Sazuna/UAT_keywords huggingface dataset:
The Jetted Tidal Disruption Event AT 2022cmc: Investigating Connections to the Optical Tidal Disruption Event Population and Spectral Subclasses through Late-time Follow-up. AT 2022cmc is the first on-axis jetted tidal disruption event (TDE) to be discovered at optical wavelengths. The optically bright nature of AT 2022cmc presents an unprecedented opportunity to place this jetted TDE in the context of the larger optically selected thermal TDE population and explore potential connections to optical TDE subclasses, particularly the class of luminous TDEs that lack optical spectral features. In this work, we present late-time optical observations of AT 2022cmc, both imaging and spectroscopy, that extend the optical dataset to ∼160 days from the first detection in the observed frame. The light curve clearly evolves from red to blue, which we interpret as a transition from a nonthermally dominated spectral energy distribution (SED) to thermally dominated SED. By accounting for the nonthermal emission evident in the optical SED at early times, we extract the properties of the thermal emission and compare to a sample of optically selected thermal TDEs. We find that the properties of AT 2022cmc are consistent with previous correlations found for the evolution and properties of thermal TDEs, with the thermal properties of AT 2022cmc aligning with the class of featureless and luminous TDEs. The confirmation of this similarity motivates the importance of prompt and multiwavelength follow-up of featureless and luminous TDEs in order to further explore the connection they have with jetted TDEs.

Keywords: Tidal disruption, Relativistic jets, Transient sources, Black holes
Trends in the Population of Binary Black Holes Following the Fourth Gravitational-wave Transient Catalog: A Data-driven Analysis. Current models of binary black hole distributions are difficult to interpret because inferences hinge on modeling choices, which can mask or mimic real structure. The maximum population likelihood "  formalism" provides a means to investigate features in the distribution of binary black holes using only data—no model required. It tells us whether inferred features are truly present in the data or whether they arise from model misspecification. It also provides guidance for developing new models by highlighting previously unnoticed features. We utilize the   formalism to examine the binary black hole population in the LIGO─Virgo─KAGRA (LVK) Gravitational-Wave Transient Catalog (GWTC-4). Our analysis supports the existence of a gap around 45 M⊙ in the secondary black hole mass distribution and identifies a widening in the distribution of the effective inspiral spin parameter χeff at ≍45 M⊙ as recently reported by H. Tong et al. We find support for a previously reported anticorrelation between χeff and mass ratio. However, this may be a spurious correlation arising from misspecification of the joint distribution of black hole masses. Furthermore, we identify support for dimensionless black hole spin magnitudes at χ ≍ 0.2 and χ ≍ 0.7. The data support the existence of a correlation between spin magnitudes χ1 and χ2, though subsequent study is required to determine whether this is statistically significant. The accompanying data release includes   samples, which can be used to compare theoretical predictions to LVK data and to assess assumptions in parameterized models.

Keywords: Gravitational wave astronomy, Black holes
The Role of Preprocessing in Tidal Feature Formation within Galaxy Clusters. We investigate the formation of tidal features, such as tidal tails, streams, and shell-like structures, composed of stars stripped from satellites within galaxy clusters. For this, we use multiresolution cosmological N-body simulations with the "galaxy replacement technique." We find that the fraction of satellites with tidal features increases with the mass of the host cluster but is not related to the dynamical state of the cluster. Although the strong tidal field in the cluster environment accelerates mass loss of the satellites, only 20% of tidal-featured galaxies form their tidal features purely due to tidal perturbations in the cluster environment, without any interactions with other galaxies before falling into the cluster. In contrast, the majority (80%) are affected by preprocessing, as they experienced merger events with other galaxies before falling into the cluster. Among this preprocessing population, 45% of all tidal-featured galaxies form their tidal features after passing the pericenter of the cluster, and are affected by both preprocessing and the tidal field of the cluster, whereas 35% of all tidal-featured galaxies form their tidal features before reaching the pericenter, primarily due to preprocessing. Notably, this fraction increases from 35% to 40%─50% when we focus only on galaxies with brighter surface brightness limits or higher stellar masses. Therefore, our results highlight that preprocessing is an important channel for forming tidal features within clusters. However, the importance of preprocessing may be further amplified in observations, since more massive galaxies, which are commonly associated with preprocessing, are preferentially detected.

