Papers for Friday, Nov 07 2025

We implemented a real-time data processor (rta-dp) framework that can be used to develop real-time analysis pipelines and data handling systems to manage high-throughput data streams with distributed applications in the context of ground and space astrophysical projects and high-energy instruments. The rta-dp is based on the ZeroMQ in-memory communication framework to receive input data, share data between distributed processes, and send or receive commands and pipeline configuration. The rta-dp framework has a flexible architecture that allows the implementation of distributed analysis systems customized to the requirements of several scenarios. The rta-dp framework also provides monitoring capabilities for the running processes and sends housekeeping, logging, alarms, and informative messages that a monitoring process can acquire. We are using the rta-dp in several contexts, such as acquiring and processing data from X-ray detectors to the data quality system of the ASTRI Project, as well as reprocessing and archiving data.

Dynamical friction implies a consistency check on any system where dark matter particles are hypothesised to explain orbital dynamics requiring more mass under Newtonian gravity than is directly detectable. Introducing the assumption of a dominant dark matter halo will also imply a decay timescale for the orbits in question. A self-consistency constraint hence arises, such that the resulting orbital decay timescales must be longer than the lifetimes of the systems in question. While such constraints are often trivially passed, the combined dependencies of dynamical friction timescales on the mass and orbital radius of the orbital tracer and on the density and velocity dispersion of the assumed dark matter particles leads to the existence of a number of astronomical systems where such a consistency test is failed. Here, we review cases from stars in ultrafaint dwarf galaxies, galactic bars, satellite galaxies, and, particularly, the multi-period mutual orbits of the Magellanic Clouds, as recently inferred from the star formation histories of these two galaxies, as well as the nearby M81 group of galaxies, where introducing enough dark matter to explain observed kinematics leads to dynamical friction orbital decay timescales shorter than the lifetimes of the systems in question. Taken together, these observations exclude dark matter halos made of particles as plausible explanations for the observed kinematics of these systems.

It is widely believed that the ultraviolet background produced during the epoch of reionization conspires against the formation of low-mass galaxies. Indeed, this mechanism is often invoked as a solution to the so-called `missing satellites problem.' In this paper we employ FIREbox, a large-volume cosmological simulation based on the Feedback In Realistic Environments (FIRE-2) physics model, to characterize the mechanisms governing galaxy ignition in the post-reionization era. By carefully matching recently-ignited halos (with stellar ages below $100$ Myr) to halos that failed to form any stars, we conclude that the presence of cold-dense gas and halo concentration help incite the process of galaxy formation. Concretely, we find that $100\%$ of recently-ignited halos experience cold-dense gas enhancements relative to their matched failed counterparts. Likewise, approximately $83\%$ display enhancements in both cold-dense gas and Navarro-Frenk-White concentration ($c_{\rm NFW}$), while the remaining $\sim17\%$ exhibit enhanced cold-dense gas content and suppressed $c_{\rm NFW}$ values. Lastly, our simulation suggests that galaxy ignition can occur as late as $z=2$, potentially allowing us to observationally catch this process `in the act' in the forseeable future.

The James Webb Space Telecope (JWST) opened a new window for the study of the highest redshift ($z>7$) Universe. This work presents a theoretical investigation of the very-high redshift Universe using the state-of-the-art GALaxy Evolution and Assembly (GAEA) model, run on merger trees from the Planck-Millennium $N$-body simulation. We show that GAEA successfully reproduces a wide range of high-$z$ observational estimates including: the galaxy stellar mass function up to $z\sim13$ and the total (galaxies and AGN) UV luminosity function (LF) up to $z\sim10$. We find that the AGN UV emission represents an important contribution at the bright end of the UVLF up to $z\sim8$, but it is negligible at higher redshift. Our model reproduces well the observed mass-metallicity relation at $z\leq4$, while it slightly overestimates the normalization of the relation at earlier cosmic epochs. At $z\geq11$, current UVLF estimates are at least one order of magnitude larger than model predictions. We investigate the impact of different physical mechanisms, such as an enhanced star formation efficiency coupled with a reduced stellar feedback or a negligible stellar feedback at $z>10$. In the framework of our model, both the galaxy stellar mass and UV luminosity functions at $z\geq10$ can be explained by assuming feedback-free starbursts in high-density molecular clouds. However, we show that this model variant leads to a slight increase of the normalization of the $z\geq10$ mass-metallicity relation, strengthening the tension with available data. A model with negligible stellar feedback at $z>10$ also predicts larger numbers of massive and bright galaxies aligning well with observations, but it also overestimates the metallicity of the interstellar medium. We show that these model variants can in principle be discriminated using the relation between the star formation rate and galaxy stellar mass.

