adsabs/SciX_UAT_keywords huggingface dataset:
Systematic Study of Acceleration Efficiency in Young Supernova Remnants with Nonthermal X-Ray Observations

Cutoff energy in a synchrotron radiation spectrum of a supernova remnant (SNR) contains a key parameter of ongoing particle acceleration. We systematically analyze 11 young SNRs, including all historical SNRs, to measure the cutoff energy, thus shedding light on the nature of particle acceleration at the early stage of SNR evolution. The nonthermal (synchrotron) dominated spectra in filament-like outer rims are selectively extracted and used for spectral fitting because our model assumes that accelerated electrons are concentrated in the vicinity of the shock front owing to synchrotron cooling. The cutoff energy parameter (ϵ0) and shock speed (vsh) are related as ${\varepsilon }_{0}\propto {v}_{\mathrm{sh}}^{2}{\eta }^{-1}$ with a Bohm factor of η. Five SNRs provide us with spatially resolved ϵ0-vsh plots across the remnants, indicating a variety of particle acceleration. With all SNRs considered together, the systematic tendency of η clarifies a correlation between η and an age of t (or an expansion parameter of m) as η ∝ t-0.4 (η ∝ m4). This might be interpreted as the magnetic field becomes more turbulent and self-generated, as particles are accelerated at a greater rate with time. The maximum energy achieved in SNRs can be higher if we consider the newly observed time dependence on η.

Keywords: supernova remnants; non-thermal radiation sources; x-ray sources; interstellar medium; cosmic rays; galactic cosmic rays
Water UV-shielding in the Terrestrial Planet-forming Zone: Implications for Carbon Dioxide Emission

Carbon dioxide is an important tracer of the chemistry and physics in the terrestrial planet-forming zone. Using a thermochemical model that has been tested against the mid-infrared water emission, we reinterpret the CO2 emission as observed with Spitzer. We find that both water UV-shielding and extra chemical heating significantly reduce the total CO2 column in the emitting layer. Water UV-shielding is the more efficient effect, reducing the CO2 column by ~2 orders of magnitude. These lower CO2 abundances lead to CO2-to-H2O flux ratios that are closer to the observed values, but CO2 emission is still too bright, especially in relative terms. Invoking the depletion of elemental oxygen outside of the water midplane ice line more strongly impacts the CO2 emission than it does the H2O emission, bringing the CO2-to-H2O emission in line with the observed values. We conclude that the CO2 emission observed with Spitzer-IRS is coming from a thin layer in the photosphere of the disk, similar to the strong water lines. Below this layer, we expect CO2 not to be present except when replenished by a physical process. This would be visible in the 13CO2 spectrum as well as certain 12CO2 features that can be observed by JWST-MIRI.

Keywords: protoplanetary disks; astrochemistry
A Population III-Generated Dust Screen at z 16

The search for alternative cosmological models is largely motivated by the growing discordance between the predictions of ΛCDM and the ever-improving observations, such as the disparity in the value of H 0 measured at low and high redshifts. One model in particular, known as the R h = ct universe, has been highly successful in mitigating or removing all of the inconsistencies. In this picture, however, the anisotropies in the cosmic microwave background (CMB) would have emerged at a redshift z ~ 16, rather than via fluctuations in the recombination zone at z ~ 1080. We demonstrate here that a CMB created in the early universe, followed by scattering through a Population III-generated dust screen, is consistent with all of the current data. Indeed, the Planck measurements provide a hint of an ~2%-4% frequency dependence in the CMB power spectrum, which would be naturally explained as a variation in the optical depth through the dust but not a Thomson scattering-dominated recombination environment. Upcoming measurements should be able to easily distinguish between these two scenarios, e.g., via the detection of recombination lines at z ~ 1080, which would completely eliminate the dust-reprocessing idea.

