Pairs by Ping-pong Scattering. The Kepler mission reveals a peculiar trough-peak feature in the orbital spacing of close-in planets near mean-motion resonances: a deficit and an excess that are, respectively, a couple of percent interior to and wide of the resonances. This feature has received two main classes of explanations: one involving eccentricity damping and the other scattering with small bodies. Here, we point out a few issues with the damping scenario and study the scattering scenario in more detail. We elucidate why scattering small bodies tends to repel two planets. As the small bodies random-walk in energy and angular momentum space, they tend to absorb fractionally more energy than angular momentum. This, which we call "ping-pong repulsion," transports angular momentum from the inner to the outer planet and pushes the two planets apart. Such a process, even if ubiquitous, leaves identifiable marks only near first-order resonances: diverging pairs jump across the resonance quickly and produce the mean-motion resonance asymmetry. To explain the observed positions of the trough-peaks, a total scattering mass of order a few percent of the planet masses is required. Moreover, if this mass is dominated by a handful of Mercury-sized bodies, one can also explain the planet eccentricities as inferred from transit-time variations. Last, we suggest how these conditions may have naturally arisen during the late stages of planet formation.

Keywords: Exoplanet dynamics, Celestial mechanics, Exoplanet formation, Planetary dynamics, Planet formation
Insights from Optical Fe II Emission in Quasars. The complexity of the energy levels in Fe II has made it difficult to theoretically interpret its observational emission spectrum. However, addressing this challenge could provide valuable insights into the main sequence of QSOs using "eigenvector 1" and the chemical evolution of the Universe. Although the templates based on I Zw 1 are widely used, their universality remains unexplained. To address this, we utilized the CLOUDY spectral synthesis code to generate theoretical blends of Fe II optical emission near the Hβ region. Our results indicate that the optimal cloud density and photon flux align with previous studies at gas density 1011 cm‑3 and photon flux 1020.5 cm‑2 s‑1. We discovered a broad parameter region that fits the data well, encompassing a diverse range of densities and photon fluxes. This helps to explain the general applicability of optical templates. Additionally, we investigated the effects of different spectral energy distributions (SEDs), Eddington ratios, turbulence, and cloud column densities and found that they provided a sufficiently broad range for typical emitting clouds. We found different SEDs had a negligible impact on the template shape, further expanding the usability of empirical templates. However, they significantly affected the absolute intensity of Fe II emission, consistent with previous research. Furthermore, we determined that a turbulence of approximately 100 km s‑1 is necessary to produce sufficiently strong optical Fe II, and either a column density greater than 1024 cm‑2, which is typical for Fe II UV emission, or an abundance higher than solar is preferred.

Keywords: Photoionization, Active galactic nuclei, Quasars
On the Origin of Solar Hemispheric Helicity Rules: Rise of 3D Magnetic Flux Concentrations through a Background Magnetic Field. Sunspots and active regions observed on the solar surface are widely believed to be manifestations of compact predominantly toroidal magnetic field structures ("flux tubes") that emerge by magnetic buoyancy from the deeper interior of the Sun. Much work has examined the evolution of such magnetic structures, typically considering them as idealized isolated magnetic entities and not as more realistic magnetic concentrations in a volume-filling background magnetic field. Here, we report results that explore the buoyant rise dynamics of magnetic concentrations in a volume-filling field in the full three dimensions. Earlier 2.5D work in this series established the remarkable fact that the twist orientation of a flux concentration relative to the background field affected its likelihood to rise and emerge, regardless of whether the buoyant rise took place in the absence or presence of convection. The contrasting dynamics between structures with differing orientations lead to a selection mechanism that reproduces characteristics of the "solar hemispheric helicity rule(s)" observations strikingly well. Here, we show that this two-dimensional selection mechanism persists in the face of the added complexity of three-dimensional dynamics. Arching of the magnetic structure in the third dimension, as might be expected in the solar application, is introduced. The role of tension force leading to this selection mechanism is elucidated and subtle differences that arise due to the three-dimensional geometry are discussed.

