adsabs/SciX_UAT_keywords huggingface dataset:
The Perturbed Full Two-body Problem: Application to Post-DART Didymos

With the successful impact of the NASA Double Asteroid Redirection Test (DART) spacecraft in the Didymos-Dimorphos binary asteroid system, we provide an initial analysis of the post-impact perturbed binary asteroid dynamics. To compare our simulation results with observations, we introduce a set of "observable elements" calculated using only the physical separation of the binary asteroid, rather than traditional Keplerian elements. Using numerical methods that treat the fully spin-orbit-coupled dynamics, we estimate the system's mass and the impact-induced changes in orbital velocity, semimajor axis, and eccentricity. We find that the changes to the mutual orbit depend strongly on the separation distance between Didymos and Dimorphos at the time of impact. If Dimorphos enters a tumbling state after the impact, this may be observable through changes in the system's eccentricity and orbit period. We also find that any DART-induced reshaping of Dimorphos would generally reduce the required change in orbital velocity to achieve the measured post-impact orbit period, and will be assessed by the ESA Hera mission in 2027.

Keywords: asteroid dynamics; asteroid satellites; near-earth objects; small solar system bodies; gravitational interaction
Foraging with MUSHROOMS: A Mixed-integer Linear Programming Scheduler for Multimessenger Target of Opportunity Searches with the Zwicky Transient Facility

Electromagnetic follow-up of gravitational-wave detections is very resource intensive, taking up hours of limited observation time on dozens of telescopes. Creating more efficient schedules for follow-up will lead to a commensurate increase in counterpart location efficiency without using more telescope time. Widely used in operations research and telescope scheduling, mixed-integer linear programming is a strong candidate to produce these higher-efficiency schedules, as it can make use of powerful commercial solvers that find globally optimal solutions to provided problems. We detail a new target-of-opportunity scheduling algorithm designed with Zwicky Transient Facility in mind that uses mixed-integer linear programming. We compare its performance to gwemopt, the tuned heuristic scheduler used by the Zwicky Transient Facility and other facilities during the third LIGO-Virgo gravitational-wave observing run. This new algorithm uses variable-length observing blocks to enforce cadence requirements and to ensure field observability, along with having a secondary optimization step to minimize slew time. We show that by employing a hybrid method utilizing both this scheduler and gwemopt, the previous scheduler used, in concert, we can achieve an average improvement in detection efficiency of 3%-11% over gwemopt alone for a simulated binary neutron star merger data set consistent with LIGO-Virgo's third observing run, highlighting the potential of mixed-integer target of opportunity schedulers for future multimessenger follow-up surveys.

Keywords: gravitational wave astronomy; astronomical methods; gravitational waves; transient detection; transient sources; time domain astronomy
Dynamical Evolution of Cosmic Supermassive Binary Black Holes and Their Gravitational-wave Radiation

We investigate the evolution of supermassive binary black holes (BBHs) in galaxies with realistic property distributions and the gravitational-wave (GW) radiation from the cosmic population of these BBHs. We incorporate a comprehensive treatment of the dynamical interactions of the BBHs with their environments by including the effects of galaxy triaxial shapes and inner stellar distributions, and generate a large number of BBH evolution tracks. By combining these BBH evolution tracks, galaxy mass functions, galaxy merger rates, and supermassive black hole-host galaxy relations into our model, we obtain statistical distributions of surviving BBHs, BBH coalescence rates, the strength of their GW radiation, and the stochastic GW background (GWB) contributed by the cosmic BBH population. About ∼1%-3% (or $\sim 10 \% $ ) of supermassive BHs at nearby galactic centers are expected to be binaries with mass ratio $\gt 1/3$ (or $\gt 1/100$ ). The characteristic strain amplitude of the GWB at frequency $1\,{\mathrm{yr}}^{-1}$ is estimated to be $\sim {2.0}_{-0.8}^{+1.4}\times {10}^{-16}$ , and the upper bound of its results obtained with the different BH-host galaxy relations can be up to $5.4\times {10}^{-16}$ , which await testing by future experiments (e.g., the Square Kilometer Array, FAST, Next-Generation Very Large Array). The turnover frequency of the GWB spectrum is at $\sim 0.25\,\mathrm{nHz}$ . The uncertainties on the above estimates and prospects for detecting individual sources are also discussed. The application of the cosmic BBH population to the Laser Interferometer Space Antenna (LISA) band provides a lower limit to the detection rate of BBHs by LISA, $\sim 0.9\,{\mathrm{yr}}^{-1}$ .

