Sazuna/UAT_keywords huggingface dataset:
Pitch-angle Anisotropy Imprinted by Relativistic Magnetic Reconnection. Radiation emitted by nonthermal particles accelerated during relativistic magnetic reconnection is critical for understanding the nonthermal emission in a variety of astrophysical systems, including blazar jets, black hole coronae, pulsars, and magnetars. By means of fully kinetic particle-in-cell simulations, we demonstrate that reconnection-driven particle acceleration imprints an energy-dependent pitch-angle anisotropy and gives rise to broken power laws in both the particle energy spectrum and the pitch-angle anisotropy. The particle distributions depend on the relative strength of the non-reconnecting (guide field) versus the reconnecting component of the magnetic field (B  g /B 0) and the lepton magnetization (σ 0). Below the break Lorentz factor γ 0 (injection), the particle energy spectrum is ultra-hard (p &lt; &lt; 1), while above γ 0, the spectral index p &gt; is highly sensitive to B  g /B 0. Particles' velocities align with the magnetic field, reaching minimum pitch angle α at a Lorentz factor ${\gamma }_{\min \alpha }$ controlled by B  g /B 0 and σ 0. The energy-dependent pitch-angle anisotropy, evaluated through the mean of ${\sin }^{2}\alpha $ of particles at a given energy, exhibits power-law ranges with negative (m &lt;) and positive (m &gt;) slopes below and above ${\gamma }_{\min \alpha }$ , becoming steeper as B  g /B 0 increases. The generation of anisotropic pitch-angle distributions has important astrophysical implications. We address their effects on regulating synchrotron luminosity, spectral energy distribution, polarization, particle cooling, the synchrotron burn-off limit, emission beaming, and temperature anisotropy.

Keywords: High energy astrophysics, Plasma physics, Non-thermal radiation sources, Magnetic fields, Particle astrophysics
Spacecraft Charging Simulations of Probe B1 of Comet Interceptor during the Cometary Flyby. Comet Interceptor will be the first mission to make a flyby of a long-period or interstellar comet. After launch, the spacecraft will wait at the Sun-Earth Lagrange point L2 for a yet-to-be-discovered comet to appear. The mission comprises three spacecraft: One main spacecraft, A, developed by ESA, and two subprobes, B1 and B2, developed by JAXA and ESA, respectively. All spacecraft will carry plasma instruments for a three-dimensional sampling of the cometary plasma environment. The plasma measurements will likely be affected by the spacecraft potential and by particles emitted from the spacecraft surface. In this work, we use the Spacecraft Plasma Interaction Software and the ElectroMagnetic Spacecraft Environment Simulator to make particle-in-cell simulations of the spacecraft-plasma interactions of probe B1 in different environments during the cometary flyby. This is done for two production rates of the target comet and two relative flyby velocities of the probe. At low flyby velocities, the spacecraft potential varies from 9 V in the solar wind to -5 V in the inner coma for a comet similar to comet 67P/Churyumov-Gerasimenko. For a comet similar to 1P/Halley, the potential is slightly less negative in the inner coma due to the more effective collisional cooling of the electrons in the environment. At high flyby velocities, secondary electron emissions from neutral gas impacts dominate the currents, charging the probe to positive potentials in most of the studied environments.

Keywords: Space plasmas, Comets
The Implication of the Helium-to-proton Flux Ratio in Galactic Cosmic Rays. The measurement of daily proton and helium fluxes by AMS-02 shows that the helium-to-proton flux ratio (He/H) is negatively correlated with the solar activity at rigidity 1.7-7 GV. What is the behavior of He/H at rigidity lower than 1.7 GV? How can this phenomenon be described quantitatively and linked to the underlying mechanisms? In this work, based on a theoretical derivation, we find that the slope (S) of $\mathrm{ln}(\mathrm{He}/{\rm{H}})$ versus ln(H) is a good indicator of the variation of He/H. S &gt; 0 means the variation of He/H is anticorrelated with the solar activity, and vice versa. Furthermore, the value of S is quantitatively related to the difference in protons and helium nuclei in the local interstellar spectrum (LIS) and in solar modulation. A 3D time-dependent numerical model is used to reproduce the observed proton and helium data. The results of the simulation show that, with increasing rigidity, the parameter S increases from negative values to positive values at around 1 GV, reaches a maximum value at around 2 GV, and then decreases until it approaches 0. Interestingly, S is equal to 0 at around 1 GV. This means that He/H at this rigidity is almost unchanged with the variation in solar activity. Finally, the expression for S is validated by changing the LIS used in the numerical procedure. This shows that the overall profile of S as a function of rigidity is mainly determined by the mass-to-charge ratio, and the specific value of S is strongly affected by the difference in the LIS between protons and helium nuclei.