Keywords: Magnetohydrodynamics, Solar interior, Sunspots, Solar dynamo, Solar magnetic fields
Exploring the Archives: A Search for Novae in UVIT Snapshots of M31. Extensive multiwavelength studies of novae have been carried out in our galaxy and in M31 for decades. However, UV studies of extragalactic novae are limited, especially those in quiescence. For the first time, we present a UV catalog of novae in M31 using the archival AstroSat Ultraviolet Imaging Telescope (UVIT) imaging data. We used two image subtraction techniques to retrieve objects located deep into the M31 central region. We have found 42 novae in total in the UVIT images, 15 of which have been detected in multiple filters in the far-ultraviolet (FUV) and near-ultraviolet. The novae detected at quiescence show signatures of accretion disk from their UV spectral energy distributions, whereas those in the outburst phase show signatures of a pseudo-photosphere. A few novae were also detected in multiple epochs. Some show a near-constant FUV magnitude at quiescence, while others caught near the outburst reveal pre-eruption dips in their light curves. We conclude with a discussion on the significance of UV surveys in illuminating theoretical predictions for novae systems, including detecting the elusive early UV flash.

Keywords: Accretion, High energy astrophysics, Light curves, Novae, Ultraviolet astronomy, Extinction, Spectral energy distribution, Transient detection, Stellar accretion disks, Cataclysmic variable stars, Andromeda Galaxy, Astronomy image processing
Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy. We present the projected rotational velocity and molecular abundances for HD 33632 Ab obtained via Keck Planet Imager and Characterizer (KPIC) high-resolution spectroscopy. HD 33632 Ab is a nearby benchmark brown dwarf companion at a separation of ∼20 au that straddles the L–T transition. Using a forward-modeling framework with on-axis host star spectra, which provides self-consistent substellar atmospheric and retrieval models for HD 33632 Ab, we derive a projected rotational velocity of 53 ± 3 km s‑1 and carbon monoxide and water mass fractions of logCO = ‑2.3 ± 0.3 and logH2O = ‑2.7 ± 0.2, respectively. The inferred carbon-to-oxygen ratio (C/O = 0.58 ± 0.14), molecular abundances, and metallicity ([C/H] = 0.0 ± 0.2 dex) of HD 33632 Ab are consistent with its host star. Although detectable methane opacities are expected in L–T transition objects, we did not recover methane in our KPIC spectra, partly due to the high v sin i and to disequilibrium chemistry at the pressures to which we are sensitive. We parameterize the spin as the ratio of rotation to the breakup velocity, and compare HD 33632 Ab to a compilation of &gt;200 very low-mass objects (M ≲ 0.1 M ⊙) that have spin measurements in the literature. There appears to be no clear trend for the isolated low-mass field objects versus mass, but a tentative trend is identified for low-mass companions and directly imaged exoplanets, similar to previous findings. A larger sample of close-in gas giant exoplanets and brown dwarfs will critically examine our understanding of their formation and evolution through rotation and chemical abundance measurements.

