adsabs/SciX_UAT_keywords huggingface dataset:
Cosmological-model-independent Determination of Hubble Constant from Fast Radio Bursts and Hubble Parameter Measurements

We establish a cosmological-model-independent method to determine the Hubble constant H 0 from the localized fast radio bursts (FRBs) and the Hubble parameter measurements from cosmic chronometers and obtain a first such determination H 0 = 71 ± 3 km s-1 Mpc-1, with an uncertainty of 4%, from the eighteen localized FRBs and nineteen Hubble parameter measurements in the redshift range 0 < z ≤ 0.66. This value, which is independent of the cosmological model, is consistent with the results from the nearby Type Ia supernovae (SNe Ia) data calibrated by Cepheids and the Planck cosmic microwave background radiation observations at the 1σ and 2σ confidence level, respectively. Simulations show that the uncertainty of H 0 can be decreased to the level of that from the nearby SNe Ia when mock data from 500 localized FRBs with 50 Hubble parameter measurements in the redshift range of 0 < z ≤ 1 are used. Since localized FRBs are expected to be detected in large quantities, our method will be able to give a reliable and more precise determination of H 0 in the very near future, which will help us to figure out the possible origin of the Hubble constant disagreement.

Keywords: cosmology
Angular Momentum Transport in Binary Star Formation: The Enhancement of Magnetorotational Instability and Role of Outflows

The formation of binary stars is highly influenced by magnetic fields, which play a crucial role in transporting angular momentum. We conducted 3D numerical simulations of binary star accretion via a circumbinary disk, taking into account a magnetic field perpendicular to the disk and an infalling envelope. Our simulations reproduce the following phenomena: (1) the spiral arms associated with circumstellar disks; (2) the turbulence in the circumbinary disk, induced by magnetorotational instability (MRI); (3) a fast outflow launched from each circumstellar disk; and (4) a slow outflow from the circumbinary disk. The binary models exhibit a higher α-parameter than the corresponding single-star models, indicating that the binary stars enhance the MRI turbulence. Moreover, an infalling envelope also enhances the turbulence, leading to a high α-parameter. While the spiral arms promote radial flow, causing the transfer of mass and angular momentum within the circumbinary disk, the MRI turbulence and outflows are the main drivers of angular momentum transfer to reduce the specific angular momentum of the system.

Keywords: star formation; binary stars; circumstellar disks; stellar jets; magnetohydrodynamical simulations
Coronal Heating and Solar Wind Formation in Quiet Sun and Coronal Holes: A Unified Scenario

Coronal holes (CHs) are darker than the quiet Sun (QS) when observed in coronal channels. This study aims to understand the similarities and differences between CHs and QS in the transition region using the Si IV 1394 Å line, recorded by the Interface Region Imaging Spectrograph, by considering the distribution of magnetic field measured by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We find that Si IV intensities obtained in CHs are lower than those obtained in QS for regions with identical magnetic flux densities. Moreover, the difference in intensities between CHs and QS increases with increasing magnetic flux. For the regions with equal magnetic flux density, QS line profiles are more redshifted than those measured in CHs. Moreover, the blueshifts measured in CHs show an increase with increasing magnetic flux density unlike in the QS. The non-thermal velocities in QS, as well as in CHs, show an increase with increasing magnetic flux. However, no significant difference was observed in QS and CHs, albeit a small deviation at small flux densities. Using these results, we propose a unified model for the heating of the corona in the QS and in CHs and the formation of solar wind.

Keywords: quiet sun; solar coronal holes; solar wind; solar coronal heating; solar magnetic fields; fast solar wind; slow solar wind; solar transition region
Improving Geometric and Dynamical Constraints on Cosmology with Intrinsic Alignments of Galaxies

We show that the spatial correlation of the intrinsic alignments (IAs) of galaxies, measured in galaxy redshift surveys, offers a precision route to improve the geometrical and dynamical constraints on cosmology. The IA has been treated as a contaminant against cosmological probes such as weak gravitational lensing experiments. However, the large-scale correlation of IAs is expected to follow the coherent large-scale matter inhomogeneities. Here, making use of its anisotropic nature, we show that the large-scale IA correlations help to improve the measurements of the geometric distances and growth of structure. In combination with the conventional galaxy clustering statistics, we find that constraints on equation-of-state parameter for dark energy and Hubble parameter can be tighter than those from the clustering statistics alone by a factor of more than 1.5.

