Sazuna/UAT_keywords huggingface dataset:
Magnetic Fields in Massive Star-forming Regions (MagMaR). V. The Magnetic Field at the Onset of High-mass Star Formation. A complete understanding of the initial conditions of high-mass star formation and what processes determine multiplicity requires the study of the magnetic field in young massive cores. Using Atacama Large Millimeter/submillimeter Array (ALMA) 250 GHz polarization observations (0 3 = 1000 au) and ALMA 220 GHz high-angular-resolution observations (0 05 = 160 au), we have performed a full energy analysis including the magnetic field at core scales and have assessed what influences the multiplicity inside a massive core previously believed to be in the prestellar phase. With a mass of 31 M⊙, the G11.92 MM2 core has a young CS molecular outflow with a dynamical timescale of a few thousand years. At high resolution, the MM2 core fragments into a binary system, with a projected separation of 505 au and a binary mass ratio of 1.14. Using the Davis–Chandrasekhar–Fermi method with an angle dispersion function analysis, we estimate in this core a magnetic field strength of 6.2 mG and a mass-to-magnetic-flux ratio of 18. The MM2 core is strongly subvirialized, with a virial parameter of 0.064, including the magnetic field. The high mass-to-magnetic-flux ratio and low virial parameter indicate that this massive core is very likely undergoing runaway collapse, which is in direct contradiction with the core accretion model. The MM2 core is embedded in a filament that has a velocity gradient consistent with infall. In line with clump-fed scenarios, the core can grow in mass at a rate of 1.9–5.6 × 10‑4 M⊙ yr‑1. In spite of the magnetic field having only a minor contribution to the total energy budget at core scales (a few thousands of astronomical units), it likely plays a more important role at smaller scales (a few hundreds of astronomical units) by setting the binary properties. Considering energy ratios and a fragmentation criterion at the core scale, the binary system could have been formed by core fragmentation. The binary system properties (projected separation and mass ratio), however, are also consistent with radiation-magnetohydrodynamic simulations with super-Alfvenic or supersonic (or sonic) turbulence that form binaries by disk fragmentation.

Keywords: Binary stars, Star forming regions, Massive stars, Magnetic fields, Young stellar objects, Star formation, Dust continuum emission, Polarimetry
Study of Long-term Spectral Evolution and X-Ray and γ-Ray Correlation of Blazars Seen by HAWC. The HAWC Observatory collected 6 yr of extensive data, providing an ideal platform for long-term monitoring of blazars in the very high energy (VHE) band, without bias toward specific flux states. HAWC continuously monitors blazar activity at TeV energies, focusing on sources with a redshift of z ≤ 0.3, based on the Third Fermi-LAT Catalog of High-Energy sources. We specifically focused our analysis on Mrk 421 and Mrk 501, as they are the brightest blazars observed by the HAWC Observatory. With a data set of 2143 days, this work significantly extends the monitoring previously published, which was based on 511 days of observation. By utilizing HAWC data for the VHE γ-ray emission in the 300 GeV─100 TeV energy range, in conjunction with Swift-XRT data for the 0.3─10 keV X-ray emission, we aim to explore potential correlations between these two bands. For Mrk 501, we found evidence of a long-term correlation. Additionally, we identified a period in the light curve where the flux was very low for more than 2 yr. On the other hand, our analysis of Mrk 421 measured a strong linear correlation for quasi-simultaneous observations collected by HAWC and Swift-XRT. This result is consistent with a linear dependence and a multiple-zone synchrotron self-Compton model to explain the X-ray and γ-ray emission. Finally, as suggested by previous findings, we confirm a harder-when-brighter behavior in the spectral evolution of the flux properties for Mrk 421. These findings contribute to the understanding of blazar emissions and their underlying mechanisms.

