Sazuna/UAT_keywords huggingface dataset:
Multifrequency VLBI Observations of the M84 Inner Jet/Counterjet. Observational studies of the innermost regions of the edge-on jets in nearby active galactic nuclei (AGN) are crucial to understanding their kinematics and morphology. For the inner jet of the nearby low-luminosity AGN in M84, we present new high-sensitivity observations with very long baseline Interferometry since 2019, as well as archival Very Long Baseline Array observations in 2014. We find that the compact core in M84 has an inverted-to-flat spectrum from 1.5-88 GHz. Based on the turnover frequency of 4.2 ± 0.2 GHz in the spectrum, we estimated a magnetic field strength of 1 ~ 10 mG and an electron number density of ~105 cm-3 in the core region. Three inner jet components within ~3 mas of the core are identified and traced in the images at 22 GHz, whose apparent speeds are 0.11 c, 0.27 c, and 0.32 c, respectively. We calculate the viewing angle of ${58}_{-18}^{{+17}^\circ} $ for the inner jet based on the proper motion and the flux ratio of jet to counterjet. A propagating sinusoidal model with a wavelength of ~3.4 mas is used to fit the helical morphology of the jet extended to 20 mas (~2.2 × 104 Schwarzschild radii).

Keywords: Very long baseline interferometry, Relativistic jets, Low-luminosity active galactic nuclei
Deblending Galaxies with Generative Adversarial Networks. Deep generative models including generative adversarial networks (GANs) are powerful unsupervised tools in learning the distributions of data sets. Building a simple GAN architecture in PyTorch and training on the CANDELS data set, we generate galaxy images with the Hubble Space Telescope (HST) resolution starting from a noise vector. We proceed by modifying the GAN architecture to improve Subaru Hyper Suprime-Cam (HSC) ground-based images by increasing their resolution to the HST resolution. We use the super-resolution GAN on a large sample of blended galaxies, which we create using CANDELS cutouts. In our simulated blend sample, ~20% would unrecognizably be blended even in the HST-resolution cutouts. In the HSC-like cutouts this fraction rises to ~90%. With our modified GAN we can lower this value to ~50%. We quantify the blending fraction in the high, low, and GAN resolutions over the whole manifold of angular separation, flux ratios, sizes, and redshift difference between the two blended objects. The two peaks found by the GAN deblender result in improvement by a factor of 10 in the photometry measurement of the blended objects. Modifying the architecture of the GAN, we also train a multiwavelength GAN with HST cutouts in seven optical + near-infrared bands. This multiwavelength GAN improves the fraction of detected blends by another ~10% compared to the single-band GAN. This is most beneficial to the current and future precision cosmology experiments (e.g., LSST, SPHEREx, Euclid, Roman), specifically those relying on weak gravitational lensing, where blending is a major source of systematic error.

Keywords: Weak gravitational lensing, Convolutional neural networks, Observational astronomy, Galaxy photometry
Solar Polar Magnetic Fields: Comparing Full-disk and High-resolution Spectromagnetograph Data. This is the first systematic comparison between photospheric polar magnetic field data from a full-disk synoptic observing program, the National Solar Observatory's Synoptic Optical Long-term Investigations of the Sun Vector Spectromagnetograph (SOLIS/VSM), and a high-resolution vector spectromagnetograph, the Hinode Solar Optical Telescope Spectropolarimeter (SOT/SP). Polar magnetic fluxes derived from longitudinal magnetic field measurements from both telescopes and from SOT/SP full-Stokes vector data are all compared in the form of polar synoptic maps. Measurements taken over 35 day periods with advantageous rotation axis tilt angle are used; observations extend to the poles, and no synthetic pole-filling is needed. Polar fluxes are derived from longitudinal data assuming an approximately radial field, whereas those derived from vector data are based on measured vector magnitude and direction. However, the full-vector measurements may have a detection problem: polar fields are observed as mostly transverse from (near) Earth, and Zeeman sensitivity to transverse fields is significantly lower than for longitudinal fields. Accordingly, the SOT/SP vector-based polar fluxes are lower than the longitudinal-based fluxes from both telescopes, a result driven by pixels without sufficient Q and U signals for the full-Stokes inversions to detect significant radial field but with good Stokes V signal implying a significant field. Furthermore, the SOT/SP longitudinal-based fluxes are significantly higher than their VSM counterparts because of superior seeing-free spatial resolution and longer observation time. The SOT/SP longitudinal-based polar fluxes appear large enough to account for radial interplanetary field measurements whereas the SOT/SP vector-based and the VSM ones are generally too low.