Gas accretion, hot ($\sim 10^6\,{\rm K}$) atmospheres, and a tilt between the rotation axes of the disc and the atmosphere are all robust predictions of standard cosmology for massive star-forming galaxies at low redshift. Using idealized hydrodynamic simulations, we demonstrate that the central regions of hot galaxy atmospheres continuously condense into cool ($\sim10^4\,{\rm K}$) discs, while being replenished by an inflow from larger scales. The size and orientation of the condensed disc are determined by the angular momentum of the atmosphere, so it is large and often tilted with respect to the pre-existing galaxy disc. Continuous smooth accretion from hot atmospheres can thus both provide the necessary fuel for star formation and explain the observed ubiquity of extended and warped HI discs around local spirals. In this hot accretion scenario, cool gas observations cannot be used to trace the source of the HI, warps out to halo radii, consistent with recent indications of a lack of $21\,{\rm cm}$ emission from the halos of nearby galaxies (the `HI desert'). Observations of HI warps formed via hot accretion can be used to constrain the angular momentum, accretion rate, and gas metallicity of hot galaxy atmospheres, important parameters for disc galaxy evolution that are hard to determine by other means.

White Dwarfs (WDs), the final evolutionary stage of most stars, are frequently modeled considering only a dense plasma matter. However, their potential interaction with dark matter (DM), especially in galactic halos where DM is expected to be prevalent, may lead to significant consequences. This work proposes a novel EoS (EoS) that consistently incorporates both hot dense plasma and cold dark matter (CDM) contributions in hot WDs. The hot dense plasma EoS is extended to include thermal and radiative contributions. At the same time, the CDM component is modeled as a linear fluid, with the coupling constant $\alpha$ determined self-consistently within the star. A smooth phase transition between hot dense plasma and CDM regimes is introduced via a hyperbolic mixing function that depends on local energy density and stellar temperature. Our results show that the inclusion of CDM leads to an increase in the WD radius by approximately $12\%$ and a total mass enhancement of $0.7\%$, compared to standard hot WD models without lattice effects. These results highlight the importance of considering CDM in stellar modeling and suggest that WDs may serve as indirect probes for the astrophysical properties of dark matter.

Photometric redshifts (photo-$z$s) are an essential tool for galaxy evolution science with JWST. However, for deep surveys with more limited filter sets (i.e. $N_{\text{filt}} \sim6$) such as large pure parallel surveys, the most commonly used template-fitting based photo-$z$ approaches can yield highly confident but spurious results for high-$z$ populations of interest. The utility and legacy value of these datasets could therefore be negatively impacted. To address this challenge, we present an application of machine learning (ML) based photo-$z$ techniques to deep JWST photometric datasets. We employ two different ML algorithms, using Gaussian processes and nearest-neighbour estimates, alongside a more standard template fitting approach. We show that simple nearest-neighbour based estimates can provide more accurate photo-$z$s than template fitting out to $z\sim8$, as well as reducing the fraction of catastrophic outliers by a factor of $\sim2-3$. Additionally, `hybrid' estimates combining template and ML can yield further improvements in overall accuracy and reliability while retaining some ability to predict photo-$z$ out to $z > 10$. The nearest-neighbour only or hybrid estimates can achieve photo-$z$s with robust scatter of $\sigma_{\text{NMAD}}\sim0.03-0.04$ and outlier fractions of $\sim3-10\%$ between $0 < z \lesssim 8$ from just 6 NIRCam bands, with negligible additional computational costs compared to standard template fitting. Our methodology is easily adaptable to alternative datasets, filter combinations or training samples. Overall, our results highlight the potential for even simple ML techniques to enhance the scientific return of JWST pure parallel and wide-area surveys.

