adsabs/SciX_UAT_keywords huggingface dataset:
A Comprehensive Power Spectral Density Analysis of Astronomical Time Series. I. The Fermi-LAT Gamma-Ray Light Curves of Selected Blazars

We present the results of the Fermi-Large Area Telescope 10 yr long light curve (LC) modeling of selected blazars: six flat-spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs), examined in 7, 10, and 14 day binning. The LCs and power spectral densities (PSDs) were investigated with various methods: Fourier transform, Lomb-Scargle periodogram (LSP), wavelet scalogram, autoregressive moving average (ARMA) process, continuous-time ARMA (CARMA), Hurst exponent (H), and the ${ \mathcal A }\mbox{--}{ \mathcal T }$ plane. First, with extensive simulations we showed that parametric modeling returns unreliable parameters, with a high dispersion for different realizations of the same stochastic model. Hence, any such analysis should be supported with Monte Carlo simulations. For our blazar sample, we find that the power-law indices β calculated from the Fourier and LSP modeling mostly fall in the range 1 ≲ β ≲ 2. Using the wavelet scalograms, we confirm a quasi-periodic oscillation (QPO) in PKS 2155-304 at a 3σ significance level, but do not detect any QPOs in other objects. The ARMA fits reached higher orders for 7 day binned LCs and lower orders for 10 and 14 day binned LCs for the majority of blazars, suggesting there might exist a characteristic timescale for the perturbations in the jet and/or accretion disk to die out. ARMA and CARMA modeling revealed breaks in their PSDs at timescales of a few hundred days. The estimation of H was performed with several methods. We find that most blazars exhibit H > 0.5, indicating long-term memory. Finally, the FSRQ and BL Lac subclasses are clearly separated in the ${ \mathcal A }\mbox{--}{ \mathcal T }$ plane.

Keywords: active galactic nuclei; blazars; light curves; time series analysis; high energy astrophysics; bl lacertae objects; quasars
Detection Limits for Chiral Amino Acids Using a Polarization Camera

The detection of biosignatures on a planetary surface is of high scientific interest, and enantiomeric excesses of organic molecules are one such signature. Enantiomeric excesses can be detected by their polarizing effects on transmitted light. As part of instrument development work for a microscopic imager, the Cold Lightweight Imager for Europa (C-LIFE), we assess the potential of polarization measurements to quantify enantiomeric excesses. We investigated the optical rotation of the amino acids serine and phenylalanine for a range of enantiomeric abundances. Measurements were made with mixtures of serine and phenylalanine as well as Europa-relevant salts to determine how well these combinations can be detected. We also conducted a small number of measurements on samples of bacteria taken from glacial environments. We found that concentrations greater than 10-3 M are needed to detect serine and concentrations greater than 10-4 M are needed to detect phenylalanine, with larger concentrations needed for smaller enantiomeric excesses. Salts do not have a significant effect on the optical rotation. Optical rotation of bacterial samples were detected at concentrations >106 cells ml-1. Systematic errors in our polarization detector limited our sensitivity to optical activity changes of ∼0.008°, leading to an inability to distinguish enantiomeric abundances separated by 5%, but tests show that improvements to our laboratory technique can yield a factor of 20 improvement in sensitivity.

Keywords: astrobiology; biosignatures; jovian satellites; polarimetry
The Evolution of Plasma Composition during a Solar Flare

We analyze the coronal elemental abundances during a small flare using Hinode/EIS observations. Compared to the preflare elemental abundances, we observed a strong increase in coronal abundance of Ca XIV 193.84 Å, an emission line with low first ionization potential (FIP < 10 eV), as quantified by the ratio Ca/Ar during the flare. This is in contrast to the unchanged abundance ratio observed using Si X 258.38 Å/S X 264.23 Å. We propose two different mechanisms to explain the different composition results. First, the small flare-induced heating could have ionized S, but not the noble gas Ar, so that the flare-driven Alfvén waves brought up Si, S, and Ca in tandem via the ponderomotive force which acts on ions. Second, the location of the flare in strong magnetic fields between two sunspots may suggest fractionation occurred in the low chromosphere, where the background gas is neutral H. In this region, high-FIP S could behave more like a low-FIP than a high-FIP element. The physical interpretations proposed generate new insights into the evolution of plasma abundances in the solar atmosphere during flaring, and suggests that current models must be updated to reflect dynamic rather than just static scenarios.

