Sazuna/UAT_keywords huggingface dataset:
Semi-analytical Model for the Dynamical Evolution of Planetary Systems via Giant Impacts. In the standard model of terrestrial planet formation, planets are formed through giant impacts of planetary embryos after the dispersal of the protoplanetary gas disk. Traditionally, N-body simulations have been used to investigate this process. However, they are computationally too expensive to generate sufficient planetary populations for statistical comparisons with observational data. A previous study introduced a semi-analytical model that incorporates the orbital and accretionary evolution of planets due to giant impacts and gravitational scattering. This model succeeded in reproducing the statistical features of planets in N-body simulations near 1 au around solar-mass stars. However, this model is not applicable to close-in regions (around 0.1 au) or low-mass stars because the dynamical evolution of planetary systems depends on the orbital radius and stellar mass. This study presents a new semi-analytical model applicable to close-in orbits around stars of various masses, validated through comparison with N-body simulations. The model accurately predicts the final distributions of planetary mass, semimajor axis, and eccentricity for wide ranges of orbital radius, initial planetary mass, and stellar mass, with significantly reduced computation time compared to N-body simulations. By integrating this model with other planet-forming processes, a computationally low-cost planetary population synthesis model can be developed.

Keywords: Planetary system evolution, Exoplanet astronomy, Exoplanet formation, Planetary dynamics, Planet formation
A Systematic Search for MeV–GeV Pulsar Wind Nebulae without Gamma-Ray Detected Pulsars. An increasing number of pulsar wind nebulae (PWNe) are being identified in the TeV band by ground-based Imaging Air Cherenkov Telescopes such that they constitute the dominant source class of Galactic TeV emitters. However, MeV–GeV PWN counterparts are still largely lacking. To date, only a dozen PWNe are identified by the Fermi–Large Area Telescope (LAT) in the MeV–GeV band. Most PWNe are located along the Galactic plane embedded within the prominent, diffuse Galactic γ-ray emission, which makes these sources difficult to disentangle from the bright diffuse background. We present a systematic search for γ-ray counterparts to known PWNe in the 300 MeV–2 TeV energy band using the Fermi–LAT. We target the locations of previously identified PWNe that lack detected Fermi–LAT pulsars to minimize associated pulsar contamination. The sample includes six previously identified Fermi PWNe and eight Fermi–LAT sources associated with PWNe. We report the analysis of 58 regions of interest and classify Fermi–LAT detected sources as either a likely PWN or a candidate PWN counterpart based on their morphological and spectral characteristics across the broadband spectrum. There are nine unidentified Fermi–LAT sources that we consider as likely PWN counterparts, which, if confirmed to be PWNe, would greatly increase the PWN population detected by the Fermi–LAT from 12 to 21. The remaining Fermi–LAT detected sources are considered weaker PWN candidates. A second approach in the systematic search for γ-ray emitting PWNe will involve studying the off-pulse phases of Fermi–LAT detected pulsars for the presence of an obscured PWN and will be reported in a subsequent paper.

Keywords: Gamma-ray astronomy, Core-collapse supernovae, High energy astrophysics, Pulsar wind nebulae
Planetary Obliquity Excitation through Pre-main-sequence Stellar Evolution. A planet's axial tilt ("obliquity") substantially affects its atmosphere and habitability. It is thus essential to comprehend the various mechanisms that can excite planetary obliquities, particularly at the primordial stage. Here, we explore planetary obliquity excitation induced by the early evolution of the host star. A young, distended star spins rapidly, resulting in a large gravitational quadrupole moment that induces nodal recession of the planet's orbit. As the star contracts and spins down, the nodal recession frequency decreases and can cross the planet's spin axis precession frequency. An adiabatic encounter results in the planet's capture into a secular spin–orbit resonance and excites the obliquity to large values. We find that planets within a ≲ 1 au are most affected, but adiabatic capture depends on the initial stellar radius and spin rate. The overall picture is complicated by other sources of perturbation, including the disk, multiple planets, and tidal dissipation. Tides make it such that stellar oblateness-induced obliquity excitation is transient since tidal perturbations cause the resonance to break once high obliquities are reached. However, this early transient excitation is important because it can prime planets for long-term capture in a secular spin–orbit resonance induced by planet–planet interactions. Thus, although stellar oblateness-induced resonances are short-lived, they facilitate the prevalence of long-lived nonzero obliquities in exoplanets.