Though Rossby waves have been observed on the Sun, their radial eigenfunctions remain a mystery. The prior theoretical work either considers quasi-2D systems, which do not apply to the solar interior, or only considers fully radiative or fully convective atmospheres. This project calculates the radial eigenfunctions for Rossby waves in a deep atmosphere for a general stratification. Here, we use the $\beta$-plane approximation to derive a vertical equation in terms of the Lagrangian pressure fluctuation $\delta P$, and we then calculate radial eigenfunctions for Rossby waves in a standard solar model, Model S. We find that working in the Lagrangian pressure fluctuation results in cleaner wave equations that lack internal singularities that have been encountered in prior work. The resulting radial wave equation makes it abundantly clear that there are two wave cavities in the solar interior, one in the radiative interior and another in the convection zone. Surprisingly, our calculated radial vorticity eigenfunctions for the radiative interior modes are nearly constant throughout the convection zone, raising the possibility that they may be observable at the solar surface.

Light orbiting an accreting black hole may impact the disk or jet multiple times before escaping to the observer, at a variety of angles with respect to the local magnetic field. In this letter, we characterize the imprints of these long path lengths and disparate magnetic field impacts in synchrotron spectra of hot accretion disks, as the strongly lensed ``photon ring'' exhibits a higher synchrotron turnover frequency in each lensed sub-image. We apply tools of varying complexity: first, we develop a minimal, unlensed one-zone model that isolates the first two sub-images of the accretion flow. By varying the magnetic field geometry encountered by each sub-image, we show that distinctive spectral signatures emerge in both total intensity and fractional linear polarization. Second, we examine a semi-analytic radiatively inefficient accretion flow (RIAF) model, in which we find that there is generally a frequency at which the first indirect image outshines the direct image even in total flux density. Lastly, we demonstrate that even general relativistic magnetohydrodynamic (GRMHD) simulation snapshots show this spectral character. We find a typical correction to the unresolved spectrum of order $10\%$ near the turnover frequency that grows with increasing viewing inclination, growing to order unity at higher frequencies. We predict sensitive spectral studies of the cores of Messier 87* and Sagittarius A* at frequencies exceeding $300$ GHz to constrain the existence of the photon ring even without imaging, with prospects for photon ring detection even in other sources with unresolved shadows.

Solar activity is a process driven by many independent but interconnected phenomena. Although the 11-year cycle is the result of operation of the dynamo mechanism, the cause of longer secular variations is not clear. In search of such a cause, it was proposed to take into account the influence of the planetary system. In order to verify the idea, we consider the action of all planets in the solar system reduced to the effect of a single barycenter. The tidal force is decomposed into radial and meridional components. The radial tidal force is too small compared to the powerful radial gravity of the Sun. The meridional force is not compensated for by solar gravity and depends on latitude. As the latitude of the barycenter changes quite slowly, the sign of this component changes over a characteristic time scale of about 5 years, during which the meridional acceleration constantly acts on the surface of the Sun. This could ultimately lead to speeds of several meters per second and, in principle, could significantly change the speeds of the meridional currents involved in generating the magnetic field. However, it turned out that the calculated speed variation does not agree with the observed periodicity of solar activity. Earlier, the relation was analyzed between the activity periods on solar-type stars and the rotation periods of exoplanets, and no correspondence was observed either. Thus, the planetary hypothesis as a cause of long-term modulation of solar activity is not confirmed.