Keywords: large-scale structure of the universe; cosmological parameters from large-scale structure; baryon acoustic oscillations; dark energy; observational cosmology
Detection of Extragalactic Anomalous Microwave Emission in NGC 2903 Using KVN Single-dish Observations

We present the results of the single-dish observations using the Korean VLBI Network to search for anomalous microwave emission (AME) in nearby galaxies. The targets were selected from 'Mapping the dense molecular gas in the strongest star-forming galaxies' (MALATANG), a legacy survey project of the James Clerk Maxwell Telescope. The MALATANG galaxies are good representatives of local galaxies with enhanced nuclear activity associated with star formation and/or active galactic nuclei (AGNs), providing IR-bright galaxy samples; thus, they are good candidates for AME hosts. Combining with ancillary data, we investigated the radio–IR spectral energy distribution (SED), while searching for AME signals in five galaxies. The AME in NGC 2903 was well detected at a significant confidence level, whereas that in NGC 2146 and M82 was marginal. NGC 1068 and Arp 299 indicated no significant hints, and we provide upper limits for the AME. The best-fit SED exhibited local peaks of the AME components at higher frequencies and with stronger peak fluxes than those in previous studies. This suggested that AME originates from denser environments such as molecular clouds or photodissociation regions rather than warm neutral/ionized medium as commonly suggested by previous studies. Further, our AME-detected targets were observed to exhibit higher specific star formation rates than the other extragalactic AME hosts. Furthermore, AME favored starburst galaxies among our sample rather than AGN hosts. Consequently, this might imply that AGNs are excessively harsh environments for tiny dust to survive.

Keywords: very small grains; interstellar dust; infrared excess galaxies; spectral energy distribution
Evidence that a Novel Type of Satellite Wake Might Exist in Saturn's E Ring

Saturn's E ring consists of micron-sized particles launched from Enceladus by that moon's geological activity. A variety of small-scale structures in the E ring's brightness have been attributed to tendrils of material recently launched from Enceladus. However, one of these features occurs at a location where Enceladus's gravitational perturbations should concentrate background E-ring particles into structures known as satellite wakes. While satellite wakes have been observed previously in ring material drifting past other moons, these E-ring structures would be the first examples of wakes involving particles following horseshoe orbits near Enceladus's orbit. The predicted intensity of these wake signatures is particularly sensitive to the fraction E-ring particles on orbits with low eccentricities and semimajor axes just outside of Enceladus's orbit, and so detailed analyses of these and other small-scale E-ring features should place strong constraints on the orbital properties and evolution of E-ring particles.

Keywords: planetary rings; saturnian satellites; astrodynamics; orbital motion; celestial mechanics; three-body problem
Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT

We report results on the timing analysis of the 2020 giant outburst of 1A 0535+262, using broadband data from Insight-HXMT. The analysis of the pulse profile evolution from the subcritical-luminosity to the supercritical-luminosity regime is presented for the first time. We found that the observed pulse profile exhibits a complex dependence on both energy and luminosity. A dip structure at the energy of the cyclotron resonant scattering features is found for the first time in the pulse fraction-energy relation of 1A 0535+262, when the outburst evolves in a luminosity range from 4.8 × 1037 to 1.0 × 1038 erg s-1. The observed structure is luminosity dependent and appears around the source critical luminosity (~6.7 × 1037 erg s-1).

