Sazuna/UAT_keywords huggingface dataset:
The Brown-dwarf Desert Persists as a Mass-ratio Desert around Low-mass Stars. Sun-like stars are known to host a paucity of brown-dwarf companions at close separations. Direct imaging surveys of intermediate-mass stars have suggested that the brown-dwarf desert may be fundamentally a feature in the mass ratio. Microlensing surveys provide a unique opportunity to investigate the nature of this desert around low-mass stars, as microlensing hosts have typical masses of 0.05─0.8 M⊙. Here, we perform a statistical analysis of homogeneously selected binary-lens microlensing events in the literature, and identify a companion mass-ratio desert at 0.02 ≲ q ≲ 0.05 and projected separations around 1─5 au. We derive a statistically significant truncation to the giant-planet mass-ratio distribution at q ≃ 0.02, above which the occurrence rate density drops by approximately an order of magnitude. Due to the possibility that the small number of detected companions in this desert orbit white dwarfs, this mass-ratio desert may be closer to being completely dry around main-sequence stars. Below this desert, we derive a giant-planet (q &gt; 4 × 10−4) occurrence rate density of 5.8% ± 0.8% per decade of projected separation. Our analysis furthers the hypothesis that the brown-dwarf desert is fundamentally a feature in the mass ratio, separating distinct populations of planetary and nonplanetary companions that are likely formed via core accretion and gravitational instability, respectively. The persistence of this desert across stellar types suggests that both gas-giant planets and substellar companions form in a scale-invariant fashion, with planets growing to a maximum of approximately 2% of their host masses.

Keywords: Gravitational microlensing exoplanet detection, Brown dwarfs, Exoplanets, Binary lens microlensing
Surprisingly Large Doppler Shifts in Hinode EUV Imaging Spectrometer (EIS) Solar Spectra Resulting from an Inconspicuous Small-scale Jet in Extreme-ultraviolet Images. Strong EUV line shifts in solar spectra are generally indicative of highly dynamic and explosive events that are easily detected in comparable-wavelength EUV images, with the strongest such line shifts (several 100 km s−1) occurring in solar flares. Here we present observations of exceptionally strong line shifts detected in Hinode EUV Imaging Spectrometer (EIS) spectra outside the time of a flare-like brightening, with 195 Å blueshifts of ∼200 km s−1. Although the likely culprit is too weak to register in GOES soft X-ray fluxes, EIS pinpoints the source at the edge of an active region. Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA) images and Helioseismic and Magnetic Imager (HMI) magnetograms show a nondescript small-scale eruptive event at this location. We find this event likely to be an inconspicuous coronal jet, apparently triggered by converging/canceling magnetic flux patches, with a plane-of-sky velocity of ∼159± 29 km s−1. AIA and HMI observations of this faint transient feature, together with observations of a slightly brighter jetting event near the same location 1 hr earlier, suggest that the strong EIS Doppler shifts are indeed due to a coronal jet that is hard to detect in AIA images. These observations, together with other recent studies, show that EUV Doppler maps are a much more sensitive tool for detecting small-scale eruptions than are EUV images, and those eruptions are frequently triggered by magnetic flux cancellation episodes. Such-detected small-scale eruptions, which often produce small-scale coronal-jet-like features, might propagate into and help drive the solar wind.

Keywords: Solar corona, Solar magnetic fields, Solar magnetic reconnection
Crustal Quakes Spark Magnetospheric Blasts: Imprints of Realistic Magnetar Crust Oscillations on the Fast Radio Burst Signal. Many transients believed to originate from magnetars are thought to be triggered by crustal activity, which feeds back on the surrounding magnetosphere. These perturbations, through a variety of proposed mechanisms, can convert a fraction of the magnetic energy stored in the magnetosphere, as well as the energy injected by crustal activity itself into electromagnetic emission, including X-ray bursts and fast radio bursts. We here provide a first glimpse of this process by coupling magnetoelastic dynamics simulations of the crust to fully three-dimensional relativistic resistive force-free electrodynamic simulations of the magnetosphere. Our simulations demonstrate that the elastodynamical motions of the surface launch a series of fast magnetosonic and Alfvén waves into the magnetosphere. These waves rapidly enter a nonlinear regime, ultimately giving rise to a wide range of phenomena, including monster shock formation, relativistic blast waves, trapped Alfvén waves, nonlinear Alfvén wave ejecta, and transient equatorial current sheets interacting with these waves. After the initial nonlinear phase, the magnetosphere is partially combed out, resembling a strongly perturbed split monopole configuration. Our results can offer hints and potential constraints on fast radio burst emission mechanisms, in particular for hyperactive repeating sources, by placing tight bounds on energy conversion efficiency and possible quasiperiodic imprints on magnetospheric waves by elastic oscillations of the crust.