The detection of ultra-high-energy (UHE) neutrinos in the EeV range is the goal of current and future in-ice radio arrays at the South Pole and in Greenland. Here, we present a deep neural network that can reconstruct the main neutrino properties of interest from the raw waveforms recorded by the radio antennas: the neutrino direction, the energy of the particle shower induced by the neutrino interaction, and the event topology, thereby estimating the neutrino flavor. For the first time, we predict the full posterior PDF for the energy and direction reconstruction via neural posterior estimation utilizing conditional normalizing flows, enabling event-by-event uncertainty prediction. We improve over previous reconstruction algorithms and obtain a median resolution of 0.30 log(E) and 18 square degrees for a 'shallow' detector component and 0.08 log(E) and 28 square degrees for a 'deep' detector component for neutral current (NC) events at a shower energy of 1 EeV. This deep learning approach also allows us to reconstruct the more stochastic $\nu_e$ - charged current (CC) events. We quantify the impact of different antenna types and systematic uncertainties on the reconstruction and derive a goodness-of-fit score to test the compatibility of measured neutrino signals with the Monte Carlo simulations used to train the neural network.

We present a refined deep-learning-based method to reconstruct the three-dimensional dark matter density, gravitational potential, and peculiar velocity fields in the Zone of Avoidance (ZOA), a region near the galactic plane with limited observational data. Using a convolutional neural network (V-Net) trained on A-SIM simulation data, our approach reconstructs density or potential fields from galaxy positions and radial peculiar velocities. The full 3D peculiar velocity field is then derived from the reconstructed potential. We validate the method with mocks that mimic the spatial distribution of the Cosmicflows-4 (CF4) catalog and apply it to actual data. Given CF4's significant observational uncertainties and since our model does not yet account for them, we use peculiar velocities corrected via an existing Hamiltonian Monte Carlo reconstruction, rather than raw catalog distances. Our results demonstrate that the reconstructed density field recovers known galaxy clusters detected in an H \textsc{i} survey of the ZOA, despite this dataset not being used in the reconstruction. This agreement underscores the potential of our method to reveal structures in data-sparse regions. Most notably, streamline convergence and watershed analysis identify a mass concentration consistent with the Great Attractor, at $(l, b) = (308.4^\circ \pm 2.4^\circ, 29.0^\circ \pm 1.9^\circ)$ and $cz = 4960.1 \pm 404.4,{\rm km/s}$, for 64\% of realizations. Our method is particularly valuable as it does not rely on data point density, enabling accurate reconstruction in data-sparse regions and offering strong potential for future surveys with more extensive galaxy datasets.

In this paper, we first present observations of SN~2024acyl, a normal Type Ibn supernova with a large projected offset ($\sim$35~kpc) from its host galaxy. The low star-formation rate measured at the explosion site raises the possibility that the progenitor of SN~2024acyl may not have been a massive star. We then examine, more broadly, the spectral diversity of Type Ibn supernovae around 20--35 days after peak brightness and identify two distinct groups: Group I, which shows bluer rest-frame optical color and narrower He~I emission lines; and Group II, which shows redder rest-frame optical color and broader He~I lines. Group~I also tends to show higher peak luminosities. The diversity we identify appears to be closely connected to the diversity observed around peak and to persist into late phases ($>80$ days after peak). Given its redder color and broader He~I lines, we classify SN~2024acyl as belonging to Group II. Based on the current dataset, we find no clear connection between this spectral diversity and either the host environments of Type Ibn SNe or their pre-explosion activity. The observed diversity in Type Ibn SNe likely reflects differences in circumstellar material properties and/or explosion energetics. These differences could result from a range of progenitor properties, such as different helium star mass, orbital period and companion type if they are in binary systems, and may indicate fundamentally diverse progenitors. Whether a continuous distribution exists between the two groups remains to be determined and will require further data to explore.

