Papers

We present a neural network classification (NNC) method for photometric redshift estimation that produces well-calibrated redshift probability density functions (PDFs). The method discretizes the redshift space into ordered bins and optimizes the Continuous Ranked Probability Score (CRPS), which respects the ordinal nature of redshift and naturally provides uncertainty quantification. Unlike traditional regression approaches that output single point estimates, our method can capture multi-modal posterior distributions arising from color-redshift degeneracies. We apply this method to the DESI Legacy Imaging Surveys Data Release 10 (LSDR10) and Pan-STARRS Data Release 2 (PS1DR2), using an unprecedented spectroscopic training sample from DESI DR1 and SDSS DR19. Our method achieves $\sigma_{\mathrm{NMAD}} = 0.0153$ and $\eta = 0.50\%$ on LSDR10, and $\sigma_{\mathrm{NMAD}} = 0.0222$ and $\eta = 0.34\%$ on PS1DR2 combined with unWISE infrared photometry. The NNC method outperforms Random Forest, XGBoost, and standard neural network regression. We demonstrate that DESI DR1 significantly improves photo-$z$ performance at $z > 1$, while the combination of deep optical photometry and mid-infrared coverage is essential for achieving high precision across the full redshift range. We provide a unified photometric redshift catalog combining LSDR10 and PS1DR2 with a hierarchical model selection strategy based on available photometry. The well-calibrated PDFs produced by our method are valuable for cosmological studies and can be extended to next-generation surveys such as CSST, Euclid, and LSST.

The values of the Hubble constant ($\rm{H_0}$) inferred from the cosmic microwave background (CMB) and local measurements via the distance ladder exhibit a $\sim5\sigma$ tension. In this work we propose that the tension might be partially alleviated if a subcomponent of the dark matter undergoes decays triggered by spontaneous symmetry breaking in the dark sector, where dark energy couples to the daughter species, but not the parent. This then allows interactions between dark matter and dark energy to turn on at a particular redshift, which can reduce fifth-force constraints, since early time interactions are absent. We provide an example of such an effective field theory whose structure is partially motivated by the desire for a plausible UV completion. We find that such a construction can naturally incorporate a possible self-interacting dark matter candidate with a velocity-dependent scattering cross section as a by-product of gauge invariance, though this is not necessary for alleviating the Hubble tension. This is relevant for addressing tensions between $\Lambda$CDM and small-scale structure, such as the core-cusp problem.

{Early-type galaxies host low-luminosity active galactic nuclei, traced by radio emission spanning parsec- to kiloparsec scales.} {We investigate the Eddington-scaled radio luminosity distribution of 117 nearby early-type galaxies to test for bimodality and assess the role of host-galaxy properties, extending results from a 62-galaxy sample \cite{Wojtowicz2023}.} {We compile galaxies with directly measured black hole masses and 1.4,GHz and 3,GHz flux densities. Statistical tests assess bimodality, while VLASS imaging, host-galaxy kinematics, and central stellar structure characterize radio-dim and -bright sources.} {Using the 117-galaxy sample, we confirm that $L_{\rm 1.4,GHz}/L_{\mathrm{Edd}}$ is bimodal, with an antimode at $\approx -8.6$, which disappears when black hole masses are inferred from the $M_{\rm BH}$-$\sigma_\star$ relation. Radio-bright galaxies host resolved jets, while radio-dim systems show compact nuclear emission often exceeding that expected from star formation (FIR-radio correlation). Radio-bright galaxies are mainly slow rotators with depleted cores; radio-dim galaxies are predominantly fast rotators.} {Nearby early-type galaxies show a clear bimodality in Eddington-scaled radio luminosity, separating compact, radio-dim nuclei from extended, radio-bright systems. The dichotomy correlates with host-galaxy kinematics and central structure, indicating that sustained jet production depends primarily on galaxy assembly history and feeding mode rather than black hole mass or accretion rate alone. Radio-dim emission likely reflects intermittent, stochastic delivery of magnetized gas, plausibly via tidal disruption of giant-branch stars near the SMBH.}