Keywords: Magnetospheric radio emissions, Plasma astrophysics, Radio bursts, Alfven waves, Magnetars, Magnetic fields, Radio transient sources
The First Triple Radio Active Galactic Nucleus in an Ongoing Galaxy Merger. Galaxy mergers are predicted to be a critical stage of merger-driven SMBH growth and galaxy evolution. Systems exhibiting multiple active galactic nuclei (AGN) are an important observational tool for constraining the prevalence and properties of merging SMBHs. Most multi-AGN selection methods focus on the identification of AGN pairs, while few focus on the more elusive triple AGN, which are a prediction of hierarchical growth and natural laboratories for studying SMBH dynamics. These systems are rare; only two confirmed cases exist locally (z &lt; 0.1). Here, we present a new, confirmed triple AGN system, WISEJ121857.42+103551.2/WISEJ121901.77+103515.0, with nuclear separations of 22.6 and 97 kpc, identified within a sample of spatially resolved mid-IR dual AGN. The system exhibits multiwavelength evidence for three distinct AGN hosted in an ongoing galaxy merger. To confirm the nature of this system, we present new radio observations with the Karl G. Jansky Very Large Array in A-configuration at 3, 10, and 15 GHz, providing subarcsecond resolutions, and the Very Long Baseline Array at 4.9 GHz, providing milliarcsecond resolutions. These observations confirm this system as a triple AGN, and the first triple AGN in which all three nuclei host radio AGN.

Keywords: Radio active galactic nuclei, Radio astronomy
ZTF25abjmnps (AT2025ulz) and S250818k: A Candidate Superkilonova from a Subthreshold Subsolar Gravitational-wave Trigger. On 2025 August 18, the LIGO─Virgo─KAGRA collaboration reported gravitational waves from a subthreshold binary neutron star merger. If astrophysical, this event would have a surprisingly low chirp mass, suggesting that at least one neutron star was below a solar mass. The Zwicky Transient Facility mapped the coarse localization and discovered a transient, ZTF 25abjmnps (AT2025ulz), which was spatially and temporally coincident with the gravitational-wave trigger. The first week of follow-up suggested properties reminiscent of a GW170817-like kilonova. Subsequent follow-up suggests properties most similar to a young, stripped-envelope, Type IIb supernova. Although we cannot statistically rule out chance coincidence, we undertake due diligence analysis to explore the possible association between ZTF 25abjmnps and S250818k. Theoretical models have been proposed wherein subsolar neutron star(s) may form (and subsequently merge) via accretion-disk fragmentation or core fission inside a core-collapse supernova—i.e., a "superkilonova." Here, we qualitatively discuss our multiwavelength dataset in the context of the superkilonova picture. Future higher-significance gravitational-wave detections of subsolar neutron star mergers with extensive electromagnetic follow-up would conclusively resolve this tantalizing multimessenger association.

Keywords: Neutron stars, Core-collapse supernovae, Surveys, Transient sources, Gravitational waves, Compact objects
The First out-of-Ecliptic Observations of the Polar Magnetic Field of the Sun. Direct remote-sensing observations of the solar poles have been hindered by the restricted view obtained from the ecliptic plane. For the first time ever, Solar Orbiter with its remote-sensing instruments observed the poles of the Sun from out of the ecliptic in the spring of 2025. Here, we report the first measurements of the magnetic field of the solar poles taken when Solar Orbiter was at heliographic latitudes ranging between 14 .° 9 and 16 .° 7. The data sets were collected by the High Resolution Telescope of the Polarimetric and Helioseismic Imager on board Solar Orbiter (SO/PHI-HRT). Two sets of observations, approximately one month apart, for the south and north pole are considered in this work. The magnetic flux and flux density measured during these campaigns are reported as a function of the heliographic latitude observed by SO/PHI-HRT. The net fluxes show a different latitudinal distribution for the two polar caps. We also discuss the observed dependence of the measured fluxes on the viewing angle. These first results highlight the importance of high-resolution direct measurements of the polar field, paving the way for the high-latitude observations planned for SO/PHI-HRT in the coming years.