Keywords: High resolution spectroscopy, Brown dwarfs, L dwarfs, Atmospheric composition, Stellar rotation, High angular resolution
The Incompressible Magnetohydrodynamic Energy Cascade Rate Upstream of Mars: Effects of the Total Energy and the Cross-helicity on Solar Wind Turbulence. Solar wind turbulence is a dynamical phenomenon that evolves with heliocentric distance. Orbiting Mars since 2014 September, Mars Atmosphere and Volatile EvolutioN offers a unique opportunity to explore some of its main properties beyond ∼1.38 au. Here, we analyze solar wind turbulence upstream of Mars' bow shock, utilizing more than 5 years of magnetic field and plasma measurements. This analysis is based on two complementary methodologies: (1) the computation of magnetohydrodynamic (MHD) invariants characterizing incompressible fluctuations; (2) the estimation of the incompressible energy cascade rate at MHD scales (i.e., 〈ɛ  T 〉MHD). Our results show the solar wind incompressible fluctuations are primarily in a magnetically dominated regime, with the component traveling away from the Sun having a higher median pseudoenergy. Moreover, turbulent fluctuations have a total energy per mass of up to ∼ 300 km2 s‑2, a range smaller than reported at 1 au. For these conditions, we determine the probability distribution function of 〈ɛ  T 〉MHD ranges mainly between ∼ ‑1 × 10‑16 and ∼1 × 10‑16 J m‑3 s ‑1, with a median equal to ‑1.8 × 10‑18 J m‑3  s ‑1, suggesting back transfer of energy. Our results also suggest that ∣〈ɛ  T 〉MHD∣ is correlated with the total energy per mass of fluctuations and that the median of 〈ɛ  T 〉MHD does not vary significantly with the cross-helicity. We find, however, that the medians of the inward and outward pseudoenergy cascade rates vary with the solar wind cross-helicity. Finally, we discuss these results and their implications for future studies that can provide further insight into the factors affecting the solar wind energy transfer rate.

Keywords: Space plasmas, Interplanetary turbulence, Mars, Solar wind, Magnetic fields
FREmu: Power Spectrum Emulator for f(R) Gravity. To investigate gravity in the nonlinear regime of cosmic structure using measurements from stage IV surveys, it is imperative to accurately compute large-scale structure observables, such as nonlinear matter power spectra, for gravity models that extend beyond general relativity. However, the theoretical predictions of nonlinear observables are typically derived from N-body simulations, which demand substantial computational resources. In this study, we introduce a novel public emulator, termed FREmu, designed to provide rapid and precise forecasts of nonlinear power spectra specifically for the Hu–Sawicki f(R) gravity model across scales 0.0089h Mpc‑1 &lt; k &lt; 0.5h Mpc‑1 and redshifts 0 &lt; z &lt; 3. FREmu leverages principal component analysis and artificial neural networks to establish a mapping from parameters to power spectra, utilizing training data derived from the Quijote-MG simulation suite. With a parameter space encompassing seven dimensions, including Ω m , Ω b , h, n  s , σ 8, M  ν , and  fR0 , the emulator achieves an accuracy exceeding 95% for the majority of cases, thus proving to be highly efficient for constraining parameters.

Keywords: Cosmology, Non-standard theories of gravity, Large-scale structure of the universe
Late Pebble Accretion of Comet 81P/Wild 2 Nucleus: Evidence from a Plagioclase-bearing Chondrule Fragment, Pyxie. Comet 81P/Wild 2 is a ∼4.5 km-sized primordial object that almost has not been modified by internal heating by 26Al decay. Its nucleus could have been formed by hierarchical agglomeration or gravitational collapse of pebble swarms concentrated by streaming instability. To shed light on the cometesimal formation mechanism from laboratory sample analysis, we reexamined the 26Al–26Mg isotope systematics of the plagioclase-bearing fragment, Pyxie (from Wild 2 track 81), with significantly improved analytical precision. The revised upper limit of the initial (26Al/27Al)0 of Pyxie is ≤1.5 × 10‑6, 2 times smaller than those estimated from other Wild 2 fragments. Assuming homogenous distribution of 26Al in the early solar system, the minimum crystallization age of Pyxie is estimated to be &gt;3.6 Ma after calcium–aluminum-rich inclusions. Additional petrologic examination demonstrated that it is a chondrule fragment formed in disk environments enriched in moderately volatile elements comparable to the Si-rich rim of CR chondrules before accreting by comet Wild 2. The late accretion of the Wild 2 nucleus with most silicates likely from a common source are not favored by the hierarchical agglomeration model that considers early and continuous accretion. Instead, the results are more in line with comet formation by gentle gravitational collapse of pebbles when the 26Al abundance is extremely low (26Al/27Al ≤ 1.5 × 10‑6) before gas dispersal.