In this work, we present a transit timing variation analysis for 20 hot Jupiter systems, which we interpret with theoretical tidal dissipation models. For the majority of the sample, we conclude that a constant orbital period model represents the timing data best. Only WASP-12 b, TrES-1 b and WASP-121 b exhibit a changing orbital period, according to the most up-to-date results. We updated the orbital decay rate of WASP-12 b to $\dot{P} = -29.4 \pm 4.0 \mathrm{~ms~yr^{-1}}$ and the corresponding stellar tidal quality factor to $Q_*^{\prime} = 1.72 \pm 0.18 \times 10^5$. For TrES-1 b, the median quadratic model suggests a period decrease at a rate of $-14.9 \pm 0.6 \mathrm{~ms~yr^{-1}}$, but the corresponding $Q_*^{\prime} = 570 \pm 60$ does not agree with the theoretical estimates, which suggest $Q_*^{\prime} \sim 10^6$ due to internal gravity wave dissipation. Lastly, WASP-121 b exhibits orbital growth at a rate of $15.1 \pm 0.8 \mathrm{~ms~yr^{-1}}$, and theoretical results support outward migration due to strong inertial wave dissipation.

V658 Car (HD 92406) is a newborn resp. rejuvenated shell star binary system at the age of only 1 Myr after the end of mass transfer. In this renewed study the peculiarities of the Be star are at first by-passed by the determination of the properties of the contracting hot subdwarf precursor, but finally resolved by combining photometric data and radial velocity results with existing stellar models. For the effective temperatures, radii and masses we get about 12900 K, 1.92/2.20 Rsun and 4.49 Msun for the Be star, and about 18400 K, 1.87 Rsun and 0.56 Msun for its companion star. The Be star has a rotational velocity of 336 km/s and is surrounded and dimmed in our view by a large and luminous equatorial decretion disk having a radius of ~ 42 Rsun. According to stellar models these results fit to a surprisingly low metallicity Z of 0.003 and a Teff ~ 5400 K higher than observational expectations for the Be star, which hence should belong to the chemically peculiar stars, in spite of its rapid rotation.

We conduct an in-depth study of the quasi-periodic oscillation (QPO) properties of RE J1034+396, by constructing QPO phase-folded light curves from 10 XMM-Newton observations during 2020-2021. Our analysis reveals that the QPO in the source exhibits two mutually convertible lag-energy modes: "hard lag" and "soft lag". Despite different lag characteristics, the energy dependency of the root mean square (RMS) amplitude of the QPO under both modes are consistent, suggesting the two types of QPO originate from the same physical mechanism. By performing a spectral analysis, we further find a correlation between time-lag modes and spectral states: the soft lag mode typically corresponds to harder X-ray spectra and higher blackbody temperatures. Through comprehensive comparison of multiple theoretical models, we propose that the relativistic precession model (RPM) of the corona provides a plausible qualitative explanation for the observed complex phenomena, including time-lag mode transitions, and variations of spectral hardness and QPO signal strength.

We present three-dimensional simulations of the ultra-hot Jupiter (UHJ) WASP-121b from the planetary surface to extended outflows, coupling hydrodynamics with consistent non-equilibrium thermochemistry, ray-tracing radiative transfer, and hydrodynamics using the GPU-accelerated Kratos framework. The fiducial model exhibits several atmospheric layers, including the lower atmospheres controlled by day-night circulation, and transonic photoevaporative outflows at higher altitudes shaped into two spiral arms by the stellar gravity and orbital motion effects. Different species could trace different regions: Fe probes rotation-dominated inner layers, Na maps dense spiral arms where recombination balances photoionization, and H$\alpha$ and He 10830 A features trace progressively more extended, ionized gas. With spiral arm velocities reaching ~ 40 km/s projected along the line of sight, this morphology naturally reproduces the velocity pattern of observed high-velocity Na and H$\alpha$ absorption features without requiring significant super-rotation jet streams, although the absolute absorption amplitudes could carry uncertainties from stellar UV luminosity and trace elemental abundances. Parametric studies reveal complex dependencies on stellar irradiation: enhanced FUV intensifies outflows and extends spiral arms spatially and kinematically, while EUV and X-ray expands spiral structures into attenuated, ionized regions. Stellar wind confinement compresses the dayside outflow and enhances metastable helium absorption. This work demonstrates that current and future transmission spectral observations that probe multiple species can provide important constraints on astrophysical environments of UHJs by comparing state-of-the-art simulations.

