adsabs/SciX_UAT_keywords huggingface dataset:
Millisecond Pulsars in Dense Star Clusters: Evolution, Scaling Relations, and the Galactic-center Gamma-Ray Excess

The number of millisecond pulsars (MSPs) observed in Milky Way globular clusters has increased explosively in recent years, but the underlying population is still uncertain due to observational biases. We use state-of-the-art N-body simulations to study the evolution of MSP populations in dense star clusters. These cluster models span a wide range in initial conditions, including different initial masses, metallicities, and virial radii, which nearly cover the full range of properties exhibited by the population of globular clusters in the Milky Way. We demonstrate how different initial cluster properties affect the number of MSPs, for which we provide scaling relations as a function of cluster age and mass. As an application, we use our formulae to estimate the number of MSPs delivered to the Galactic center from inspiralling globular clusters to probe the origin of the Galactic-center gamma-ray excess detected by Fermi. We predict about 400 MSPs in the Galactic center from disrupted globular clusters, which can potentially explain most of the observed gamma-ray excess.

Keywords: star clusters; astronomical simulations; n-body simulations; pulsars; galactic center
Arecibo Planetary Radar Observations of Near-Earth Asteroids: 2017 December-2019 December

We successfully observed 191 near-Earth asteroids using the Arecibo Observatory's S-band planetary radar system from 2017 December through 2019 December. We present radar cross sections for 167 asteroids; circular-polarization ratios for 112 asteroids based on Doppler-echo-power spectra measurements; and radar albedos, constraints on size and spin periods, and surface-feature and shape evaluation for 37 selected asteroids using delay-Doppler radar images with a range resolution of 75 m or finer. Out of 33 asteroids with an estimated effective diameter of at least 200 m and sufficient image quality to give clues of the shape, at least 4 (~12%) are binary asteroids, including 1 equal-mass binary asteroid, 2017 YE5, and at least 10 (~30%) are contact-binary asteroids. For 5 out of 112 asteroids with reliable measurements in both circular polarizations, we measured circular-polarization ratios greater than 1.0, which could indicate that they are E-type asteroids, while the mean and the 1σ standard deviation were 0.37 ± 0.23. Further, we find a mean opposite-sense circular-polarization radar albedo of 0.21 ± 0.11 for 41 asteroids (0.19 ± 0.06 for 11 S-complex asteroids). We identified two asteroids, 2011 WN15 and (505657) 2014 SR339, as possible metal-rich objects based on their unusually high radar albedos, and discuss possible evidence of water ice in 2017 YE5.

Keywords: near-earth objects; radar telescopes; planetary science; remote sensing; asteroids
Multiwavelength Temporal Variability of the Blazar PKS 1510-089

We perform correlation and periodicity search analyses on long-term multiband light curves of the flat-spectrum radio quasar PKS 1510-089 observed by the space-based Fermi-Large Area Telescope in γ-rays, the SMARTS and Steward Observatory telescopes in optical and near-infrared (NIR), and the 13.7 m radio telescope in Metsähovi Radio Observatory between 2008 and 2018. The z-transform discrete correlation function method is applied to study the correlation and possible time lags among these multiband light curves. Among all pairs of wavelengths, the γ-ray versus optical/NIR and optical versus NIR correlations show zero time lags; however, both the γ-ray and optical/NIR emissions precede the radio radiation. The generalized Lomb-Scargle periodogram, weighted wavelet z-transform, and REDFIT techniques are employed to investigate the unresolved core emission-dominated 37 GHz light curve and yield evidence for a quasi period around 1540 days, although given the length of the whole data set it cannot be claimed to be significant. We also investigate the optical/NIR color variability and find that this source shows a simple redder-when-brighter behavior over time, even in the low-flux state.