Keywords: cosmic microwave background radiation; population iii stars; reionization; cosmological parameters; large-scale structure of the universe
Establishing the Nonprimordial Origin of Black Hole-Neutron Star Mergers

Primordial black holes (PBHs) from the early universe constitute attractive dark matter candidates. First detections of black hole-neutron star (BH-NS) candidate gravitational wave events by the LIGO/Virgo collaboration, GW200105 and GW200115, already prompted speculations about nonastrophysical origin. We analyze, for the first time, the total volumetric merger rates of PBH-NS binaries formed via two-body gravitational scattering, finding them to be subdominant to the astrophysical BH-NS rates. In contrast to binary black holes, a significant fraction of which can be of primordial origin, either formed in dark matter halos or in the early universe, PBH-NS rates cannot be significantly enhanced by contributions preceding star formation. Our findings imply that the identified BH-NS events are of astrophysical origin, even when PBH-PBH events significantly contribute to the gravitational wave observations.

Keywords: primordial black holes; cold dark matter; neutron stars; gravitational wave astronomy; gravitational wave sources; gravitational waves
Asteroseismology Applied to Constrain Structure Parameters of δ Scuti Stars

Asteroseismology is a powerful tool to probe stellar structure. Spaceborne instruments like CoRoT, Kepler, and TESS have observed the oscillations of numerous stars, among which δ Scutis are particularly interesting, owing to their fast rotation and complex pulsation mechanisms. In this work, we inferred model-dependent masses, metallicities, and ages of 60 δ Scuti stars from photometric, spectroscopic, and asteroseismic observations using least-squares minimization. These statistics have the potential to explain why only a tiny fraction of δ Scuti stars pulsate in a very clean manner. We find most of these stars with masses around 1.6 M ⊙ and metallicities below Z = 0.010. We observed a bimodality in age for these stars, with more than half the sample younger than 30 Myr, while the remaining ones were inferred to be older, i.e., hundreds of Myrs. This work emphasizes the importance of the large-frequency separation (Δν) in studies of δ Scutis. We also designed three machine-learning (ML) models that hold the potential for inferring these parameters at lower computational cost and much more rapidly. These models further revealed that constraining dipole modes can help in significantly improving age estimation and that radial modes succinctly encode information regarding luminosity and temperature. Using the ML models, we also gained qualitative insight into the importance of stellar observables in estimating mass, metallicity, and age. The effective temperature T eff strongly affects the inference of all structure parameters, and the asteroseismic offset parameter ϵ plays an essential role in the inference of age.

Keywords: delta scuti variable stars
The Thermal and Gravitational Energy Densities in the Large-scale Structure of the Universe

As cosmic structures form, matter density fluctuations collapse gravitationally and baryonic matter is shock-heated and thermalized. We therefore expect a connection between the mean gravitational potential energy density of collapsed halos, ${{\rm{\Omega }}}_{W}^{\mathrm{halo}}$ , and the mean thermal energy density of baryons, Ωth. These quantities can be obtained using two fundamentally different estimates: we compute ${{\rm{\Omega }}}_{W}^{\mathrm{halo}}$ using the theoretical framework of the halo model, which is driven by dark matter statistics, and measure Ωth using the Sunyaev-Zeldovich (SZ) effect, which probes the mean thermal pressure of baryons. First, we derive that, at the present time, about 90% of ${{\rm{\Omega }}}_{W}^{\mathrm{halo}}$ originates from massive halos with M > 1013 M⊙. Then, using our measurements of the SZ background, we find that Ωth accounts for about 80% of the kinetic energy of the baryons available for pressure in halos at z ≲ 0.5. This constrains the amount of nonthermal pressure, e.g., due to bulk and turbulent gas motion sourced by mass accretion, to be about Ωnon-th ≃ 0.4 × 10-8 at z = 0.

Keywords: cosmology; large-scale structure of the universe; sunyaev-zeldovich effect; gravitational energy; galaxy dark matter halos; galaxy clusters
Comparison of Two Methods for Deriving the Magnetic Field in a Filament Channel