Keywords: the sun; solar physics; solar flares; solar abundances
LEGWORK: A Python Package for Computing the Evolution and Detectability of Stellar-origin Gravitational-wave Sources with Space-based Detectors

We present LEGWORK (LISA Evolution and Gravitational Wave Orbit Kit), an open-source Python package for making predictions about stellar-origin gravitational-wave sources and their detectability in LISA or other space-based gravitational-wave detectors. LEGWORK can be used to evolve the orbits of sources due to gravitational-wave emission, calculate gravitational-wave strains (using post-Newtonian approximations), compute signal-to-noise ratios, and visualize the results. It can be applied to a variety of potential sources, including binaries consisting of white dwarfs, neutron stars, and black holes. Although we focus on double compact objects, in principle LEGWORK can be used for any system with a user-specified orbital evolution, such as those affected by a third object or gas drag. We optimized the package to make it efficient for use in population studies, which can contain tens of millions of sources. This paper describes the package and presents several potential use cases. We explain in detail the derivations of the expressions behind the package as well as identify and clarify some discrepancies currently present in the literature. We hope that LEGWORK will enable and accelerate future studies triggered by the rapidly growing interest in gravitational-wave sources.

Keywords: open source software; gravitational waves; gravitational wave detectors; compact objects; orbital evolution; white dwarf stars; neutron stars; stellar mass black holes
Direct Simulation Monte Carlo Modeling of Ammonia in Comet C/2014 Q2 (Lovejoy)

Ammonia (NH3), likely the most abundant nitrogen-bearing molecule in cometary ices followed by hydrogen cyanide, is believed to be stored in the nucleus predominantly as a parent ice. However, spatial profiles of NH3 observed in comet C/2014 Q2 (Lovejoy) in the near-infrared region are consistent with a distributed source contribution (Dello Russo et al. 2022). We developed the direct simulation Monte Carlo model of ammonia in cometary coma and applied it to comet C/2014 Q2 (Lovejoy). Results suggest that NH3 molecules in the coma of C/2014 Q2 (Lovejoy) can plausibly originate from a combination of parent molecules of NH3 in the coma and a NH3 nucleus source. We demonstrate that the parents of NH3 having photodissociation lifetimes of several hundreds of seconds or longer (at 1 au from the Sun) can explain the observed spatial profile of NH3 in comet C/2014 Q2 (Lovejoy). Even though ammonia salts are possible candidates for parents of NH3, some simple ammonium salts such as NH4CN or NH4Cl may dissociate thermally within very short lifetimes after sublimation from the nucleus, so the contribution from those ammonium salts may be indistinguishable from the nucleus source. The lack of experimental data on photoprocesses for potential NH3 parent molecules prevent us from identifying the origin of NH3 in comets. Experimental and theoretical studies of photodissociation/ionization reactions of potential NH3 parent molecules by the solar UV radiation field are encouraged for the future identification of NH3 parents in comets.

Keywords: comet volatiles; comet nuclei; comae
Impact Rates in the Outer Solar System

Previous studies of cometary impacts in the outer solar system used the spatial distribution of ecliptic comets (ECs) from dynamical models that assumed ECs began on low-inclination orbits (≲5°) in the Kuiper Belt. In reality, the source population of ECs-the trans-Neptunian scattered disk-has orbital inclinations reaching up to ~30°. In Nesvorný et al., we developed a new dynamical model of ECs by following comets as they evolved from the scattered disk to the inner solar system. The model was absolutely calibrated from the population of Centaurs and active ECs. Here we use our EC model to determine the steady-state impact flux of cometary/Centaur impactors on Jupiter, Saturn, Uranus, and their moons. Relative to previous work, we find slightly higher impact probabilities on the outer moons and lower impact probabilities on the inner moons. The impact probabilities are smaller when comet disruption is accounted for. The results provide a modern framework for the interpretation of the cratering record in the outer solar system.