Keywords: Gamma-ray observatories, High energy astrophysics, Blazars, Gamma-ray detectors, Active galactic nuclei, X-ray observatories, Gamma-ray astronomy
Statistics of the Interplanetary Magnetic Field from 0.1 to 30 au. I. Distribution Character. This study investigates the directional and intensity distributions of the interplanetary magnetic field (IMF) across a heliocentric distance range of approximately 0.1–30 au. Measurements from multiple spacecraft reveal that these distributions align closely with the Parker spiral configuration in general. Nevertheless, the deviation from the model is significant and regular. To analyze these deviations, we organized the IMF observations based on the orientation and intensity predicted by the Parker model. The average angular deviation from the Parker spiral increases between 0.1 and 1 au, stabilizing from 1 to 30 au. The magnetic field components perpendicular to the Parker spiral are more likely to lay in the latitudinal and longitudinal directions during the solar maximum and minimum, respectively. The normalized intensity distribution follows a log-normal distribution, with its broadening positively correlated with increasing heliocentric distance. These characteristics cannot be fully attributed to Alfvénic fluctuations or the nonradial component near the potential field source surface. Instead, interactions of flux tubes in the outer heliosphere play a significant role in shaping the IMF. Our results provide a comprehensive assessment of the frequency with which planets encounter non-Parker upstream conditions.

Keywords: Planetary magnetospheres, Solar wind, Interplanetary magnetic fields
Metallicity and α-abundance for 48 Million Stars in Low-extinction Regions in the Milky Way. We estimate ([M/H], [α/M]) for 48 million giants and dwarfs in low-dust extinction regions from the Gaia DR3 XP spectra by using tree-based machine learning models trained on APOGEE DR17 and a metal-poor star sample from Li et al. The root mean square error of our estimation is 0.0890 dex for [M/H] and 0.0436 dex for [α/M], when we evaluate our models on the test data that are not used in training the models. Because the training data is dominated by giants, our estimation is most reliable for giants. The high-[α/M] stars and low-[α/M] stars selected by our ([M/H], [α/M]) show different kinematical properties for giants and low-temperature dwarfs. We further investigate how our machine learning models extract information on ([M/H], [α/M]). Intriguingly, we find that our models seem to extract information on [α/M] from Na D lines (589 nm) and Mg I line (516 nm). This result is understandable given the observed correlation between Na and Mg abundances in the literature. The catalog of ([M/H], [α/M]) as well as their associated uncertainties is publicly available.

Keywords: Astroinformatics, Stellar abundances, Milky Way disk, Milky Way stellar halo, Spectroscopy
Galaxies Lighting Up: Discovery of Seventy New Turn-on Changing-look Active Galactic Nuclei. "Changing-look active galactic nuclei" (CL AGN) show dramatic, rapid changes in optical/UV continuum and broad-line emission. The majority of CL AGN have been found dimming as "turn-off" CL AGN because most selection methods start from samples of spectroscopically confirmed quasars. We present here a sample of 82 spectroscopically confirmed "turn-on" CL AGN, 70 of which are newly identified. The turn-on CL AGN are selected from spectroscopically classified galaxies with subsequent significant and dramatic variability in both the optical and mid-infrared bands, indicating a mechanism of changing accretion rate of the supermassive black holes (BHs) rather than variable obscuration. Based on their bright state Eddington ratios, turn-on CL AGN are associated with lower accretion rates compared to turn-off CL AGN or typical Sloan Digital Sky Survey quasars with similar redshift and magnitude distributions, even though turn-on CL AGN have lower BH masses. Most turn-on CL AGN reside in host galaxies that follow local relations between the central BH mass and host galaxy properties, such as stellar mass and velocity dispersion. However, their host galaxies have higher mass than normal inactive galaxies, with star formation rates more similar to hosts of Type 2 AGN than to the overall galaxy population.

Keywords: AGN host galaxies, Supermassive black holes, Active galactic nuclei, Quasars
Constraints on Relativistic Jets from the Fast X-Ray Transient 210423 Using Prompt Radio Follow-up Observations. Fast X-ray transients (FXTs) are a new observational class of phenomena with no clear physical origin. This is at least partially a consequence of limited multiwavelength follow-up of this class of transients in real time. Here we present deep optical (g- and i-band) photometry with Keck, and prompt radio observations with the Very Large Array of FXT 210423 obtained at δ t ≈ 14–36 days since the X-ray trigger. We use these multiband observations, combined with publicly available data sets, to constrain the presence and physical properties of on-axis and off-axis relativistic jets such as those that can be launched by neutron star mergers and tidal disruption events, which are among the proposed theoretical scenarios of FXTs. Considering a wide range of possible redshifts z ≤ 3.5, circumstellar medium density n = 10‑6–10‑1 cm‑3, and isotropic-equivalent jet kinetic energy E  k,iso = 1048–1055 erg, we find that we can rule out wide jets with opening angle θ  j  = 15° viewed within 10° off-axis. For more collimated jets (θ  j  = 3°) we can only rule out on-axis (θ obs = 0°) orientations. This study highlights the constraining power of prompt multiwavelength observations of FXTs discovered in real time by current (e.g., Einstein Probe) and future facilities.