Keywords: cosmological evolution; galaxy mergers; gravitational wave astronomy; galaxy dynamics; gravitational waves; supermassive black holes; galaxy nuclei; astrodynamics
On the Diversity of M-star Astrospheres and the Role of Galactic Cosmic Rays Within

With upcoming missions such as the James Webb Space Telescope, the European Extremely Large Telescope, and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, we soon will be on the verge of detecting and characterizing Earth-like exoplanetary atmospheres for the first time. These planets are most likely to be found around smaller and cooler K- and M-type stars. However, recent observations showed that their radiation environment might be much harsher than that of the Sun. Thus, the exoplanets are most likely exposed to an enhanced stellar radiation environment, which could affect their habitability, for example, in the form of a hazardous flux of energetic particles. Knowing the stellar radiation field, and being able to model the radiation exposure on the surface of a planet, is crucial to assess its habitability. In this study, we present 3D magnetohydrodynamic-based model efforts investigating M-stars, focusing on V374 Peg, Proxima Centauri, and LHS 1140, chosen because of their diverse astrospheric quantities. We show that V374 Peg has a much larger astrosphere (ASP) than our Sun, while Proxima Centauri and LHS 1140 most likely have ASPs comparable to or even much smaller than the heliosphere, respectively. Based on a 1D transport model, for the first time, we provide numerical estimates of the modulation of Galactic cosmic rays (GCRs) within the three ASPs. We show that the impact of GCRs on the Earth-like exoplanets Proxima Centauri b and LHS 1140 b cannot be neglected in the context of exoplanetary habitability.

Keywords: stellar winds; magnetohydrodynamics; galactic cosmic rays; stellar wind bubbles; interstellar medium
Formation of Moons and Equatorial Ridge around Top-shaped Asteroids after Surface Landslide

Top-shaped asteroids have been observed among near-Earth asteroids. About half of them are reported to have moons (on the order of ~1 wt.% of the top-shaped primary) and many of them have an equatorial ridge. A recent study has shown that the enigmatic top-shaped figure of asteroids (e.g., Ryugu, Bennu, and Didymos) could result from an axisymmetric landslide of the primary during a fast spin-up near the breakup rotation period. Such a landslide would inevitably form a particulate disk around an asteroid with a short timescale (~3 hr). However, the long-term full dynamical evolution is not investigated. Here, we perform a continuous simulation (~700 hr) that investigates the sequence of events from the surface landslide that forms a top-shaped asteroid and a particulate disk to disk evolution. We show that the disk quickly spreads and produces moons (within ~300 hr). The mass of the formed moon is consistent with what is observed around the top-shaped asteroids. We also demonstrate that an equatorial ridge is naturally formed because a fraction of the disk particles re-accretes selectively onto the equatorial region of the primary. We envision that Ryugu and Bennu could once have an ancient moon that was later lost due to a successive moon's orbital evolution. Alternatively, at a top-shaped asteroid that has a moon, such as Didymos, no significant orbital evolution of the moon has occurred that would result in its loss. Our study would also be qualitatively applicable to any rubble-pile asteroids near the breakup rotation period.

