Sazuna/UAT_keywords huggingface dataset:
Thermonuclear <SUP>17</SUP>O(n, γ)<SUP>18</SUP>O Reaction Rate and Its Astrophysical Implications. A new thermonuclear 17O(n,γ)18O rate is derived based on a complete calculation of the direct-capture (DC) and resonant-capture contributions, for a temperature region up to 2 GK of astrophysical interest. We have first calculated the DC and subthreshold contributions in the energy region up to 1 MeV, and estimated the associated uncertainties by a Monte Carlo approach. It shows that the present rate is remarkably larger than that adopted in the JINA REACLIB in the temperature region of 0.01 ~ 2 GK, by up to a factor of ~80. The astrophysical impacts of our rate have been examined in both s-process and r-process models. In our main s-process model, which simulates flash-driven convective mixing in metal-deficient asymptotic giant branch stars, both 18O and 19F abundances in interpulse phases are enhanced dramatically by factors of ~20-40 due to the new larger 17O(n,γ)18O rate. It shows, however, that this reaction hardly affects the weak s-process in massive stars since the 17O abundance never becomes significantly large in the massive stars. For the r-process nucleosynthesis, we have studied impacts of our rate in both the collapsar and neutron burst models, and found that the effect can be neglected, although an interesting loophole effect is found owing to the enhanced new rate, which significantly changes the final nuclear abundances if fission recycling is not involved in the model; however, these significant differences are almost completely eliminated if the fission recycling is considered.

Keywords: S-process, R-process, Nuclear astrophysics, Reaction rates
Orbit Tomography of Binary Supermassive Black Holes with Very Long Baseline Interferometry. In this work, we study how to infer the orbit of a supermassive black hole binary (SMBHB) by time-dependent measurements with very long baseline interferometry, such as the Event Horizon Telescope (EHT). Assuming a pointlike luminosity image model, we show that with multiple years of observations by EHT, it is possible to recover the SMBHB orbital parameters-eccentricity, (rescaled) semimajor axis, orbital frequency, and orbital angles-from their time-varying visibilities even if the binaries' orbital periods are a few times longer than the duration of observation. Together with the future gravitational wave detections of resolved sources of SMBHBs with the pulsar timing array, and/or the detections of optical-band light curves, we will be able to further measure the individual mass of the binary, and also determine the Hubble constant if the total mass of the binary is measured through the light curves of the two black holes or measured by alternative methods.

Keywords: Radio astronomy
Cosmic Ray Streaming in the Turbulent Interstellar Medium. We study the streaming instability of GeV-100 GeV cosmic rays (CRs) and its damping in the turbulent interstellar medium (ISM). We find that the damping of streaming instability is dominated by ion-neutral collisional damping in weakly ionized molecular clouds, turbulent damping in the highly ionized warm medium, and nonlinear Landau damping in the Galactic halo. Only in the Galactic halo is the streaming speed of CRs close to the Alfvén speed. Alfvénic turbulence plays an important role in both suppressing the streaming instability and regulating the diffusion of streaming CRs via magnetic field line tangling, with the effective mean free path of streaming CRs in the observer frame determined by the Alfvénic scale in super-Alfvénic turbulence. The resulting diffusion coefficient is sensitive to Alfvén Mach number, which has a large range of values in the multiphase ISM. Super-Alfvénic turbulence contributes to additional confinement of streaming CRs, irrespective of the dominant damping mechanism.

Keywords: Galactic cosmic rays, Magnetohydrodynamics, Interstellar medium
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: Space plasmas, Solar wind, Plasma physics
The Maximum Mass-loss Efficiency for a Photoionization-driven Isothermal Parker Wind. Observations of present-day mass-loss rates for close-in transiting exoplanets provide a crucial check on models of planetary evolution. One common approach is to model the planetary absorption signal during the transit in lines like He I 10830 with an isothermal Parker wind, but this leads to a degeneracy between the assumed outflow temperature T 0 and the mass-loss rate $\dot{M}$ that can span orders of magnitude in $\dot{M}$ . In this study, we re-examine the isothermal Parker wind model using an energy-limited framework. We show that in cases where photoionization is the only heat source, there is a physical upper limit to the efficiency parameter ɛ corresponding to the maximal amount of heating. This allows us to rule out a subset of winds with high temperatures and large mass-loss rates as they do not generate enough heat to remain self-consistent. To demonstrate the utility of this framework, we consider spectrally unresolved metastable helium observations of HAT-P-11b, WASP-69b, and HAT-P-18b. For the former two planets, we find that only relatively weak ( $\dot{M}\lesssim {10}^{11.5}$ g s-1) outflows can match the metastable helium observations while remaining energetically self-consistent, while for HAT-P-18b all of the Parker wind models matching the helium data are self-consistent. Our results are in good agreement with more detailed self-consistent simulations and constraints from high-resolution transit spectra.