Understanding the magnetic structure of filament channels is difficult but essential for identifying the mechanism (s) responsible for solar eruptions. In this paper we characterize the magnetic field in a well-observed filament channel with two independent methods, prominence seismology and magnetohydrodynamics flux-rope modeling, and compare the results. In 2014 May and June, active region 12076 exhibited a complex of filaments undergoing repeated oscillations over the course of 12 days. We measure the oscillation periods in the region with both Global Oscillation Network Group Hα and Solar Dynamics Observatory (SDO) Advanced Imaging Assembly EUV images, and then utilize the pendulum model of large-amplitude longitudinal oscillations to calculate the radius of curvature of the fields supporting the oscillating plasma from the derived periods. We also employ the regularized Biot-Savart laws formalism to construct a flux-rope model of the field of the central filament in the region based on an SDO Helioseismic and Magnetic Imager magnetogram. We compare the estimated radius of curvature, location, and angle of the magnetic field in the plane of the sky derived from the observed oscillations with the corresponding magnetic-field properties extracted from the flux-rope model. We find that the two models are broadly consistent, but detailed comparisons of the model and specific oscillations often differ. Model observation comparisons such as these are important for advancing our understanding of the structure of filament channels.

Keywords: solar physics; solar prominences; solar active region filaments; solar filaments; solar atmosphere; solar magnetic fields
Simulating Observations of Ices in Protoplanetary Disks

Ices are an important constituent of protoplanetary disks. New observational facilities, notably the James Webb Space Telescope (JWST), will greatly enhance our view of disk ices by measuring their infrared spectral features. We present a suite of models to complement these upcoming observations. Our models use a kinetics-based gas-grain chemical evolution code to simulate the distribution of ices in a disk, followed by a radiative transfer code using a subset of key ice species to simulate the observations. We present models reflecting both molecular inheritance and chemical reset initial conditions. We find that near-to-mid-IR absorption features of H2O, CO2, and CH3OH are readily observable in disk-integrated spectra of highly inclined disks while CO, NH3, and CH4 ice do not show prominent features. CH3OH ice has low abundance and is not observable in the reset model, making this species an excellent diagnostic of initial chemical conditions. CO2 ice features exhibit the greatest change over disk lifetime, decreasing and increasing for the inheritance and reset models, respectively. Spatially resolved spectra of edge-on disks, possible with JWST's integral field unit observing modes, are ideal for constraining the vertical distribution of ices and may be able to isolate features from ices closer to the midplane (e.g., CO) given sufficient sensitivity. Spatially resolved spectra of face-on disks can trace scattered-light features from H2O, CO2, and CH3OH, plus CO and CH4 from the outermost regions. We additionally simulate far-IR H2O ice emission features and find they are strongest for disks viewed face-on.

Keywords: protoplanetary disks; astrochemistry
Distribution Functions of Energetic Particles Experiencing Compound Subdiffusion

There are indications that the perpendicular transport of energetic particles is sometimes subdiffusive for intermediate timescales. This corresponds to a scenario where particles follow diffusive magnetic field lines while they also move diffusively in the parallel direction. This type of transport should occur at times after the ballistic regime but before the particles experience the transverse complexity of the turbulence. In this article we present a detailed analytical investigation of distribution functions of particles experiencing compound subdiffusion. Simple approximations of particle distributions are derived which can easily be used in applications. We also compare our findings with test-particle simulations performed for slab turbulence corresponding to the case of vanishing transverse turbulence structure.

Keywords: solar energetic particles; galactic cosmic rays; interplanetary turbulence
Numerical Simulations of (10199) Chariklo's Rings with a Resonant Perturber

The discovery of two thin rings around the ∼ 250 km sized Centaur Chariklo was the first of its kind, and their formation and evolutionary mechanisms are not well understood. Here, we explore a single shepherd satellite as a mechanism to confine Chariklo's rings. We also investigate the impact of such a perturber on reaccretion, which is a likely process for material located outside the Roche limit. We have modified N-body code that was developed for Saturn's rings to model the Chariklo system. Exploration of a reasonable parameter space indicates that rings like those observed could be stable as the result of a single satellite with a mass of a few ×1013 kg that is in orbital resonance with the rings. There is a roughly linear relationship between the model optical depth and the mass of the satellite required to confine a ring. Ring particles do not accrete into moonlets during hard-sphere simulations. However, a reasonable fraction of the ring material forms into moonlets after a few tens of orbits for soft-sphere collisions. The ring-particle properties are thus key parameters in terms of moonlet accretion or destruction in this system.