Keywords: X-ray transient sources
Constraints on the Variation of the Fine-structure Constant at 3 &lt; z &lt; 10 with JWST Emission-line Galaxies. We present constraints on the spacetime variation of the fine-structure constant α at redshifts 2.5 ≤ z &lt; 9.5 using JWST emission-line galaxies (ELGs). The galaxy sample consists of 621 high-quality spectra with strong and narrow [O III] λλ4959,5007 doublet emission lines from 578 galaxies, including 232 spectra at z &gt; 5. The [O III] doublet lines are arguably the best emission lines to probe the variation in α. We divide our sample into six subsamples based on redshift and calculate the relative variation Δα/α for the individual subsamples. The calculated Δα/α values are consistent with zero within 1σ at all redshifts, suggesting no time variation in α above a level of (1–2) × 10‑4 (1σ) in the past 13.2 billion yr. When the whole sample is combined, the constraint is improved to be Δα/α = (0.2 ± 0.7) × 10‑4. We further test the spatial variation in α using four subsamples of galaxies in four different directions on the sky. The measured Δα/α values are consistent with zero at a 1σ level of ∼2 × 10‑4. While the constraints in this work are not as stringent as those from lower-redshift quasar absorption lines in previous studies, this work uses an independent tracer and provides the first constraints on Δα/α at the highest redshifts. With the growing number of ELGs from JWST, we expect to achieve stronger constraints in the future.

Keywords: Interdisciplinary astronomy, Galaxy spectroscopy, Emission line galaxies
Dust Dynamics in Radially Convective Regions of Protoplanetary Disks. Hydrodynamic instabilities likely operate in protoplanetary disks. One candidate, convective overstability (COS), can be triggered in regions with a negative radial entropy gradient. The ensuing turbulence and flow structures are expected to affect dust dynamics directly. We revisit the interaction between dust and the COS with high-resolution spectral simulations in the unstratified, axisymmetric Boussinesq shearing box framework. We find zonal flows, or pressure bumps, formed by the COS trap dust, as expected, but dust densities increase at most by a factor of O(10) over its background value due to the zonal flows' unsteady nature. Furthermore, dust feedback can impede the formation of zonal flows, even at small dust-to-gas ratios ϵ ∼ O(0.1). We interpret this phenomenon as a competition between the negative gas angular momentum flux associated with zonal flow formation and the positive dust angular momentum flux associated with its drift toward pressure maxima. Dust concentration significantly weakens when a large-scale radial pressure gradient induces a background dust drift. Ultimately, we find that dust concentration by COS-induced zonal flows is limited to ϵ ≲ 1. Whether this can be improved under more realistic geometries must be addressed with stratified and full 3D simulations at equivalent resolutions.

Keywords: Hydrodynamical simulations, Hydrodynamics, Protoplanetary disks, Astrophysical fluid dynamics, Planet formation
Fluctuations Driven by Multicomponent Pickup Ion Distributions in the Outer Heliosheath. The stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability analysis and hybrid simulations. Linear instability analysis shows that the excited oblique mirror waves and the parallel/quasi-parallel Alfvén-cyclotron (AC) waves have lower growth rates than those obtained previously by A. Mousavi et al. for the PUI velocity distributions given by J. Heerikhuisen et al. The PUI scattering by each of the two modes alone is studied. In contrast to the previous investigations, our current simulations using the updated realistic distributions indicate that mirror waves alone do not effectively scatter PUIs in pitch angle. Instead, they primarily contribute to reducing the thermal spread anisotropy of the PUIs originating from the neutral solar wind. The unstable AC waves exhibit lower growth rates but higher saturation levels than the mirror waves. Two-dimensional (2D) simulation results show that when all unstable waves are present, the predominant contributor to the fluctuating magnetic field energy is the AC mode. The AC waves quickly scatter the PUIs with pitch angles away from 90∘ toward isotropy, while the PUIs near 90∘ pitch angle maintain a degree of anisotropy within our simulation timeframe. Moreover, several 1D and 2D hybrid simulations with different numbers of particles per cell are performed to examine the impact of numerical noise on PUI scattering. Finally, the implications of these results for the Interstellar Boundary Explorer energetic neutral atom ribbon are discussed.