Keywords: x-ray binary stars; pulsars; x-ray astronomy
A JWST/NIRSpec First Census of Broad-line AGNs at z = 4-7: Detection of 10 Faint AGNs with M BH 106-108 M ⊙ and Their Host Galaxy Properties

We present the first statistical sample of faint type 1 AGNs at z > 4 identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at z spec = 3.8-8.9 confirmed with NIRSpec, our systematic search for broad-line emission reveals 10 type 1 AGNs at z = 4.015-6.936 whose broad component is only seen in the permitted Hα line and not in the forbidden [O III]λ5007 line that is detected with greater significance than Hα. The broad Hα line widths of FWHM ≃ 1000-6000 km s-1 suggest that the AGNs have low-mass black holes with M BH ~ 106-108 M ⊙, remarkably lower than those of low-luminosity quasars previously identified at z > 4 with ground-based telescopes. JWST and Hubble Space Telescope high-resolution images reveal that the majority of them show extended morphologies indicating significant contribution to the total lights from their host galaxies, except for three compact objects two of which show red spectral energy distributions, probably in a transition phase from faint AGNs to low luminosity quasars. Careful AGN-host decomposition analyses show that their host's stellar masses are systematically lower than the local relation between the black hole mass and the stellar mass, implying a fast black hole growth consistent with predictions from theoretical simulations. A high fraction of the broad-line AGNs (~5%), higher than z ~ 0, indicates that the number density of such faint AGNs is higher than an extrapolation of the quasar luminosity function, implying a large population of AGNs in the early universe. Such faint AGNs contribute to cosmic reionization, while the total contribution is not large, up to ~50% at z ~ 6, because of their faint nature.

Keywords: galaxy formation; galaxy evolution; agn host galaxies; active galactic nuclei
The Relationship between Photometric Measurements and Visual Magnitude Estimates for Red Stars

The nature of the relationship between visual brightness estimates for red stars and the corresponding V magnitudes has been investigated by comparing visual estimates in the American Association of Variable Star Observers database to photoelectric photometry of 39 semiregular variable stars obtained at Grinnell College over a 30 yr period. A general mathematical description of this relationship has been developed, but it applies only approximately for many individual stars because the actual relationship can be quite different for different stars. The overall trends should apply to visual magnitude estimates for red stars generally. These results are based on far more data over a wider range of color than was the case in earlier work and should provide a more robust description of the relationship between photometric measurements and visual estimates. A number of other issues related to visual magnitude estimates are also addressed.

Keywords: visual observation; photoelectric photometry; semi-regular variable stars; color equation
DFT Study on Interstellar PAH Molecules with Aliphatic Side Groups

Polycyclic aromatic hydrocarbon (PAH) molecules have been long adjudged to contribute to the frequently detected distinct emission features at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with weaker and blended features distributed in the 3-20 μm region. The comparatively weaker 3.4 μm emission feature has been attributed to have an aliphatic origin as carrier. PAH with an aliphatic functional group attached to it is one of the proposed potential candidate carriers for the 3.4 μm emission band, however, the assignment of carrier is still enigmatic. In this work, we employ density functional theory calculation on a symmetric and compact PAH molecule; coronene (C24H12) with aliphatic side group to investigate any spectral similarities with observed features at 3-4 μm. The side groups considered in this study are -H (hydrogenated), -CH3 (methyl), -CH2-CH3 (ethyl), and -CH=CH2 (vinyl) functional groups. Considering the possible presence of deuterium (D) in PAHs, we also include D in the aliphatic side group to study the spectral behavior. We present a detailed analysis of the IR spectra of these molecules and discuss possible astrophysical implications.

Keywords: astrochemistry; interstellar dust extinction; interstellar medium; interstellar molecules; infrared astronomy
Assessment of Systematic Uncertainties in the Cosmological Analysis of the SDSS Supernovae Photometric Sample

