Sazuna/UAT_keywords huggingface dataset:
Modeling of Condensations in Coronal Loops Produced by Impulsive Heating with Variable Frequencies and Locations. We present the results of models of impulsively heated coronal loops using the 1D hydrodynamic Adaptively Refined Godunov Solver code. The impulsive heating events (which we refer to as nanoflares) are modeled by discrete pulses of energy along the loop. We explore the occurrence of cold condensations due to the effective equivalent of thermal nonequilibrium in loops with steady heating, and examine its dependence on nanoflare timing and intensity and also nanoflare location along the loop, including randomized distributions of nanoflares. We find that randomizing the distribution of nanoflares, both in time/intensity and location, diminishes the likelihood of condensation occurring as compared to distributions with regularly occurring nanoflares with the same average properties. The usual criteria that condensation is favored for heating near loop footpoints and with high cadences are more strict for randomized (as opposed to regular) nanoflare distributions, and for randomized distributions the condensations stay in the loop for a shorter amount of time. That said, condensation can sometimes occur in cases where the average values of parameters (frequency or location) are beyond the critical limits above which condensation does not occur for corresponding steady, non-randomized values of those parameters. These properties of condensation occurring due to randomized heating can be used in the future to investigate the diagnostics of coronal heating mechanisms.

Keywords: Solar coronal loops, Solar physics, Solar coronal heating, Solar corona
Likely Common Coronal Source of Solar Wind and <SUP>3</SUP>He-enriched Energetic Particles: Uncoupled Transport from the Low Corona to 0.2 au. Parker Solar Probe (PSP) observations of a small dispersive event on 2022 February 27 and 28 indicate scatter-free propagation as the dominant transport mechanism between the low corona and greater than 35 solar radii. The event occurred during unique orbital conditions that prevailed along specific flux tubes that PSP encountered repeatedly between 25 and 35 Rs during outbound orbit 11. This segment of the PSP orbit exhibits almost stationary angular motion relative to the rotating solar surface, such that in the rotating frame, PSP's motion is essentially radial. The time dispersion often observed in impulsive solar energetic particle (SEP) events continues in this case down to velocities including the core solar-wind ion velocities. Especially at the onset of this event, the 3He content is much larger than the usual SEP abundances seen in the energy range from ∼100 keV to several MeV for helium. Later in the event, iron is enhanced. The compositional signatures suggest this to be an example of an acceleration mechanism for generating the seed energetic particles required by shock (or compression) acceleration models in SEP events to account for the enrichment of various species above solar abundances in such events. A preliminary search of similar orbital conditions over the PSP mission has not revealed additional such events, although favorable conditions (isolated impulsive acceleration and well-ordered magnetic field connection with minimal magnetic field fluctuation) that would be required are infrequently realized, given the small fraction of the PSP trajectory that meets these observation conditions.

Keywords: Solar energetic particles, Solar wind, Solar abundances, Solar physics, Solar activity
A Linear Model for Inertial Modes in a Differentially Rotating Sun. Inertial wave modes in the Sun are of interest owing to their potential to reveal new insight into the solar interior. These predominantly retrograde-propagating modes in the solar subsurface appear to deviate from the thin-shell Rossby–Haurwitz model at high azimuthal orders. We present new measurements of sectoral inertial modes at m &gt; 15 where the modes appear to become progressively less retrograde compared to the canonical Rossby–Haurwitz dispersion relation in a corotating frame. We use a spectral eigenvalue solver to compute the spectrum of solar inertial modes in the presence of differential rotation. Focussing specifically on equatorial Rossby modes, we find that the numerically obtained mode frequencies lie along distinct ridges, one of which lies strikingly close to the observed mode frequencies in the Sun. We also find that the n = 0 ridge is deflected strongly in the retrograde direction. This suggests that the solar measurements may not correspond to the fundamental n = 0 Rossby–Haurwitz solutions as was initially suspected, but to those for a higher n. The numerically obtained eigenfunctions also appear to sit deep within the convection zone—unlike those for the n = 0 modes—which differs substantially from solar measurements and complicates inference.