Keywords: Galaxy clusters, Galaxy formation, Computational methods, Galaxy evolution, Tidal interaction
Long-lived Magnetic Switchbacks Tracked across 0.32 au through BepiColombo─Solar Orbiter Radial Alignment. Magnetic switchbacks, often observed in the near-Sun solar wind, have received increased interest in recent years due to their potential role in mediating the heating and acceleration of the solar wind, but their origin remains debated. In this work, we present a coordinated observation of a switchback cluster by BepiColombo (0.35 au) and Solar Orbiter (0.67 au), obtained during the alignment between 2021 October 6 and 8, which enabled the first direct investigation of switchback evolution across heliocentric distances. In particular, the stream observed by the spacecraft can be tracked back to the boundary of an equatorial coronal hole. Large-scale switchbacks exhibit strong sublinear expansion, thus appearing almost unevolved in morphology during the propagation when the spacecraft cutting-angle effect is taken into account. The stable magnetic configuration of the analyzed switchbacks suggests that they can be identified as small-scale flux ropes. Indeed, for shear-driven instabilities triggered by stream interaction with the background slow wind, short-living (one eddy turnover time, τ ∼ 1 hr) switchbacks would be expected compared to the travel time from BepiColombo to Solar Orbiter (∼38 hr). These findings provide critical insights on switchback origin and evolution, potentially constraining future phenomenologies on their formation. A useful consequence of our observations is that statistical analyses on switchback evolution should always account for the cutting-angle effect.

Keywords: Solar wind, Interplanetary physics
Simulations of Tidal Disruption of Supernova in Galaxy Nuclear Region: A Novel Model for Ambiguous Nuclear Transients. An increasing number of ambiguous nuclear transients, including some extreme nuclear transients with very shallow light-curve declines and weak active galactic nucleus (AGN) activity in their host galaxies, have been reported. Stars that form in or are captured by AGN disks will grow and migrate inward, potentially exploding as supernovae once the inner cold accretion disk disappears in low-luminosity AGNs. We propose that the tidal disruption of a supernova (TDS) by a supermassive black hole (SMBH) can produce nuclear transients that are more energetic and evolve more slowly than typical tidal disruption events (TDEs), without the black hole mass limit as in TDEs. In this scenario, the SMBH captures the supernova ejecta, which subsequently self-intersects and circularizes into an accretion disk. Based on hydrodynamical simulations, we find that the accretion rate of the TDS disk exhibits a slow decline that can last for months to decades. The peak accretion rate of a typical core-collapse supernova scenario can exceed the Eddington limit for SMBHs with MBH ≲ 107.5 M⊙, while it remains sub-Eddington for more massive SMBHs. This model provides a mechanism for triggering an energetic TDE-like flare with luminosity ≳1045 erg s−1 in weak AGNs even with SMBH masses much larger than 108 M⊙ or triggering turn-on changing-look AGNs.

Keywords: Accretion, Hydrodynamics, Tidal disruption, Active galactic nuclei, Supernovae
A Wind-driven Origin for the Firework Morphology of the Supernova Remnant Pa 30. Pa 30—the likely remnant of the Galactic Type Iax supernova of 1181 AD—displays an unusual, firework-like morphology, consisting of radial filaments extending from a common center, where a white dwarf (WD) currently drives a very fast wind (speed ≳104 km s−1). We propose the filaments arose from the Rayleigh─Taylor-unstable nature of the interface between the circumstellar medium (CSM) and the shocked wind launched by the natal WD; the filaments then elongated intact due to the Kelvin─Helmholtz-stable nature of the large initial density contrast between the wind and CSM, supplemented by the slowly declining wind density profile (relative to homologously expanding ejecta). To support this interpretation, we present two-dimensional hydrodynamical simulations and derive the filament properties, including their speed, density, and temperature, all of which are consistent with observations. We suggest the filaments elongate until the wind and CSM densities become comparable at the contact discontinuity, which occurs within 1─10 yr, and then truncate because the Rayleigh─Taylor instability (RTI) halts. The subsequent Kelvin─Helmholtz instability growth timescale across the current width of the filaments is longer than the age of Pa 30, so they remain intact. The filament-less central region in Pa 30 is therefore more likely a consequence of the finite timescale over which the RTI operates, rather than a wind termination shock. In general, firework-like filaments may form in other systems, provided there is a sufficiently large density contrast between the ejecta and its surroundings.