Keywords: Exoplanet astronomy, Exoplanet evolution, Planetary atmospheres, Exoplanet atmospheres
The Central 300 pc of the Galaxy Probed by Infrared Spectra of H<SUB>3</SUB> <SUP>+</SUP> and CO. III. Locations of Sgr B2 and Star Iota. Using a simple relation between the radial expansion velocity of diffuse gas in the Central Molecular Zone (CMZ) of the Galaxy and its distance from Sgr A* we estimate the physical depths within the CMZ of Star ι (2MASS J17470898-2829561) and two Sgr B2 far-infrared continuum sources with respect to the location of Sgr A*. To do this we use velocity profiles of infrared absorption lines of ${{\rm{H}}}_{3}^{+}$ and of far-infrared absorption lines of H2O+, OH+, and 13CH+. The distances to Star ι and to the Sgr B2 sources are found to be ~90 pc greater than the distance to Sgr A*. Our conclusion that Sgr B2 lies toward the rear of the CMZ is contrary to most previous models in which it has been placed shallower than Sgr A*.

Keywords: Interstellar molecules, Galactic center, High energy astrophysics, Interstellar line absorption, Astrochemistry
Three-polarizer Treatment of Linear Polarization in Coronagraphs and Heliospheric Imagers. Linearly polarized light has been used to view the solar corona for over 150 years. While the familiar Stokes representation for polarimetry is complete, it is best matched to a laboratory setting and therefore is not the most convenient representation either for coronal instrument design or for coronal data analysis. Over the last 100 years of development of coronagraphs and heliospheric imagers, various representations have been used for both direct measurement and analysis. These systems include famous representations such as the (B, pB) system, which is analogous to the Stokes system in solar observing coordinates, and also internal representations such as in-instrument Stokes parameters with fixed or variable "vertical" direction, and brightness values through a particular polarizing optic or set thereof. Many polarimetric instruments currently use a symmetric three-polarizer measurement and representation system (which we refer to as "(M, Z, P)") to derive the (B, pB) or Stokes parameters. We present a symmetric derivation of (B, pB) and Stokes parameters from (M, Z, P), analyze the noise properties of (M, Z, P) in the context of instrument design, develop (M, Z, P) as a useful intermediate system for data analysis including background subtraction, and draw a helpful analogy between linear polarimetric systems and the large existing body of work on photometric colorimetry.

Keywords: Solar K corona, Solar instruments, Polarimeters, Polarimetry, Color equation
Probing the Local Interstellar Medium with Scintillometry of the Bright Pulsar B1133 + 16. The interstellar medium hosts a population of scattering screens, most of unknown origin. Scintillation studies of pulsars provide a sensitive tool for resolving these scattering screens and a means of measuring their properties. In this paper, we report our analysis of 34 yr of Arecibo observations of PSR B1133 + 16, from which we have obtained high-quality dynamic spectra and their associated scintillation arcs, arising from the scattering screens located along the line of sight to the pulsar. We have identified six individual scattering screens that are responsible for the observed scintillation arcs, which persist for decades. Using the assumption that the scattering screens have not changed significantly in this time, we have modeled the variations in arc curvature throughout the Earth's orbit and extracted information about the placement, orientation, and velocity of five of the six screens, with the highest-precision distance measurement placing a screen at just ${5.46}_{-0.59}^{+0.54}$ pc from the Earth. We associate the more distant of these screens with an underdense region of the Local Bubble.

Keywords: Interstellar scattering, Interstellar medium, Pulsars
Panchromatic HST/WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae. I. NGC 6302. We present the results of a comprehensive, near-UV-to-near-IR Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging study of the young planetary nebula (PN) NGC 6302, the archetype of the class of extreme bilobed, pinched-waist PNe that are rich in dust and molecular gas. The new WFC3 emission-line image suite clearly defines the dusty toroidal equatorial structure that bisects NGC 6302's polar lobes, and the fine structures (clumps, knots, and filaments) within the lobes. The most striking aspect of the new WFC3 image suite is the bright, S-shaped 1.64 μm [Fe II] emission that traces the southern interior of the east lobe rim and the northern interior of the west lobe rim, in point-symmetric fashion. We interpret this [Fe II] emitting region as a zone of shocks caused by ongoing, fast (~100 km s-1), collimated, off-axis winds from NGC 6302's central star(s). The [Fe II] emission and a zone of dusty, N- and S-rich clumps near the nebular symmetry axis form wedge-shaped structures on opposite sides of the core, with boundaries marked by sharp azimuthal ionization gradients. Comparison of our new images with earlier HST/WFC3 imaging reveals that the object previously identified as NGC 6302's central star is a foreground field star. Shell-like inner lobe features may instead pinpoint the obscured central star's actual position within the nebula's dusty central torus. The juxtaposition of structures revealed in this HST/WFC3 imaging study of NGC 6302 presents a daunting challenge for models of the origin and evolution of bipolar PNe.