Keywords: Solar cycle, Quiet sun, Solar magnetic fields, Heliosphere
SPYGLASS. III. The Fornax-Horologium Association and Its Traceback History within the Austral Complex. The study of young associations is essential for building a complete record of local star formation processes. The Fornax-Horologium association (FH), including the χ 1 Fornacis cluster, represents one of the nearest young stellar populations to the Sun. This association has recently been linked to the Tuc-Hor, Carina, and Columba associations, building an extensive "Austral Complex" almost entirely within 150 pc. Using Gaia astrometry and photometry in addition to new spectroscopic observations, we perform the deepest survey of FH to date, identifying over 300 candidate members, nearly doubling the known population. By combining this sample with literature surveys of the other constituent populations, we produce a contiguous stellar population covering the entire Austral Complex, allowing the definitions of subpopulations to be reassessed along with connections to external populations. This analysis recovers new definitions for FH, Tuc-Hor, Columba, and Carina, while also revealing a connection between the Austral complex and the Sco-Cen-affiliated Platais 8 cluster. This suggests that the Austral complex may be just a small component of a much larger and more diverse star formation event. Computing ages and tracing stellar populations back to formation reveals two distinct nodes of cospatial and continuous formation in the Austral Complex, one containing Tuc-Hor, and the other containing FH, Carina, and Columba. This mirrors recent work showing similar structure elsewhere, suggesting that these nodes, which only emerge through the use of traceback, may represent the clearest discrete unit of local star formation, and a key building block needed to reconstruct larger star-forming events.

Keywords: Pre-main sequence stars, Star formation, Stellar ages, Stellar associations
Thermal Energy Budget of Electrons in the Inner Heliosphere: Parker Solar Probe Observations. We present an observational analysis of the electron thermal energy budget using data from Parker Solar Probe. We use the macroscopic moments, obtained from our fits to the measured electron distribution function, to evaluate the thermal energy budget based on the second moment of the Boltzmann equation. We separate contributions to the overall budget from reversible and irreversible processes. We find that an irreversible thermal energy source must be present in the inner heliosphere over the heliocentric distance range from 0.15 to 0.47 au. The divergence of the heat flux is positive at heliocentric distances below 0.33 au, while beyond 0.33 au, there is a measurable degradation of the heat flux. Expansion effects dominate the thermal energy budget below 0.3 au. Under our steady-state assumption, the free streaming of the electrons is not sufficient to explain the observed thermal energy density budget. We conjecture that the most likely driver for the required heating process is turbulence. Our results are consistent with the known nonadiabatic polytropic index of the electrons, which we measure as 1.18 in the explored range of heliocentric distances.

Keywords: The Sun, Solar wind, Heliosphere, Plasma physics
High-precision Redshifts for Type Ia Supernovae with the Nancy Grace Roman Space Telescope P127 Prism. We present results from simulating slitless spectroscopic observations with the Nancy Grace Roman Space Telescope's (Roman) Wide-Field Instrument P127 prism spanning from 0.75 to 1.8 μm. We quantify the efficiency of recovered Type Ia supernova (SN Ia) redshifts, as a function of P127 prism exposure time, to guide planning for future observing programs with the Roman prism. Generating the two-dimensional dispersed images and extracting one-dimensional spectra is done with the slitless spectroscopy package pyLINEAR along with custom-written software. From the analysis of 1698 simulated SN Ia P127 prism spectra, we show the efficiency of recovering SN redshifts to z ≲ 3.0, highlighting the exceptional sensitivity of the Roman P127 prism. Redshift recovery is assessed by setting a requirement of ${\sigma }_{z}=(\left|z-{z}_{\mathrm{true}}\right|)/(1+z)\leqslant 0.01$ . We find that 3 hr exposures are sufficient for meeting this requirement, for ≳50% of the sample of mock SNe Ia at z ≈ 2 and within ±5 days of rest-frame maximum light in the optical. We also show that a 1 hr integration of Roman can achieve the same precision in completeness to a depth of 24.4 ± 0.06 AB mag (or z ≲ 1). Implications for cosmological studies with Roman P127 prism spectra of SNe Ia are also discussed.