Keywords: Helioseismology, The Sun, Hydrodynamics, Computational methods
Correlations between Ca II H and K Emission and the Gaia M Dwarf Gap. The Gaia M dwarf gap, also known as the Jao Gap, is a novel feature discovered in the Gaia Data Release 2 G versus BP-RP color–magnitude diagram. This gap represents a 17% decrease in stellar density in a thin magnitude band around the convective transition mass (∼0.35 M ⊙) on the main sequence. Previous work has demonstrated a paucity of Hα emission coincident with the G magnitude of the Jao Gap in the solar neighborhood. The exact mechanism that results in this paucity is as of yet unknown; however, the authors of the originating paper suggest that it may be the result of complex variations to a star's magnetic topology driven by the Jao Gap's characteristic formation and breakdown of stars' radiative transition zones. We present a follow-up investigating another widely used magnetic activity metric, Calcium II H and K emission. Ca II H and K activity appears to share a similar anomalous behavior as Hα does near the Jao Gap magnitude. We observe an increase in star-to-star variation of magnetic activity near the Jao Gap. We present a toy model of a star's magnetic field evolution, which demonstrates that this increase may be due to stochastic disruptions to the magnetic field originating from the periodic-mixing events characteristic of the convective kissing instabilities that drive the formation of the Jao Gap.

Keywords: Stellar evolutionary models, Stellar evolution
Measuring the Variance of the Macquart Relation in Redshift–Extragalactic Dispersion Measure Modeling. The Macquart relation describes the correlation between the dispersion measure (DM) of fast radio bursts (FRBs) and the redshift z of their host galaxies. The scatter of the Macquart relation is sensitive to the distribution of baryons in the intergalactic medium including those ejected from galactic halos through feedback processes. The variance of the distribution in DMs from the cosmic web (DMcosmic) is parameterized by a fluctuation parameter F. In this work, we present a new measurement of F using 78 FRBs of which 21 have been localized to host galaxies. Our analysis simultaneously fits for the Hubble constant H 0 and the DM distribution due to the FRB host galaxy. We find that the fluctuation parameter is degenerate with these parameters, most notably H 0, and use a uniform prior on H 0 to measure ${\mathrm{log}}_{10}F\gt -0.86$ at the 3σ confidence interval and a new constraint on the Hubble constant ${H}_{0}={85.3}_{-8.1}^{+9.4}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . Using a synthetic sample of 100 localized FRBs, the constraint on the fluctuation parameter is improved by a factor of ∼2. Comparing our F measurement to simulated predictions from cosmological simulation (IllustrisTNG), we find agreement between redshifts 0.4 &lt; z and z &lt; 2.0. However, at z &lt; 0.4, the simulations underpredict F, which we attribute to the rapidly changing extragalactic DM excess distribution at low redshift.

Keywords: Cosmological parameters, Hubble constant, Radio bursts, Intergalactic medium, Radio transient sources
Revisiting the Polarization of the Emission of the Internal Shock in the Jet of Blazars. Recent Imaging X-ray Polarimetry Explorer (IXPE) observations of blazars tend to support the shock model for the X-ray emission, but report a low degree of polarization (Π ∼ 10%) in X-rays compared with the previous theoretical expectations in the shock model. In order to reconcile the theoretical expectations with observations, we revisit the polarization of the shock emission by considering different types of directions in the distribution of the shock-generated magnetic fields (sgMFs). Here, ${w}_{\mathrm{sg}}^{{\prime} }\propto {(\sin \theta ^{\prime} )}^{{\zeta }_{\mathrm{sg}}}$ &lt;?MML w sg ' ∝ ( sin θ ' ) ζ sg ?&gt; with $\theta ^{\prime} =0$ &lt;?MML θ ' = 0 ?&gt; along the shock normal direction is used to describe the direction in the distribution of sgMFs in the shock comoving frame. It is found that the polarization in the X-ray and radio emission for a general jet in blazars can be described as ${\rm{\Pi }}\sim 44.5[1-\exp (-{\zeta }_{\mathrm{sg}}/2.6)] \% $ &lt;?MML Π ∼ 44.5 [ 1 ‑ exp ( ‑ ζ sg / 2.6 ) ] % ?&gt; and ${\rm{\Pi }}\sim 20[1-\exp (-{\zeta }_{\mathrm{sg}}/2.4)] \% $ &lt;?MML Π ∼ 20 [ 1 ‑ exp ( ‑ ζ sg / 2.4 ) ] % ?&gt; , respectively. Correspondingly, one can have ζ sg ∼ 1‑1.5 according to IXPE observations. Besides the sgMFs, the magnetic fields generated by the Richtmyer–Meshkov instability (RMI) (rmMFs) are supposed to be present in the jets. The direction of the rmMFs is mainly distributed along the shock normal in the simulations and thus ${w}_{\mathrm{rm}}^{{\prime} }\propto {(\cos \theta ^{\prime} )}^{{\zeta }_{\mathrm{rm}}}$ &lt;?MML w rm ' ∝ ( cos θ ' ) ζ rm ?&gt; is adopted to describe the direction of the distribution in rmMFs. We find that rmMFs are likely to significantly affect the polarization properties at low-frequency emission, especially when the sgMFs decay rapidly. Based on contemporaneous radio and X-ray observations, we find that the emission of electrons in rmMFs makes a significant contribution to the low-frequency emission and the ordered background magnetic fields can be neglected.