Keywords: Pickup ions
Delay of Near-relativistic Electrons with Respect to Type III Radio Bursts throughout the Inner Heliosphere. Energetic electrons accelerated by solar eruptive events are frequently observed to have inferred injection times that appear significantly delayed with respect to electromagnetic emission including type III radio bursts. This is noteworthy because type III radio emission is produced by streaming suprathermal electrons, and thus this observed delay implies either a delayed injection/release of higher-energy electrons, compared with the suprathermal population, and/or a delay of the electrons observed in situ in transit through the interplanetary medium. A number of studies have investigated these delays with spacecraft located at 1 au. In this study, we examine energetic electron onsets and type III radio bursts observed by the Integrated Science Investigation of the Sun (IS⊙IS) and the FIELDS Radio Frequency Spectrometer instrument on Parker Solar Probe at a variety of heliocentric distances. With these observations, we can uniquely decouple the effects of acceleration and transport and shed light on the source of these delays. We present a survey of electron events observed by IS⊙IS within the first ∼6 yr of the mission, including their delays with respect to type III emission between ∼0.1 and 0.8 au. These results suggest that energetic electron delays with respect to type III radio bursts are not purely produced by a delayed injection/release as has been suggested, implying that transport processes play a role.

Keywords: Solar energetic particles, Solar radio emission, Interplanetary physics
First Detection of Radio Emission from the Intermediate-mass Black Hole in POX 52: Deep Multiband Observations with ATCA and VLA. We present the first multiband centimeter detection of POX 52, a nearby dwarf galaxy believed to harbor a robust intermediate-mass black hole. We conducted the deep observations using the Australia Telescope Compact Array (ATCA), spanning frequencies from 4.5 to 10 GHz, as well as the sensitive observations from the Karl G. Jansky Very Large Array (VLA) operating in its most extended A configuration at S band (2–4 GHz) and C band (4–8 GHz). In the ATCA observations, the source shows a compact morphology, with only one direction marginally resolved. The higher resolution of the VLA allowed us to slightly resolve the source, fitting it well with a two-dimensional Gaussian model. The detected radio emission confirms the presence of active galactic nucleus (AGN) activity, indicating either a low-power jet or AGN-driven winds/outflows. Our dual-epoch observations with ATCA and VLA, together with previous nondetection flux density upper limits, reveal radio emission variability spanning two decades. In addition, we find that POX 52 aligns well with the low-mass extension of the fundamental plane for high-accretion, radio-quiet massive AGNs.

Keywords: Radio continuum emission, Intermediate-mass black holes, Seyfert galaxies, Dwarf galaxies
Modeling the Saddle-like GeV–TeV Spectrum of HESS J1809–193: Gamma Rays Arising from Reverse-shocked Pulsar Wind Nebula?. The evolution of pulsar wind nebulae (PWNe) could be expected to leave imprints in gamma rays. We suggest that the intriguing GeV–TeV spectral energy distribution (SED) of HESS J1809–193 and Fermi-LAT source J1810.3–1925e is very likely to be the gamma-ray signature of PWN J1809–193 in light of the scenario that the PWN was struck by the reverse shock of the parent supernova remnant. Based on the evolutionary theory of PWNe, we consider that, when the PWN was disrupted during a collision by the reverse shock, some VHE electrons escaped impulsively. The remaining electrons stayed in the relic PWN, which was displaced from the pulsar. The VHE part of the remaining electrons was depleted by the strong magnetic field that was enhanced by the reverse shock compression in the reverberation stage, leaving the other part of them generating GeV emission. The particles injected from the pulsar after the disruption enter the relic PWN through the newly formed tunnel called the cocoon. The gamma-ray emission from the escaped electrons can account for the TeV spectrum of component A of HESS J1809–193 or the TeV halo, while the electrons remaining after disruption can account for the GeV spectrum of J1810.3–1925e. Thus, the combination of contributions from these two populations of electrons naturally reproduces the saddle-like SED of HESS 1809–193 and J1810.3–1925e from 5 GeV to 30 TeV, together with the spectral hardening around 100 GeV. We also show that the post-disruption injection of electrons can explain the spectrum of the relatively faint gamma-ray emission of component B of HESS J1809–193.