Keywords: Type Ia supernovae, Galaxies
Observations of Rapidly Growing Whistler Waves in Front of Space Plasma Shock due to Resonance Interaction between Fluctuating Electron Velocity Distributions and Electromagnetic Fields. The whistler-mode wave extending from the fast-magnetosonic wave branch is a fundamental perturbation of electromagnetic fields and plasmas in various environments including planetary space, laboratory, and astrophysics. The origin and evolution of the waves is a long-standing question due to the limited instrumental capability in resolving highly variable plasma and electromagnetic fields. Here, we analyze observational data with a high time resolution from the Magnetospheric Multiscale spacecraft in front of the terrestrial bow shock (e.g., foreshock). We develop a novel approach to extract the three-dimensional fluctuating electron velocity distributions (δf e( V )) from their background (f e0( V )), and have successfully captured the coherent resonance between fluctuating electrons (δf e( V )) and wavelike electromagnetic fields (δ B , δ E ) at an unprecedentedly high frequency (&gt;1 Hz) for investigating wave-particle interactions. We provide that the unstable whistler wave grows rapidly over a timescale that is much shorter than the proton gyro-period. Regarding the energy origin for the waves, we find the ion distributions consisting of the solar wind ion flows and the ion beams reflected from the shock play crucial roles in providing the free energy and determining the eigenmode disturbances of fields and electrons. The quantification of wave growth rate and the characterization of wave-particle interactions for the instability driver can significantly advance the understandings of wave evolution and energy conversion between multisource multispecies particles and wave electromagnetic fields.

Keywords: Space plasmas, Solar wind, Planetary bow shocks
Vortex Pinning in Neutron Stars, Slipstick Dynamics, and the Origin of Spin Glitches. We study pinning and unpinning of superfluid vortices in the inner crust of a neutron star using three-dimensional dynamical simulations. Strong pinning occurs for certain lattice orientations of an idealized, body-centered-cubic lattice and occurs generally in an amorphous or impure nuclear lattice. The pinning force per unit length is ~1016 dyn cm-1 for a vortex-nucleus interaction that is repulsive and ~1017 dyn cm-1 for an attractive interaction. The pinning force is strong enough to account for observed spin jumps (glitches). Vortices forced through the lattice move with a slipstick character; for a range of superfluid velocities, the vortex can be in either a cold, pinned state or a hot, unpinned state, with strong excitation of Kelvin waves on the vortex. This two-state nature of vortex motion sets the stage for large-scale vortex movement that creates an observable spin glitch. We argue that the vortex array is likely to become tangled as a result of repeated unpinnings and repinnings. We conjecture that during a glitch, the Kelvin-wave excitation spreads rapidly along the direction of the mean superfluid vorticity and slower in the direction perpendicular to it, akin to an anisotropic deflagration.

Keywords: Neutron stars, Nuclear astrophysics, Compact objects
A Red Giants' Toy Story. In spite of the spectacular progress accomplished by stellar evolution theory, some simple questions remain unanswered. One of these questions is "Why do stars become red giants?". Here we present a relatively simple analytical answer to this question. We validate our analysis by constructing a quantitative toy model of a red giant and comparing its predictions to full stellar evolutionary models. We find that the envelope forces the value of ${\rm{\nabla }}=d\mathrm{ln}T/d\mathrm{ln}P$ at, and above, the burning shell into a very narrow range of possible values. Together with the fact that the stellar material at the burning shell both provides and transports most of the stellar luminosity, this leads to tight relations between the thermodynamic variables at the burning shell and the mass and radius of the core-T  s (M  c , R  s ), P  s (M  c , R  s ), and ρ  s (M  c , R  s ). When complemented by typical mass-radius relations of the helium cores, this implies that for all stellar masses the evolution of the core dictates the values of T  s , P  s , and ρ  s . We show that for all stellar masses evolution leads to an increase in the pressure and density contrasts between the shell and the core, forcing a huge expansion of the layers on top of the burning shell. Besides explaining why stars become red giants our analysis also offers a mathematical demonstration of the so-called shell homology relations, and provides simple quantitative answers to some properties of low-mass red giants.