Keywords: comet dynamics; comet origins; natural satellite evolution; irregular satellites; natural satellite surfaces; impact phenomena; craters
High-cadence Timing of Binary Pulsars with CHIME

We performed near-daily observations of the binary pulsars PSR J0218+4232, PSR J1518+4904, and PSR J2023+2853 with the Canadian Hydrogen Intensity Mapping Experiment (CHIME). For the first time, we detected the Shapiro time delay in all three pulsar binary systems, using only 2–4 yr of CHIME/Pulsar timing data. We measured the pulsar masses to be ${1.49}_{-0.20}^{+0.23}$ M ⊙, ${1.470}_{-0.034}^{+0.030}$ M ⊙, and ${1.50}_{-0.38}^{+0.49}$ M ⊙, respectively. The companion mass to PSR J0218+4232 was found to be ${0.179}_{-0.016}^{+0.018}$ M ⊙. We constrained the mass of the neutron star companion of PSR J1518+4904 to be ${1.248}_{-0.029}^{+0.035}$ M ⊙, using the observed apsidal motion as a constraint on the mass estimation. The binary companion to PSR J2023+2853 was found to have a mass of ${0.93}_{-0.14}^{+0.17}$ M ⊙; in the context of the near-circular orbit, this mass estimate suggests that the companion to PSR J2023+2853 is likely a high-mass white dwarf. By comparing the timing model obtained for PSR J0218+4232 with previous observations, we found a significant change in the observed orbital period of the system of $\dot{{P}_{{\rm{b}}}}=0.14(2)\times {10}^{-12}$ ; we determined that this variation arises from "Shklovskii acceleration" due to the relative motion of the binary system, and used this measurement to estimate a distance of d = (6.7 ± 1.0) kpc to PSR J0218+4232. This work demonstrates the capability of high-cadence observations, enabled by the CHIME/Pulsar system, to detect and refine general-relativistic effects of binary pulsars over short observing timescales.

Keywords: pulsars; observational astronomy; interferometers
Using the Sun to Measure the Primary Beam Response of the Canadian Hydrogen Intensity Mapping Experiment

We present a beam pattern measurement of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) made using the Sun as a calibration source. As CHIME is a pure drift-scan instrument, we rely on the seasonal north-south motion of the Sun to probe the beam at different elevations. This semiannual range in elevation, combined with the radio brightness of the Sun, enables a beam measurement that spans ~7200 square degrees on the sky without the need to move the telescope. We take advantage of observations made near solar minimum to minimize the impact of solar variability, which is observed to be <10% in intensity over the observation period. The resulting data set is highly complementary to other CHIME beam measurements-both in terms of angular coverage and systematics-and plays an important role in the ongoing program to characterize the CHIME primary beam.

Keywords: radio telescopes; interferometers; calibration; quiet sun
ALMA ACA Detection of Submillimeter Emission Associated with the Western Hot Spot of the Radio Galaxy Pictor A

In order to investigate the far-infrared excess detected from the western hot spot of the radio galaxy Pictor A with the Herschel observatory, submillimeter photometry is performed with the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array at Band 8 with the reference frequency of 405 GHz. A submillimeter source is discovered at the radio peak of the hot spot. Because the 405 GHz flux density of the source, 80.7 ± 3.1 mJy, agrees with the extrapolation of the synchrotron radio spectrum, the far-infrared excess is suggested to exhibit no major contribution at the ACA band. In contrast, by subtracting the power-law spectrum tightly constrained by the radio and ACA data, the significance of the excess in the Herschel band is well confirmed. No diffuse submillimeter emission is detected within the ACA field of view, and thus, the excess is ascribed to the western hot spot itself. In comparison to the previous estimate based on the Herschel data, the relative contribution of the far-infrared excess is reduced by a factor of ~1.5. The spectrum of the excess below the far-infrared band is determined to be harder than that of the diffusive shock acceleration. This strengthens the previous interpretation that the excess originates via the magnetic turbulence in the substructures within the hot spot. The ACA data are utilized to evaluate the magnetic field strength of the excess and of diffuse radio structure associated with the hot spot.