Keywords: active galactic nuclei; blazars; flat-spectrum radio quasars; observational astronomy
Using Photometrically Derived Properties of Young Stars to Refine TESS's Transiting Young Planet Survey Completeness

The demographics of young exoplanets can shed light on their formation and evolution processes. Exoplanet properties are derived from the properties of their host stars. As such, it is important to accurately characterize the host stars since any systematic biases in their derivation can negatively impact the derivation of planetary properties. Here we present a uniform catalog of photometrically derived stellar effective temperatures, luminosities, radii, and masses for 4865 young (<1 Gyr) stars in 31 nearby clusters and moving groups within 200 pc. We compared our photometrically derived properties to a subset of those derived from spectra and found them to be in good agreement. We also investigated the effect of stellar properties on the detection efficiency of transiting short-period young planets with TESS as calculated in Fernandes et al. (2022) and found an overall increase in the detection efficiency when the new photometrically derived properties were taken into account. Most notably, there is a 1.5 × increase in the detection efficiencies for sub-Neptunes/Neptunes (1.8-6 R ⊕) implying that, for our sample of young stars, better characterization of host star properties can lead to the recovery of more small transiting planets. Our homogeneously derived catalog of updated stellar properties, along with a larger unbiased stellar sample and more detections of young planets, will be a crucial input to the accurate estimation of the occurrence rates of young short-period planets.

Keywords: exoplanets; hot neptunes; mini neptunes; young star clusters; transits; exoplanet detection methods; planet hosting stars
Plasma Waves near the Electron Cyclotron Frequency in the Near-Sun Solar Wind

Data from the first two orbits of the Sun by Parker Solar Probe reveal that the solar wind sunward of 50 solar radii is replete with plasma waves and instabilities. One of the most prominent plasma wave power enhancements in this region appears near the electron cyclotron frequency (fce). Most of this wave power is concentrated in electric field fluctuations near 0.7 fce and fce, with strong harmonics of both frequencies extending above fce. At least two distinct, often concurrent, wave modes are observed, preliminarily identified as electrostatic whistler-mode waves and electron Bernstein waves. Wave intervals range in duration from a few seconds to hours. Both the amplitudes and number of detections of these near-fce waves increase significantly with decreasing distance to the Sun, suggesting that they play an important role in the evolution of electron populations in the near-Sun solar wind. Correlations are found between the detection of these waves and properties of solar wind electron populations, including electron core drift, implying that these waves play a role in regulating the heat flux carried by solar wind electrons. Observation of these near-fce waves is found to be strongly correlated with near-radial solar wind magnetic field configurations with low levels of magnetic turbulence. A scenario for the growth of these waves is presented, which implies that regions of low-turbulence near-radial magnetic field are a prominent feature of the solar wind structure near the Sun.

Keywords: solar wind; space plasmas; solar physics; solar particle emission; solar energetic particles
Does or Did the Supernova Remnant Cassiopeia A Operate as a PeVatron?

For decades, supernova remnants (SNRs) have been considered the prime sources of Galactic cosmic rays (CRs). But whether SNRs can accelerate CR protons to PeV energies and thus dominate CR flux up to the knee is currently under intensive theoretical and phenomenological debate. The direct test of the ability of SNRs to operate as CR PeVatrons can be provided by ultrahigh-energy (UHE; E γ ≥ 100 TeV) γ-rays. In this context, the historical SNR Cassiopeia A (Cas A) is considered one of the most promising targets for UHE observations. This paper presents the observation of Cas A and its vicinity by the LHAASO KM2A detector. The exceptional sensitivity of LHAASO KM2A in the UHE band, combined with the young age of Cas A, enabled us to derive stringent model-independent limits on the energy budget of UHE protons and nuclei accelerated by Cas A at any epoch after the explosion. The results challenge the prevailing paradigm that Cas A–type SNRs are major suppliers of PeV CRs in the Milky Way.