A head-tail galaxy is thought to be a radio galaxy with bent active galactic nuclei (AGN) jets interacting with the intracluster medium (ICM). Study of head-tail galaxies provides us with fruitful insights into the mechanisms of shock waves and turbulence, as well as magnetic-field amplification and cosmic-ray acceleration. A recent MeerKAT observation revealed that a head-tail galaxy in the galaxy cluster, Abell 3322, exhibits a peculiar ``Omega" structure in its shape. In this paper, we investigated this Omega-tail galaxy using the upgraded Giant Meterwave Radio Telescope (GMRT) and the Australia Telescope Compact Array (ATCA). We found that the southern jet tends to be brighter than the northern jet, with a brightness ratio of about 2. This can be attributed to Doppler boost and the inclination of the jets. Our broadband data suggest that the radio spectrum becomes steeper along the jet propagation direction, and the cosmic-ray aging model with a weak reacceleration of cosmic rays is preferable to explain the index profile. We further found a gradient of the spectral index perpendicular to the jet propagation. We discussed the origin of the gradient and suggested that a shock wave along one side of the jets is present. The resultant ram pressure as well as the backflow made at the early stage of the jet may produce the tail component of this Omega-tail galaxy, while the observed Omega-shape structure is more likely due to a twin vortex seen in the low Reynolds number flow.

Transport coefficients are calculated for a partially ionized plasma consisting of approximately 90% hydrogen and 10\% helium, representative of a model solar atmosphere with an assumed magnetic field profile. The ion Hall parameter, defined as the ratio of ion cyclotron to ion collision frequency, is determined by considering dominant resonance charge exchange processes alongside less significant nonresonant ion neutral collisions. Based on these calculations, we derive profiles for various transport coefficients. Our results demonstrate that thermal conductivity in partially ionized media, both parallel and perpendicular to the ambient magnetic field, is dominated by neutral particles. The perpendicular thermal conductivity components show weak dependence on the ion Hall parameter and remain comparable in magnitude to their parallel counterparts. Wave damping through neutral thermal conductivity may contribute significantly to solar atmospheric heating. These findings indicate that perpendicular thermal conductivity components are essential for accurate modelling of partially ionized regions, including photosphere-chromosphere transition layers, spicules, and coronal prominences.

We characterize the physical conditions and energy budget of the M16 H II region using SOFIA FEEDBACK observations of the [C II] 158 $\mu$m line. The O stars in the $\sim 10^{4}~{\rm M}_{\odot}$ NGC 6611 cluster powering this H II region have blown at least 2 cavities into the giant molecular cloud: the large M16 cavity and the small N19 bubble. We detect the spectroscopic signature of an expanding photodissociation region shell towards N19, and traces of a thin, fragmented expanding shell towards M16. Our [C II] observations are resolved to 0.5 km s$^{-1}$ and 15.5$^{\prime\prime}$ and analyzed alongside similarly resolved CO J=3$-$2 observations as well as archival data ranging from the radio to X-ray tracing a variety of gas phases spanning dense $\sim$10 K molecular gas, $10^{4}$ K photoionized gas, and million-K collisionally ionized plasma. With this dataset, we evaluate the coupling of energetic feedback from NGC 6611 and the O9 V star within N19 to the surrounding gas. Winds from NGC 6611 have blown a 20 pc radius cavity constrained in size along the major axis of the natal giant molecular filament, and much of the mechanical wind energy ($>$90%) has escaped through breaches in the $\lesssim 10^{4}~{\rm M}_{\odot}$ shell. Reservoirs of dense gas remain within a few parsecs of the cluster. N19, younger than M16 by $\gtrsim 10^6$ yr, is driven by a combination of mechanical wind energy and thermal pressure from photoionized gas and has swept up $\sim 10^{3}~{\rm M}_{\odot}$ into neutral atomic and molecular shells.