Keywords: radio hot spots; relativistic jets; non-thermal radiation sources; fanaroff-riley radio galaxies; magnetic fields; radio interferometers
Detection of PO in Orion-KL: Phosphorus Chemistry in the Plateau Outflow

The PO molecule (X2Πr) has been detected toward Orion-KL via its J = 2.5 → 1.5 transition near 109 GHz using the 12 m telescope of the Arizona Radio Observatory. This transition consists of a quartet of lines, generated by lambda-doubling and phosphorus hyperfine interactions, creating a distinct pattern of doublets of doublets. All four features (F = 3 → 2, e, f and 2 → 1, e, f ) were detected. The line profiles measured were relatively broad, with ΔV1/2 ∼ 21-25 km s-1, and VLSR ∼ 10 km s-1, clearly identifying the molecule as arising from the Orion "plateau" region. The J = 2 → 1 transition of PN (X1Σ) at 94 GHz was also measured, and its line profile indicates a plateau origin in Orion, as found previously by Ziurys. Therefore, PO and PN arise from the same gas. There was no evidence of a "hot core" or "ridge" component in either molecule. The column densities determined for PO and PN in the Orion plateau are Ntot ≈ 5.4(0.2) × 1013 and 2.0(0.4) × 1013 cm-2, respectively, with corresponding abundances, relative to H2, of f ∼ 1.6(0.1) × 10-10 and 6.1(0.6) × 10-11, resulting in PO/PN ∼ 3. The PO and PN line profiles also resemble those of SiO and SiS, suggesting that the phosphorus molecules are produced by shocks in the plateau outflow. The observed PO/PN ratio in Orion-KL is very close in value to that measured in other warm molecular clouds, indicating a common synthesis pathway for these two molecules in outflows caused by star formation.

Keywords: astrochemistry; star formation; interstellar abundances; interstellar molecules; molecular clouds; astrobiology
Gamma-Ray and Neutrino Emissions due to Cosmic-Ray Protons Accelerated at Intracluster Shocks in Galaxy Clusters

We examine the cosmic-ray protons (CRp) accelerated at collisionless shocks in galaxy clusters using cosmological structure formation simulations. We find that in the intracluster medium (ICM) within the virial radius of simulated clusters, only ∼7% of shock kinetic energy flux is dissipated by the shocks that are expected to accelerate CRp - that is, supercritical, quasi-parallel (Q∥) shocks with sonic Mach number Ms ≥ 2.25. The rest is dissipated at subcritical shocks and quasi-perpendicular shocks, both of which may not accelerate CRp. Adopting the diffusive shock acceleration (DSA) model recently presented in Ryu et al., we quantify the DSA of CRp in simulated clusters. The average fraction of the shock kinetic energy transferred to CRp via DSA is assessed at ∼(1-2) × 10-4. We also examine the energization of CRp through reacceleration using a model based on the test-particle solution. Assuming that the ICM plasma passes through shocks three times on average through the history of the universe and that CRp are reaccelerated only at supercritical Q∥-shocks, the CRp spectrum flattens by ∼0.05-0.1 in slope and the total amount of CRp energy increases by ∼40%-80% from reacceleration. We then estimate diffuse γ-ray and neutrino emissions, resulting from inelastic collisions between CRp and thermal protons. The predicted γ-ray emissions from simulated clusters lie mostly below the upper limits set by Fermi-LAT for observed clusters. The neutrino fluxes toward nearby clusters would be ≲10-4 of the IceCube flux at Eν = 1 PeV and ≲10-6 of the atmospheric neutrino flux in the energy range of Eν ≤ 1 TeV.

Keywords: cosmic rays; galaxy clusters; gamma-rays; shocks; neutrino astronomy
Cosmological Insights into the Early Accretion of r-process-enhanced Stars. I. A Comprehensive Chemodynamical Analysis of LAMOST J1109+0754