Improvements to the precision of measurements of cosmological parameters with Type Ia supernovae (SNe Ia) are expected to come from large photometrically identified (photometric) supernova (SN) samples. Here we reanalyze the Sloan Digital Sky Survey (SDSS) photometric SN sample, with roughly 700 high-quality, likely but unconfirmed SNe Ia light curves, to develop new analysis tools aimed at evaluating systematic uncertainties on the dark energy equation-of-state parameter w. Since we require a spectroscopically measured host-galaxy redshift for each SN, we determine the associated selection efficiency of host galaxies in order to simulate bias corrections. We determine that the misassociation rate of host galaxies is 0.6%; ignoring this effect in simulated bias corrections leads to a w-bias of Δw = +0.0007, where w is evaluated from SNe Ia and priors from measurements of baryon acoustic oscillations and the cosmic microwave background. We assess the uncertainty in our modeling of the host-galaxy selection efficiency and find the associated w uncertainty to be -0.0072. Finally, we explore new core-collapse (CC) models in simulated training samples and find that adjusting the CC luminosity distribution to be in agreement with previous Pan-STARRS analyses yields a better match to the SDSS data. The impact of ignoring this adjustment is Δw = -0.0109; the impact of replacing the new CC models with those used by Pan-STARRS is Δw = -0.0028. These systematic uncertainties are subdominant to the statistical constraints from the SDSS sample, but must be considered in future photometric analyses of large SN samples such as those from the Dark Energy Survey (DES), the Large Synoptic Survey Telescope (LSST), and the Wide Field Infrared Survey Telescope (WFIRST).

Keywords: type ia supernovae; cosmology; dark energy
Observations and Modeling of the Opposition Surges of the Icy Moons of Saturn Based on Cassini Visual Infrared Mapping Spectrometer Data

Observations of the opposition surges on the main moons of Saturn (Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus) during Cassini's prime and extended missions are reduced and analyzed. The main data set comes from the Visual Infrared Mapping Spectrometer (VIMS) with wavelength coverage in the visible and near-infrared out to 3.60 μm, covering 99% of the solar spectrum. Imaging Science Subsystem images and Ultraviolet Imaging Spectrometer data augment the VIMS data set. Hapke models are fit to Dione and Rhea, and Irvine's simpler shadowing model is fit to the sparser data sets of Enceladus, Dione, and Rhea. The high porosities (~95% void space in the optically active portion of the regolith) and forward-scattering properties of the surfaces are similar to other icy moons and to Pluto. A change in the character of their opposition surge at 3.60 μm can be attributed largely to the noninteraction of long-wavelength photons with small particles on these moons' surfaces. The opposition surge on the low- and high-albedo regions of Dione are similar. However, the low-albedo terrain of Iapetus exhibits a less robust surge than the high-albedo regions, which we attribute to differences in surface texture. The low-albedo hemisphere of Iapetus seems to be akin to the small number of bodies in the solar system that lack an appreciable opposition surge, possibly due to the accumulation of low-albedo dust. With observations over the range of the solar spectrum, we compute new values for the bolometric Bond albedos of these moons.

Keywords: saturnian satellites; infrared photometry; opposition
The Effect of Solar Wind Expansion and Nonequilibrium Ionization on the Broadening of Coronal Emission Lines

When observing spectral lines in the optically thin corona, line-of-sight (LOS) effects can strongly affect the interpretation of the data, especially in regions just above the limb. We present a semiempirical forward model, called the Global Heliospheric Optically thin Spectral Transport Simulation (GHOSTS), to characterize these effects. GHOSTS uses inputs from several other models to compute nonequilibrium ionization states (which include the solar-wind freezing-in effect) for many ions. These are used to generate ensembles of simulated spectral lines that are examined in detail, with emphasis on (1) relationships between quantities derived from observables and the radial variation of the observed quantities, (2) the behavior of thermal and nonthermal components of the line width, and (3) relative contributions of collisionally excited and radiatively scattered photons. We find that rapidly changing temperatures in the low corona can cause ion populations to vary dramatically with height. This can lead to line width measurements that are constant with height (a "plateau" effect) even when the temperature is increasing rapidly, as the plane of sky becomes evacuated and the foreground/background plasma dominates the observation. We find that LOS effects often drive the velocity width to be close to the plane-of-sky value of the wind speed, despite it flowing perpendicularly to the LOS there. The plateau effect can also cause the nonthermal component of the line width to greatly exceed the solar wind velocity at the observation height. Lastly, we study how much of the LOS is significant to the observation, and the importance of including continuum in the solar spectrum when computing the radiatively scattered emission.