Keywords: Exoplanet dynamics, Early stellar evolution, Exoplanets, Exoplanet tides, Star-planet interactions
Varstrometry for Off-nucleus and Dual Sub-Kpc AGN (VODKA): A Mix of Singles, Lenses, and True Duals at Cosmic Noon. Dual active galactic nuclei (AGNs), a phase in some galaxy mergers during which both central supermassive black holes (SMBHs) are active, are expected to be a key observable stage leading up to SMBH mergers. Constraining the population of dual AGNs in both the nearby and high-z Universe has proven to be elusive until very recently. We present a multiwavelength follow-up campaign to confirm the nature of a sample of 20 candidate dual AGNs at cosmic noon (z ∼ 2) from the VODKA sample. Through a combination of Hubble Space Telescope and Very Large Array imaging, we refute the possibility of gravitational lensing in all but one target. We find evidence of dual AGNs in three systems, while seven exhibit a single AGN in galaxy pairs, through either strong radio emission or ancillary emission-line data. The remaining systems are confirmed as either quasar‑star superpositions (seven) or nonlensed pairs (two) that require further investigations to establish AGN activity. Among the systems with radio detections, we find a variety of radio spectral slopes and UV/optical colors suggesting that our sample contains a range of AGN properties, from obscured radio-quiet objects to those with powerful synchrotron-emitting jets. This study presents one of the largest dedicated multiwavelength follow-up campaigns to date searching for dual AGNs at high redshift. We confirm several of the highest-z systems at small physical separations, thus representing some of the most evolved dual-AGN systems at the epoch of peak quasar activity known to date.

Keywords: Black hole physics, Double quasars, Quasars, Surveys, Active galaxies
Comparative Statistical Analysis of Prompt and Afterglow X-Ray Flares in Gamma-Ray Bursts: Insights into Extended Central Engine Activity. Gamma-ray bursts (GRBs) are the most energetic phenomena in the Universe, characterized by prompt gamma-ray emission followed by multiwavelength afterglows. X-ray flares, observed during the afterglow phase, are generally believed to originate from the prolonged activity of the central engine, though direct evidence has been scarce. In this study, we present a comprehensive statistical analysis of X-ray flares from 315 GRBs observed by the Swift/X-ray Telescope over nearly two decades. We categorize flares into prompt flares (occurring during the prompt emission phase) and afterglow flares and compare their temporal and luminosity properties. Our analysis reveals that both types of flares exhibit similar morphological characteristics, with prompt flares being brighter and occurring earlier than afterglow flares. We find strong correlations between flare parameters, such as peak time, duration, and luminosity, which follow consistent patterns across both flare types. These findings suggest that X-ray flares, regardless of their timing, share a common origin in the central engine's activity. Our results imply that the central engine's activity duration extends beyond the prompt gamma-ray emission phase, highlighting the importance of considering X-ray flares when studying GRB progenitors and central engine properties. This work provides robust statistical evidence supporting the central engine origin of X-ray flares and underscores the need for future observations with missions like the Space-based multi-band astronomical Variable Objects Monitor and Einstein Probe to further elucidate the nature of GRB central engines.

