Sazuna/UAT_keywords huggingface dataset:
Observational Signatures of a Previous Dynamical Instability in Multi-planet M-dwarf Systems. We identify observational signatures suggesting a history of dynamical instability in 26 out of 34 M-dwarf multi-planet systems containing no large planets. These systems may have primarily formed in a gas-rich environment, potentially hosted more planets, and were more compact. We extend previous simulations of the formation of the TRAPPIST-1 system to 100 Myr to test the stability of these systems without gas. We find that the absence of a strong mean motion resonance in the innermost planet pair and the absence of three-body resonances throughout the system are likely to result in the merging and ejection of planets after the gas disk disperses. The runs that experience such an instability tend to produce final systems with lower multiplicities, period ratios larger than two, increased orbital spacings, higher planetary angular momentum deficits, and slightly smaller mass ratios between adjacent planets. Remarkably, we find these same trends in the observations of M-dwarf multi-planet systems containing no large planets. Our work allows us to identify specific systems that may have experienced an instability, and it suggests that only ∼25% of these systems formed in their current observed state, while most systems were likely more compact and multiplicitous earlier in time. Previous research indicates that planets that have experienced a late-stage giant impact may potentially be more habitable than those that did not. With this in mind, we suggest systems around M-dwarfs that contain period ratios larger than two be given priority in the search for habitable worlds.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation, Extrasolar rocky planets
A Counterintuitive Correlation between Neutron Star Radii Inferred from Pulse Modeling and Surface Emission Beaming. Thermal X-ray emission from rotation-powered millisecond pulsars, shaped by gravitational lensing and the beaming of the surface radiation, provides critical insights into neutron star properties. This approach has been the focus of observations with the Neutron Star Interior Composition Explorer (NICER) mission. Using a semianalytic model to calculate pulse profiles, we investigate the effects of adopting incorrect beaming models on the inferred compactness of neutron stars. We demonstrate that assuming a more centrally peaked beaming pattern when fitting data from a more isotropic emitter leads to an underestimation of compactness in the case of two antipodal polar caps. We present a detailed analysis of this counterintuitive result, offering both qualitative insights and quantitative estimates. If the atmospheric heating in the millisecond pulsars observed with NICER is shallow, the inferred radii for these sources could be significantly overestimated, with important implications for neutron star structure and equation-of-state constraints.

Keywords: X-ray astronomy, Neutron stars, Millisecond pulsars
Accreting Binary Eccentricities Follow Predicted Equilibrium Values. We investigate observations of circumbinary disks (CBDs) to find evidence for an equilibrium eccentricity predicted by current binary accretion theory. Although stellar binary demographics in the Milky Way show no evidence for a preferred eccentricity for binary systems, we show that actively accreting systems lie on a predicted equilibrium eccentricity curve. We constrain our sample to only systems that have well-defined orbital parameters (e.g., eccentricity, mass ratio, inclination angle). We find observations are consistent with theory for stellar binaries that are aligned with the disk and that are separated enough that tidal circularization is negligible. This suggests that eccentricity in these systems evolves after the dissipation of the CBD, given the flat eccentricity distribution of binary systems in the Milky Way.