Keywords: Solar surface, Solar physics, Spectropolarimetry, Solar magnetic fields
Fractional Dynamics in Galactic Nuclei: Nonlocal Transport, Transient Phenomena, and the Nullification of the Schwarzschild Barrier. We investigate the application of fractional calculus to model stellar dynamics, focusing on resonant relaxation (RR) near a supermassive black hole. Standard theories use the local Fokker─Planck (FP) equation, restricted to Gaussian processes under the central limit theorem (CLT). We argue this is inadequate for RR. We demonstrate that gravitational interactions inherently produce infinite variance in stochastic torques, violating the CLT. Consequently, RR is governed by the generalized CLT and constitutes a superdiffusive Lévy flight. We apply the space-fractional FP equation (space-FFPE), utilizing nonlocal operators, to explore resolutions to observational discrepancies. In transient regimes, the FFPE predicts immediate linear flux (Γ(t) ∝ t), consistent with high tidal disruption event (TDE) rates in poststarburst galaxies, whereas local FP models predict significant exponential delay. Furthermore, we demonstrate analytically that nonlocal integral operators permit "barrier jumping," bypassing bottlenecks like the Schwarzschild Barrier, which local models interpret as severely suppressing extreme-mass-ratio-inspiral (EMRI) rates. We present proof-of-concept N-body simulations that confirm nonlocal RR transport, although the resolution must be improved to rule out enhanced two-body relaxation in the small-N setup. The fractional framework offers a compelling alternative description for nonlocal transport, potentially resolving TDE and EMRI rate questions.

Keywords: Supermassive black holes, Stellar diffusion, Stellar dynamics, Hydrodynamics
Stellar Rotation in an Old Solar Twin Using ESPRESSO/VLT Validates Gyrochronology. We report the detection of rotation in the old (∼7 Gyr) solar twin HIP 73815. This result provides new insight into the validity of gyrochronology beyond the solar age, a subject of intense debate in recent years. Previous claims in the literature often relied on merged or fragmented time series or on model-dependent proxies, leading to ambiguous interpretations. Thanks to ESPRESSO's service mode, we obtained an unprecedented, single, coherent data set spanning over 80 days and covering more than two full rotation cycles of this old solar twin. We measure a rotation period of  PGP=31.1−1.1+1.3  days, consistent with predictions from gyrochronology, in contrast with recent studies suggesting that these relations break down past the solar age. Our result demonstrates that gyrochronology remains a reliable method for estimating stellar ages for Sun-like stars at least up to ∼7 Gyr, beyond the solar age, where its validity has been under debate. Moreover, we show that with a carefully designed ground-based observational strategy, precise and accurate rotation periods can be measured even in old stars, enabling robust age determinations for Sun-like stars and providing critical calibration for independent dating methods.

Keywords: Observational astronomy, Stellar ages, Fundamental parameters of stars, Stellar activity, Spectroscopy, Radial velocity, Stellar rotation
ALMA Reveals Diverse Dust-to-gas Mass Ratios and Quenching Modes in Old Quiescent Galaxies. Recent discoveries of dust and molecular gas in quiescent galaxies (QGs) up to z ∼ 4 challenge the long-standing view that the interstellar medium depletes rapidly once star formation ceases, raising key questions of whether dust and gas coevolve in QGs, and how their depletion links to stellar aging. We present deep Atacama Large Millimeter/submillimeter Array Band 6 continuum and CO(3─2) observations of 17 QGs at z ∼ 0.4 in the COSMOS field. Using the dust-to-molecular gas mass ratio (δDGR) as a key diagnostic, we trace postquenching evolution of the cold interstellar medium. Our study triples the number of QGs with direct δDGR estimates, constraining 12 systems with stellar population ages of ∼5─10 Gyr. For the first time, we show that δDGR in QGs ranges from ∼8× below to ∼2.5× above the canonical value of δDGR ∼ 1/100. Despite uniformly low molecular gas fractions (median  fH2=MH2/M⋆∼4.1% ), QGs follow diverse evolutionary paths: about half exhibit rapid (∼700 Myr) exponential dust decline with age, while the rest show mild decline over ≳2 Gyr, maintaining elevated δDGR ≳ 1/100. Our results support simulations' predictions of dust and molecular gas evolving independently postquenching, without a preferred quenching mode. This challenges the use of dust continuum as a H2 tracer, implying that quenching cannot be robustly linked to interstellar medium conditions when relying solely on dust or gas.