Keywords: Analytical mathematics, Shocks, Type Ia supernovae, Hydrodynamics
What is the Most Massive Gravitational-wave Source?. In the presence of significant measurement uncertainties, the events that appear to be the most extreme are very likely to be those exhibiting the greatest statistical fluctuations. It is therefore particularly important to exercise care when interpreting such events and to use the entire observed population for context. Here, I attempt to pedagogically illustrate this using the example of the most massive binary black hole so far detected in gravitational-wave data, GW231123. I argue that its total mass may be significantly lower than  238−49+28  M⊙ as reported by the LIGO─Virgo─KAGRA collaborations. The maximum total binary black hole mass from an analysis of the entire detected population is below 170 M⊙ if the same priors that are used for individual event analyses in the GWTC catalogs, including for the analysis of GW231123, are applied to the population as a whole. However, this value is very sensitive to assumptions about the population distribution.

Keywords: Gravitational wave astronomy, Astrophysical black holes
Cosmographic Footprints of Dynamical Dark Energy. We introduce a novel cosmographic framework to trace the late-time kinematics of the Universe without assuming any underlying dynamics. The method relies on generalized Padé (2, 1) expansions around arbitrary pivot redshifts, which, compared to state-of-the-art calculations, reduce truncation errors by up to two orders of magnitude at high redshift and yield more precise constraints by defining cosmographic parameters exactly where the data lie. This avoids extrapolations, mitigates degeneracies, and enables a clean disentangling of their effects. Using the latest low-redshift datasets, we center the generalized expansion in multiple bins across z ∈ [0, 1] and obtain precise constraints on the redshift evolution of cosmographic parameters. We find that all key parameters deviate from their ΛCDM predictions in a redshift-dependent way that can be naturally explained within dynamical dark energy scenarios. The deceleration parameter q(z) follows a redshift evolution consistent with the Chevallier─Polarski─Linder (CPL) parameterization, while the generalized Om(z) diagnostic shows deviations of up to ∼4σ from the constant ΛCDM expectation, closely matching the CPL predictions. Taken together, these results point to footprints of dynamical dark energy in the kinematics of the Universe at z ≲ 1.

Keywords: Cosmology, Cosmological constant, Deceleration parameter, Dark energy
Driving Mechanisms of Solar Active Region Geysers: The Role of Interacting Magnetic Flux. Active region (AR) recurrent jets are manifestations of episodic magnetic energy release processes driven by complex interactions in the lower solar atmosphere. While magnetic flux emergence and cancellation are widely recognized as key contributors to jet formation, the mechanisms behind repeated magnetic reconnection remain poorly understood. In this Letter, we report a sequence of nine recurrent jets originating from AR 12715 during its decay phase, where the jet activity was associated with a complex distribution of fragmented magnetic flux. Nonlinear force-free field extrapolations reveal the presence of low-lying, current-carrying loops beneath overarching open magnetic fields near the jet footpoints. These magnetic structures were perturbed by: (1) emerging flux elements; and (2) interactions between oppositely polarized moving magnetic features (MMFs). To interpret these observations, we compare them with a 3D radiative MHD simulation from the Bifrost model, which reproduces jet formation driven by interacting bipolar MMFs, leading to subsequent flux cancellation in the photosphere. Our results emphasize the critical role of MMF-driven flux interactions in initiating and sustaining recurrent jet activity in ARs.