$\delta$ Scuti stars are pulsating variable stars that exhibit both radial and non-radial pulsations, making them key objects for understanding stellar evolution and internal structures. The current classification of $\delta$ Scuti stars into High-Amplitude $\delta$ Scuti (HADS) and Low-Amplitude $\delta$ Scuti (LADS) stars is based on the peak-to-peak amplitude of their light curves (>0.3 mag). Nevertheless, this classification may not fully capture the complexity of their pulsation mechanisms and non-linear effects, leading to possible misclassifications. This investigation aims to challenge the existing classification of $\delta$ Scuti stars according to amplitude, employing the exploration of frequency domain features and non-linear mechanisms in order to identify intrinsic subgroups. The objective is to get a deeper understanding of the properties of $\delta$ Scuti stars. We use machine learning clustering techniques, specifically hierarchical clustering (HC) with Ward's linkage, to analyze a sample of 142 $\delta$ Scuti stars observed by space telescopes such as CoRoT, Kepler, and TESS. We focus on frequency-domain features, including fundamental and overtone modes, as well as non-linear features such as harmonic, sums, and subtraction frequencies, to uncover intrinsic subgroups within $\delta$ Scuti stars. The results of the clustering process indicate that the present amplitude-based classification (HADS/LADS) exhibits partial alignment with the clusters identified by using features from the frequency-domain. However, the study identified additional sub-groups, suggesting a greater variety of nonlinear effects that are not captured by the amplitude alone. It highlights the importance of non-linear features, such as the number of subtraction combinations, which may be indicative of resonance effects or other internal physical mechanisms.

We study a mechanism for producing heavy particles during inflation through a transient quadratic $U(1)$-breaking interaction of a complex scalar coupled derivatively to the inflaton. The rolling inflaton induces an effective chemical potential, while sufficiently strong symmetry breaking creates a tachyonic instability that amplifies the scalar fluctuations. The finite duration of the instability limits their growth, allowing efficient production of particles heavier than the Hubble scale in regimes where homogeneous backreaction remains small. The amplified fluctuations source a peaked gravitational-wave spectrum through their anisotropic stress. We calculate this spectrum by following the full time evolution of the source. For suitable parameters and production times, our idealized forecasts suggest that the signal could be observable with LISA, subject to the assumed switching profile and reheating history.

Recent observations have revealed that the ion-neutral drift velocity in star-forming molecular clouds and dense cores is on the order of 100 m s^-1. Theoretical studies have shown that, in ambipolar diffusion, the process responsible for the differential motion between ions and neutrals, the dust size distribution has a significant impact on the magnetic resistivities. In this study, we perform simulations to investigate how dust growth through accretion and coagulation affects the ion-neutral drift velocity in molecular clouds and cores. We find that, on core scales, both dust growth and a magnetic field strength of 200 microgauss are required to reproduce the observed drift velocity. We suggest that measurements of ion-neutral drift velocity, particularly on core scales, may serve as a new diagnostic to constrain the dust size distribution and magnetic field strength in such environments.

Current observations indicate that an inverse exponential form of the inflaton potential provides an excellent description of single-field inflation. This potential fits the SPA$+$BK$+$DESI data sets well with in the $1\sigma$ bound in the $n_{\rm s}$-$r$ plane, thereby offering a simple and observationally viable single field inflationary scenario. To describe post-inflationary evolution and reheating, we extend the inverse exponential potential by adding a steep exponential term that remains negligible during inflation but becomes important afterwards. The resulting full potential develops a minimum after the end of inflation, leading to oscillations of the scalar field and consequently reheating of the Universe. We find that the maximum reheating temperature attainable in this scenario is of order $10^{13}\,\mathrm{GeV}$. The inverse exponential potential therefore emerges as a compelling candidate for early-Universe inflation, combining theoretical simplicity with robust observational viability.

Analysis of {\gamma}-rays in solar flares has suggested a distinct continuum component dominating at MeV energies, which differs from the well-studied X-ray continuum produced by flare-accelerated electrons with spectra steeply falling with energy. The origin, precise spatial location, and extent of this mysterious MeV component have been unknown up to now. If it is produced by bremsstrahlung, such a {\gamma}-ray component requires an unusual population of electrons peaked at a few MeV. Here we report a joint study of this MeV-peaked electron population in the 2017-Sep-10 solar flare with Fermi MeV {\gamma}-ray data and EOVSA spatially resolved microwave imaging spectroscopy data. We demonstrate that the microwave spectrum from the MeV-peaked distribution has a distinctly different shape from that produced by the electrons with falling energy spectrum. We inspected microwave maps of the flare and identified an evolving area where the measured microwave spectra matched the theoretically expected one for the MeV-peaked population, thus pinpointing the site where this MeV component resides. The locations are in a coronal volume adjacent to the region where prominent release of magnetic energy and bulk electron acceleration were detected, which implies that transport effects play a key role in forming this population.