Keywords: Stellar accretion disks, Binary stars, Protoplanetary disks, Stellar accretion
Magnetic Activity Evolution of Solar-like Stars. II. S<SUB>ph</SUB>–Ro Evolution of Kepler Main-sequence Targets. There is now a large sample of stars observed by the Kepler satellite with measured rotation periods and photometric activity index Sph. We use this data, in conjunction with stellar interiors models, to explore the interplay of magnetism, rotation, and convection. Stellar activity proxies other than Sph are correlated with the Rossby number, Ro, or ratio of rotation period to convective overturn timescale. We compute the latter using the Yale Rotating Evolution Code stellar models. We observe different Sph–Ro relationships for different stellar spectral types. Though the overall trend of decreasing magnetic activity versus Rossby number is recovered, we find a localized dip in Sph around Ro/Ro⊙ ∼ 0.3 for the G and K dwarfs. F dwarfs show little to no dependence of Sph on Rossby number due to their shallow convective zone, further accentuated as Teff increases. The dip in activity for the G and K dwarfs corresponds to the intermediate rotation period gap, suggesting that the dip in Sph could be associated with the redistribution of angular momentum between the core and convective envelope inside stars. For G-type stars, we observe enhanced magnetic activity above the solar Rossby number. Compared to other Sun-like stars with similar effective temperature and metallicity, we find that the Sun's current level of magnetic activity is comparable to its peers and lies near the transition to increasing magnetic activity at high Rossby number. We confirm that metal-rich stars have a systematically larger Sph level than metal-poor stars, which is likely a consequence of their deeper convective zones.

Keywords: Magnetic stars, Late-type stars, Solar analogs, Stellar types, Low mass stars, Stellar oscillations, Asteroseismology
The Origin of a Preeruptive Magnetic Structure with Significant Nonneutralized Electric Current. The buildup of the preeruptive magnetic field configuration and the eruption onset mechanism are critical yet poorly understood in solar eruptions. Coronal structures like sigmoids and filaments have been identified as preeruptive magnetic structures; their associated preflare motions as well as preflare brightenings have been identified as precursor signatures, yet none of these definitively lead to eruptions, and the cause and effect is contentious. Most importantly, how the preeruptive coronal structure evolves with the photospheric magnetic field is elusive. Here we report the development of the photospheric nonneutralized electric current associated with the buildup of a preeruptive coronal structure observed as a bundle of hot low-lying coronal loops collectively taking a sigmoidal shape. The significant nonneutralized electric current appeared several hours ahead of the formation of the preeruptive structure. The buildup of the preeruptive structure in the corona was simultaneous with the gradual extension of the nonneutralized electric current in the photosphere. The synchronous evolution seemed to stop when intermittent brightening occurred along the preeruptive structure in the corona. The preflare brightening lasted for about 4 hr, with two ribbon-like structures matching the nonneutralized electric current. Eventually, the preeruptive structure evolved into a magnetic flux rope (MFR) and erupted. Quantitative measurements indicate that the significant nonneutralized electric current also flows through the footpoints of the erupting MFR, which are well identified by a pair of conjugate dimmings. The evolution of the photospheric nonneutralized electric current is demonstrated to signal the buildup of the preeruptive structure and the imminent eruption.

Keywords: Solar magnetic fields, Solar flares, Solar coronal mass ejections
Zonal Flow and Self-regulating Mechanism in a Hydrodynamic Disk. This study addresses key aspects of momentum transport in hydrodynamic disks, which is critical for understanding zonal flow generation and turbulence in compressible hydrodynamic disks. We find that nonlinear momentum/density transport leads to the formation of zonal flows from the Rossby wave instability in disks. We analytically derive the generation and location of zonal flows and describe a modified Taylor identity applicable to compressible disk flows. We further present a self-regulation model, revealing a dynamic interplay between zonal flow and fluctuations driven by Rossby wave instability that regulates the nonlinear saturation state. This theoretical framework contributes insights into the dynamics of disks such as protoplanetary disks, shedding light on the intricate processes governing momentum/density transport and the emergence of zonal flows in the saturation of protoplanetary disks.

