adsabs/SciX_UAT_keywords huggingface dataset:
Soft No More: Gas Shielding Protects Soft Binaries from Disruption in Gas-rich Environments

Binaries in dense environments are traditionally classified as soft or hard based on their binding energy relative to the kinetic energy of surrounding stars. Heggie's law suggests that stellar encounters tend to soften soft binaries and harden hard binaries, altering their separations. However, interactions with gas in such environments can significantly modify this behavior. This study investigates the impact of gas on binary softening and its consequences. We find that gas interactions can actually harden binaries, extending the soft–hard boundary to larger separations. This introduces a "shielding radius" within which binaries are likely to harden due to gas interactions, surpassing the traditional soft–hard limit. Consequently, a notable portion of binaries initially classified as "soft" may become "hard" when both gas and stars are considered. We propose a two-stage formation process for hard binaries: initial soft binary formation, either dynamically or through gas-assisted capture, followed by gas-induced hardening before eventual disruption. In environments with low gas density but high gas content, the shielding radius could exceed the typical hard–soft limit by 1 order of magnitude, leading to a significant fraction of originally soft binaries effectively becoming hard. Conversely, in high-gas-density environments, gas-induced hardening may dominate, potentially rendering the entire binary population hard. Gas hardening emerges as a crucial factor in shaping binary populations in gas-rich settings, such as clusters, star-forming regions, and possibly active galactic nucleus disks. This highlights the complex interplay between gas dynamics and stellar interactions in binary evolution within dense environments.

Keywords: binary stars; multiple stars
Electromagnetic Emission Produced by Three-wave Interactions in a Plasma with Continuously Injected Counterstreaming Electron Beams

Three-wave interactions between Langmuir and electromagnetic waves in plasma with unstable electron flows are believed to be the main cause of type II and III solar radio emissions. The narrow band of type II bursts requires assuming that this radiation is generated in some local regions of shock fronts traveling in the solar corona, where the specific conditions for the enhancement of electromagnetic emissions near the plasma frequency harmonics are created. The reason for such enhancement at the second harmonic may be the formation of counterstreaming electron beams. There are different opinions in the literature on whether the second harmonic electromagnetic emission in the presence of an additional beam can be efficient enough to markedly dominate emissions produced by a single beam. In the present paper, we carry out particle-in-cell simulations of the collision of two symmetric electron beams in plasma with open boundary conditions and show that the efficiency of beam-to-radiation power conversion can be significantly increased compared to models with periodic boundary conditions and reach the level of a few percent if three-wave interactions with electromagnetic waves near the second harmonic of the plasma frequency becomes available for the most unstable, oblique, beam-driven modes.

Keywords: plasma physics; solar radio emission; radio bursts
Local and Global Gas Metallicity versus Stellar Age Relation in MaNGA Galaxies

The search for new global scaling relations linking the physical properties of galaxies has a fundamental interest. Furthermore, their recovery from spatially resolved relations has been in the spotlight of integral field spectroscopy (IFS). In this study, we investigate the existence of global and local relations between stellar age (Age⋆) and gas-phase metallicity (Zg). To this aim, we analyze IFS data for a sample of 736 star-forming disk galaxies from the MaNGA survey. We report a positive correlation between the global Zg and D(4000) (an indicator of stellar age), with a slope that decreases with increasing galaxy mass. Locally, a similar trend is found when analyzing the Zg and D(4000) of the star-forming regions, as well as the residuals resulting from removing the radial gradients of both parameters. The local laws have systematically smaller slopes than the global one. We ascribe this difference to random errors that cause the true slope of the Age⋆-Zg relation to be systematically underestimated when performing a least-squares fitting. The explored relation is intimately linked with the already known relation between gas metallicity and star formation rate at fixed mass, both presenting a common physical origin.