We introduce a variable-slope smooth-$k$ (VSMK) filter within the Press-Schechter formalism to model halo mass functions derived from damped and oscillatory matter power spectra. While the standard smooth-$k$ approach successfully captures small-scale suppression effects, it intrinsically couples these to oscillatory features at intermediate scales. The VSMK filter generalizes this framework by allowing the effective logarithmic slope of the $k$-space window function to vary smoothly between two asymptotic regimes, thereby decoupling the small-scale suppression of halo abundances from the intermediate-scale oscillatory features characteristic of dark acoustic oscillations (DAO). We compare the analytic predictions obtained with the VSMK filter to $N$-body simulations for warm dark matter and ETHOS-based models with DAO, showing that a single parameter set reproduces both regimes simultaneously. The VSMK filter thus provides a unified and flexible analytic framework for modeling halo abundances in non-cold dark matter scenarios with damped and oscillatory power spectra.

The direct detection of gravitational waves (GWs) by LIGO has confirmed general relativity (GR), but testing GR via GWs requires estimating parameterized post-Einsteinian (ppE) deviation parameters in waveform models. Traditional Bayesian inference methods like Markov chain Monte Carlo (MCMC) provide reliable estimates but suffer from prohibitive computational costs, failing to meet the real-time demands and surging data volume of future GW detectors. Here, we propose a factorized neural posterior estimation framework: we construct independent normalizing flow models for each of the nine ppE deviation parameters, and effectively integrate prior information from other source parameters via a conditional embedding network. Leveraging a hybrid neural network with a convolutional neural network and a Residual Neural Network for feature extraction, our method performs rapid and statistically reliable posterior inference directly from binary black hole signals. Compared to conventional MCMC, our approach achieves millisecond-scale inference time with a speedup factor of $9 \times 10^4$. Comprehensive validations show that the posterior estimates pass the Kolmogorov-Smirnov test and achieve empirical coverage probabilities close to theoretical targets. We apply this method to the GW150914 event and find that the resulting posterior distributions are in good agreement with existing results. This work demonstrates the great potential of deep learning for GW parameter estimation and provides a viable technical solution for real-time GR tests with next-generation detectors.

We examine entropy production in reduced descriptions of collisionless plasmas. Introducing a closure dependent entropy hierarchy, we show that non-conservative moment closures generate a residual entropy associated with irreversible information loss, whereas invariant closures remain reversible. The monotonic growth of this residual entropy imposes a statistical realizability constraint on macroscopic plasma states, excluding regions of phase space independent of dynamical stability. For anisotropic plasmas, we evaluate entropy production within a second-order moment closure, identifying contributions from transport and magnetic field inhomogeneity. The resulting entropy exclusion boundary is broadly consistent with observed anisotropy distributions in space plasmas. Statistical realizability thus emerges as an organizing principle for reduced collisionless plasma descriptions.

The study of the spatial layout of Christian churches has been of great interest since late Antiquity and the beginning of the Early Middle Ages, and has received a new impetus in recent literature when it was recognized that the orientation of their main axes represents a key feature of their architecture. From the earliest Christian communities, the orientation of the church allowed the faithful to pray facing the east, towards the rising Sun. Several authors were careful to point this out in their writings; in particular, prior to the Council of Nicaea (325 AD), the Apostolic Constitutions indicated: "And let it be, first, the elongated building, with its head facing east". We present a detailed analysis of the spatial orientation of the historic churches located in the Jesuit towns of Chiquitania (Bolivia). We have measured in situ the main characteristics of eight churches currently standing and the ruins of a ninth construction. In all cases, we carry out a thorough survey of the landscape surrounding each church, trying to find some common pattern, possibly astronomical, that explains its orientations. To our list we also add the orientation measures of a tenth church based on work with plans and satellite maps. We complement our data with a detailed cultural and historical study of the characteristics of missionary towns. Unlike the churches of the Guarani towns of the historic province of Paraquaria where the meridian orientations stand out, in the case of the Jesuit churches of Chiquitos, half of the measured constructions show orientations that fall within the solar range, with three churches oriented equinoctially with high precision. We analyze the reasons for these orientations and delve further on the possible relevance that lighting effects could have had for the architects of these churches, which represent true hidden cathedrals in the virgin tropical forest.