Keywords: Hydrodynamical simulations, Astrophysical fluid dynamics, Protoplanetary disks, Hydrodynamics
Discovery of 15 New Pulsars at High Galactic Latitudes with FAST. We present the discovery and timing results for 15 pulsars discovered in a high-Galactic-latitude survey conducted with the Five-hundred-meter Aperture Spherical Telescope. The survey targeted a region as close as possible to the Galactic center, encompassing an area near the Galactic bulge. The newly discovered pulsars consist of 11 normal pulsars and four millisecond pulsars (MSPs). Among the MSPs, three are identified in binary systems with orbital periods of ∼3.1, 4.6, and 12.5 days, respectively. We have successfully obtained coherent timing solutions for three of the normal pulsars (PSRs J1745‑0059, J1746‑0156, and J1800‑0059). Furthermore, within our data set, we found that four pulsars (three new and one known) show mode-changing and/or subpulse-drifting phenomena. Comparing our discoveries with simulations of the Galactic disk and bulge MSP populations indicates that these new pulsars are most likely located in the disk. Nonetheless, our discoveries demonstrate that deep surveys at high Galactic latitudes have significant potential to enhance our understanding of the MSP population in the direction of the bulge.

Keywords: Millisecond pulsars, Binary pulsars, Radio pulsars
The Radio and Microwave Sky as Seen by Juno on its Mission to Jupiter. We present six nearly full-sky maps made from data taken by radiometers on the Juno satellite during its 5 yr flight to Jupiter. The maps represent integrated emission over ∼4% passbands spaced approximately in octaves between 600 MHz and 21.9 GHz. Long-timescale offset drifts are removed in all bands, and, for the two lowest-frequency bands, gain drifts are also removed from the maps via a self-calibration algorithm similar to the NPIPE pipeline used by the Planck Collaboration. We show that, after this solution is applied, statistical noise in the maps is consistent with thermal radiometer noise and expected levels of correlated noise on the gain and noise drift solutions. We verify our map solutions with several consistency tests and end-to-end simulations. We also estimate the level of systematic pixelization noise and polarization leakage via simulations.

Keywords: Interstellar dust, Cosmic microwave background radiation, Milky Way Galaxy, Interstellar synchrotron emission
Unusual Intraburst Variations of Polarization States in FRB 20210912A and FRB 20230708A: Effects of Plasma Birefringence?. Fast radio bursts (FRBs) are highly energetic events of short-duration intense radio emission, the origin of which remains elusive. Polarization of the FRB signals carries information about the emission source as well as the magnetoionic media the signal passes through before reaching terrestrial radio telescopes. Currently known FRBs show a diverse range of polarization, sometimes with complex features, making it challenging to describe them in a unified model. FRB 20230708A and FRB 20210912A are two bright and highly polarized (apparently) one-off FRBs detected in the Commensal Real-time ASKAP Fast Transients survey with the Australian Square Kilometre Array Pathfinder (ASKAP) that exhibit time-dependent conversion between linear and circular polarizations as well as intraburst (apparent) variation of the Faraday rotation measure. We investigate the intraburst temporal evolution of the polarization state of radio emission in these two events using the Poincaré sphere representation and find that the trajectories of the polarization state are well described by great circles on the Poincaré sphere. These polarization features may be signatures of a transition between two partially coherent orthogonal polarization modes or propagation through a birefringent medium. We find that the observed variations of the polarization states of these two FRBs are qualitatively consistent with a magnetospheric origin of the bursts and the effects of propagation through a birefringent medium with linearly polarized modes located close to the emission source—likely in the outer magnetosphere or near-wind region of a neutron star.

Keywords: Radio bursts, Time domain astronomy, Radio transient sources
No Evidence of Asymmetrically Enhanced Star Formation in Infalling Galaxies in UNIONS. Ram pressure stripping is a well-known environmental quenching mechanism that removes gas from galaxies infalling into groups and clusters. In some extreme examples of ram pressure stripping, galaxies with extended gas tails show evidence of enhanced star formation prior to quenching. In this work we use a sample of 5277 local satellite galaxies in which a stripped tail of gas has not necessarily been observed, to quantify the strength of ram-pressure-enhanced star formation and compare these results to a control sample of 8360 field galaxies. We use u-band imaging from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) as a star formation tracer and several metrics to quantify star formation asymmetry. We compare these results to environmental properties of the galaxy, such as their time since infall and host halo mass, to constrain the degree of ram-pressure-enhanced star formation as a function of environment. We find no significant differences between the satellite and the field samples. We further restrict our sample to galaxies which we most expect to be experiencing significant ram pressure but find no strong evidence of these galaxies having systematically enhanced star formation. Finally, we investigate the properties of the most asymmetric galaxies in our sample and again find no strong evidence of ram-pressure-induced star formation enhancement. We conclude that any star formation enhancement must be small for infalling galaxies, suggesting that this effect is either uncommon or short-lived.