Keywords: Galactic cosmic rays, Solar activity, Heliosphere
Linking Circumstellar Disk Lifetimes to the Rotational Evolution of Low-mass Stars. The high-energy radiation emitted by young stars can have a strong influence on their rotational evolution at later stages. This is because internal photoevaporation is one of the major drivers of the dispersal of circumstellar disks, which surround all newly born low-mass stars during the first few million years of their evolution. Employing an internal EUV/X-ray photoevaporation model, we have derived a simple recipe for calculating realistic inner disk lifetimes of protoplanetary disks. This prescription was implemented into a magnetic-morphology-driven rotational evolution model and is used to investigate the impact of disk locking on the spin evolution of low-mass stars. We find that the length of the disk locking phase has a profound impact on the subsequent rotational evolution of a young star, and the implementation of realistic disk lifetimes leads to an improved agreement of model outcomes with observed rotation period distributions for open clusters of various ages. However, for both young star-forming regions tested in our model, the strong bimodality in rotation periods that is observed in h Per could not be recovered. h Per is only successfully recovered if the model is started from a double-peaked distribution with an initial disk fraction of 65%. However, at an age of only ~1 Myr, such a low disk fraction can only be achieved if an additional disk dispersal process, such as external photoevaporation, is invoked. These results therefore highlight the importance of including realistic disk dispersal mechanisms in rotational evolution models of young stars.

Keywords: Stellar rotation, Stellar evolutionary models, Protoplanetary disks, Circumstellar disks
Chemical Analysis of the Brightest Star of the Cetus II Ultrafaint Dwarf Galaxy Candidate. We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, abundances or upper limits of 18 elements from carbon to europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the α-elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, and Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova originating from a star with a mass of ~11.2 M ☉. In addition, the star has a potassium abundance of [K/Fe] = 0.81, which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature that is also present in a number of UFD galaxies. A comparison including globular clusters and stellar stream stars suggests that high K is a specific characteristic of some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Stellar abundances, Chemical abundances
Long-rising Type II Supernovae in the Zwicky Transient Facility Census of the Local Universe. SN 1987A was an unusual hydrogen-rich core-collapse supernova originating from a blue supergiant star. Similar blue supergiant explosions remain a small family of events, and are broadly characterized by their long rises to peak. The Zwicky Transient Facility Census of the Local Universe (CLU) experiment aims to construct a spectroscopically complete sample of transients occurring in galaxies from the CLU galaxy catalog. We identify 13 long-rising (&gt;40 days) Type II supernovae from the volume-limited CLU experiment during a 3.5 yr period from 2018 June to 2021 December, approximately doubling the previously known number of these events. We present photometric and spectroscopic data of these 13 events, finding peak r-band absolute magnitudes ranging from -15.6 to -17.5 mag and the tentative detection of Ba II lines in nine events. Using our CLU sample of events, we derive a long-rising Type II supernova rate of ${1.37}_{-0.30}^{+0.26}\times {10}^{-6}$ Mpc-3 yr-1, ≈1.4% of the total core-collapse supernova rate. This is the first volumetric rate of these events estimated from a large, systematic, volume-limited experiment.