A significant fraction of galaxies show warps in their discs, usually noticeable at its periphery. The exact origin of this phenomenon is not fully established, although multiple warp formation mechanisms are proposed. In this study, we create a sample of more than 1000 distant ($z \lesssim 2.5$) edge-on galaxies imaged by HST and JWST. For these galaxies, we measurd characteristics of warps and finally analyse how their parameters and frequency change with time. We focus on our main result that galaxies with strong warps were more prevalent in the past compared to the modern epoch. We check how selection effects and varying image quality between objects in our sample could influence our results and conclude that varying fraction of warped galaxies is not caused by observational effects, but represents a genuine evolution. Such a trend may be consistent with mergers and interactions between galaxies being the primary mechanism of warp formation, as number density of galaxies decreases with time, implying higher rate of mergers and interactions in the past.

The Dark Ages 21cm signal, observed at frequencies below 50 MHz, can serve as a powerful probe of cosmology, as the standard cosmological model predicts a well-defined 21cm spectral shape, while several non-standard scenarios produce distinctive spectral features. In this work, we present a Bayesian-evidence-based assessment of the detectability of representative Dark Ages 21cm signals and of the ability to discriminate among their spectral templates. We compare multiple cosmological signal templates within a common analysis framework, adopting physically motivated foreground models, optimistic error levels, and several observing strategies. This framework allows us to quantify how frequency coverage and sampling affect both the detectability and the ability to distinguish among different spectral shapes. Using Bayesian model comparison, we show that observations covering 1-50MHz provide evidence for a non-zero 21cm signal for all the models considered in this work. In particular, without observations below 3MHz, the standard cosmological signal cannot be detected even after 10,000h of integration, because the free-free absorption component is insufficiently constrained. Regarding template discrimination, the $\Lambda$CDM signal can be distinguished from other models except models with similar spectral shapes and an excess radio background model with a wide band observation. Furthermore, even with observations measured at 5 MHz intervals over the frequency range 1-50 MHz, the 21cm signal can be identified if the errors are sufficiently small. This indicates that the intrinsic 21cm spectral shape can be captured without foreground degeneracy even with a limited number of frequency channels. These results quantify, within the idealized assumptions adopted in this work, how much of the intrinsic Dark Ages 21cm spectral information can be retained under limited frequency sampling.

We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and 4 protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converge into a dense central region, forming a hub-filament system (HFS). High velocity gradients (10 - 20 km s$^{-1}$ pc$^{-1}$) derived from PV analysis of H$^{13}$CO$^{+}$ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than $10^{3}$ M$_{\odot}$ Myr$^{-1}$ along the filaments is indicating that the central hub is capable of forming massive star(s). Investigation of H$^{13}$CO$^{+}$ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in hub-region is significantly higher in comparison to those located along the filaments. The mass-radius relationship of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results are supporting a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.

We extend shapelets for the analysis of astronomical images to be available in a phase space, introducing Wigner function shapelets(WFSs). Whereas conventional shapelets expand images separately in configuration or Fourier space using Hermite-Gaussian or Laguerre-Gaussian modes, WFSs represent images directly in the four-dimensional phase space with symplectic group $\mathrm{Sp}(4,\mathbb{R})$, which is quantized by a phase-space cell $2\pi\lambdabar$ that determines a resolution limit of a telescope. WFSs consist of a bilinear form of the cross-Wigner function of the Laguerre-Gaussian modes as an orthogonal and complete basis for the Wigner function of an image, carrying out $\mathrm{SU}(2)$ irreducible representations of the phase space with the Hopf tori. We introduce a scalar function $\mathcal{W}_{k\ell} (Q_0,Q_2)$ from the $\mathrm{U}(1)\times \mathrm{U}(1)$ - covariant tori to a two-dimensional space of constants of motion $(Q_0,Q_2)$ – the harmonic energy and axial angular momentum – thereby yielding a natural phase-space “band structure”, given a pair of winding number $(k,\ell) \in \mathbb{Z}^2$. % The WFSs leverage key properties of the Wigner function for image analysis: (i) it encodes full information of an image in a symmetry-preserving way; (ii) its trasport equation naturally involves with a Liouville equation at $\lambdabar \rightarrow 0$; (iii) it admits positive/negative oscillatory patterns on $(Q_0,Q_2)$ plane that can be sensitive spatial coherent structure of galaxy morphology and cosmological imprints; and (iv) systematics and noise can be manipulated as a quantum channel operation. This paper aims to bring together all the formulae related to the Wigner function in the context of astrophysics and cosmology, formally organizing them in terminologies of both astronomy and of quantum information theory.