Keywords: Galaxy clusters, Galaxy environments, Galaxy infall, Galaxy groups, Galaxy evolution, Galaxies
Estimating the Sonic Mach Number in the Interstellar Medium with Convolutional Neural Networks. Understanding the role of turbulence in shaping the interstellar medium (ISM) is crucial for studying star formation, molecular cloud evolution, and cosmic-ray propagation. Central to this is the measurement of the sonic Mach number (Ms), which quantifies the ratio of turbulent velocity to the sound speed. In this work, we introduce a convolutional-neural-network-(CNN)-based approach for estimating Ms directly from spectroscopic observations. The approach leverages the physical correlation between increasing Ms and the shock-induced small-scale fluctuations that alter the morphological features in intensity, velocity centroid, and velocity channel maps. These maps, derived from 3D magnetohydrodynamic turbulence simulations, serve as inputs for the CNN training. By learning the relationship between these structural features and the underlying turbulence properties, CNNs can predict Ms under various conditions, including different magnetic fields and levels of observational noise. The median uncertainty of the CNN-predicted Ms ranges from 0.5 to 1.5 depending on the noise level. While intensity maps offer lower uncertainty, channel maps have the advantage of predicting the 3D Ms distribution, which is crucial in estimating 3D magnetic field strength. Our results demonstrate that machine-learning-based tools can effectively characterize complex turbulence properties in the ISM.

Keywords: Interstellar line emission, Convolutional neural networks, Interstellar plasma, Intercloud medium, Magnetohydrodynamical simulations
Systematic Study of the Composition of Type I X-Ray Burst Ashes: Neutron Star Structure versus Reaction Rate Uncertainties. In this study, we calculate for the first time the impacts of neutron star (NS) structure on the type I X-ray burst ashes using the MESA code. We find an increased mass fraction of the heavier elements with increasing surface gravity (increased mass or decreased radius), resulting in a higher average mass number (Aash) of burst ashes (except for higher-mass NSs due to the competition between the envelope temperature and the recurrence time). The burst strength (α) increases as the surface gravity increases, which indicates the positive correlation between Aash and α with changes in surface gravity. If the α value is higher, heavier p-nuclei should be produced by the type I X-ray burst nucleosynthesis. Besides, the effects of various burst input parameters, e.g., base heating (Qb), metallicity (Z), and some new reaction rates, are calculated for comparison. We find that the heavier nucleus synthesis is inversely correlated with the base heating/metallicity; the smaller the base heating/metallicity, the greater the mass fraction of the heavier elements. The α value decreases as Qb or Z decreases, which also indicates the positive correlation between Aash and α with variation in Qb or Z. The new reaction rates from the (p, γ) reactions on 17F, 19F, 26P, 56Cu, and 65As and the (α, p) reaction on 22Mg have only minimal effects on burst ashes. In hydrogen-rich X-ray binary systems, nuclei heavier than 64Ge are fertile, produced with larger NS mass, smaller NS radius, smaller base heating, and smaller metallicity.