Keywords: Stellar interiors, Stellar structures, Giant branch, Red giant stars
The Radius of PSR J0740+6620 from NICER with NICER Background Estimates. We report a revised analysis for the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, studied previously with joint fits to NICER and XMM-Newton data by Riley et al. (2021) and Miller et al. (2021). We perform a similar Bayesian estimation for the pulse-profile model parameters, except that instead of fitting simultaneously the XMM-Newton data, we use the best available NICER background estimates to constrain the number of photons detected from the source. This approach eliminates any potential issues in the cross-calibration between these two instruments, providing thus an independent check of the robustness of the analysis. The obtained neutron star parameter constraints are compatible with the already published results, with a slight dependence on how conservative the imposed background limits are. A tighter lower limit causes the inferred radius to increase, and a tighter upper limit causes it to decrease. We also extend the study of the inferred emission geometry to examine the degree of deviation from antipodality of the hot regions. We show that there is a significant offset to an antipodal spot configuration, mainly due to the non-half-cycle azimuthal separation of the two emitting spots. The offset angle from the antipode is inferred to be above 25° with 84% probability. This seems to exclude a centered-dipolar magnetic field in PSR J0740+6620.

Keywords: X-ray astronomy, Neutron stars
An Overview of Sunspot Observations in 1727-1748. Solar activity generally exhibits cyclic behavior in terms of sunspot group number and sunspot positions every ≈11 yr. These sunspot data have therefore played key roles in numerous analyses of solar-terrestrial physics. However, their reconstructions prior to the 1830s have remained controversial and included significant data gaps, especially from the 1720s to the 1740s. Therefore, this study reviewed contemporary sunspot observations for 1727-1748 to add several forgotten records by Van Coesfelt in 1728-1729, Dûclos in 1736, Martin in 1737, and Cassini and Maraldi in 1748. On the basis of these records, this study revised the sunspot group number and newly derived the sunspot positions in this interval. The results show clearer solar cycles in sunspot group number than those of previous studies and indicate regular solar cycles with limited hemispheric asymmetry over Solar Cycles 0 to -2. The sunspot positions also show sunspot groups mostly at heliographic latitude φ fulfilling ∣φ∣ &lt; 35° in both solar hemispheres, with slight equatorward motions. Furthermore, the solar minima between Solar Cycles -2 and -1 and between Solar Cycles -1 and 0 have been located around 1733.5 ± 0.5 and 1743 ± 0.5, indicating cycle lengths of 11.7 ± 0.5 yr and 10.0 ± 1.0 yr, respectively. Our results provide a chronological missing link between the Maunder Minimum and the regular solar cycles observed since Staudach's observations from 1749 onward. This lets us better understand the transition of solar activity from the grand minimum to the regular solar cycles.

Keywords: Solar cycle, Sunspot groups, Sunspot number, Sunspots, Solar-terrestrial interactions, Sunspot cycle
High-precision Nuclear Chronometer for the Cosmos. Nuclear chronometers, which predict the ages of the oldest stars by comparing the present and initial abundances of long-lived radioactive nuclides, provide an independent dating technique for the cosmos. The idea of synchronizing Th/X, U/X, and Th/U chronometers can impose stringent constraints on the astrophysical conditions in the r-process simulations, giving rise to the Th-U-X chronometer. It is found that the astrophysical uncertainties of nuclear cosmochronology are significantly reduced from more than ±2 billion years to about 0.3 billion years. The Th-U-X chronometer is then applied to estimate the ages of the six metal-poor stars with observed uranium abundances, and the predicted ages are compatible with the cosmic age of 13.8 billion years predicted from the cosmic microwave background radiation but contradict the cosmic age of 11.4 billion years from the gravitational lens measurement.