Keywords: Sky surveys, Core-collapse supernovae, Surveys, Type II supernovae, Spectroscopy, Supernovae, Galaxies
Cosmological Tensions and the Transitional Planck Mass Model. In this follow-up analysis, we update previous constraints on the transitional Planck mass (TPM) modified gravity model using the latest version of EFTCAMB and provide new constraints using South Pole Telescope (SPT) and Planck anisotropy data along with Planck cosmic microwave background lensing, baryon acoustic oscillations, and Type Ia supernovae data and a Hubble constant, H 0, prior from local measurements. We find that large shifts in the Planck mass lead to large suppression of power on small scales that is disfavored by both the SPT and Planck data. Using only the SPT temperature-polarization-polarization-polarization (TE-EE) data, this suppression of power can be compensated for by an upward shift of the scalar index to n  s  = 1.003 ± 0.016, resulting in ${H}_{0}\,=\,{71.94}_{-0.85}^{+0.86}$ km m-1 Mpc-1 and a ~7% shift in the Planck mass. Including the Planck temperature-temperature (TT) ℓ ≤ 650 and Planck TE-EE data restricts the shift to be &lt;5% at 2σ with H 0 = 70.65 ± 0.66 km m-1 Mpc-1. Excluding the H 0 prior, the SPT and Planck data constrain the shift in the Planck mass to be &lt;3% at 2σ with a best-fit value of 0.04%, consistent with the Λ cold dark matter limit. In this case ${H}_{0}\,=\,{69.09}_{-0.68}^{+0.69}$ km s-1 Mpc-1, which is partially elevated by the dynamics of the scalar field in the late Universe. This differs from early dark energy models that prefer higher values of H 0 when the high-ℓ Planck TT data are excluded. We additionally constrain TPM using redshift space distortion data from BOSS DR12 and cosmic shear, galaxy-galaxy lensing, and galaxy clustering data from DES Y1, finding both disfavor transitions close to recombination, but earlier Planck mass transitions are allowed.

Keywords: Cosmology, Cosmological models, Cosmological parameters, Dark energy
Separated Twins or Just Siblings? A Multiplanet System around an M Dwarf Including a Cool Sub-Neptune. We report the discovery of two TESS sub-Neptunes orbiting the early M dwarf TOI-904 (TIC 261257684). Both exoplanets, TOI-904 b and c, were initially observed in TESS Sector 12 with twin sizes of ${2.426}_{-0.157}^{+0.163}$ and ${2.167}_{-0.118}^{+0.130}$ R ⊕, respectively. Through observations in five additional sectors in the TESS primary mission and the first and second extended missions, the orbital periods of the planets were measured to be 10.887 ± 0.001 and 83.999 ± 0.001 days, respectively. Reconnaissance radial velocity measurements (taken with EULER/CORALIE and SMARTS/CHIRON) and high-resolution speckle imaging with adaptive optics (obtained from SOAR/HRCAM and Gemini South/ZORRO) show no evidence of an eclipsing binary or a nearby companion, which, together with the low false-positive probabilities calculated with the statistical validation software TRICERATOPS, establishes the planetary nature of these candidates. The outer planet, TOI-904 c, is the longest-period M dwarf exoplanet found by TESS, with an estimated equilibrium temperature of 217 K. As the three other validated planets with comparable host stars and orbital periods were observed by Kepler around much dimmer stars (J mag &gt; 12), TOI-904 c, orbiting a brighter star (J mag = 9.6), is the coldest M dwarf planet easily accessible for atmospheric follow-up. Future mass measurements and transmission spectroscopy of the similar-sized planets in this system could determine whether they are also similar in density and composition, suggesting a common formation pathway, or whether they have distinct origins.