Keywords: Gamma-ray bursts
CLUES. III. Do User Choices Impact the Results of SED Fitting? Tests of "Off-the-shelf" Stellar Population and Dust Extinction Models in the CLUES Sample. The simple stellar population models produced by stellar population and spectral synthesis (SPS) codes are used as spectral templates in a variety of astrophysical contexts. In this paper, we test the predictions of four commonly used stellar population synthesis codes (YGGDRASIL, BPASS, FSPS, and a modified form of GALAXEV, which we call GALAXEVneb) by using them as spectral templates for photometric spectral energy distribution (SED) fitting with a sample of 18 young stellar clusters. All clusters have existing Hubble Space Telescope (HST) Cosmic Origins Spectrograph far-UV spectroscopy that provides constraints on their ages as well as broadband photometry from HST Advanced Camera for Surveys and Wide Field Camera 3. We use model spectra that account for both nebular and stellar emission, and additionally test four extinction curves at different values of R  V . We find that for individual clusters, choice of extinction curve and SPS model can introduce significant scatter into the results of SED fitting. Model choice can introduce scatter of 34.8 Myr in age, a factor of 9.5 in mass, and 0.40 mag in extinction. Extinction curve choice can introduce scatter of up to a factor of 32.3 Myr in age, a factor of 10.4 in mass, and 0.41 mag in extinction. We caution that because of this scatter, one-to-one comparisons between the properties of individual objects derived using different SED fitting setups may not be meaningful. However, our results also suggest that SPS model and extinction curve choice do not introduce major systematic differences into SED fitting results when the entire cluster population is considered. The distribution of cluster properties for a large enough sample is relatively robust to user choice of SPS code and extinction curve.

Keywords: Astronomy data modeling, Stellar populations, Young star clusters, Ultraviolet spectroscopy, Interstellar dust extinction, Spectral energy distribution, Broad band photometry
ALMA Lensing Cluster Survey: Physical Characterization of Near-infrared-dark Intrinsically Faint ALMA Sources at z = 2─4. We present results from Atacama Large Millimeter/submillimeter Array (ALMA) spectral line-scan observations at 3 mm and 2 mm bands of three near-infrared-dark (NIR-dark) galaxies behind two massive lensing clusters MACS J0417.5-1154 and RXC J0032.1+1808. Each of these three sources is a (sub)millimeter faint (delensed S1.2 mm &lt; 1 mJy) triply lensed system originally discovered in the ALMA Lensing Cluster Survey. We have successfully detected CO and [C I] emission lines and confirmed that their spectroscopic redshifts are z = 3.652, 2.391, and 2.985. By utilizing a rich multiwavelength data set, we find that the NIR-dark galaxies are located on the star formation main sequence in the intrinsic stellar mass range of log (M*/M⊙) = 9.8─10.4, which is about 1 order of magnitude lower than that of typical submillimeter galaxies (SMGs). These NIR-dark galaxies show a variety in gas depletion times and spatial extent of dust emission. One of the three is a normal star-forming galaxy with gas depletion time consistent with a scaling relation, and its infrared surface brightness is an order of magnitude smaller than that of typical SMGs. Since this galaxy has an elongated axis ratio of ∼0.17, we argue that normal star-forming galaxies in an edge-on configuration can be heavily dust-obscured. This implies that existing deep WFC3/F160W surveys may miss a fraction of typical star-forming main-sequence galaxies due to their edge-on orientation.

Keywords: Starburst galaxies, Strong gravitational lensing, High-redshift galaxies, Millimeter-wave spectroscopy
Ultradense Dark Matter Halos with Poisson Noise from Stellar-mass Primordial Black Holes. In this work, we investigate the impact of Poisson noise from stellar-mass primordial black holes (PBHs) on the formation of ultradense dark matter halos (UDMHs). Our findings reveal that the discrete spatial distribution of PBHs significantly enhances small-scale density fluctuations, particularly for massive stellar-mass PBHs. Our results indicate that the modified power spectrum, incorporating both adiabatic and isocurvature contributions from PBH-induced Poisson noise, strongly depends on PBH mass and fraction. Specifically, increasing PBH mass shifts the differential mass function of UDMHs toward higher masses, while variations in the suppression parameter n modulate the efficiency of UDMH formation at small scales. For lower values of n, our findings show a significant boost in UDMH abundance, favoring multicomponent dark matter scenarios. Conversely, at higher values of n, the predicted UDMH distributions align more closely with single-component models dominated by stellar-mass PBHs. Furthermore, our analysis demonstrates that more realistic halo mass functions, which account for angular momentum and dynamical friction, consistently predict higher UDMH abundances compared to the traditional Press–Schechter formalism.