Keywords: Stellar ages, Nucleosynthesis, R-process, Nuclear astrophysics, Cosmochronology
Searching for Extremely Blue UV Continuum Slopes at z = 7-11 in JWST/NIRCam Imaging: Implications for Stellar Metallicity and Ionizing Photon Escape in Early Galaxies. The ultraviolet (UV) continuum slope (β, where f  λ  ∝ λ  β ) of galaxies is sensitive to a variety of properties, from the metallicity and age of the stellar population to dust attenuation throughout the galaxy. Considerable attention has focused on identifying reionization-era galaxies with very blue UV slopes (β &lt; -3). Not only do such systems provide a signpost of low-metallicity stars, but they also identify galaxies likely to leak ionizing photons from their H II regions as such blue UV slopes require the reddening effect of nebular continuum to be diminished. In this paper we present a search for reionization-era galaxies with very blue UV colors in recent JWST/NIRCam imaging of the Extended Groth Strip field. We characterize UV slopes for a large sample of z ≃ 7-11 galaxies, finding a median of β = -2.0. Two lower luminosity (M UV ≃ -19.5) and lower stellar mass (6-10 × 107 M ⊙) systems exhibit extremely blue UV slopes (β = -2.9 to -3.1) and rest-optical photometry indicating weak nebular line emission. Each system is very compact (r  e  ≲ 260 pc) with very high star formation-rate surface densities. We model the spectral energy distributions (SEDs) with a suite of BEAGLE models with varying levels of ionizing photon escape. The SEDs cannot be reproduced with our fiducial (f esc,H II  = 0) or alpha-enhanced (Z ⋆ &lt; Z ISM) models. The combined blue UV slopes and weak nebular emission are best-fit by models with significant ionizing photon escape from H II regions (f esc,H II  = 0.5-0.8) and extremely low-metallicity massive stars (Z ⋆ = 0.01-0.06 Z ⊙). The discovery of these galaxies highlights the potential for JWST to identify large numbers of candidate Lyman continuum leaking galaxies in the reionization era and suggests low-metallicity stellar populations may be common in dwarf galaxies at z &gt; 7.

Keywords: Chemical abundances, Reionization, Metallicity, High-redshift galaxies, Galaxies
Magnetohydrodynamic Model of Late Accretion onto a Protoplanetary Disk: Cloudlet Encounter Event. Recent observations suggest late accretion, which is generally nonaxisymmetric, onto protoplanetary disks. We investigated nonaxisymmetric late accretion considering the effects of magnetic fields. Our model assumes a cloudlet encounter event at a few hundred astronomical units scale, where a magnetized gas clump (cloudlet) encounters a protoplanetary disk. We studied how the cloudlet size and the magnetic field strength affect the rotational velocity profile in the disk after the cloudlet encounter. The results show that a magnetic field can either decelerate or accelerate the rotational motion of the cloudlet material, primarily depending on the relative size of the cloudlet to the disk thickness. When the cloudlet size is comparable to or smaller than the disk thickness, magnetic fields only decelerate the rotation of the colliding cloudlet material. However, if the cloudlet size is larger than the disk thickness, the colliding cloudlet material can be super-Keplerian as a result of magnetic acceleration. We found that the vertical velocity shear of the cloudlet produces a magnetic tension force that increases the rotational velocity. The acceleration mechanism operates when the initial plasma β is β ≲ 2 × 101. Our study shows that magnetic fields modify the properties of spirals formed by tidal effects. These findings may be important for interpreting observations of late accretion.

Keywords: Stellar accretion disks, Protoplanetary disks, Magnetohydrodynamical simulations
Tidal Distortions as a Bottleneck on Constraining Exoplanet Compositions. Improvements in the number of confirmed planets and the precision of observations imply a need to better understand subtle effects that may bias interpretations of exoplanet observations. One such effect is the distortion of a short period planet by its host star, affecting its derived density. We extend the work of Burton et al., Correia, and others, using a gravitational potential formulation to a sample of nearly 200 planets with periods less than 3 days. We find five planets exhibiting density variations of &gt;10% and as many as 20 planets with deviations &gt;5%. We derive an analytic approximation for this deviation as a function of the orbital period, transit depth, and mass ratio between the planet and host star, allowing for rapid determination of such tidal effects. We find that current density error bars are typically larger than tidal deviations but that reducing the uncertainty on transit depth and radial velocity (RV) amplitude by a factor of 3 causes tidal effects to dominate density errors (&gt;50%) in &gt;40% of planets in our sample, implying that in the near future upgraded observational precision will cause shape deviations to become a bottleneck with regards to analysis of exoplanet compositions. These two parameters are found to dominate uncertainties compared to errors on stellar mass and radius. We identify a group of eight planets (including WASP-19 b, HAT-P-7 b, and WASP-12 b) for which current density uncertainties are as much as 4× smaller than the potential shift due to tides, implying a possible 4σ bias on their density estimates.

Keywords: Exoplanet astronomy, Tidal distortion, Exoplanet structure, Exoplanets