Keywords: galaxy abundances; galaxy formation; galaxy chemical evolution; star formation
Efficient Direct Method for Self-gravity in 3D, Accelerated by a Fast Fourier Transform

Self-gravity calculations for 3D are expensive in terms of computational time. Several methods exist for this computation, for example multigrid and spectral methods. Unfortunately, these approaches require the imposition of boundary conditions, which can be either numerically expensive (direct Newtonian sums), artificial (periodicity assumptions), or potentially imprecise (multipolar expansions). In this work we present a novel direct numerical method to calculate the gravitational potential and forces by solving the Poisson equation without the need to prescribe artificial boundary conditions; this method, despite being direct, turns out to be efficient due to the possibility of using a fast Fourier transform for its implementation. For a grid having N zones in each dimension, the computational complexity of the method presented here is $O({N}^{3}\mathrm{log}{N}^{3})$ , which is comparable with multigrid methods under no consideration of boundary settings. Finally, a numerical study shows this proposed method can achieve second order for calculations of both potential and forces.

Keywords: fast fourier transform
A Relativistic Formula for the Multiple Scattering of Photons

We have discovered analytical expressions for the probability density function (PDF) of photons that are multiply scattered in relativistic flows, under the assumption of isotropic and inelastic scattering. These expressions characterize the collective dynamics of these photons, ranging from free-streaming to diffusion regions. The PDF, defined within the light cone to ensure the preservation of causality, is expressed in a three-dimensional space at a constant time surface. This expression is achieved by summing the PDFs of photons that have been scattered n times within four-dimensional space-time. We have confirmed that this formulation accurately reproduces the results of relativistic Monte Carlo simulations. We found that the PDF in three-dimensional space at a constant time surface can be represented in a separable variable form. We demonstrate the behavior of the PDF in the laboratory frame across a wide range of Lorentz factors for the relativistic flow. When the Lorentz factor of the fluid is low, the behavior of scattered photons evolves sequentially from free propagation to diffusion, and then to dynamic diffusion, where the mean effective velocity of the photons equates to that of the fluid. On the other hand, when the Lorentz factor is large, the behavior evolves from anisotropic ballistic motion, characterized by a mean effective velocity approaching the speed of light, to dynamic diffusion.

Keywords: radiative processes; radiative transfer; relativity; relativistic fluid dynamics; astrophysical fluid dynamics; active galactic nuclei; gamma-ray astronomy; gamma-ray bursts; supernova dynamics; supernova neutrinos; cosmic rays; accretion
Strong [O III] λ5007 Emission-line Compact Galaxies in LAMOST DR9: Blueberries, Green Peas, and Purple Grapes

Green Pea and Blueberry galaxies are well known for their compact size, low mass, strong emission lines, and analogs to high-z Lyα-emitting galaxies. In this study, 1547 strong [O III] λ5007 emission-line compact galaxies with 1694 spectra are selected from LAMOST DR9 at the redshift range from 0.0 to 0.59. According to the redshift distribution, these samples can be separated into three groups: Blueberries, Green Peas, and Purple Grapes. Optical [Mg II] λ2800 line feature, BPT diagram, multiwavelength spectral energy distribution (SED) fitting, mid-IR (MIR) color, and MIR variability are deployed to identify 23 active galactic nucleus candidates from these samples, which are excluded for the following star formation rate (SFR) discussions. We perform the multiwavelength SED fitting with GALEX UV and WISE MIR data. Color excess from the Balmer decrement shows that these strong [O III] λ5007 emission-line compact galaxies are not highly reddened. The stellar mass of the galaxies is obtained by fitting LAMOST calibrated spectra with the emission lines masked. We find that the SFR is increasing with the increase of redshift, while for the sources within the same redshift bin the SFR increases with mass with a similar slope to the star-forming main sequence. These samples have a median metallicity of 12 + log(O/H) of 8.10. The metallicity increases with mass, and all the sources are below the mass-metallicity relation. The direct-derived T e -based metallicity from the [O III] λ4363 line agrees with the empirical N2-based empirical gas-phase metallicity. Moreover, these compact strong [O III] λ5007 lines are mostly in a less dense environment.