The appearance and specific properties of the structures in the local Universe are studied by means of the Vlasov kinetic technique. The role of the cosmological constant in the local structure formation is considered via the theorem on the general function satisfying the identity of the gravity of sphere and of point mass. Then, the Hubble tension is naturally explained as a result of two flows, local and global one, with non-coinciding Hubble parameters. The linearized Vlasov-Poisson equation with the cosmological term is shown to lead to van Kampen's waves, of Landau damping and then to aperiodic structures. The aperiodicity thus is emerging as a intrinsic feature of the filamentary and void structure of the local Universe, revealing the self-consistent field mechanism of its formation. The damping of the aperiodicity then is predicted and can be observationally traced upon the increase of the scale of the filaments.

In this work, we compare galaxies from the NIHAO and HESTIA simulation suites to ultra-diffuse galaxies (UDGs) with spectroscopically measured dynamical masses. For each observed UDG, we identify the simulated dark matter halo that best matches its dynamical mass. In general, observed UDGs are matched to simulated galaxies with lower stellar masses than they are observed to have. These simulated galaxies also have halo masses much less than would be expected given the observed UDG's stellar mass and the stellar mass -- halo mass relationship. We use the recently established relation between globular cluster (GC) number and halo mass, which has been shown to be applicable to UDGs, to better constrain their observed halo masses. This method indicates that observed UDGs reside in relatively massive dark matter halos. This creates a striking discrepancy: the simulated UDGs are matched to the dynamical masses of observed ones, but not their total halo masses. In other words, simulations can produce UDGs in halos with the correct inner dynamics, but not with the massive halos implied by GC counts. We explore several possible explanations for this tension, from both the observational and theoretical sides. We propose that the most likely resolution is that observed UDGs may have fundamentally different dark matter halo profiles than those produced in NIHAO and HESTIA. This highlights the need for a simulation that self-consistently produces galaxies of a stellar mass of $\sim 10^8 M_\odot$ in dark matter halos that exhibit the full range of large dark matter cores to cuspy NFW-like halos.

We present CosmicANNEstimator (Cosmological Parameters Artificial Neural Network Estimator), a machine learning approach for constraining cosmological parameters within the Lambda Cold Dark Matter ($\Lambda$CDM) framework. Our methodology employs two specialized artificial neural networks (ANNs) designed to analyze Hubble parameter and Supernova data independently. The estimator is trained on synthetic data covering broad parameter ranges, with Gaussian random noise incorporated to simulate observational uncertainties. Our results demonstrate parameter estimates and associated uncertainties comparable to traditional Markov Chain Monte Carlo (MCMC) methods, establishing machine learning as an efficient alternative for cosmological parameter estimation. This work underscores the potential of neural network-based inference to complement traditional Bayesian methods and accelerate future cosmological analyses.

The Moon has been long regarded as a natural resonator of gravitational waves (GWs) since 1960, showing great potential to fill the frequency gap left behind GW detections by ground- or space-based laser interferometry. However, the spatial variation of this amplification capacity on the Moon remains unclear. Here, we numerically simulate the lunar response to GWs by fully considering the fluctuant topography and laterally heterogeneous interior structures. Our results show that most regions on the Moon can amplify GWs with a ratio over 2, a finding significantly higher than previous estimations. Particularly, the amplification ratio can even reach factors of tens at the resonant frequency of ~0.015 Hz on the highlands surrounding the South Pole-Aitken (SPA) basin, where the regional crust is the thickest. Our findings establish the thick-crust regions as critical zones of GW amplification, which is essential for future landing site selection and instrumental setting for GW detection on the Moon.

This decade has seen the first measurements of extrasolar planetary obliquities, characterizing how an exoplanet's spin axis is oriented relative to its orbital axis. These measurements are enabled by combining projected rotational velocities, planetary rotation periods, and astrometric orbits for directly-imaged super-Jupiters. This approach constrains both the spin axis and orbital inclination relative to the line of sight, allowing obliquity measurements for individual systems and offering new insights into their formation. To test whether these super-Jupiters form more like scaled-up planets or scaled-down stars, we develop a hierarchical Bayesian framework to infer their population-level obliquity distribution. Using a single-parameter Fisher distribution, we compare two models: a planet-like formation scenario ($\kappa=5$) predicting moderate alignment, versus a brown dwarf-like formation scenario ($\kappa=0$) predicting isotropic obliquities. Based on a sample of four young super-Jupiter systems, we find early evidence favoring the isotropic case with a Bayes factor of 15, consistent with turbulent fragmentation.