Keywords: Solar active region magnetic fields, Solar active regions, Solar magnetic reconnection
Unified Kraft Break at ∼6500 K: A Newly Identified Single-star Obliquity Transition Matches the Classical Rotation Break. The stellar obliquity transition, defined by a Teff cut separating aligned from misaligned hot Jupiter systems, has long been assumed to coincide with the rotational Kraft break. Yet the commonly quoted obliquity transition (6100 or 6250 K) sits a few hundred kelvins cooler than the rotational break (∼6500 K), posing a fundamental inconsistency. We show this offset arises primarily from binaries/multiple-star systems, which drive the cooler stellar obliquity transition ( 6105−133+123  K), although the underlying cause remains ambiguous. After removing binaries and higher-order multiples, the single-star stellar obliquity transition shifts upward to  6447−119+85  K, in excellent agreement with the single-star rotation break ( 6510−127+97  K). This revision has two immediate consequences for understanding the origin and evolution of spin─orbit misalignment. First, the upward shift reclassifies some hosts previously labeled "hot" into the cooler regime; consequently, there are very few Rossiter─McLaughlin measurements of non-hot-Jupiter planets around genuinely hot stars (Teff ≳ 6500 K), and previously reported alignment trends for these classes of systems (e.g., warm Jupiters and compact multiplanet systems) are insufficient to dispute central question: Are large misalignments unique to hot-Jupiter-like planets that can be delivered by high-e migration, or are hot stars intrinsically more misaligned across architectures? Second, a single-star stellar obliquity transition near 6500 K, coincident with the rotational break, favors tidal dissipation in outer convective envelopes; as these envelopes thin with increasing Teff, inertial-wave damping and magnetic braking weaken in tandem.

Keywords: Exoplanet dynamics, Planetary theory, Stellar structures, Exoplanets, Planetary alignment, Exoplanet systems, Star-planet interactions
Energy Transfer from Magnetohydrodynamic-scale Slow-mode Waves to Kinetic-scale Ion Acoustic Waves. Large-amplitude slow-mode waves are commonly observed near Earth's magnetopause. Recent observations show that these waves can occur simultaneously with kinetic-scale ion acoustic waves (IAWs). The amplitude of the IAWs is enhanced near the magnetic field peaks of the slow-mode wave, suggesting that the slow-mode waves may drive the generation of IAWs. To test this hypothesis, we conduct a hybrid simulation using observation-based parameters. The simulation results demonstrate that large-amplitude slow-mode waves generate counterstreaming ion beams, which in turn excite IAWs and relax the ion beams. Our study reveals a clear energy transfer channel from magnetohydrodynamic-scale slow-mode waves to kinetic-scale IAWs.

Keywords: Plasma physics
Search for Gravitational-wave Memory in PPTA and EPTA Data: A Complete Signal Model. We perform searches for gravitational-wave memory in the data of two major Pulsar Timing Array (PTA) experiments located in Europe and Australia. Supermassive black hole binaries (SMBHBs) are the primary sources of gravitational waves in PTA experiments. We develop and carry out the first search for late inspirals and mergers of these sources based on full numerical relativity waveforms with null (nonlinear) gravitational-wave memory. Additionally, we search for generic bursts of null gravitational-wave memory, exploring the possibilities of reducing the computational costs of these searches through kernel density estimation and normalizing flow approximations of the posteriors. We rule out mergers of SMBHBs with a chirp mass of 1010 M⊙ up to 700 Mpc over 18 yr of observation at 95% credibility. We rule out the observation of generic displacement memory bursts with strain amplitudes &gt;10−14 in brief periods of observation time but across the sky, or over the whole observation time but for certain preferred sky positions, at 95% credibility.

Keywords: Black holes, Astronomy data analysis, Gravitational waves, Pulsars
Line Polarization of Si II λ6355 Å in Type Ia Supernovae: A New Statistical Approach to Probe the Explosion Physics and Diversity. Spectropolarimetry provides a unique probe of ejecta asphericities, offering direct insights into the underlying explosion physics of Type Ia supernovae (SNe Ia). We analyze the statistical properties of premaximum spectropolarimetric data for 24 SNe Ia observed with the FOcal Reducer and low dispersion Spectrograph on the Very Large Telescope, focusing on the Si II λ6355 Å line. Previous studies have revealed a correlation between the peak Si II polarization degree and the expansion velocity. Here, we combine these observations with multidimensional nonthermodynamical equilibrium radiative transfer simulations. We consider two asphericity classes: (i) lopsided abundance distributions produced by off-center delayed-detonation transitions in near-MCh white dwarfs (WDs) or, for example, WD collisions (class I), and (ii) global axisymmetric density asphericities such as those arising from explosions of rapidly rotating WDs or mergers (class II). Our model grid spans normal to subluminous SNe Ia and successfully reproduces the observed Si II velocity─polarization trend, with higher velocities associated with stronger asphericities. Consistent with observations, transitional SNe Ia and the faint end of the normal SN Ia population show the highest Si II polarization and are best explained by class I scenarios. In contrast, subluminous SNe Ia are dominated by class II asphericities, characterized by lower Si II polarization but significant continuum polarization. The observed distribution of Si II polarization depends on both the observer's viewing angle θ and the intrinsic asphericity. Statistical analysis of these spectropolarimetric snapshots enables the separation of class I and class II contributions and highlights the intrinsic diversity among SNe Ia. Our results imply viewing-angle-dependent luminosities in our local sample, which may have implications when using high-redshift SNe Ia as evidence for the need for nonstandard cosmology.