In this paper, we report quasi-periodic herringbone structures during the impulsive phase of an X-class flare, coinciding with the distinct acceleration phase of eruptive prominence ejection on 2023 December 31. The prominence propagates non-radially in the southeast direction with an inclination angle of $\sim$35$\fdg$4. The fast coronal mass ejection (CME) at a speed of $\sim$2852 km s$^{-1}$ drives a shock wave and a coronal EUV wave. The herringbone structures lasting for $\sim$4 minutes take place at the initial stage of a group of type II radio burst. The herringbones in the frequency range 20$-$70 MHz are characterized by simultaneous forward-drift and reverse-drift bursts with average durations of $\sim$2.5 s and $\sim$3.1 s. The frequency drift rates of these bursts fall in a range of 1.3$-$9.4 MHz s$^{-1}$ with average values of $\sim$3.6 and $\sim$4.1 MHz s$^{-1}$, respectively. The speeds of electron beams producing the herringbones are estimated to be 0.04$-$0.41 $c$, with average values of $\sim$0.23 $c$ and $\sim$0.11 $c$ for forward-drifting and reverse-drift bursts, respectively. The heights of particle acceleration regions are estimated to be 0.64$-$0.78 $R_{\sun}$ above the photosphere, which are consistent with the height of CME front ($\sim$0.75 $R_{\sun}$) when the shock forms. Quasi-periodic pulsations with periods of 17.5$-$21.3 s are found in the radio fluxes of herringbones, suggesting that electrons are accelerated by the CME-driven shock intermittently.

Recent Pulsar Timing Array datasets provide compelling evidence for a nano-Hertz gravitational-wave background, but robust detection requires characterizing statistical fluctuations of the Hellings-Downs (HD) correlation expected from a finite population of discrete sources. Building on the variance calculation of Allen (2023), we derive the third central moment (skewness) of the HD correlation for a single unpolarized point source and an ensemble of many interfering point sources in the confusion-noise regime. To isolate the intrinsic non-Gaussianity of the background, we extend the pulsar-averaging formalism to third order by introducing a three-point averaged correlation function, which allows us to define the cosmic skewness. We find that the skewness remains non-zero in the large-source-number limit and is controlled by a new geometric three-point function. These results suggest that incorporating higher-order moments could provide additional information on source discreteness beyond standard Gaussian analyses.

We conduct a comparative analysis of galaxy kinematics using IllustrisTNG simulations and integral-field spectroscopy (IFS) observations. We identify 2,342 early-type galaxies (ETGs) from the TNG100 simulation and 236 ETGs from the TNG50 simulation, comparing them with observations from MaNGA and ATLAS$^{3D}$. For these systems, we measure key kinematic parameters: the intrinsic spin parameter $\lambda_{R,\mathrm{intr}}$ (measured edge-on), the cylindrical rotational energy fraction $\kappa_{\mathrm{rot}}$, and structural mass ratios including the spheroid mass fraction $f_{\mathrm{spheroid}}$ and stellar halo mass fraction $f_{\mathrm{halo}}$. Our study reveals that standard classifiers–the $\lambda_{R}(R_e)=0.31\sqrt{\varepsilon}$ relation and $\overline{k_5}$ coefficient (higher-order Fourier term of velocity fields)–fail to align with observed kinematic bimodality. We propose revised thresholds: $\lambda_{R,\mathrm{intr}} \sim 0.4$, $\kappa_{\mathrm{rot}} \sim 0.5$, and $f_{\mathrm{spheroid}} \sim 0.6$, which classify galaxies into rotation-dominated (fast rotators) and random motion-dominated (slow rotators). Scaling relations from TNG enable observational estimates of $\kappa_{\mathrm{rot}}$ and $f_{\mathrm{spheroid}}$. The simulations exhibit a bimodality deficit, characterized by a lack of fast rotators and suppressed $\lambda_{R,\mathrm{intr}}$, attributed to excess galaxies with intermediate rotation and high spheroid/stellar halo mass. We introduce a novel method to estimate $f_{\mathrm{halo}}$ from IFS kinematics, though uncertainties remain.