Keywords: Circumstellar matter, Planetary nebulae, Jets, Stellar mass loss
Gravitational Lensing by a Massive Object in a Dark Matter Halo. II. Shear, Phase, and Image Geometry. We study the gravitational lensing influence of a massive object in a dark matter halo, using a simple model of a point mass embedded in a spherical Navarro-Frenk-White halo. Building on the analysis of critical curves and caustics presented in the first part of this work, we proceed to explore the geometry of images formed by the lens. First, we analyze several lensing quantities including shear, phase, and their weak-lensing approximations, illustrating the results with image-plane maps. We derive formulae and present a geometric interpretation for the shear and phase of a combination of two axially symmetric mass distributions. In the case of our lens model, we describe the occurrence of zero-shear points and specify the conditions under which they become umbilic points. Second, we use the eigenvalue decomposition of the inverse of the lens-equation Jacobian matrix to compute the magnification and flattening of lensed images. Based on this, we introduce the convergence-shear diagram, a novel and compact way of visualizing the properties of images formed by a particular gravitational lens. We inspect relative deviations of the analyzed lensing quantities in order to evaluate the perturbing effect of the point mass and the applicability of the weak-lensing approximation. We explore the dependence of the results on the point-mass parameters by studying grids of plots for different combinations of its position and mass. We provide analytical explanations for important patterns arising in these plots and discuss the implications for the lensing influence of isolated compact bodies in dark matter halos.

Keywords: Galaxy clusters, Galaxy dark matter halos, Cross-validation , Supermassive black holes, Dwarf galaxies
Causes and Consequences of Magnetic Complexity Changes within Interplanetary Coronal Mass Ejections: A Statistical Study. We present the first statistical analysis of complexity changes affecting the magnetic structure of interplanetary coronal mass ejections (ICMEs), with the aim of answering the questions: How frequently do ICMEs undergo magnetic complexity changes during propagation? What are the causes of such changes? Do the in situ properties of ICMEs differ depending on whether they exhibit complexity changes? We consider multispacecraft observations of 31 ICMEs by MESSENGER, Venus Express, ACE, and STEREO between 2008 and 2014 while radially aligned. By analyzing their magnetic properties at the inner and outer spacecraft, we identify complexity changes that manifest as fundamental alterations or significant reorientations of the ICME. Plasma and suprathermal electron data at 1 au, and simulations of the solar wind enable us to reconstruct the propagation scenario for each event, and to identify critical factors controlling their evolution. Results show that ~65% of ICMEs change their complexity between Mercury and 1 au and that interaction with multiple large-scale solar wind structures is the driver of these changes. Furthermore, 71% of ICMEs observed at large radial (&gt;0.4 au) but small longitudinal (&lt;15°) separations exhibit complexity changes, indicating that propagation over large distances strongly affects ICMEs. Results also suggest that ICMEs may be magnetically coherent over angular scales of at least 15°, supporting earlier theoretical and observational estimates. This work presents statistical evidence that magnetic complexity changes are consequences of ICME interactions with large-scale solar wind structures, rather than intrinsic to ICME evolution, and that such changes are only partly identifiable from in situ measurements at 1 au.

Keywords: Interplanetary magnetic fields, Solar wind, Corotating streams, Solar coronal mass ejections
Solar Flare Irradiance: Observations and Physical Modeling. We examine Solar Dynamics Observatory (SDO)/EUV Variability Experiment (EVE) data to better understand solar flare irradiance, and how that irradiance may vary for large events. We measure scaling laws relating Geostationary Orbital Environmental Satellites (GOES) flare classes to irradiance in 21 lines measured with SDO/EVE, formed across a wide range of temperatures, and find that this scaling depends on the line-formation temperature. We extrapolate these irradiance values to large events, exceeding X10. In order to create full spectra, however, we need a physical model of the irradiance. We present the first results of a new physical model of solar flare irradiance, NRLFLARE, that sums together a series of flare loops to calculate the spectral irradiance ranging from the X-rays through the far-UV (≈0 to 1250 Å), constrained only by GOES/X-ray Sensors observations. We test this model against SDO/EVE data. The model spectra and time evolution compares well in high-temperature emission, but cooler lines show large discrepancies. We speculate that the discrepancies are likely due to both a nonuniform cross-section of the flaring loops as well as opacity effects. We then show that allowing the cross-sectional area to vary with height significantly improves agreement with observations, and is therefore a crucial parameter needed to accurately model the intensity of spectral lines, particularly in the transition region from $4.7\lesssim \mathrm{log}T\lesssim 6$ .