Keywords: Interstellar dust, Interstellar molecules, Galaxy evolution
A Carbon-rich Atmosphere on a Windy Pulsar Planet. A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR J2322─2650b, uniquely resembles a hot-Jupiter exoplanet, due to its minimum density of 1.8 g cm−3 and its ∼1900 K equilibrium temperature. We use JWST to observe PSR J2322─2650b's emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star, we find an atmosphere rich in molecular carbon (C3, C2) with strong westward winds. Our observations open up new exoplanetary chemical (ultrahigh C/O and C/N ratios of &gt;100 and &gt;10,000, respectively) and dynamical regimes (ultrafast rotation with external irradiation) to observational study. The extreme carbon enrichment poses a severe challenge to the current understanding of "black-widow" companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores.

Keywords: High energy astrophysics, Hot Jupiters, Carbon planets, Pulsar planets, Stellar atmospheres
On the Connection of Coronal Loop Plasma with the Ambient Magnetic Field. Solar coronal loops are magnetically confined plasma structures whose properties are closely linked to the ambient magnetic field. Using 3D magnetohydrodynamic simulations of kink-unstable coronal flux tubes, we investigate how the intensity of the ambient magnetic field influences the thermal regime of coronal loops. The simulations, performed with the PLUTO code, explore field strengths between 10 and 80 G under continuous photospheric twisting that drives magnetic reconnection and heating through anomalous resistivity. After an initial transient, the system reaches a statistically steady state characterized by persistent nanoflare-like energy release. We find that the differential emission measure distributions increase in magnitude and shift to higher temperatures with increasing magnetic field strength, while being largely insensitive to other parameters such as resistivity and resolution. Extending the classical Rosner─Tucker─Vaiana scaling laws, we derive a scaling relation for the loop temperature, T ∝ B4/7, which quantitatively matches the simulation results. This study demonstrates that the strength of the ambient coronal magnetic field is the primary factor determining the thermal state of coronal loops, providing a physically grounded connection between magnetic field measurements and observed coronal temperatures.

Keywords: Solar activity, Solar physics, Solar magnetic fields, Solar magnetic reconnection
The Detection-versus-retrieval Challenge: Titan as an Exoplanet. Cassini observations of Titan's atmosphere are exemplary benchmarks for exoplanet atmospheric studies owing to their precision, their spectral coverage, and our independent knowledge of Titan. We carry out atmospheric retrievals of Titan's transmission spectrum to test the sensitivity of interpretations to the range of molecular species included in the retrieval (i.e., set a priori as "detectable"). We find that hydrocarbons (HCs) such as ethane or isopropane can be "retrieved" from Titan's 3.3 μm band. However, given that a multitude of HC species exhibit overlapping features in this region, such retrievals cannot be claimed as bona fide "detections," particularly given the limited accuracy and availability of associated cross sections. The choices of HCs used in the retrieval process can vary the retrieved abundance of key absorbers like methane by ∼0.5 dex (a factor of ∼3). This underscores the broader issue that beyond the possible misidentification of molecular features (e.g., the inventory debate surrounding dimethyl sulfide in K2-18 b), the inventory of molecular species, often dictated by computational considerations, can bias the retrieved atmospheric parameters. We thus recommend a sensitivity analysis to assess the dependencies of atmospheric inferences on such a priori selections, in tandem with complementary information (e.g., chemistry models). Finally, we show an independent path to constrain the dominant atmospheric constituent, even when lacking observable absorption features (e.g., H2 and N2) through scale height.