Magnetic fields play a central role in accretion physics around black holes, yet their physical origin within accretion flows remains an open problem. In this work, we investigate the generation and subsequent evolution of magnetic fields triggered by anisotropic radiation fields in black hole accretion discs with compact rotating inner corona. We self-consistently evolve the magnetic field using the generalized field evolution MHD equation, including advection, shear-driven induction, and Hall effects. The radiation field acts as a primary field generator, while azimuthal rotation in the magnetized plasma provides rapid amplification. We find that radiation-generated fields efficiently reach a dominant toroidal component by Keplerian rotation, leading to magnetic field strengths of order $\sim 10^{8}\,\mathrm{G}$ in the vicinity of a 10 solar mass black hole and accretion disc-corona emitting at luminosity equivalent to the Eddington unit. These magnetic fields are achieved within viscous timescales and reach or exceed local equipartition estimates based on gas pressure. When vertical outflows are included, the amplified magnetic fields are advected into the corona, magnetizing disc-launched winds and jet precursors with field strengths of similar order. Our results demonstrate that radiation is not merely a passive component of accretion flows, but provides a robust and unavoidable trigger for the generation of dynamically significant magnetic fields. Our results provide a physically grounded explanation for the origin of large-scale, structured magnetic fields in and around accretion discs. This mechanism offers a pathway for magnetizing accretion discs and their outflows without invoking externally supplied magnetic flux, with broad implications for X-ray binaries, active galactic nuclei and other transients such as gamma-ray bursts (GRBs).

Tide-locked lava worlds are surface-melted rocky planets under 1:1 tidally locked orbit (i.e., synchronously rotating) with orbital period being equal to rotation period and with permanent hot dayside and cold nightside. Previous studies on this type of planets employed scaling analyses and two-dimensional (2D) simulations. This work is a continuation of the previous researches but including the effect of the Coriolis force and the simulation domain is extended to a 3D global sphere. We find that under the condition with thermal-only forcing (without surface wind stresses), the area-mean ocean depth is about 50–300 m (depending on vertical diffusivity) and the area-mean effect of horizontal ocean heat transport (in the order of 10$^{3}$ to 10$^{4}$ W m$^{-2}$) is significantly smaller than stellar radiation (in the order of 10$^{6}$ W m$^{-2}$ at the substellar region), being consistent with previous results. Different from 2D results, due to the effect of the Coriolis force, large-scale horizontal gyres form on the dayside, ocean currents near the west boundaries are much stronger than that near the east boundaries (called as “western intensification”), the deepest ocean is not right at the substellar point but in the middle latitudes as the vertical diffusivity is moderate or large, and meanwhile there exists significant asymmetry between the west and the east of the substellar point. These results establish a first picture for the 3D thermal-driven ocean circulation and confirm that the lava ocean should be shallow on tide-locked lava worlds.

The peculiar gamma-ray burst GRB 250702B is the longest event ever observed, lasting about one day and exhibiting four prompt-emission flares of $\sim100$ s with irregular recurrence intervals of at least one hour. To explain this hierarchy of timescales, we consider a scenario in which a stellar object undergoes repeated partial tidal disruptions by a black hole (BH). We find that if a white dwarf (WD) is on a highly eccentric orbit ($e\approx0.97$) around an intermediate-mass black hole (BH) with $M_{\rm BH}\lesssim10^{6}\,M_\odot$ and $a = 50\,R_\odot\left(M_{\rm BH}/10^{6}\,M_\odot\right)^{1/3}$, the observed properties of GRB 250702B can be naturally reproduced. In this framework, the duration of each flare is determined by the viscous accretion timescale of material stripped near pericenter, with a typical mass $\Delta M \approx 2\times10^{-2}\,M_\odot$. The minimum recurrence time corresponds to the orbital period, while the total activity period is set by the secular orbital evolution timescale leading to the complete disruption of the WD. Furthermore, if $M_{\rm BH}\gtrsim10^{5}\,M_\odot$ and the orbit has a minimum polar angle relative to the BH equatorial plane of $\theta_{\rm min}\gtrsim0.12 {\rm rad}$, relativistic frame dragging induces $\gtrsim0.1$ rad precession of the orbital angular momentum between successive pericenter passages, comparable to a typical GRB jet half-opening angle, resulting in intermittent alignment with the observer and irregular flare spacing. The WD experiences $\approx40$ jet-launch episodes before complete disruption, but only four are expected to be observed on-axis. The remaining off-axis jets become visible at late times, enhancing the radio afterglow by about an order of magnitude, providing a testable prediction of this scenario.

We construct a charged Bardeen black hole (BH) surrounded by perfect fluid dark matter (PFDM) and coupled to a cloud of strings (CS). The metric function combines the magnetic monopole charge from nonlinear electrodynamics, the PFDM logarithmic correction, and the CS parameter that renders the spacetime asymptotically non-flat. We analyze the horizon structure, identifying parameter ranges yielding non-extremal BHs, extremal configurations, and naked singularities. The null geodesics, photon sphere radius, and shadow are computed, revealing that both CS and PFDM enlarge the shadow. For neutral particle dynamics, we derive the specific energy, angular momentum, and innermost stable circular orbit location. Quasiperiodic oscillations (QPOs) are examined through the azimuthal, radial, and vertical epicyclic frequencies, where notably the azimuthal frequency is independent of the CS parameter. Scalar field perturbations governed by the Klein-Gordon equation yield an effective potential whose peak decreases with both parameters, yet the transmission and reflection probabilities respond oppositely to CS and PFDM variations. The greybody factor bounds are obtained using semi-analytical methods. Our results demonstrate that the distinct effects of $\alpha$ and $\beta$ on various observables could allow independent constraints on these parameters through shadow measurements, QPO timing, and gravitational wave ringdown observations.