We investigate the cosmological constraints from the void-lensing cross-correlation assuming the $w$CDM model for the Chinese Space Station Survey Telescope (CSST) photometric survey. Using Jiutian simulations, we construct a mock galaxy catalog to $z=3$ covering 100 deg$^2$, which incorporates the instrumental and observational effects of the CSST. We divide the galaxy sample into seven photometric-redshift (photo-$z$) tomographic bins and identify 2D voids within each bin using the Voronoi tessellation and watershed algorithm. We measure the angular cross-power spectrum between the void distribution and the weak lensing signal, and estimate the covariance matrix via jackknife resampling combined with pseudo-$C_{\ell}$ approach to account for the partial sky correction. We employ the Halo Void Dust Model (HVDM) to model the void-matter cross-power spectrum and adopt the Markov Chain Monte Carlo (MCMC) technique to implement the constraints on the cosmological and void parameters. We find that our method can accurately extract the cosmological information, and the constraint accuracies of some cosmological parameters from the void-lensing analysis are comparable or even tighter than the weak lensing only case. This demonstrates that the void-lensing serves as an effective cosmological probe and a valuable complement to galaxy photometric surveys, particularly for the Stage-IV surveys targeting the high-redshift Universe.

Magnetohydrodynamic (MHD) turbulence plays a central role in many astrophysical processes in the interstellar medium (ISM), including star formation, heat conduction, and cosmic-ray scattering. MHD turbulence can be decomposed into three fundamental modes-fast, slow, and Alfvén-each contributing differently to the dynamics of the medium. However, characterizing and separating the energy fractions of these modes was challenging due to the limited information available from observations. To address this difficulty, we use 3D isothermal and multiphase MHD turbulence simulations to examine how mode energy fractions vary under different physical conditions. Overall, we find that the Alfvén and slow modes carry comparable kinetic-energy fractions and together dominate the turbulent energy budget in multiphase media, while the fast mode contributes the smallest fraction. Relative to isothermal conditions, multiphase simulations exhibit an enhanced fast-mode energy fraction. We further introduce a machine-learning-based approach that employs a conditional Residual Neural Network to infer these fractions directly from spectroscopic data. The method leverages the fact that the three MHD modes imprint distinct morphological signatures in spectroscopic maps owing to their differing anisotropies and compressibilities. Our model is trained on a suite of isothermal and multiphase simulations covering typical ISM conditions. We further demonstrate that our machine learning model can robustly recover the mode fractions from spectroscopic observables, achieving mean absolute errors of approximately 0.05 for seen data and 0.1 for unseen data.

The formation of the first stars in the universe could be significantly impacted by the effects of Dark Matter (DM). Namely, if DM is in the form of Weakly Interacting Massive Particles (WIMPs), it could lead to the formation (at $z\sim 25-10$) of stars that are powered by DM annihilations alone, i.e. Dark Stars (DSs). Those objects can grow to become supermassive ($M\sim 10^6 \Msun$) and shine as bright as a galaxy ($L\sim 10^8 \Msun)$. Using a simple $\chi^2$ minimization, the first three DSs photometric candidates (i.e. \JADESeleven, \JADEStwelve, and \JADESzthirteen) were identified by \cite{Ilie:2023JADES}. Our goal is to develop tools to streamline the identification of such candidates within the rather large publicly available high redshift JWST data sets. We present here the key first step in achieving this goal: the development and implementation of a feed-forward neural network (FFNN) search for Dark Star candidates, using data from the JWST Advanced Deep Extragalactic Survey (JADES) photometric catalog. Our method reconfirms JADES-GS-z13 and JADES-GS-z11 as dark star candidates, based on the chi-squared goodness of fit test, yet they are $\sim10^4$ times faster than the Neadler-Mead $\chi^2$ minimization method used in \cite{Ilie:2023JADES}. We further identify six {\it new photometric} Dark Star candidates across redshifts $z \sim 9$ to $z \sim 14$. These findings underscore the power of neural networks in modeling non-linear relationships and efficiently analyzing large-scale photometric surveys, advancing the search for Dark Stars.