Keywords: Solar flares, Solar spectral irradiance, Solar flare spectra, Solar x-ray flares, Solar activity
The Missing Metal Problem in Galaxy Clusters: Characterizing the Early Enrichment Population. Rich and poor galaxy clusters have the same measured halo metallicity, 0.35-0.4 Z ☉, even though they are an order of magnitude apart in stellar fraction, M */M gas. The measured intracluster medium (ICM) metallicity in high-mass clusters cannot be explained by the visible stellar population as stars typically make up 3%-20% of the total baryon mass. The independence of metallicity of M */M gas suggests an external and universal source of metals such as an early enrichment population (EEP). Galaxy cluster RX J1416.4+2315, classified as a fossil system, has a stellar fraction of M */M gas = 0.054 ± 0.018, and here we improve the halo metallicity determination using archival Chandra and XMM-Newton observations. We determine the ICM metallicity of RXJ1416 to be 0.303 ± 0.053 Z ☉ within 0.3 &lt; R/R 500 &lt; 1, excluding the central galaxy. We combine this measurement with other clusters with a wider range of M */M gas, resulting in the fit of Z tot = (0.36 ± 0.01) + (0.10 ± 0.17)(M */M gas). This fit is largely independent of M */M gas and shows that for a low M */M gas system, the observed stellar population can make only 10%-20% of the total metals. We quantify the Fe contribution of the EEP further by adopting a standard Fe yield for visible stellar populations, and find that Z EEP = (0.36 ± 0.01) - - (0.96 ± 0.17)(M */M gas). To account for the observed Fe mass, a supernova (SN) rate of 10 ± 5 SNe yr-1 (Type Ia) and 40 ± 19 SNe yr-1 (core collapse) is required over the redshift range 3 &lt; z &lt; 10 for a single galaxy cluster with mass ~3 × 1014 M ☉ at z = 0. These SNe might be visible in observations of high-redshift clusters and protoclusters with the James Webb Space Telescope.

Keywords: Galaxy clusters, Population II stars, Intracluster medium, X-ray astronomy
Magnetospheric Curvature Radiation by Bunches as Emission Mechanism for Repeating Fast Radio Bursts. Coherent curvature radiation as the radiation mechanism for fast radio bursts (FRBs) has been discussed since FRBs were discovered. We study the spectral and polarization properties of repeating FRBs within the framework of coherent curvature radiation by charged bunches in the magnetosphere of a highly magnetized neutron star. The spectra can be generally characterized by multisegmented broken power laws, and evolve as bunches move and the line of sight sweeps. Emitted waves are highly linear polarized and polarization angles are flat across the burst envelopes, if the line of sight is confined to the beam within an angle of 1/γ, while a circular polarization fraction becomes strong for off-beam cases. The spectro-temporal pulse-to-pulse properties can be a natural consequence due to the magnetospheric geometry. We investigate the relationship between drift rate, central frequency, and temporal duration. The radius-to-frequency mapping is derived and simulated within the assumptions of both dipolar and quadrupolar magnetic configurations. The geometric results show that FRBs are emitted in field lines more curved than open field lines for a dipolar geometry. This suggests that there are most likely existing multipolar magnetic configurations in the emission region.

Keywords: Neutron stars, Radio bursts, Radiative processes, Magnetars, Radio transient sources
The DR21(OH) Trident-Resolving the Massive Ridge into Three Entangled Fibers as the Initial Condition of Cluster Formation. DR21(OH) ridge, the central part of a high-mass star- and cluster-forming hub-filament system, is resolved spatially and kinematically into three nearly parallel fibers (f1, f2, and f3) with a roughly north-south orientation, using the observations of molecular transitions of H13CO+ (1 - 0), N2H+ (1 - 0), and NH2D (11,1 - 10,1) with the Combined Array for Research in Millimeter Astronomy. These fibers are all mildly supersonic (σ velocity dispersions about 2 times the sound speed), having lengths around 2 pc and widths about 0.1 pc, and they entangle and conjoin in the south where the most active high-mass star formation takes place. They all have line masses 1-2 orders of magnitude higher than their low-mass counterparts and are gravitationally unstable both radially and axially. However, only f1 exhibits high-mass star formation all the way along the fiber, yet f2 and f3 show no signs of significant star formation in their northern parts. A large velocity gradient increasing from north to south is seen in f3, and can be well reproduced with a model of freefall motion toward the most massive and active dense core in the region, which corroborates the global collapse of the ridge and suggests that the disruptive effects of the tidal forces may explain the inefficiency of star formation in f2 and f3. On larger scales, some of the lower-density, peripheral filaments are likely to be the outer extensions of the fibers, and provide hints on the origin of the ridge.

Keywords: Interstellar line emission, Interstellar filaments, Star forming regions, Young massive clusters, Dense interstellar clouds, Star formation, Dust continuum emission