Keywords: Supernova remnants, Gamma-ray sources, Cosmic rays, Pulsar wind nebulae
The Timing and Spectral Properties of the 2022 Outburst of SGR J1935+2154 Observed with NICER. The magnetar SGR J1935+2154 entered a new active episode on 2022 October 10, with X-ray bursts and enhanced persistent emission. At the tail of a high burst rate interval, lasting several hours, radio bursts were detected, revealing the connection between the X-ray activities and radio emissions. We analyzed observations of SGR J1935+2154 for nearly 3 months, using data from the Neutron Star Interior Composition Explorer. We report the timing and spectral results following the onset of this outburst. In general, the X-ray flux of the persistent emission decays exponentially. While a flare is evident on the light curve, a fast radio burst (FRB) was detected immediately following the peak of this flare. We found a phase jump in the pulse profile, with a deviation of a 0.16 ± 0.03 phase, which is related to the glitch. The spectra are well fit with the combination of a blackbody and a power-law (PL) model. The decay of the outburst is dominated by the drop in the nonthermal component, which also leads to an increase in thermal proportion. The photon index of the PL is inversely correlated with both the unabsorbed flux and the burst rate. We find that unlike the large variety of the persistent emission around FRB 221014, the X-ray properties are very stable when FRBs 221021 and 221201 happened. These results manifest the connection between the glitch, phase jump, X-ray burst, and radio burst, crucial for studying the mutation in twisted magnetic fields and constraining the trigger mechanism of radio bursts.

Keywords: Neutron stars, Magnetars, X-ray transient sources
A Systematic Study of Inverting Overlappograms: MaGIXS—A Case Study. Slitless (or wide-field) imaging spectroscopy provides simultaneous imaging and spectral information from a wide field of view, allowing for rapid spectroscopic data collection from extended sources. Depending on the size of the extended source, combined with the spatial resolution and spectral dispersion of the instrument, there may be locations in the focal plane where spectral lines from different spatial locations overlap on the detector. An unfolding method is successfully developed and demonstrated on the recent rocket flight of the Marshall Grazing Incidence X-ray Spectrometer, which observed several strong emission lines in the 8–30 Å wavelength range from two X-ray bright points and a portion of an active region. In this paper, we present a systematic investigation of the parameters that control and optimize the inversion method for unfolding slitless spectrograph data.

Keywords: Direct imaging, Solar x-ray emission, Spectroscopy, X-ray telescopes
Tracking Star-forming Cores as Mass Reservoirs in Clustered and Isolated Regions Using Numerical Passive Tracer Particles. Understanding the physical properties of star-forming cores as mass reservoirs for protostars and the impact of turbulence is crucial in star formation studies. We implemented passive tracer particles in clump-scale numerical simulations with turbulence strengths of  . Unlike core identification methods used in observational studies, we identified 260 star-forming cores using a new method based on tracer particles falling onto protostars. Our findings reveal that star-forming cores do not necessarily coincide with high-density regions when nearby stars are present, as gas selectively accretes onto protostars, leading to clumpy, fragmented structures. We calculated convex hull cores from star-forming cores and defined their filling factors. Regardless of turbulence strength, convex hull cores with lower filling factors tend to contain more protostars and have larger masses and sizes, indicating that cores in clustered regions are more massive and larger than those in isolated regions. Thus, the filling factor serves as a key indicator for distinguishing between isolated and clustered star-forming regions and may provide insights into the star formation processes within clustered regions. We also found that most convex hull cores are gravitationally bound. However, in the   model, there are more low-mass, unbound convex hull cores compared to the   model. In the   model, 16% of the convex hull cores are unbound, which may be explained by the inertial-inflow model. These findings highlight the influence of turbulence strength on the mass and gravitational stability of cores.

Keywords: Protostars, Star forming regions, Star formation, Molecular clouds