This study presents a comprehensive chemodynamical analysis of LAMOST J1109+0754, a bright (V = 12.8), extremely metal-poor ([Fe/H] = -3.17) star, with a strong r-process enhancement ([Eu/Fe] = +0.94 ± 0.12). Our results are based on the 7D measurements supplied by Gaia and the chemical composition derived from a high-resolution (R ∼ 110,000), high signal-to-noise ratio ( ${\rm{S}}/{\rm{N}}\sim 60)$ optical spectrum obtained by the 2.4 m Automated Planet Finder Telescope at Lick Observatory. We obtain chemical abundances of 31 elements (from lithium to thorium). The abundance ratios ([X/Fe]) of the light elements (Z ≤ 30) suggest a massive Population III progenitor in the 13.4-29.5 M⊙ mass range. The heavy-element (30 < Z ≤ 90) abundance pattern of J1109+075 agrees extremely well with the scaled-solar r-process signature. We have developed a novel approach to trace the kinematic history and orbital evolution of J1109+0754 with a cOsmologically deRIved timE-varyiNg Galactic poTential (the ORIENT) constructed from snapshots of a simulated Milky Way analog taken from the Illustris-TNG simulation. The orbital evolution within this Milky Way-like galaxy, along with the chemical abundance pattern, implies that J1109+0754 likely originated in a low-mass dwarf galaxy located ∼60 kpc from the center of the Galaxy, which was accreted ∼6-7 Gyr ago, and that the star now belongs to the outer-halo population.

Keywords: chemically peculiar stars; population iii stars; r-process; stellar kinematics; chemical abundances; stellar dynamics; orbits; galaxy dynamics
The Multicomponent Fitting to the Star Formation Histories in the TNG Simulation

The star formation history (SFH) is a key issue in the evolution of galaxies. In this work, we developed a model based on a Gaussian and gamma function mixture to fit SFHs with varying numbers of components. Our primary objective was to use this model to reveal the shape of SFHs and the corresponding physical driving factors. Specifically, we applied this model to fit SFHs from the TNG100-1 simulation. Our study led to the following findings. (1) Our model fits with TNG star formation histories well, especially for high-mass and red galaxies; (2) a clear relationship exists between the number and shape of fitted components and the mass and color of galaxies, with notable differences observed between central/isolated and satellite galaxies. (3) Our model allows us to extract different episodes of star formation within star formation histories with ease and analyze the duration and timing of each star formation episode. Our findings indicate a strong relationship between the timing of each star formation episode and galaxy mass and color.

Keywords: galaxy formation; hydrodynamical simulations
Ultracool Dwarf Absolute Magnitude Versus Spectral Type Relations for Euclid and Roman Near-infrared Filters

We synthesize Euclid Near Infrared Spectrometer and Photometer photometry for the Y E J E H E filters and Roman Wide Field Instrument photometry for the F106, F129, F146, F158, F184 and F213 filters using SpeX prism spectra and parallaxes of 688 field-age and 151 young (≲200 Myr) ultracool dwarfs (spectral types M6–T9). For the above filters, we derive empirical absolute magnitude-spectral type polynomial relations that enable the calculation of photometric distances for ultracool dwarfs to be observed with Euclid and Roman, in the absence of parallax measurements. The synthesized photometry can also be used to generate color–color figures to distinguish high-redshift galaxies from brown dwarf interlopers.

Keywords: brown dwarfs; photometry; absolute magnitude; stellar spectral types
Solar Cycle Evolution of Filaments over a Century: Investigations with the Meudon and McIntosh Hand-drawn Archives

Hand-drawn synoptic maps from the Meudon Observatory (1919 onwards) and the McIntosh archive (1967 onwards) are two important sources of long-term, manually recorded filament observations. In this study, we calibrate the Meudon maps and subsequently identify filaments through an automated method. We extract physical parameters from this filament database and perform a comparative study of their long-term evolution focusing on the cotemporal period of the McIntosh and Meudon observations. The spatiotemporal evolution of filaments manifests in the form of a filament butterfly diagram, further indicating that they are intimately related to the large-scale solar cycle. Physical descriptors such as the number and length of filaments, which are tracers of the solar surface magnetic field, have cycles which are phase locked with the ~11 yr sunspot cycle. The tilt-angle distribution of filaments-both near to or distant from active region locations-indicates that their origin is due to either large-scale surface magnetic field or inter-active-region field evolution. This study paves the way for constructing a composite series of hand-drawn filament data with minimal gaps stretching over the time span of solar filament observations up to a century. On the one hand, this would serve as a useful constraint for models of magnetic field emergence and evolution on the Sun's surface over multiple solar cycles, and on the other hand, this filament database may be used to guide the reconstruction of filament/prominence associated eruptive events before the space age.

Keywords: solar cycle; solar filaments; solar activity