Keywords: compact galaxies
Considering the Single and Binary Origins of the Type IIP SN 2017eaw

Current population synthesis modeling suggests that 30%-50% of Type II supernovae originate from binary progenitors; however, the identification of a binary progenitor is challenging. One indicator of a binary progenitor is that the surrounding stellar population is too old to contain a massive single star. Measurements of the progenitor mass of SN 2017eaw are starkly divided between observations made temporally close to core collapse, which show a progenitor mass of 13-15 M ⊙ (final helium-core mass ${M}_{\mathrm{He},\mathrm{core}}=4.4\mbox{--}6.0\,{M}_{\odot }$ -which is a more informative property than initial mass) and those from the stellar population surrounding the SN, which find M ≤ 10.8 M ⊙ ( ${M}_{\mathrm{He},\mathrm{core}}\leqslant 3.4\,{M}_{\odot }$ ). In this paper, we reanalyze the surrounding stellar population with improved astrometry and photometry, finding a median age of ${16.8}_{-1.0}^{+3.2}$ Myr for all stars younger than 50 Myr ( ${M}_{\mathrm{He},\mathrm{core}}=4.7{M}_{\odot }$ ) and ${85.9}_{-6.5}^{+3.2}$ Myr for stars younger than 150 Myr. 16.8 Myr is now consistent with the helium-core mass range derived from the temporally near-explosion observations for single stars. Applying the combined constraints to population synthesis models, we determine that the probability of the progenitor of SN 2017eaw being an initially single star is 65% compared to 35% for prior binary interaction. 85.9 Myr is inconsistent with any formation scenarios. We demonstrate that combining progenitor age constraints with helium-core mass estimates from red supergiant SED modeling, late-time spectra, and indirectly from light-curve modeling can help to differentiate single and binary progenitor scenarios and provide a framework for the application of this technique to future observations.

Keywords: stellar populations; binary stars; type ii supernovae; stellar evolutionary models; late stellar evolution; massive stars
Prediction Capability of Geomagnetic Events from Solar Wind Data Using Neural Networks

Multiple neural network architectures, with different structural composition and complexity, are implemented in this study with the aim of providing multi-hour-ahead warnings of severe geomagnetic disturbances, based on in situ measurements of the solar wind plasma and magnetic field acquired at the Lagrangian point L1. First, a statistical analysis of the interplanetary data was performed to point out which are the most relevant parameters to be provided as input to the neural networks, and a preprocessing of the data set was implemented to face its heavy imbalance (the Earth's magnetosphere is in fact mostly at rest). Then, neural networks were tested to evaluate their performance. It turned out that, in a binary classification problem, recurrent approaches are best at predicting critical events both 1 and 8 hr in advance, achieving a balanced accuracy of 94% and 70%, respectively. Finally, in an attempt at multistep prediction of the criticality of future geomagnetic events from 1-8 hr ahead, more complex neural networks, built by merging the different types of basic convolutional and recurrent architectures, have been shown to outperform single-step and state-of-the-art approaches with a balanced accuracy of at least 70%. Interestingly, the accuracy peaks at 4 hr, corresponding to the waiting time between the detection of solar drivers at L1 and the onset of the geomagnetic storm (as previously obtained by statistical investigations), suggesting that on average this is the time the Earth's magnetosphere takes to react to the solar event.