Keywords: solar coronal holes; solar ultraviolet emission; solar wind; spectroscopy; radiative transfer simulations; ionization
Polytropic Behavior in the Structures of Interplanetary Coronal Mass Ejections

The polytropic process characterizes the thermodynamics of space plasma particle populations. The polytropic index, γ, is particularly important as it describes the thermodynamic behavior of the system by quantifying the changes in temperature as the system is compressed or expanded. Using Wind spacecraft plasma and magnetic field data during 1995 February-2015 December, we investigate the thermodynamic evolution in 336 interplanetary coronal mass ejection (ICME) events. For each event, we derive the index γ in the sheath and magnetic ejecta structures, along with the pre- and post-event regions. We then examine the distributions of all γ indices in these four regions and derive the entropic gradient of each, which is indicative of the ambient heating. We find that in the ICME sheath region, where wave turbulence is expected to be highest, the thermodynamics takes longest to recover into the original quasi-adiabatic process, while it recovers faster in the quieter ejecta region. This pattern creates a thermodynamic cycle, featuring a near adiabatic value γ ~ γ a (=5/3) upstream of the ICMEs, γ a - γ ~ 0.26 in the sheaths, γ a - γ ~ 0.13 in the ICME ejecta, and recovers again to γ ~ γ a after the passage of the ICME. These results expose the turbulent heating rates in the ICME plasma: the lower the polytropic index from its adiabatic value and closer to its isothermal value, the larger the entropic gradient, and thus, the rate of turbulent heating that heats the ICME plasma.

Keywords: solar coronal mass ejections; space plasmas; polytropes
Langmuir-Slow Extraordinary Mode Magnetic Signature Observations with Parker Solar Probe

Radio emission from interplanetary shocks, planetary foreshocks, and some solar flares occurs in the so-called "plasma emission" framework. The generally accepted scenario begins with electrostatic Langmuir waves that are driven by a suprathermal electron beam on the Landau resonance. These Langmuir waves then mode-convert to freely propagating electromagnetic emissions at the local plasma frequency f pe and/or its harmonic 2f pe . However, the details of the physics of mode conversion are unclear, and so far the magnetic component of the plasma waves has not been definitively measured. Several spacecraft have measured quasi-monochromatic Langmuir or slow extraordinary modes (sometimes called z-modes) in the solar wind. These coherent waves are expected to have a weak magnetic component, which has never been observed in an unambiguous way. Here we report on the direct measurement of the magnetic signature of these waves using the Search Coil Magnetometer sensor of the Parker Solar Probe/FIELDS instrument. Using simulations of wave propagation in an inhomogeneous plasma, we show that the appearance of the magnetic component of the slow extraordinary mode is highly influenced by the presence of density inhomogeneities that occasionally cause the refractive index to drop to low values where the wave has strong electromagnetic properties.

Keywords: solar wind; plasma physics; space plasmas
Early Hard X-Rays from the Nearby Core-collapse Supernova SN 2023ixf

We present NuSTAR observations of the nearby SN 2023ixf in M101 (d = 6.9 Mpc) that provide the earliest hard X-ray detection of a nonrelativistic stellar explosion to date at δ t ≈ 4 days and δ t ≈ 11 days. The spectra are well described by a hot thermal bremsstrahlung continuum with T > 25 keV shining through a thick neutral medium with a neutral hydrogen column that decreases with time (initial N Hint = 2.6 × 1023 cm-2). A prominent neutral Fe Kα emission line is clearly detected, similar to other strongly interacting supernovae (SNe) such as SN 2010jl. The rapidly decreasing intrinsic absorption with time suggests the presence of a dense but confined circumstellar medium (CSM). The absorbed broadband X-ray luminosity (0.3-79 keV) is L X ≈ 2.5 × 1040 erg s-1 during both epochs, with the increase in overall X-ray flux related to the decrease in the absorbing column. Interpreting these observations in the context of thermal bremsstrahlung radiation originating from the interaction of the SN shock with a dense medium we infer large particle densities in excess of n CSM ≈ 4 × 108 cm-3 at r < 1015 cm, corresponding to an enhanced progenitor mass-loss rate of $\dot{M}\approx 3\times {10}^{-4}$ M ⊙ yr-1 for an assumed wind velocity of v w = 50 km s-1.

Keywords: core-collapse supernovae