Keywords: supernova remnants; galactic cosmic rays; gamma-rays
X-Ray Properties of Young Radio Quasars at z > 4.5

We present a comprehensive analysis of Chandra X-ray observations of 15 young radio quasars at redshifts 4.5 < z < 5.0. All sources are detected in the 0.5-7.0 keV energy band. Emission spectra are extracted, and the average photon index for the sample is measured to be 1.5 ± 0.1. Unabsorbed rest-frame 2-10 keV luminosities are found to range between (0.5-23.2) × 1045 erg s-1. The optical-X-ray power-law spectral index ${\alpha }_{\mathrm{ox}}$ is calculated for each source using optical/UV data available in the literature. The ${\alpha }_{\mathrm{ox}}$ -UV relationship is compared with other quasar surveys, and an anticorrelation is observed that agrees with independent estimates. Rest-frame radio and X-ray luminosities are established for the sample, and a correlation between the luminosities is detected. These multiwavelength results reinforce a lack of spectral evolution for quasars over a broad redshift range. We additionally identify three quasars from our multiwavelength analysis that are statistically significant outliers, with one source being a Compton-thick candidate in the early universe, and discuss each in detail.

Keywords: high-redshift galaxies; active galactic nuclei; high energy astrophysics; active galaxies
The Stars in M15 Were Born with the r-process

High-resolution spectroscopy of stars on the red giant branch (RGB) of the globular cluster M15 has revealed a large (∼1 dex) dispersion in the abundances of r-process elements such as Ba and Eu. Neutron star mergers (NSMs) have been proposed as a major source of the r-process. However, most NSM models predict a delay time longer than the timescale for cluster formation. One possibility is that a NSM polluted the surfaces of stars in M15 long after the cluster finished forming. In this case, the abundances of the polluting elements would decrease in the first dredge-up as stars turn on to the RGB. We present Keck/DEIMOS abundances of Ba in 66 stars along the entire RGB and the top of the main sequence. The Ba abundances have no trend with stellar luminosity (evolutionary phase). Therefore, the stars were born with the Ba that they have today, and Ba did not originate in a source with a delay time longer than the timescale for cluster formation. In particular, if the source of Ba was a NSM, it would have had a very short delay time. Alternatively, if Ba enrichment took place before the formation of the cluster, an inhomogeneity of a factor of 30 in Ba abundance needs to be able to persist over the length scale of the gas cloud that formed M15, which is unlikely.

Keywords: globular star clusters; r-process; nucleosynthesis
Optimizing the Resolution of Hydrodynamic Simulations for MCRaT Radiative Transfer Calculations

Despite their discovery about half a century ago, the gamma-ray burst (GRB) prompt emission mechanism is still not well understood. Theoretical modeling of the prompt emission has advanced considerably due to new computational tools and techniques. One such tool is the PLUTO hydrodynamics code, which is used to numerically simulate GRB outflows. PLUTO uses Adaptive Mesh Refinement to focus computational efforts on the portion of the grid that contains the simulated jet. Another tool is the Monte Carlo Radiation Transfer (MCRaT) code, which predicts the electromagnetic signatures of GRBs by conducting photon scatterings within a jet using PLUTO. The effects of the underlying resolution of a PLUTO simulation with respect to MCRaT post-processing radiative transfer results have not yet been quantified. We analyze an analytic spherical outflow and a hydrodynamically simulated GRB jet with MCRaT at varying spatial and temporal resolutions and quantify how decreasing both resolutions affects the resulting mock observations. We find that changing the spatial resolution changes the hydrodynamic properties of the jet, which directly affect the MCRaT mock observable peak energies. We also find that decreasing the temporal resolution artificially decreases the high-energy slope of the mock observed spectrum, which increases both the spectral peak energy and the luminosity. We show that the effects are additive when both spatial and temporal resolutions are modified. Our results allow us to understand how decreased hydrodynamic temporal and spatial resolutions affect the results of post-processing radiative transfer calculations, allowing for the optimization of hydrodynamic simulations for radiative transfer codes.

Keywords: radiative transfer; radiative transfer simulations; hydrodynamical simulations; gamma-ray bursts; special relativity
The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment

Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H2O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust traps, which loses its icy content to sublimation upon reaching the snow line. We find that the vapor abundance in the inner disk is strongly affected by the fragmentation velocity (v f) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence (α ≤ 1 × 10-3) and a range of v f, radial locations and gap depths (especially those of the innermost gaps) can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that for realistic v f (≤10 m s-1), the presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk.