Keywords: Neutron stars, Low-mass x-ray binary stars, Reaction rates, X-ray bursts
Argon in β Pictoris–Entrapment and Release of Volatile in Disks. Chemical compositions of planets reveal much about their formation environments. Such information is well sought-after in studies of solar system bodies and extrasolar ones. Here, we investigate the composition of planetesimals in the β Pictoris debris disk by way of its secondary gas disk. We are stimulated by the recent JWST detection of an Ar II emission line and aim to reproduce extensive measurements from the past four decades. Our photoionization model reveals that the gas has to be heavily enriched in C, N, O, and Ar (but not S and P), by a uniform factor of about 100 relative to other metals. Such an abundance pattern is both reminiscent of, and different from, that of Jupiter's atmosphere. The fact that Ar, the most volatile and therefore the hardest to capture into solids, is equally enriched as C, N, and O suggests that the planetesimals were formed in a very cold region (T ≤ 20–35 K), possibly with the help of entrapment if water ice is overabundant. In the debris disk phase, these volatiles are preferentially outgassed from the dust grains, likely via photodesorption. The debris grains must be "dirty" aggregates of icy and refractory clusters. Lastly, the observed strength of the Ar II line can only be explained if the star β Pic (a young A6V star) has sizable chromospheric and coronal emissions, on par with those from the modern Sun. In summary, observations of the β Pic gas disk rewind the clock to reveal the formation environment of planetesimals.

Keywords: Photoionization, A stars, Stellar chromospheres, Chemical abundances, Protoplanetary disks, Planetesimals, Stellar coronae, Debris disks
Redshift Distributions of Fast Radio Bursts Inferred Using Clustering in Dispersion Measure Space. Fast radio bursts (FRBs), millisecond-duration radio transient events, possess the potential to serve as excellent cosmological probes. The FRB redshift distribution contains information about the FRB sources, providing key constraints on the types of engines. However, it is quite challenging to obtain the FRB redshifts due to the poor localization and the faintness of the host galaxies. This reality severely restricts the application prospects and study of the physical origins of FRBs. We propose that the clustering of observed FRBs can be an effective approach to address this issue without needing to accurately model dispersion measure (DM) contributions from the host galaxy and the immediate environment of the source. Using the clustering of 5 × 107 simulated FRBs from future observations with sensitivity similar to the second phase of the Square Kilometre Array, we show that in extragalactic DM space, the redshift distributions can be accurately reconstructed, and the mean redshift for FRBs between 384.8 and 1450.3 pc cm‑3 can be constrained to ∼0.001 ± 0.003(1 + z). The results demonstrate the potential of FRB clustering to constrain redshift distributions and provide valuable insights into FRB source models and cosmological applications.

Keywords: Large-scale structure of the universe, Astronomy data analysis, Radio transient sources
RUBIES: JWST/NIRSpec Resolves Evolutionary Phases of Dusty Star-forming Galaxies at z ∼ 2. The dearth of high-quality spectroscopy of dusty star-forming galaxies (DSFGs)—the main drivers of the assembly of dust and stellar mass at the peak of activity in the Universe—greatly hinders our ability to interpret their physical processes and evolutionary pathways. We present JWST/NIRSpec observations from RUBIES of four submillimeter-selected, Atacama Large Millimeter/submillimeter Array (ALMA)-detected DSFGs at cosmic noon, z ∼ 2.3–2.7. While photometry uniformly suggests vigorous ongoing star formation for the entire sample in line with canonical DSFGs, the spectra differ: one source has spectroscopic evidence of an evolved stellar population, indicating a recent transition to a post-starburst phase, while the remainder show strong spectroscopic signatures of ongoing starbursts. All four galaxies are infrared luminous (log10 LIR/L⊙ &gt; 12.4), massive (log10 M⋆/M⊙ &gt; 11), and very dust obscured (AV ∼ 3–4 ABmag). Leveraging detections of multiple Balmer and Paschen lines, we derive an optical attenuation curve consistent with Calzetti overall, yet an optical extinction ratio RV ∼ 2.5, potentially indicating smaller dust grains or differences in star-dust geometry. This case study provides some of the first detailed spectroscopic evidence that the DSFGs encompass a heterogeneous sample spanning a range of star formation properties and evolutionary stages, and illustrates the advantages of synergistic JWST and ALMA analysis of DSFGs.

Keywords: Interstellar dust, Submillimeter astronomy, Galaxy spectroscopy, Starburst galaxies