Keywords: Titan, Exoplanet atmospheres, Transmission spectroscopy
SHELLQs─JWST Perspective on the Intrinsic Mass Relation between Supermassive Black Holes and Their Host Galaxies at z &gt; 6. The relation between the masses of supermassive black holes (SMBHs) and their host galaxies encodes information on their mode of growth, especially at the earliest epochs. The James Webb Space Telescope (JWST) has opened such investigations by detecting the host galaxies of active galactic nuclei (AGN) and more luminous quasars within the first billion years of the Universe (z ≳ 6). Here, we evaluate the relation between the mass of SMBHs and the total stellar mass of their host galaxies using a sample of nine quasars at 6.18 ≤ z ≤ 6.4 from the Subaru High-z Exploration of Low-luminosity Quasars survey with NIRCam and NIRSpec observations. We find that the observed location of these quasars in the SMBH─galaxy mass plane ( logMBH/M⊙∼8 ─9;  logM*/M⊙∼9.5 ─11) is consistent with a nonevolving intrinsic mass relation with dispersion ( 0.80−0.28+0.23  dex) higher than the local value (∼0.3─0.4 dex) of their more massive descendants. Our analysis is based on a forward model of systematics and includes a consideration of the impact of selection effects and measurement uncertainties with an assumption on the slope of the mass relation. While degeneracies between parameters persist, the best-fit solution has a reasonable AGN fraction (2.3%) of galaxies at z ∼ 6 with an actively growing UV-unobscured black hole. In particular, models with a substantially higher normalisation in MBH would require an unrealistically low intrinsic dispersion (∼0.22 dex). Consequently, our results predict a large population of AGN at lower black hole masses, as are now just starting to be discovered in focused efforts with JWST.

Keywords: AGN host galaxies, Supermassive black holes, Early universe, Scaling relations, High-redshift galaxies
Probing the Evolution of Solar Wind Temperature Anisotropies in the Inner Heliosphere. Using solar wind measurements from Solar Orbiter, we investigated the distribution and evolution of the temperature anisotropy of alpha-particles (the ratio of perpendicular to parallel temperatures) in the inner heliosphere, between 0.29 and approximately 1 au. We also compared these observations with the corresponding proton temperature anisotropy to better understand the evolution of ion thermal properties in the expanding solar wind. We found that the slow wind (≤400 km s−1) exhibits higher alpha-particle anisotropy compared to the fast wind (≥600 km s−1), where the anisotropy values are mostly below one. The alpha-particle anisotropy increases as solar wind speed decreases, in contrast to protons, where anisotropy increases with solar wind speed. Additionally, we find that, regardless of the distance from the Sun, alpha-particle anisotropy is greater than proton anisotropy when the normalized differential speed between alpha-particles and protons (∆V/VA) is less than 0.3. However, when ∆V/VA exceeds 0.4, the trend reverses, and proton anisotropy becomes larger. The radial evolution also shows distinct differences between fast and slow wind. In the fast wind, proton anisotropy decreases with distance from 0.29 to 1 au, while alpha-particle anisotropy shows no clear radial trend and remains nearly constant. In the slow wind, both proton and alpha anisotropies decrease with distance from the Sun. These results reveal distinct behaviors of alpha-particles and protons in the expanding solar wind, highlighting the dependence of ion heating on solar wind speed and differential flow.

Keywords: Solar wind
Velocity-space Turbulent Cascade in the Near-Sun Solar Wind: First Insights from the Parker Solar Probe Mission. In space plasmas, the rarity of collisions leads to complex structures in the velocity space where a turbulent cascade of the velocity distribution function (VDF) fluctuations is thought to occur. Previous studies have explored this phenomenon using the Hermite decomposition of the ion VDF in both magnetosheath data and numerical simulations. In this work, we investigate the Hermite spectrum of the ion VDFs measured by the Parker Solar Probe in the inner heliosphere. We analyze a super-Alfvénic stream at a radial distances of R ≍ 28R⊙ and a sub-Alfvénic stream at R ≍ 11R⊙, the former characterized by a prevalence of VDFs with suprathermal beams (also known as hammerhead distributions). The Hermite analysis is also compared with various proxies of energization and dissipation, in order to establish a connection between turbulent cascades in real space and those in the velocity space. A qualitative agreement between the energization proxies and the Hermite analysis is observed. The results are suggestive of the presence of a dual cascade in real and velocity space.

Keywords: Interplanetary turbulence, Solar coronal heating, Interplanetary magnetic fields