Keywords: protoplanetary disks; planet formation
Comparing SCUBA-2 and ALMA Selections of Faint Dusty Star-forming Galaxies in A2744

We make a comparison of deep SCUBA-2 450 and 850 μm imaging on the massive lensing cluster field A2744 with Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm data. Our primary goal is to assess how effective the wider-field SCUBA-2 sample, in combination with red JWST priors, is for finding faint dusty star-forming galaxies (DSFGs) compared to the much more expensive mosaicked ALMA observations. We cross-match our previously reported direct (>5σ) SCUBA-2 sample and red JWST NIRCam prior-selected (>3σ) SCUBA-2 sample to direct ALMA sources from the DUALZ survey. We find that roughly 95% are confirmed by ALMA. The red priors also allow us to probe deeper in the ALMA image. Next, by measuring the 450 and 850 μm properties of the full ALMA sample, we show that 46/69 of the ALMA sources are detected at 850 μm and 24/69 are detected at 450 μm in the SCUBA-2 images, with a total detection fraction of nearly 75%. All of the robust (>5σ) ALMA sources that are not detected in at least one SCUBA-2 band lie at 1.2 mm fluxes ≲0.6 mJy and are undetected primarily due to the higher SCUBA-2 flux limits. We also find that the SCUBA-2 detection fraction drops slightly beyond z = 3, which we attribute to the increasing 1.2 mm to 850 μm and 1.2 mm to 450 μm flux ratios combined with the ALMA selection. The results emphasize the power of combining SCUBA-2 data with JWST colors to map the faint DSFG population.

Keywords: submillimeter astronomy; galaxy evolution; starburst galaxies
Application of Neural Networks to Estimation and Prediction of Seeing at the Large Solar Telescope Site

Optical turbulence limits the angular resolution of ground-based astronomical telescopes. The key parameter of optical turbulence is seeing. In this study, seasonal variations of seeing estimated from differential image motion monitor measurements at the Large Solar Telescope site are discussed. The Large Solar Telescope will be located at an elevation of 2000 m above sea level ( $51^\circ 37^{\prime} 18^{\prime\prime} $ N, $100^\circ 55^{\prime} 07^{\prime\prime} {\rm{E}}$ ). The highest seeing values are observed in winter. The median of seeing is 2.″1. In summer, the median decreases to 1.″1. The best atmospheric conditions are observed in April-May, when the medians of seeing are low and the standard deviations are high. During this period, atmospheric situations with low values of seeing (~0.″5-0.″6) are often observed. We simulated multilayer neural networks for the measured seeing by applying a group method of data handling. Modeled seeing is well described in terms of mean meteorological parameters, which include wind speed components and large-scale vorticity of air flows at different altitudes in the atmosphere. The 12-layer optimal neural network obtained has a high correlation coefficient between modeled and measured seeing values. The linear correlation coefficient is 0.77.

Keywords: astronomical seeing; astronomical methods; astronomical optics; astronomical research; astronomy data analysis; atmospheric refraction; observatories
S8 Tension in the Context of Dark Matter-Baryon Scattering

We explore an interacting dark matter (IDM) model that allows for a fraction of dark matter (DM) to undergo velocity-independent scattering with baryons. In this scenario, structure on small scales is suppressed relative to the cold DM scenario. Using the effective field theory of large-scale structure, we perform the first systematic analysis of BOSS full-shape galaxy clustering data for the IDM scenario, and we find that this model ameliorates the S 8 tension between large-scale structure and Planck data. Adding the S 8 prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ~3σ preference for a nonvanishing DM-baryon scattering cross section, assuming ~10% of DM is interacting and has a particle mass of 1 MeV. This result produces a modest ~20% suppression of the linear power at k ≲ 1 h Mpc-1, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolve S 8 tension between cosmological data sets. The validity of the specific IDM model explored here will be critically tested with upcoming galaxy surveys at the interaction level needed to alleviate the S 8 tension.