Keywords: Blazars, Shocks, Relativistic jets
Resonant Absorption of Magnetohydrodynamic Body Modes under Photospheric Conditions. Observations reveal that surface and body modes exist in solar pores under photospheric conditions. While the effects of resonant absorption on photospheric surface modes are well established, its effect on body modes is not known yet. In this paper, we investigate resonant absorption for the body modes under photospheric conditions. We numerically solve the dispersion relation induced by thin boundary approximation and obtain the wave dispersion curves and damping rates of three arbitrarily chosen body modes for sausage and kink waves, respectively. The results show that resonant absorption for the body modes is weaker than for the slow surface modes in both cusp and Alfvén continua. The damping behavior of body modes is similar to slow surface modes while the higher body mode has stronger resonant absorption.

Keywords: Solar atmosphere, Magnetohydrodynamics, Solar photosphere, Solar physics, Alfven waves, Solar oscillations, Magnetic fields
Suppression of Star Formation in Galaxy Pairs. We investigate the suppression of star formation in galaxy pairs based on the isolated galaxy pair sample derived from the Sloan Digital Sky Survey survey. By comparing the star formation rate between late-type galaxies (LTGs) in galaxy pairs and those in the isolated environment, we detect a signal of the suppression of star formation in galaxy pairs at d p &lt; 100 kpc and 200 kpc &lt; d p &lt; 350 kpc. The occurrence of the suppression of star formation in these LTGs requires their companion galaxies to have an early-type morphology (n  s  &gt; 2.5). The suppression of star formation in wide galaxy pairs at 200 kpc &lt; d p &lt; 350 kpc mainly occurs in massive LTGs, while in close galaxy pairs at d p &lt; 100 kpc, it only appears in LTGs with a massive companion ( $\mathrm{log}{M}_{\star }\gt 11.0$ ), nearly independent of their own stellar mass. Based on these findings, we infer that the suppression of star formation in wide galaxy pairs is actually a result of galaxy conformity, while in close galaxy pairs, it stems from the influence of hot circumgalactic medium surrounding companion galaxies.

Keywords: Galaxy interactions, Galaxy pairs, Galaxies
Parallel Diffusion Coefficient of Energetic Charged Particles in the Inner Heliosphere from the Turbulent Magnetic Fields Measured by Parker Solar Probe. Diffusion coefficients of energetic charged particles in turbulent magnetic fields are a fundamental aspect of diffusive transport theory but remain incompletely understood. In this work, we use quasi-linear theory to evaluate the spatial variation of the parallel diffusion coefficient κ ∥ from the measured magnetic turbulence power spectra in the inner heliosphere. We consider the magnetic field and plasma velocity measurements from Parker Solar Probe made during Orbits 5–13. The parallel diffusion coefficient is calculated as a function of radial distance from 0.062 to 0.8 au, and the particle energy from 100 keV to 1 GeV. We find that κ ∥ increases exponentially with both heliocentric distance and energy of particles. The fluctuations in κ ∥ are related to the episodes of large-scale magnetic structures in the solar wind. By fitting the results, we also provide an empirical formula of κ ∥ = (5.16 ± 1.22) × 1018 r 1.17±0.08 E 0.71±0.02 (cm2 s‑1) in the inner heliosphere, which can be used as a reference in studying the transport and acceleration of solar energetic particles as well as the modulation of cosmic rays.