Keywords: asteroids; asteroid satellites; near-earth objects; small solar system bodies
No Activity among 13 Centaurs Discovered in the Pan-STARRS1 Detection Database

Centaurs are small bodies orbiting in the giant planet region that were scattered inward from their source populations beyond Neptune. Some members of the population display comet-like activity during their transition through the solar system, the source of which is not well understood. The range of heliocentric distances where the active Centaurs have been observed and their median lifetime in the region suggest that this activity is driven neither by water-ice sublimation nor entirely by supervolatiles. Here we present an observational and thermodynamical study of 13 Centaurs discovered in the Pan-STARRS1 detection database aimed at identifying and characterizing active objects beyond the orbit of Jupiter. We find no evidence of activity associated with any of our targets at the time of their observations with the Gemini North telescope in 2017 and 2018, or in archival data from 2013 to 2019. Upper limits on the possible volatile and dust production rates from our targets are 1-2 orders of magnitude lower than production rates in some known comets and are in agreement with values measured for other inactive Centaurs. Our numerical integrations show that the orbits of six of our targets evolved interior to r ~ 15 au over the past 100,000 yr, where several possible processes could trigger sublimation and outgassing, but their apparent inactivity indicates that either their dust production is below our detection limit or the objects are dormant. Only one Centaur in our sample-2014 PQ70-experienced a sudden decrease in semimajor axis and perihelion distance attributed to the onset of activity for some previously known inactive Centaurs, and therefore it is the most likely candidate for any future outburst. This object should be a target of high interest for any further observational monitoring.

Keywords: centaur group; comets; trans-neptunian objects
Resolving Linear Polarization due to Emission and Extinction of Aligned Dust Grains on NGC 1333 IRAS4A with JVLA and ALMA

We report high angular resolution observations of linearly polarized dust emission toward the Class 0 young stellar object NGC1333 IRAS4A (hereafter IRAS4A) using the Karl G. Jansky Very Large Array at K (11.5-16.7 mm), Ka (8.1-10.3 mm), and Q bands (6.3-7.9 mm), and using the Atacama Large Millimeter Array (ALMA) at Band 6 (1.3 mm) and Band 7 (0.85-0.89 mm). On 100-1000 au scales, all of these observations consistently trace the hourglass-shaped magnetic field topology as shown in the previous studies. In the innermost 100 au region of IRAS4A1, the polarization position angles (E field) detected at 6.3-16.7 mm are consistent; however, they are nearly 90° offset from those detected at 1.3 mm and 0.85-0.89 mm. Such a 90° offset may be explained by the inner ∼100 au area being optically thick at wavelengths shorter than ∼1.5 mm, whereby the observations probe the absorption of aligned dust against the weakly or unpolarized warm dust emission from the innermost region. This can also consistently explain why the highest angular resolution ALMA images at Band 7 show that the polarization percentage increases with dust brightness temperature in the inner ∼100 au region of IRAS4A1. Following this interpretation and assuming that the dust grains are aligned with the magnetic fields, the inferred magnetic field position angle based on the 90° rotated at 6.3-7.9 mm in the central peak of IRAS4A1 is ∼-22°, which is approximately consistent with the outflow direction of ∼-9°.

Keywords: star formation; magnetic fields; polarimetry; interstellar medium; protostars
Inferring Halo Masses with Graph Neural Networks

Understanding the halo-galaxy connection is fundamental in order to improve our knowledge on the nature and properties of dark matter. In this work, we build a model that infers the mass of a halo given the positions, velocities, stellar masses, and radii of the galaxies it hosts. In order to capture information from correlations among galaxy properties and their phase space, we use Graph Neural Networks (GNNs), which are designed to work with irregular and sparse data. We train our models on galaxies from more than 2000 state-of-the-art simulations from the Cosmology and Astrophysics with MachinE Learning Simulations project. Our model, which accounts for cosmological and astrophysical uncertainties, is able to constrain the masses of the halos with a ~0.2 dex accuracy. Furthermore, a GNN trained on a suite of simulations is able to preserve part of its accuracy when tested on simulations run with a different code that utilizes a distinct subgrid physics model, showing the robustness of our method. The PyTorch Geometric implementation of the GNN is publicly available on GitHub (https://github.com/PabloVD/HaloGraphNet).