Keywords: solar coronal mass ejections; neural networks; heliosphere; solar-terrestrial interactions; solar wind; solar storm; geomagnetic fields
Supercriticality of the Dynamo Limits the Memory of the Polar Field to One Cycle

The polar magnetic field precursor is considered to be the most robust and physics-based method for the prediction of the next solar cycle strength. However, to make a reliable prediction of a cycle, is the polar field at the solar minimum of the previous cycle enough or do we need the polar field of many previous cycles? To answer this question, we performed several simulations using Babcock-Leighton-type flux-transport dynamo models with a stochastically forced source for the poloidal field (α term). We show that when the dynamo is operating near the critical dynamo transition or only weakly supercritical, the polar field of cycle n determines the amplitude of the next several cycles (at least three). However, when the dynamo is substantially supercritical, this correlation of the polar field is reduced to one cycle. This change in the memory of the polar field from multiple to one cycle with the increase of the supercriticality of the dynamo is independent of the importance of various turbulent transport processes in the model. Our this conclusion contradicts the existing idea. We further show that when the dynamo operates near the critical transition, it produces frequent extended episodes of weaker activity, resembling the solar grand minima. The occurrence of grand minima is accompanied by the multicycle correlation of the polar field. The frequency of grand minima decreases with the increase of supercriticality of the dynamo.

Keywords: solar cycle; solar dynamo; solar magnetic fields
A SuperWASP Light Curve Displaying a Single Long-duration Transit: A Jupiter Size Exoplanet in a Very Distant Orbit?

We present the SuperWASP light curve of a 10th magnitude A7V star containing a single, well-defined U-shaped transit-like event lasting around 11 days with a depth of 1.1%. The star is otherwise non-variable throughout the 8 yr duration of the observations. If the event is modeled as an exoplanet transit, it is compatible with a 1.8 R J exoplanet in a ~205 au orbit with a period of ~2200 yr.

Keywords: exoplanets; transit photometry
Regulation of Star Formation by a Hot Circumgalactic Medium

Galactic outflows driven by supernovae (SNe) are thought to be a powerful regulator of a galaxy's star-forming efficiency. Mass, energy, and metal outflows (η M , η E , and η Z , here normalized by the star formation rate, the SNe energy, and metal production rates, respectively) shape galaxy properties by both ejecting gas and metals out of the galaxy and by heating the circumgalactic medium (CGM), preventing future accretion. Traditionally, models have assumed that galaxies self-regulate by ejecting a large fraction of the gas, which enters the interstellar medium (ISM), although whether such high mass loadings agree with observations is still unclear. To better understand how the relative importance of ejective (i.e., high mass loading) versus preventative (i.e., high energy loading) feedback affects the present-day properties of galaxies, we develop a simple gas-regulator model of galaxy evolution, where the stellar mass, ISM, and CGM are modeled as distinct reservoirs which exchange mass, metals, and energy at different rates within a growing halo. Focusing on the halo mass range from 1010 to 1012 M ⊙, we demonstrate that, with reasonable parameter choices, we can reproduce the stellar-to-halo mass relation and the ISM-to-stellar mass relation with low-mass-loaded (η M ~ 0.1-10) but high-energy-loaded (η E ~ 0.1-1) winds, with self-regulation occurring primarily through heating and cooling of the CGM. We show that the model predictions are robust against changes to the mass loading of outflows but are quite sensitive to our choice of the energy loading, preferring η E ~ 1 for the lowest-mass halos and ~0.1 for Milky Way-like halos.

Keywords: circumgalactic medium; galactic winds; galaxies; galaxy evolution; galaxy physics; galactic and extragalactic astronomy
Thermophysical Investigation of Asteroid Surfaces. I. Characterization of Thermal Inertia

The thermal inertia of an asteroid is an indicator of the thermophysical properties of the regolith and is determined by the size of grains on the surface. Previous thermophysical modeling studies of asteroids have identified or suggested that object size, rotation period, and heliocentric distance (a proxy for temperature) are important factors that separately influence thermal inertia. In this work we present new thermal inertia values for 239 asteroids and model all three factors in a multivariate model of thermal inertia. Using multiepoch infrared data of this large set of objects observed by WISE, we derive the size, albedo, thermal inertia, surface roughness, and sense of spin using a thermophysical modeling approach that does not require a priori knowledge of an object's shape or spin axis direction. Our thermal inertia results are consistent with previous values from the literature for similarly sized asteroids, and we identify an excess of retrograde rotators among main-belt asteroids <8 km. We then combine our results with thermal inertias of 220 objects from the literature to construct a multivariate model and quantify the dependency on asteroid diameter, rotation period, and surface temperature. This multivariate model, which accounts for codependencies between the three independent variables, identifies asteroid diameter and surface temperature as strong controls on thermal inertia.