Keywords: Cold dark matter, Primordial black holes
Semianalytical Model for the Dynamical Evolution of Planetary Systems. II. Application to Systems Formed by a Planet Formation Model. The standard formation model of close-in low-mass planets involves efficient inward migration followed by growth through giant impacts after the protoplanetary gas disk disperses. While detailed N-body simulations have enhanced our understanding, their high computational cost limits statistical comparisons with observations. In our previous work, we introduced a semianalytical model to track the dynamical evolution of multiple planets through gravitational scattering and giant impacts after the gas disk dispersal. Although this model successfully reproduced N-body simulation results under various initial conditions, our validation was still limited to cases with compact, equally spaced planetary systems. In this paper, we improve our model to handle more diverse planetary systems characterized by broader variations in planetary masses, semimajor axes, and orbital separations and validate it against recent planet population synthesis results. Our enhanced model accurately reproduces the mass distribution and orbital architectures of the final planetary systems. Thus, we confirm that the model can predict the outcomes of postgas disk dynamical evolution across a wide range of planetary system architectures, which is crucial for reducing the computational cost of planet formation simulations.

Keywords: Extrasolar rocky planets, Planet formation, Planetary system evolution, Exoplanets
A Multispacecraft Analysis and Modeling of Type III Radio Burst Exciter Deceleration in Inhomogeneous Heliospheric Plasma. Electron beams accelerated in solar flares and escaping from the Sun along open magnetic field lines can trigger intense radio emissions known as type III solar radio bursts. Utilizing observations by Parker Solar Probe (PSP), STEREO-A, Solar Orbiter, and Wind spacecraft, the speeds and accelerations of type III exciters are derived for simple and isolated type III solar bursts. For the first time, simultaneous four spacecraft observations allow us to determine positions and correct the resulting velocities and accelerations for the location between the spacecraft and the apparent source. We observe velocities and acceleration to change as u(r) ∝ r‑0.37 ± 0.14 and a(r) ∝ r‑1.71 ± 0.20 with radial distance from the Sun r. To explain the electron beam deceleration, we develop a simple gas-dynamic description of the electron beam moving through plasma with monotonically decreasing density. The model predicts that the beam velocity decreases as u(f) ∝ f1/4(r), so the acceleration changes ∝r‑1.58 (and speed as ∝r‑0.29) for the plasma density profile n(r) ∝ r‑2.3. The deceleration is consistent with the average observation values corrected for the type III source locations. Intriguingly, the observations also show differences in velocity and acceleration of the same type III observed by different spacecraft. We suggest the difference could be related to the additional time delay caused by radio-wave scattering between the spacecraft and the source.

Keywords: Solar energetic particles, Space weather, Solar radio emission
Frequency and Abundance of Binary Supermassive Black Holes from Optical Variability Surveys (Fabulovs): Hubble Space Telescope Imaging of Radial-velocity-selected Binary Candidates. Subparsec binary supermassive black holes (BSBHs) should be common from galaxy mergers, yet direct evidence has been elusive. We present Hubble Space Telescope (HST)/WFC3IR F160W imaging for a sample of eight candidate subparsec BSBHs at redshifts z ∼ 0.1─0.5, as well as cross-comparison with a sample of ordinary quasars with archival HST/WFC3 IR F160W images. These eight candidate subparsec BSBHs were identified from multiepoch spectroscopic surveys of quasars (including both typical quasars and those with single-peaked velocity-offset broad lines), whose broad Hβ lines are significantly offset (by ≳ a few hundred kilometers per second) from the systemic redshifts. We directly test the prediction that the host galaxies of BSBHs would have a higher fraction of disturbed morphologies and younger stellar bulges from recent interactions than those of control quasars. After careful subtraction of the central quasar light, our candidate BSBH hosts show a statistically undifferentiated distribution of host asymmetry, indicative of a similar fraction of recent mergers. While a significantly larger sample is needed to place this result on a much firmer statistical ground, it opens questions as to the timescale differences between galaxy merger and BSBH formation, or the efficacy of the radial-velocity-shift-based selection of subparsec BSBH candidates.