Keywords: M dwarf stars, Exoplanet systems, Mini Neptunes, Exoplanet astronomy, Cold Neptunes, Exoplanet detection methods, Transit photometry
A Spatially Resolved X-Ray Polarization Map of the Vela Pulsar Wind Nebula. In this paper, we present a full spatially resolved polarization map for the Vela pulsar wind nebula (PWN) observed by IXPE. By employing effective background discrimination techniques, our results show a remarkably high degree of local polarization in the outskirt region, exceeding 60% (55%) with a probability of 95% (99%), which approaches the upper limit predicted by the synchrotron emission mechanism. The high degree of polarization suggests that the turbulent magnetic energy is at most 33% of the ordered one. In addition, the X-ray polarization map exhibits a toroidal magnetic field pattern that is consistent with the field revealed by radio observations across the entire nebula. This consistency reveals that the observed X-ray and radio emissions are radiated by electrons from the same magnetic field. Different from the Crab PWN, the consistency observed in the Vela PWN may be attributed to the interaction between the reverse shock of the supernova blast wave and the PWN, which leads to a displacement between the synchrotron-cooled nebula and the fresh nebula close to the pulsar. These findings deepen our understanding of the structure and evolution of the Vela PWN and the magnetohydrodynamic interaction in PWNe.

Keywords: Magnetic fields, Polarimetry, Pulsar wind nebulae
Synchrotron Polarization Signatures of Surface Waves in Supermassive Black Hole Jets. Supermassive black holes in active galactic nuclei are known to launch relativistic jets, which are observed across the entire electromagnetic spectrum and thought to be efficient particle accelerators. Their primary radiation mechanism for radio emission is polarized synchrotron emission produced by a population of nonthermal electrons. In this Letter, we present a global general relativistic magnetohydrodynamical (GRMHD) simulation of a magnetically arrested disk (MAD). After the simulation reaches the MAD state, we show that waves are continuously launched from the vicinity of the black hole and propagate along the interface between the jet and the wind. At this interface, a steep gradient in velocity is present between the mildly relativistic wind and the highly relativistic jet. The interface is, therefore, a shear layer, and due to the shear, the waves generate roll-ups that alter the magnetic field configuration and the shear layer geometry. We then perform polarized radiation transfer calculations of our GRMHD simulation and find signatures of the waves in both total intensity and linear polarization, effectively lowering the fully resolved polarization fraction. The telltale polarization signatures of the waves could be observable by future very long baseline interferometric observations, e.g., the next-generation Event Horizon Telescope.

Keywords: Supermassive black holes, Jets, Relativistic jets, Plasma astrophysics, Active galactic nuclei, Radiative transfer simulations, Polarimetry, Astrophysical black holes
Time-dependent Dynamics of the Corona. We present in this Letter the first global comparison between traditional line-tied steady-state magnetohydrodynamic models and a new, fully time-dependent thermodynamic magnetohydrodynamic simulation of the global corona. To approximate surface magnetic field distributions and magnitudes around solar minimum, we use the Lockheed Evolving Surface-Flux Assimilation Model to obtain input maps that incorporate flux emergence and surface flows over a full solar rotation, including differential rotation and meridional flows. Each time step evolves the previous state of the plasma with a new magnetic field input boundary condition, mimicking photospheric driving on the Sun. We find that this method produces a qualitatively different corona compared to steady-state models. The magnetic energy levels are higher in the time-dependent model, and coronal holes evolve more along the following edge than they do in steady-state models. Coronal changes, as illustrated with forward-modeled emission maps, evolve on longer timescales with time-dependent driving. We discuss implications for active and quiet Sun scenarios, solar wind formation, and widely used steady-state assumptions like potential field source surface calculations.

Keywords: Solar magnetic flux emergence, Solar extreme ultraviolet emission, Solar corona, Quiet solar corona, Solar magnetic fields, Magnetohydrodynamical simulations
TOI-1670 c, a 40 day Orbital Period Warm Jupiter in a Compact System, Is Well Aligned. We report the measurement of the sky-projected obliquity angle λ of the warm Jovian exoplanet TOI-1670 c via the Rossiter-McLaughlin effect. We observed the transit window during UT 2023 April 20 for 7 continuous hours with NEID on the 3.5 m WIYN Telescope at Kitt Peak National Observatory. TOI-1670 hosts a sub-Neptune (P ~ 11 days; planet b) interior to the warm Jovian (P ~ 40 days; planet c), which presents an opportunity to investigate the dynamics of a warm Jupiter with an inner companion. Additionally, TOI-1670 c is now among the longest-period planets to date to have its sky-projected obliquity angle measured. We find planet c is well aligned to the host star, with λ = - 0.°3 ± 2.°2. TOI-1670 c joins a growing census of aligned warm Jupiters around single stars and aligned planets in multiplanet systems.