Keywords: cosmology; dark matter distribution; galaxy dark matter halos; hydrodynamical simulations; neural networks
Spatial Decorrelation of Young Stars and Dense Gas as a Probe of the Star Formation-Feedback Cycle in Galaxies

The spatial decorrelation of dense molecular gas and young stars observed on ≲1 kpc scales in nearby galaxies indicates rapid dispersal of star-forming regions by stellar feedback. We explore the sensitivity of this decorrelation to different processes controlling the structure of the interstellar medium, the abundance of molecular gas, star formation, and feedback in a suite of simulations of an isolated dwarf galaxy with structural properties similar to NGC 300 that self-consistently model radiative transfer and molecular chemistry. Our fiducial simulation reproduces the magnitude of decorrelation and its scale dependence measured in NGC 300, and we show that this agreement is due to different aspects of feedback, including H2 dissociation, gas heating by the locally variable UV field, early mechanical feedback, and supernovae. In particular, early radiative and mechanical feedback affects the correlation on ≲100 pc scales, while supernovae play a significant role on ≳ 100 pc scales. The correlation is also sensitive to the choice of the local star formation efficiency per free fall time, ϵff, which provides a strong observational constraint on ϵff when the global star formation rate is independent of its value. Finally, we explicitly show that the degree of correlation between the peaks of molecular gas and star formation density is directly related to the distribution of the lifetimes of star-forming regions.

Keywords: interstellar medium; interstellar dynamics; star formation; star forming regions; hydrodynamical simulations; radiative transfer simulations; disk galaxies; dwarf galaxies; stellar feedback
A Pilot Study of Nulling in 22 Pulsars Using Mixture Modeling

The phenomenon of pulsar nulling, observed as the temporary inactivity of a pulsar, remains poorly understood both observationally and theoretically. Most observational studies that quantify nulling employ a variant of Ritchings algorithm, which can suffer significant biases for pulsars where the emission is weak. Using a more robust mixture model method, we study pulsar nulling in a sample of 22 recently discovered pulsars, for which we publish the nulling fractions for the first time. These data clearly demonstrate biases of the former approach and show how an otherwise nonnulling pulsar can be classified as having significant nulls. We show that the population-wide studies that find a positive correlation of nulling with pulsar period/characteristic age can similarly be biased because of the bias in estimating the nulling fraction. We use our probabilistic approach to find the evidence for periodicity in the nulls in a subset of three pulsars in our sample. In addition, we also provide improved timing parameters for 17 of the 22 pulsars that had no prior follow-up.

Keywords: radio pulsars; radio astronomy; neutron stars
Kinetic-scale Flux Rope in the Magnetosheath Boundary Layer

We here present a new type of kinetic-scale (∼1 ion gyroradius) flux rope (KFR) in the Earth's dayside magnetosheath boundary layer with Magnetospheric Multiscale high temporal cadence data. This structure exhibits a slight twist of magnetic field that is possibly generated by a field-aligned current, which differs from typical dayside flux ropes usually observed within the current sheet where magnetic reconnection can occur. The perpendicular electron fluxes within 19-52 eV are increased ∼10% inside the KFR. Detailed analysis shows that these perpendicular electrons may encounter their mirror point (at the position of the KFR, strong field region) when traveling from the magnetosheath toward the ionosphere and will be reflected to the magnetosheath. A possible scenario is that this KFR is different from previous flux ropes that transfer electron flux to the magnetosphere but could intercept magnetosheath large pitch angle electron flux to the magnetosphere.

Keywords: planetary magnetospheres; space plasmas; magnetohydrodynamics; geomagnetic fields; plasma physics
Investigating the Blazar TXS 0506+056 through Sharp Multiwavelength Eyes During 2017-2019