We investigate a bouncing cosmological model within the Weyl-type $f(Q)$ gravity framework, employing a power-law form of the non-metricity scalar $Q$. The model successfully resolves the initial singularity problem by demonstrating a nonsingular bounce, where the universe transitions from a contracting phase $ \dot{a}(t)<0 $ to an expanding phase ($ \dot{a}(t)>0 $) at the bouncing point $t \approx 0.$ Key features include the violation of the null energy condition (NEC) near the bounce and the crossing of the phantom divide line ($\omega=-1$) by the equation of state (EoS) parameter, indicating quintom-like behavior. The model exhibits accelerated expansion post-bounce, suggesting an inflationary phase. Stability analysis via the adiabatic index reveals instability near the bouncing point, while energy conditions highlight the dominance of dark energy. Additionally, the study explores scalar fields, showing that quintessence-like kinetic energy becomes negative and phantom-like kinetic energy peaks positively near the bounce, aligning with dark energy dynamics. The Hubble parameter, deceleration parameter, and Hubble radius further validate the bouncing scenario, with the latter displaying symmetric behaviour around the bounce. These results underscore the viability of Weyl-type $f(Q)$ gravity as a framework for nonsingular bouncing cosmologies, offering insights into early universe dynamics and dark energy behaviour.

The fundamental question of baryogenesis and the problem of matter-antimatter asymmetry motivate this study into the formation and evolution of antimatter objects in the early Universe. Hypothesize is the existence of isolated antimatter domains in a baryon-asymmetric Universe that survive until the era of first star formation ($Z \approx 20$). By assuming CPT-symmetry, the thermodynamics, mechanics, and energy dynamics of an antimatter gas cloud (composed of antihydrogen and antihelium) are treated symmetrically to their primordial matter counterparts. Analysis demonstrates the physical feasibility of the gravitational collapse process for a conservatively estimated antimatter domain ($\approx 5 \times 10^3 M_{\odot}$). The initial conditions easily satisfy the Jeans and Bonnor-Ebert mass criteria, indicating a high propensity for instability and runaway collapse. The subsequent dynamical evolution, driven by $\bar{H}_2$ cooling, is predicted to proceed identically to that of Population III star formation, leading to the formation of a dense, adiabatic anti-protostellar core. The theoretical viability of a true antistar hinges upon a critical assumption: the physical possibility of antinuclear fusion (e.g., the antiproton cycle) under extreme core conditions. Assuming this symmetry holds, the collapse is predicted to yield massive antistars ($\gtrsim 22 M_{\odot}$). This suggests that if antimatter domains formed in the early Universe, they likely underwent stellar formation. Observational constraints on the existence of these objects must rely on the detection of characteristic high-energy $\gamma$-ray or X-ray signals resulting from matter-antimatter annihilation at the domain boundaries or during mass accretion.

We used MIST isochrone fitting and a dedicated grid of stellar evolution models computed with MESA to constrain the ages of the components of the $\gamma$ Persei binary system. While individual stars can be matched to the models at specific metallicities, no joint isochrone solution reproduces both the observed masses and evolutionary states. The stellar evolutionary tracks calculated by MESA reveal a clear evolutionary mismatch. The primary component of the system is in a post-main-sequence phase consistent with the red giant branch or red clump. In contrast, the lighter secondary component lies near the turn-off point of the main sequence or is in the early phase of the subgiant branch. This discrepancy can be overcome by assuming that the $\gamma$ Persei system was born as a triple and the primary component is a rejuvenated star formed through a merger of a close-by pair of main-sequence stars. We show that the merger must have occurred no later than a few hundred megaryears after system formation, and the progenitor masses of the merging stars are restricted by a combination of stars that fall within a narrow band in the $(M_{1,a},M_{1,b})$ plane, corresponding to $M_{1,a}\simeq0.9$–$2.1\,M_\odot$ and $M_{1,b}\simeq2.3$–$2.5\,M_\odot$.