Keywords: Solar energetic particles, Interplanetary turbulence
Visit Nearby Halo Substructures Using LAMOST DR9 MRS Data. Based on the LAMOST DR9 Medium Resolution Spectra (MRS) catalog, combined with astrometries from Gaia DR3, we conducted an investigation into the substructures in the stellar halo to obtain their chemical and kinematic information. We employed the HDBSCAN algorithm in the (L  z , E, L  xy ) space for clustering and utilized Mahalanobis distance to merge the clustering results. Ultimately, within the LAMOST DR9 MRS catalog, we identified members of Gaia–Sausage–Enceladus (GSE), Helmi streams, and the high-α disk and in situ halo. Additionally, there are three clusters that cannot be correlated with known substructures. Based on their angular momentum (L  z ) characteristics, we have tentatively named two of them High-L  z -Cluster-1 (HLC-1) and High-L  z -Cluster-2 (HLC-2), both exhibiting high angular momentum (L  z ) features. The third cluster, owing to its extremely low L  z , is termed the Low-L  z -Cluster. Then detailed analysis about those substructures are executed including member stars' identification and kinematic and chemical distribution. The resulting GSE member stars exhibit a well-defined metallicity distribution function with its peak at [Fe/H] ∼ ‑1.2, consistent with previous findings, and we found there appear to be some differences in the distribution on the V total–r gal plane between GSE and its included Splash component. Regarding Helmi streams, in the [Mg/Fe]–[Fe/H] plane we detected potential traces of the α-knee phenomenon at [Fe/H] ∼ ‑1.53. Finally, we tentatively provide the possible origin for the HLC-1 and HLC-2.

Keywords: Galaxy stellar halos, Galaxy dynamics, Galaxy structure, Galaxy kinematics
Identifying Plasma Fractionation Processes in the Chromosphere Using IRIS. The composition of the solar corona differs from that of the photosphere, with the plasma thought to fractionate in the solar chromosphere according to the first ionization potential (FIP) of the different elements. This produces a FIP bias, wherein elements with a low FIP are preferentially enhanced in the corona compared to their photospheric abundance, but direct observations of this process remain elusive. Here, we use a series of spectroscopic observations of active region AR 12759 as it transited the solar disk over a period of 6 days from 2020 April 2–7 taken using the Hinode Extreme ultraviolet Imaging Spectrometer and Interface Region Imaging Spectrograph (IRIS) instruments to look for signatures of plasma fractionation in the solar chromosphere. Using the Si X/S X and Ca XIV/Ar XIV diagnostics, we find distinct differences between the FIP bias of the leading and following polarities of the active region. The widths of the IRIS Si IV lines exhibited clear differences between the leading and following polarity regions, indicating increased unresolved wave activity in the following polarity region compared to the leading polarity region, with the chromospheric velocities derived using the Mg II lines exhibiting comparable, albeit much weaker, behavior. These results are consistent with plasma fractionation via resonant/nonresonant waves at different locations in the solar chromosphere following the ponderomotive force model, and indicate that IRIS could be used to further study this fundamental physical process.

Keywords: The Sun, Solar physics, Solar chromosphere, Solar corona
The GMRT High-resolution Southern Sky Survey for Pulsars and Transients. VII. Timing of the Spider Millisecond Pulsar PSR J1242–4712, a Bridge between Redback and Black Widow Pulsars. We present a timing solution for the 5.31 ms spider millisecond pulsar (MSP) J1242‑4712, discovered with the GMRT. PSR J1242‑4712 orbits a companion of minimum mass 0.08 M ⊙ with an orbital period of 7.7 hr and occupies a relatively unexplored region in the orbital period versus companion mass space. We did not detect gamma-ray pulsations for this MSP, and also could not identify the optical counterpart for PSR J1242–4712 in available optical/near-infrared data. The profile of J1242‑4712 evolves with frequency, showing a clear single component at lower frequencies and a three-component profile at 650 MHz. PSR J1242‑4712 eclipses for a very short duration near superior conjunction (orbital phase ∼ 0.23‑0.25) below 360 MHz. Moreover, significant dispersion measure delays and errors in the pulse times of arrivals are observed near inferior conjunction (orbital phase ∼ 0.7), along with an observed eclipse in one epoch at 650 MHz. Observed eclipses and significant orbital period variability suggest that PSR J1242‑4712 is possibly not a helium star‑white dwarf binary, but has a semi- or nondegenerate companion, indicating that this is a "spider" MSP lying in a region between typical black widows and redbacks. This system may represent a distinct category of spider MSPs, displaying characteristics that bridge the gap between known black widow and redback MSPs.