Keywords: Galaxy evolution, Active galactic nuclei, Galaxy mergers, AGN host galaxies
Uncalibrated Cosmic Standards as a Robust Test on Late-time Cosmological Models. We present an assumption-minimized framework for testing late-time cosmological models using uncalibrated cosmic standards (UCS)—including standard rulers and standard candles—without relying on absolute calibrations. The method exploits a tight, model-insensitive correlation between the sound horizons at recombination and the drag epoch. By avoiding dependence on prerecombination physics and the amplitude of the cosmic microwave background (CMB) power spectra, the UCS framework reduces potential early-Universe biases while retaining much of the constraining power of full analyses. Applying UCS to the recent dynamical dark energy study that reported deviations from ΛCDM, we find the constraints shift systematically toward the ΛCDM case. If this shift is physical, it may result from the omission of some prerecombination physical processes that influence the scale dependence of the CMB spectra. We also observe a mild tension between uncalibrated standard rulers and candles, which can be largely mitigated by introducing a redshift-dependent magnitude bias in the Type Ia supernovae data. Our results highlight the importance of isolating postrecombination observables for testing late-time models in the era of precision cosmology, positioning UCS analysis as a robust framework for upcoming galaxy surveys.

Keywords: Cosmology, Cosmic microwave background radiation, Standard candles, Baryon acoustic oscillations, Dark energy
Bar-driven Streaming Motions Mimic a Massive Bulge in the Inner Milky Way. The circular speed curve of the Milky Way provides a key constraint on its mass distribution, reflecting the axisymmetric component of the gravitational potential. This is especially critical in the inner Galaxy (R ≲ 4 kpc), where nonaxisymmetric structures, such as the stellar bar and nuclear stellar disk, strongly influence dynamics. However, significant discrepancies remain between circular speed curves inferred from stellar dynamical modeling and those derived from the terminal-velocity method applied to gas kinematics. To investigate this, we perform three-dimensional hydrodynamic simulations including cooling, heating, star formation, and feedback, under a realistic gravitational potential derived from stellar dynamical models calibrated to observational data. This potential includes the Galactic bar, stellar disks, dark matter halo, nuclear stellar disk, and nuclear star cluster. We generate synthetic longitude─velocity diagrams and apply the terminal-velocity method to derive circular speeds. The simulated gas reproduces the observed terminal-velocity envelope, including a steep inner rise. We find this feature arises from bar-driven noncircular motions, which cause the terminal-velocity method to overestimate circular speeds by up to a factor of 2 at R ∼ 0.4 kpc, and enclosed mass by up to a factor of 4. These results suggest that inner gas-based rotation curves can significantly overestimate central mass concentrations. The steep inner rise in gas-derived circular speeds does not require a massive classical bulge but can be explained by bar-induced streaming motions. Rather than proposing a new mechanism, our study provides a clear, Milky Way─specific demonstration of this effect, emphasizing the importance of dynamical modeling that explicitly includes noncircular motions for accurate mass inference in the inner Milky Way.

Keywords: Hydrodynamical simulations, Milky Way dark matter halo, Galactic center, Milky Way dynamics, Milky Way rotation, Galactic bulge, Dark matter, Galactic bar
The Fate of EMRI-IMRI Pairs in Active Galactic Nucleus Accretion Disks: Hydrodynamical and Three-body Simulations. Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs) are important gravitational wave (GW) sources for the Laser Interferometer Space Antenna. It has recently been suggested that EMRIs and IMRIs can both form in the accretion disk of an active galactic nucleus (AGN). Considering the likely encounter between a stellar-mass black hole (sBH) and an intermediate-mass black hole (IMBH) during migration in the AGN disk, P. Peng &amp; X. Chen (Paper I) showed that a gap-opening IMBH can drive a surrounding sBH to migrate synchronously. In this work, we extend the study in Paper I with a more sophisticated model. We first use 3D hydrodynamical simulations to study the coevolution of the disk and the migration of an sBH in the vicinity of an IMBH. We find that the gaseous torque, together with the tidal torque exerted by the IMBH, can drive synchronized migration until ∼10 Schwarzschild radii from the central supermassive black hole. We further use a relativistic three-body code to study the final fate of the sBH in the GW-dominated regime. We find that the sBH can be either captured or kicked out by the IMBH, which will result in either two subsequent IMRIs or an EMRI followed by an IMRI. These events will bring rich information about the formation and evolution of sBHs and IMBHs in AGNs.

Keywords: Intermediate-mass black holes, Gravitational waves, Active galactic nuclei, Stellar mass black holes