Keywords: Comet nuclei, Mass spectrometry, Chondrules
Numerical Simulation of Radiatively Driven Transonic Relativistic Jets. We perform the numerical simulations of axisymmetric, relativistic, optically thin jets under the influence of the radiation field of an accretion disk. We show that starting from a very low injection velocity at the base, jets can be accelerated to relativistic terminal speeds when traveling through the radiation field. The jet gains momentum through the interaction with the radiation field. We use a relativistic equation of state for multispecies plasma, which self-consistently calculates the adiabatic index for the jet material. All the jet solutions obtained are transonic in nature. In addition to the acceleration of the jet to relativistic speeds, our results show that the radiation field also acts as a collimating agent. The jets remain well collimated under the effect of radiation pressure. We also show that if the jet starts with a rotational velocity, the radiation field will reduce the angular momentum of the jet beam.

Keywords: Black hole physics, Hydrodynamical simulations, Relativistic jets
Hierarchical Structure and Self-gravity in the Maddalena Giant Molecular Cloud. In this work, we present data from the Milky Way Imaging Scroll Painting project for the Maddalena giant molecular cloud (GMC). We decompose the 13CO emission datacube of the observed region into hierarchical substructures using a modified dendrogram algorithm. We investigate the statistical properties of these substructures and examine the role that self-gravity plays on various spatial scales. The statistics of the mass (M), radius (R), velocity dispersion (σ  v ), virial parameter (α vir), and sonic Mach number of the substructures are presented. The radius and mass distributions and the σ  v –R scaling relationship of the substructures resemble those reported in previous studies that use nonhierarchical algorithms to identify the entities. We find that for the hierarchical substructures α vir decreases as the radius or mass of the substructures increases. The majority of the substructures in the quiescent region of the Maddalena GMC are not gravitationally bound (α vir &gt; 2), while most of the substructures in the star-forming regions are gravitationally bound (α vir &lt; 2). Furthermore, we find that self-gravity plays an important role on scales of 0.8–4 pc in the IRAS 06453 star-forming region, while it is not an important factor on scales below 5 pc in the non-star-forming region.

Keywords: Surveys, Star forming regions, Molecular clouds, Interstellar clouds, Interstellar medium
Ion–Electron Instabilities in the Precursors of Weakly Magnetized, Transrelativistic Shocks. Collisionless shocks are known to induce turbulence via upstream ion reflection within the precursor region. This study elucidates the properties of electrostatic and electromagnetic instabilities, exploring their role over the transrelativistic range. Notably, the growth of oblique Buneman waves and previously overlooked, secondary, small-scale ion–electron instabilities is observed to be particularly promoted in the relativistic regime. Furthermore, the growth of large-scale electromagnetic modes encounters severe limitations in any cold, baryon-loaded precursor. It is argued that electron preheating in electrostatic modes may alleviate these constraints, facilitating the subsequent growth of large-scale filamentation modes in the precursors of transrelativistic shocks.

Keywords: Shocks, Gamma-ray bursts, Plasma astrophysics
Direct Optimal Mapping Image Power Spectrum and its Window Functions. The key to detecting neutral hydrogen during the epoch of reionization (EoR) is to separate the cosmological signal from the dominating foreground radiation. We developed direct optimal mapping (DOM) to map interferometric visibilities; it contains only linear operations, with full knowledge of point spread functions from visibilities to images. Here, we demonstrate a fast Fourier transform-based image power spectrum and its window functions computed from the DOM images. We use noiseless simulation, based on the Hydrogen Epoch of Reionization Array Phase I configuration, to study the image power spectrum properties. The window functions show &lt;10‑11 of the integrated power leaks from the foreground-dominated region into the EoR window; the 2D and 1D power spectra also verify the separation between the foregrounds and the EoR.