Keywords: small solar system bodies; centaur group; planetary rings; shepherd satellites; ring resonance; astronomy data modeling; n-body simulations
Magnetic Effects Promote Supermassive Star Formation in Metal-enriched Atomic-cooling Halos

Intermediate-mass black holes (with ≥105 M ⊙) are promising candidates for the origin of supermassive black holes (with ~109 M ⊙) in the early universe (redshift z ~ 6). Chon & Omukai first pointed out direct collapse black hole (DCBH) formation in metal-enriched atomic-cooling halos (ACHs), which relaxes the DCBH formation criterion. On the other hand, Hirano et al. showed that magnetic effects promote DCBH formation in metal-free ACHs. We perform a set of magnetohydrodynamical simulations to investigate star formation in magnetized ACHs with metallicities Z/Z ⊙ = 0, 10-5, and 10-4. Our simulations show that the mass accretion rate onto the protostars becomes lower in metal-enriched ACHs than in metal-free ACHs. However, many protostars form from gravitationally and thermally unstable metal-enriched gas clouds. Under such circumstances, the magnetic field rapidly increases as magnetic field lines wind up due to the spin of protostars. The region with the amplified magnetic field expands outwards due to the orbital motion of protostars and the rotation of the accreting gas. The amplified magnetic field extracts angular momentum from the accreting gas, promotes the coalescence of low-mass protostars, and increases the mass growth rate of the primary protostar. We conclude that the magnetic field amplification is always realized in metal-enriched ACHs regardless of the initial magnetic field strength, which affects the DCBH formation criterion. In addition, we find a qualitatively different trend from the previous unmagnetized simulations in that the mass growth rate is maximal for extremely metal-poor ACHs with Z/Z ⊙ = 10-5.

Keywords: magnetohydrodynamical simulations; primordial magnetic fields; population ii stars; star formation; protostars; supermassive black holes
Update on Global Helioseismic Observations of the Solar Torsional Oscillation 167: Command not found.

We present an up-to-date latitude-time map of the solar zonal flows at 0.99 R ⊙ from global helioseismology using data from the Global Oscillation Network Group, the Michelson Doppler Imager, and the Helioseismic and Magnetic Imager.

Keywords: solar physics; helioseismology; solar rotation
GOES-class Estimation for Behind-the-limb Solar Flares Using MESSENGER SAX

Mercury mission MESSENGER's Solar Assembly for X-rays (SAX) observed almost 700 solar flares between 2007 May 28 and 2013 August 19, as cataloged by Dennis Brian et al. The SAX instrument, part of the X-ray Spectrometer, operated at 1-10 keV, partially overlapping the energy range of the GOES X-ray spectrometers. SAX provides viewing angles different from the Earth-Sun line and can therefore be used as a GOES proxy for partially or fully occulted flares as seen from Earth. For flares with GOES classes above C2 seen on-disk for both instruments, we found an empirical relationship between the soft X-ray (SXR) fluxes measured by both SAX and GOES. Due to the different energy response of the two SXR instruments, individual events can deviate on average by about a factor of 2 from the empirical relationship, implying that predictions of the GOES class of occulted flares from SAX data are therefore accurate to within the same factor. The distinctive GOES energy response in combination with the multithermal nature of flares makes it difficult for any instrument, even other soft X-ray spectrometers, to provide a GOES proxy more accurate than a factor of 2.

Keywords: solar flares; solar x-ray flares; solar extreme ultraviolet emission
TESS Visibility—When was My Favorite Star or Asteroid Observed by TESS?

While Transiting Exoplanet Survey Satellite (TESS) covers a considerable area of the sky during routine observations and the pointing schedule is easy to follow, it is not obvious to retrieve the current and/or predicted visibility of a bulk amount of objects, considering both stationary and moving Solar System targets like asteroids or comets. The program tessvisibility is a small piece of highly portable code implemented in both C an UNIX shell, providing functionalities for such bulk retrievals at the accuracy of a TESS pixel. This accuracy includes the gaps between the focal plane CCDs, the gaps between the cameras as well as at the sector-level treatment to obtain visibility information.