The blazar TXS 0506+056 got into the spotlight of the astrophysical community in 2017 September, when a high-energy neutrino detected by IceCube (IceCube-170922A) was associated at the 3σ level with a γ-ray flare from this source. This multi-messenger photon-neutrino association remains, as per today, the most significant association ever observed. TXS 0506+056 was a poorly studied object before the IceCube-170922A event. To better characterize its broadband emission, we organized a multiwavelength campaign lasting 16 months (2017 November to 2019 February), covering the radio band (Metsähovi, OVRO), the optical/UV (ASAS-SN, KVA, REM, Swift/UVOT), the X-rays (Swift/XRT, NuSTAR), the high-energy γ rays (Fermi/LAT), and the very high-energy (VHE) γ rays (MAGIC). In γ rays, the behavior of the source was significantly different from the behavior in 2017: MAGIC observations show the presence of flaring activity during 2018 December, while the source only shows an excess at the 4σ level during the rest of the campaign (74 hr of accumulated exposure); Fermi/LAT observations show several short (on a timescale of days to a week) flares, different from the long-term brightening of 2017. No significant flares are detected at lower energies. The radio light curve shows an increasing flux trend that is not seen in other wavelengths. We model the multiwavelength spectral energy distributions in a lepto-hadronic scenario, in which the hadronic emission emerges as Bethe-Heitler and pion-decay cascade in the X-rays and VHE γ rays. According to the model presented here, the 2018 December γ-ray flare was connected to a neutrino emission that was too brief and not bright enough to be detected by current neutrino instruments.

Keywords: high energy astrophysics; jets; blazars; gamma-rays
Violent Starbursts and Quiescence Induced by Far-ultraviolet Radiation Feedback in Metal-poor Galaxies at High Redshift

JWST observations of galaxies at z ≳ 8 suggest that they are more luminous and clumpier than predicted by most models, prompting several proposals on the physics of star formation and feedback in the first galaxies. In this paper, we focus on the role of ultraviolet (UV) radiation in regulating star formation by performing a set of cosmological radiation hydrodynamics simulations of one galaxy at subparsec resolution with different radiative feedback models. We find that the suppression of cooling by far-UV (FUV) radiation (i.e., H2 dissociating radiation) from Population II stars is the main physical process triggering the formation of compact and massive star clusters and is responsible for the bursty star formation observed in metal-poor galaxies at z ≳ 10. Indeed, artificially suppressing FUV radiation leads to a less intense continuous mode of star formation distributed into numerous but low-mass open star clusters. Due to the intense FUV field, low-metallicity clouds remain warm (∼104 K) until they reach a relatively high density (≳103 cm‑3), before becoming self-shielded and transitioning to a colder (∼100 K), partially molecular phase. As a result, star formation is delayed until the clouds accumulate enough mass to become gravitationally unstable. At this point, the clouds undergo rapid star formation, converting gas into stars with high efficiency. We therefore observe exceptionally bright galaxies (10 times brighter than for continuous star formation) and subsequent quenched "dead" galaxies that did not form stars for tens of Myr.

Keywords: high-redshift galaxies; primordial galaxies
Probing the Rock Mass Fraction and Transport Efficiency inside Uranus Using 40Ar Measurements

The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces 40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of 40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected 40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial 40Ar is a potential confounding factor, especially if Ar/H2 is significantly enhanced above solar or if degassing of radiogenic 40Ar were inefficient. Unfortunately, the primordial 40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.

Keywords: planetary interior
The Spin and Orientation of the Black Hole in XTE J1908+094

NuSTAR observed the black hole candidate XTE J1908+094 during its 2013 and 2019 outbursts. We use relativistic reflection to measure the spin of the black hole through 19 different assumptions of relxill flavors and parameter combinations. The most favored model in terms of the Deviance Information Criterion (DIC) measures the spin of the black hole to be $a={0.55}_{-0.45}^{+0.29}$ , and the inclination to be $\theta ={27}_{-3}^{+2}$ degrees (1σ statistical errors). We look at the effects of coronal geometry assumptions and the density of the accretion disk on the spin prediction. All 19 tested models provide consistent spin estimates. We discuss the evolution of spin measurement techniques using relativistic reflection in X-ray binaries and discuss the implications of this spin measurement in reconciling the distributions of stellar-mass black hole spin measurements made through X-ray and gravitational wave observations.

Keywords: accretion; black hole physics; low-mass x-ray binary stars; stellar mass black holes; x-ray binary stars