Keywords: dark matter; cosmology; particle astrophysics; redshift surveys; cosmic microwave background radiation; large-scale structure of the universe
Detection of Repeating FRB 180916.J0158+65 Down to Frequencies of 300 MHz

We report on the detection of seven bursts from the periodically active, repeating fast radio burst (FRB) source FRB 180916.J0158+65 in the 300-400 MHz frequency range with the Green Bank Telescope (GBT). Emission in multiple bursts is visible down to the bottom of the GBT band, suggesting that the cutoff frequency (if it exists) for FRB emission is lower than 300 MHz. Observations were conducted during predicted periods of activity of the source, and had simultaneous coverage with the Low Frequency Array (LOFAR) and the FRB backend on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find that one of the GBT-detected bursts has potentially associated emission in the CHIME band (400-800 MHz) but we detect no bursts in the LOFAR band (110-190 MHz), placing a limit of $\alpha \gt -1.0$ on the spectral index of broadband emission from the source. We also find that emission from the source is severely band-limited with burst bandwidths as low as ∼40 MHz. In addition, we place the strictest constraint on observable scattering of the source, <1.7 ms at 350 MHz, suggesting that the circumburst environment does not have strong scattering properties. Additionally, knowing that the circumburst environment is optically thin to free-free absorption at 300 MHz, we find evidence against the association of a hyper-compact H II region or a young supernova remnant (age <50 yr) with the source.

Keywords: radio bursts; radio transient sources
A Stability Timescale for Nonhierarchical Three-body Systems

The gravitational three-body problem is a fundamental problem in physics and has significant applications to astronomy. Three-body configurations are often considered stable as long the system is hierarchical; that is, the two orbital distances are well-separated. However, instability, which is often associated with significant energy exchange between orbits, takes time to develop. Assuming two massive objects in a circular orbit and a test particle in an eccentric orbit, we develop an analytical formula estimating the time it takes for the test particle's orbital energy to change by an order of itself. We show its consistency with results from N-body simulations. For eccentric orbits in particular, the instability is primarily driven not by close encounters of the test particle with one of the other bodies, but by the fundamental susceptibility of eccentric orbits to exchange energy at their periapsis. Motivated by recent suggestions that the galactic center may host an intermediate-mass black hole (IMBH) as a companion to the massive black hole Sgr A*, we use our timescale to explore the parameter space that could harbor an IMBH for the lifetime of the S-cluster of stars surrounding Sgr A*. Furthermore, we show that the orbit of an S-star can be stable for long timescales in the presence of other orbital crossing stars, thus suggesting that the S-cluster may be stable for the lifetimes of its member stars.

Keywords: high energy astrophysics; galaxies; galactic center; intermediate-mass black holes; supermassive black holes; three-body problem; black holes; exoplanets
Hybrid Simulation and Quasi-linear Theory of Bi-Kappa Proton Instabilities

The quasi-steady states of collisionless plasmas in space (e.g., in the solar wind and planetary environments) are governed by the interactions of charged particles with wave fluctuations. These interactions are responsible not only for the dissipation of plasma waves but also for their excitation. The present analysis focuses on two instabilities, mirror and electromagnetic ion cyclotron instabilities, associated with the same proton temperature anisotropy T ⊥ > T ∥ (where ⊥, ∥ are directions defined with respect to the local magnetic field vector). Theories relying on standard Maxwellian models fail to link these two instabilities (i.e., predicted thresholds) to the proton quasi-stable anisotropies measured in situ in a completely satisfactory manner. Here we revisit these instabilities by modeling protons with the generalized bi-Kappa (bi-κ power-law) distribution, and by a comparative analysis of a 2D hybrid simulation with the velocity-moment-based quasi-linear (QL) theory. It is shown that the two methods feature qualitative and, even to some extent, quantitative agreement. The reduced QL analysis based upon the assumption of a time-dependent bi-Kappa model thus becomes a valuable theoretical approach that can be incorporated into the present studies of solar wind dynamics.

Keywords: the sun; solar wind; fast solar wind