Keywords: Pulsar timing method, Millisecond pulsars, Pulsars, Binary pulsars, Radio pulsars
Study of Magnetic Field and Turbulence in the TeV Halo around the Monogem Pulsar. Magnetic fields are ubiquitous in the interstellar medium, including extended objects such as supernova remnants and diffuse halos around pulsars. Its turbulent characteristics govern the diffusion of cosmic rays and the multiwavelength emission from pulsar wind nebulae (PWNe). However, the geometry and turbulence nature of the magnetic fields in the ambient region of PWN is still unknown. Recent gamma-ray observations from HAWC and synchrotron observations suggest a highly suppressed diffusion coefficient compared to the mean interstellar value. In this study, we present the first direct observational evidence of the orientation of the mean magnetic field and turbulent characteristics by employing a recently developed statistical parameter "Y turb" in the extended halo around the Monogem pulsar. Our study points to two possible scenarios: nearly aligned toward the line of sight (LOS) with compressible modes dominance or high inclination angle toward the LOS and characterized by Alfvénic turbulence. The first scenario appears consistent with other observational signatures. Furthermore, we report that the magnetic field has an observed correlation length of approximately 3 ± 0.6 pc in the Monogem halo. Our study highlights the pivotal role of magnetic field and turbulence in unraveling the physical processes in TeV halos and cosmic-ray transport.

Keywords: Magnetohydrodynamics, High-energy cosmic radiation, Stellar magnetic fields, Interstellar magnetic fields, Supernova remnants, Cosmic ray sources, Pulsar wind nebulae
Toward More Accurate Synthetic Reflection Spectra: Improving the Calculations of Returning Radiation. We present a new model to calculate reflection spectra of thin accretion disks in Kerr spacetimes. Our model includes the effect of returning radiation, which is the radiation that is emitted by the disk and returns to the disk because of the strong light bending near a black hole. The major improvement with respect to the existing models is that it calculates the reflection spectrum at every point on the disk by using the actual spectrum of the incident radiation. Assuming a lamppost coronal geometry, we simulate simultaneous observations of NICER and NuSTAR of bright Galactic black holes and we fit the simulated data with the latest version of relxill (modified to read the table of reflionx, which is the nonrelativistic reflection model used in our calculations). We find that relxill with returning radiation cannot fit well the simulated data when the black hole spin parameter is very high and the coronal height and disk's ionization parameter are low, and some parameters can be significantly overestimated or underestimated. We can find better fits and recover the correct input parameters as the value of the black hole spin parameter decreases and the value of the coronal height increases.

Keywords: X-ray astronomy, Accretion, Astrophysical black holes
The High-mass X-Ray Binary Luminosity Functions of Dwarf Galaxies. Drawing from the Chandra archive and using a carefully selected set of nearby dwarf galaxies, we present a calibrated high-mass X-ray binary (HMXB) luminosity function in the low-mass galaxy regime and search for an already hinted at dependence on metallicity. Our study introduces a new sample of local dwarf galaxies (D &lt; 12.5 Mpc and M * &lt; 5 × 109 M ⊙), expanding the specific star formation rates (sSFR) and gas-phase metallicities probed in previous investigations. Our analysis of the observed X-ray luminosity function indicates a shallower power-law slope for the dwarf galaxy HMXB population. In our study, we focus on dwarf galaxies that are more representative in terms of sSFR compared to prior work. In this regime, the HMXB luminosity function exhibits significant stochastic sampling at high luminosities. This likely accounts for the pronounced scatter observed in the galaxy-integrated HMXB population's L X/SFR versus metallicity for our galaxy sample. Our calibration is necessary to understand the active galactic nuclei content of low-mass galaxies identified in current and future X-ray survey fields and has implications for binary population synthesis models, as well as X-ray-driven cosmic heating in the early Universe.

Keywords: X-ray astronomy, X-ray binary stars, Dwarf galaxies, High mass x-ray binary stars, Star formation, Compact objects, Metallicity