Keywords: Exoplanet dynamics
A New Covariant Formalism for Kinetic Plasma Simulations in Curved Spacetimes. Low-density plasmas are characterized by a large-scale separation between the gyromotion of particles around local magnetic fields and the macroscopic scales of the system, often making global kinetic simulations computationally intractable. The guiding center formalism has been proposed as a powerful tool to bridge the gap between these scales. Despite its usefulness, the guiding center approach has been formulated successfully only in flat spacetimes, limiting its applicability in astrophysical settings. Here, we present a new covariant formalism that leads to kinetic equations in the guiding center limit that are valid in arbitrary spacetimes. Through a variety of experiments, we demonstrate that our equations capture all known gyrocenter drifts while overcoming one severe limitation imposed on numerical algorithms by the fast timescales of the particle gyromotion. This formalism will enable explorations of a variety of global plasma kinetic phenomena in the curved spacetimes around black holes and neutron stars.

Keywords: Accretion, Black holes, Plasma physics, Plasma astrophysics, Classical black holes
CEERS Key Paper. VII. JWST/MIRI Reveals a Faint Population of Galaxies at Cosmic Noon Unseen by Spitzer. The Cosmic Evolution Early Release Science program observed the Extended Groth Strip (EGS) with the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) in 2022. In this paper, we discuss the four MIRI pointings that observed with longer-wavelength filters, including F770W, F1000W, F1280W, F1500W, F1800W, and F2100W. We compare the MIRI galaxies with the Spitzer/MIPS 24 μm population in the EGS field. We find that MIRI can observe an order of magnitude deeper than MIPS in significantly shorter integration times, attributable to JWST's much larger aperture and MIRI's improved sensitivity. MIRI is exceptionally good at finding faint (L IR &lt; 1010 L ⊙) galaxies at z ~ 1-2. We find that a significant portion of MIRI galaxies are "mid-IR weak"-they have strong near-IR emission and relatively weaker mid-IR emission, and most of the star formation is unobscured. We present new IR templates that capture how the mid-to-near-IR emission changes with increasing infrared luminosity. We present two color-color diagrams to separate mid-IR weak galaxies and active galactic nuclei (AGN) from dusty star-forming galaxies and find that these color diagrams are most effective when used in conjunction with each other. We present the first number counts of 10 μm sources and find that there are ≲10 IR AGN per MIRI pointing, possibly due to the difficulty of distinguishing AGN from intrinsically mid-IR weak galaxies (due to low metallicities or dust content). We conclude that MIRI is most effective at observing moderate-luminosity (L IR = 109-1010 L ⊙) galaxies at z = 1-2, and that photometry alone is not effective at identifying AGN within this faint population.

Keywords: AGN host galaxies, Active galaxies, Infrared galaxies
Numerical Testing of Mirror Diffusion of Cosmic Rays. The tension between recent observations and theories on cosmic-ray (CR) diffusion necessitates exploration of new CR diffusion mechanisms. We perform the first numerical study on the mirror diffusion of CRs that is recently proposed by Lazarian &amp; Xu. We demonstrate that the perpendicular superdiffusion of turbulent magnetic fields and magnetic mirroring that naturally arise in magnetohydrodynamic (MHD) turbulence are the two essential physical ingredients for the mirror diffusion to happen. In supersonic, subsonic, and incompressible MHD turbulence, with the pitch angles of CRs repeatedly crossing 90° due to the mirror reflection, we find that the mirror diffusion strongly enhances the confinement of CRs, and their pitch-angle-dependent parallel mean free path can be much smaller than the injection scale of turbulence. With the stochastic change of pitch angles due to gyroresonant scattering, CRs stochastically undergo slow mirror diffusion at relatively large pitch angles and fast scattering diffusion at smaller pitch angles, resulting in a Lévy-flight-like propagation.

Keywords: Magnetohydrodynamics, Cosmic rays