Keywords: asteroid surfaces; asteroids; infrared astronomy; infrared photometry
The Physical Properties of Low-redshift FeLoBAL Quasars. III. The Location and Geometry of the Outflows

We present continued analysis of a sample of low-redshift iron low-ionization broad-absorption-line quasars (FeLoBALQs). Choi et al. presented SimBAL spectral analysis of broad-absorption-line (BAL) outflows in 50 objects. Leighly et al. analyzed the optical emission lines of 30 of those 50 objects and found that they are characterized by either a high accretion rate (L Bol/L Edd > 0.3) or low accretion rate (0.03 < L Bol/L Edd < 0.3). We report that the outflow velocity is inversely correlated with the BAL location among the high-accretion-rate objects, with the highest velocities observed in parsec-scale outflows. In contrast, the low-Eddington-ratio objects showed the opposite trend. We confirmed the known relationship between the outflow velocity and L Bol/L Edd and found that the scatter plausibly originates in the force multiplier (launch radius) in the low(high)-accretion-rate objects. A log volume filling factor between -6 and -4 was found in most outflows but was as high as -1 for low-velocity compact outflows. We investigated the relationship between the observed [O III] emission and that predicted from the BAL gas. We found that these could be reconciled if the emission-line covering fraction depends on the Seyfert type and BAL location. The difference between the predicted and observed [O III] luminosity is correlated with the outflow velocity, suggesting that [O III] emission in high-Eddington-ratio objects may be broad and hidden under Fe II emission. We suggest that the physical differences in the outflow properties as a function of location in the quasar and accretion rate point to different formation, acceleration, and confinement mechanisms for the two FeLoBALQ types.

Keywords: broad-absorption line quasar; quasars; active galactic nuclei
The ANTARES Astronomical Time-domain Event Broker

We describe the Arizona-NOIRLab Temporal Analysis and Response to Events System (ANTARES), a software instrument designed to process large-scale streams of astronomical time-domain alerts. With the advent of large-format CCDs on wide-field imaging telescopes, time-domain surveys now routinely discover tens of thousands of new events each night, more than can be evaluated by astronomers alone. The ANTARES event broker will process alerts, annotating them with catalog associations and filtering them to distinguish customizable subsets of events. We describe the data model of the system, the overall architecture, annotation, implementation of filters, system outputs, provenance tracking, system performance, and the user interface.

Keywords: time domain astronomy; astronomy software; computational methods; astronomical methods
X-Ray Reverberation Mapping of Ark 564 Using Gaussian Process Regression

Ark 564 is an extreme high-Eddington narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray active galactic nuclei (AGN), and for having one of the lowest temperature coronae. Here, we present a 410 ks NuSTAR observation and two 115 ks XMM-Newton observations of this unique source, which reveal a very strong, relativistically broadened iron line. We compute the Fourier-resolved time lags by first using Gaussian processes to interpolate the NuSTAR gaps, implementing the first employment of multitask learning for application in AGN timing. By simultaneously fitting the time lags and the flux spectra with the relativistic reverberation model RELTRANS, we constrain the mass at ${2.3}_{-1.3}^{+2.6}\times {10}^{6}{M}_{\odot }$ , although additional components are required to describe the prominent soft excess in this source. These results motivate future combinations of machine learning, Fourier-resolved timing, and the development of reverberation models.

Keywords: accretion; gaussian processes regression; black holes; astrostatistics techniques; high energy astrophysics; x-ray active galactic nuclei; model selection; astrostatistics