Keywords: Early universe, Reionization, Radio interferometry, H I line emission
An Analysis of Active Galactic Nucleus─driven Outflows in the Seyfert 1 Galaxy NGC 3227. We have characterized the ionized, neutral, and warm molecular gas kinematics in the Seyfert 1 galaxy NGC 3227 using observations from the Hubble Space Telescope Space Telescope Imaging Spectrograph, Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph, Gemini-North's Near-Infrared Integral Field Spectrometer, and the Atacama Large Millimeter/submillimeter Array. We fit multiple Gaussians to several spatially resolved emission lines observed with long-slit and integral-field spectroscopy and isolate the kinematics based on apparent rotational and outflowing motions. We use the kinematics to determine an orientation for the bicone along which the outflows travel and find that the biconical structure has an inclination of  40−4+5 ° from our line of sight and a half-opening angle with an inner and outer boundary of  47−2+6 ° and  68−1+1 °, respectively. We observe ionized outflows traveling 500 km s−1 at distances up to 7″ (800 pc) from the supermassive black hole (SMBH) and disturbed ionized gas up to a distance of 15″ (1.7 kpc). Our analysis reveals that the ionized outflows are launched from within 20 pc of the SMBH, at the same location as a bridge of cold gas across the nucleus detected in Atacama Large Millimeter/submillimeter Array CO(2─1) observations. We measure a turnover radius where the gas starts decelerating at a distance of 26 ± 6 pc from the active galactic nucleus. Compared to a turnover radius in the range of 31−63 pc from a radiative driving model, we confirm that radiative driving is the dominant acceleration mechanism for the narrow-line region outflows in NGC 3227.

Keywords: AGN host galaxies, Supermassive black holes, Emission line galaxies, Seyfert galaxies, Active galactic nuclei, Galaxy winds, Galaxy kinematics
Microphysics of Particle Reflection in Weibel-mediated Shocks. Particle-in-cell (PIC) simulations have shown that relativistic collisionless shocks mediated by the Weibel instability accelerate ∼1% of incoming particles, while the majority are transmitted through the shock and become thermalized. The microphysical processes that determine whether an incoming particle will be transmitted or reflected are poorly understood. We study the microphysics of particle reflection in Weibel-mediated shocks by tracking a shell of test particles in a PIC simulation of a shock in pair plasma. We find that electrons in positron-dominated filaments and positrons in electron-dominated filaments efficiently reflect off of strong magnetic structures at the shock. To participate in diffusive shock acceleration, however, these reflected particles headed toward the upstream must avoid getting advected downstream. This is enabled by incoming filaments, which trap reflected particles carrying the same sign of current as the filaments. The final injection efficiency on the order of ∼1% thus results from the effectiveness of the initial reflection at the shock and the reflected particles' probability of survival in the upstream postreflection. We develop a model that predicts the fraction of high-energy particles as a function of the properties of Weibel filamentation.

Keywords: Shocks, Plasma astrophysics, High energy astrophysics
Global Anisotropies of Ω<SUB>Λ</SUB>. An analysis of the cosmological constant ΩΛ fitted to subsamples of the Pantheon+ Type Ia supernova sample spanning 2π steradians for a grid of 432 pole positions covering the whole sky reveals two large-scale asymmetries. One of them is closely aligned with the Galactic north–south direction and the other points approximately toward R.A. ∼ 217.°5, decl. ∼ ‑26.°4, ∼50.°9 from the cosmic microwave background dipole Apex. The signal-to-noise ratio (S/N) of the multiple ΩΛ measurements in these directions is 3.2 ≲ S/N ≲ 8.4. The first asymmetry is puzzling, and would indicate a systematic effect related with the distribution of Pantheon+ supernovae on the sky and, probably, how the correction for reddening in the Galaxy is calculated. The second one, which entails a 2.8-σ tension between ΩΛ measured in opposite directions, bears strong implications on our interpretation of ΩΛ as dark energy: it is consistent with the prediction for tilted observers located in a Friedmann–Robertson–Walker universe who could measure an acceleration or a deceleration with a dipolar asymmetry, irrespective of what the universe as a whole is doing. In this case, ΩΛ would not be a physical entity, a real dark energy, but an apparent effect associated with the relativistic frame of reference transformation.

Keywords: Cosmology, Cosmological models, Interstellar dust extinction, Relativistic cosmology