Keywords: Spectropolarimetry, Type Ia supernovae
The Albedo Problem and Cloud Cover on Hot Jupiters. Observations of transiting hot Jupiters have revealed a mismatch between the values of the Bond versus geometric albedos. In the planetary science literature, the ratio of these quantities is known as the phase integral. It has been extensively measured for the solar system planets and shown to generally be nonunity in value. We use existing Cassini data on Jupiter to derive bandpass-integrated geometric albedos and phase integrals in the CHEOPS, TESS, and Ariel bandpasses, demonstrating that these quantities vary markedly across these different wavelength ranges. By performing a population study of geometric albedos and phase integrals, we demonstrate that atmospheres with partial cloud cover may be identified using measurements of the phase integral if its measured uncertainty is ∼0.1, which corresponds to an uncertainty of ∼3% on the optical/visible secondary eclipse depth. The upcoming Ariel space mission will conduct an unprecedented statistical survey of cloud cover on hot Jupiters via the simultaneous measurement of ∼100 infrared phase curves and optical secondary eclipses. Whenever available, the shape of optical phase curves of reflected light will directly constrain the phase integral, spherical albedo, degree of cloud cover, and scattering asymmetry factor.

Keywords: Exoplanets
On the Regulation of the Solar Wind Helium Abundance by the Hydrogen Compressibility. Traditionally, fast solar wind is considered to originate in solar source regions that are continuously open to the heliosphere. In contrast, slow solar wind is considered to originate in source regions that are only intermittently open to the heliosphere. In fast wind, the gradient of the solar wind helium abundance (AHe) with increasing solar wind speed (vsw) is approximately 0 and AHe is fixed at ∼50% of the photospheric value. In slow wind, this gradient is large, AHe is highly variable, and it does not exceed this ∼50% value. Although the normalized cross helicity in fast wind is typically observed to approach 1, this is not universally true, and B. L. Alterman &amp; R. D'Amicis show that  ∇vswAHe  in fast wind unexpectedly increases with decreasing ∣σc∣. We show that these large  ∇vswAHe  are due to the presence of compressive fluctuations in fast wind. Accounting for the solar wind's compressibility (∣δnH/nH∣), there exist two subsets of enhanced AHe in excess of typical fast wind values. The subset corresponding to large solar wind compressibility is likely from neither continuously nor intermittently open sources. The portion of the solar wind speed distribution over which these fluctuations are most significant corresponds to the range of Alfvén-wave-poor solar wind from continuously open source regions, which is likely analogous to the Alfvénic slow wind. The other subset corresponds to typical Alfvénic fast solar wind. Mapping the results of this work to B. L. Alterman &amp; R. D'Amicis and vice versa shows that, in any given ∣δnH/nH∣ quantile, ∣σc∣ ≲ 0.65 is an upper bound on non-Alfvénic cross helicity. Similarly, ∣δnH/nH∣ ≲ 0.15 in any given ∣σc∣ quantile is an upper bound on incompressible solar wind fluctuations. We conclude that ∣δnH/nH∣ is essential for characterizing the solar wind helium abundance and possibly regulating it.

Keywords: Slow solar wind, Magnetohydrodynamics, Abundance ratios, Fast solar wind, Interplanetary turbulence, Solar wind, Chemical abundances