Keywords: astronomy software; astrometry
The Behavior of He-weak in the Far-UV-Paper I: HD 5737

The analysis of 28 spectra of the bright B6 He-weak star HD 5737 recorded by the SWP camera on board the International Ultraviolet Explorer reveals one instance of marginal variation of the far-ultraviolet flux of this star from 1300 up to 1700 Å. All the other large aperture spectra show a remarkably constant spectral energy distribution. Over the 6 yr of the IUE mission, HD 5737 has experienced at least two episodes of very strong absorption in the C IV resonance lines at 1548.19 and 1550.77 Å,

Keywords: chemically peculiar stars; helium-weak stars
Measurement of Telescope Transmission Using a Collimated Beam Projector

With the increasingly large number of Type Ia supernova being detected by current-generation survey telescopes, and even more expected with the upcoming Rubin Observatory Legacy Survey of Space and Time, the precision of cosmological measurements will become limited by systematic uncertainties in flux calibration rather than statistical noise. One major source of systematic error in determining SNe Ia color evolution (needed for distance estimation) is uncertainty in telescope transmission, both within and between surveys. We introduce here the Collimated Beam Projector (CBP), which is meant to measure a telescope transmission with collimated light. The collimated beam more closely mimics a stellar wave front as compared to flat-field-based instruments, allowing for more precise handling of systematic errors such as those from ghosting and filter angle-of-incidence dependence. As a proof of concept, we present CBP measurements of the StarDICE prototype telescope, achieving a standard (1σ) uncertainty of 3% on average over the full wavelength range measured with a single beam illumination.

Keywords: calibration; photometry; astronomical detectors; telescopes
A Theoretical Approach to the Complex Chemical Evolution of Phosphorus in the Interstellar Medium

The study of phosphorus chemistry in the interstellar medium has become a topic of growing interest in astrobiology because it is plausible that a wide range of P-bearing molecules were introduced in the early Earth by the impact of asteroids and comets on its surface, enriching prebiotic chemistry. Thanks to extensive searches in recent years, it has become clear that P mainly appears in the form of PO and PN in molecular clouds and star-forming regions. Interestingly, PO is systematically more abundant than PN by factors typically of ~1.4-3, independently of the physical properties of the observed source. In order to unveil the formation routes of PO and PN, in this work we introduce a mathematical model for the time evolution of the chemistry of P in an interstellar molecular cloud and analyze its associated chemical network as a complex dynamical system. By making reasonable assumptions, we reduce the network to obtain explicit mathematical expressions that describe the abundance evolution of P-bearing species and study the dependences of the abundance of PO and PN on the system's kinetic parameters with much faster computation times than available numerical methods. As a result, our model reveals that the formation of PO and PN is governed by just a few critical reactions, and fully explains the relationship between PO and PN abundances throughout the evolution of molecular clouds. Finally, the application of Bayesian methods constrains the real values of the most influential reaction rate coefficients making use of available observational data.

Keywords: interstellar medium; interstellar molecules; astrochemistry; astrobiology; chemical reaction network models; bayesian statistics
Imagery and UV Spectroscopy of the LMC Supernova Remnant N103B Using HST

We present Hubble Space Telescope (HST)/Wide Field Camera 3 multiband imagery of N103B, which is the remnant of a SN Ia in the Large Magellanic Cloud, as well as HST/Cosmic Origins Spectrograph (COS) ultraviolet spectroscopy of the brightest radiatively shocked region. The images show a wide range of morphology and relative emission-line intensities, from smooth Balmer-line dominated collisionless shocks that are due to the primary blast wave to clumpy radiative shock filaments that are due to secondary shocks in density enhancements. The COS data show strong FUV line emissions, despite a moderately high extinction along this line of sight. We use the COS data with previous optical spectra to constrain the shock conditions, we refine the abundance analysis, and we find abundances that are typical of the local interstellar medium within the uncertainties. Under an assumption that the material being shocked was shed from the pre-supernova system, this finding places constraints on any significant enrichment in that material, and thus on the non-degenerate star in what was presumably a single-degenerate SN Ia.

Keywords: supernova remnants; nebulae; emission nebulae; shocks; type ia supernovae