Some of the first stars in the Universe might be powered by Dark Matter (DM) annihilations, rather than nuclear fusion. Those objects, i.e. Dark stars (DS), offer a unique window into understanding DM via the observational study of the formation and evolution of the first stars and their Black Hole (BH) remnants. In \cite{NNSMDSPhot} (Paper~I) we introduced a feedforward neural network (FFNN) trained on synthetic DS photometry in order to detect and characterize dark star {\it photometric} candidates in the early universe based on data taken with the NIRCam instrument onboard the James Webb Space Telescope (JWST). In this work we develop a FFNN trained on synthetic DS spectra in order to identify {\it spectroscopic} dark star candidates in the data taken with JWST's NIRSpec instrument. In order to validate our FFNN model we apply it to real data for the four spectroscopic Supermassive Dark Star (SMDS) candidates recently identified in \cite{ilie2025spectroscopicsupermassivedarkstar} and reconfirm that indeed \JADESeleven, \JADESzthirteen, \JADESfz, and \JADESfo have spectra that are consistent with those of Supermassive Dark Stars. The main advantage of our FFNN model, in comparison to the Nedleaer-Mead Monte Carlo parameter estimator used in \cite{ilie2025spectroscopicsupermassivedarkstar}, is that the approach introduced here predicts parameters in milliseconds, over 10,000 times faster than the traditional method used in \cite{ilie2025spectroscopicsupermassivedarkstar}. With this in mind, the FFNN model we developed and validated in this work will be adapted for Bayesian uncertainty analyses and automatic analyses of NIRSpec publicly available data for high redshift objects. This study establishes a robust and efficient tool for probing Dark Stars and understanding their role in cosmic evolution.

A hierarchical three-body model can be widely applied to diverse astrophysical settings, from satellite-planet-star systems to binaries around supermassive black holes. The octupole-order perturbation on the inner binary from the tertiary can induce extreme eccentricities and cause orbital flips of the binary, but short-range forces such as those due to General Relativity (GR) may suppress extreme eccentricity excitations. In this paper, we consider restricted hierarchical three-body systems, where the inner binary has a test-mass component. We investigate the maximum possible eccentricity (called "limiting eccentricity") attainable by the inner binary under the influence of the tertiary perturbations and GR effect. In systems with sufficiently high hierarchy, the double averaging (DA) model is a good approximation; we show that the orbits which can flip under the octupole-order perturbation reach the same limiting eccentricity, which can be calculated analytically using the quadrupole-order Hamiltonian. In systems with moderate hierarchy, DA breaks down and the so-called Brown Hamiltonian is often introduced as a correction term; we show that this does not change the limiting eccentricity. Finally, we employ the single averaging (SA) model and find that the limiting eccentricity in the SA model is higher than the one in the DA model. We derive an analytical scaling for the modified limiting eccentricity in the SA model.

Dwarf nova (DN) superoutbursts are accompanied by superhumps, which change their periods and profiles over a superoutburst. We present the TESS and ground-based observations of nine WZ Sge-type DNe and candidates in superoutburst. In TCP J23580961$+$5502508, ASASSN-23ba, PNV J19030433$-$3102187, V748 Hya, and ASASSN-25ci, we confirmed double-peaked oscillations called early superhumps, which are regarded as the unambiguous feature of WZ Sge-type DNe. On the other hand, the superhump and outburst properties of MO Psc and V1676 Her suggest that they may not be a member of WZ Sge-type DNe. The 2022 superoutburst of a confirmed WZ Sge-type DN TCP J05515391$+$6504346, however, lacked an early superhump phase. We find superhumps in a WZ Sge-type DN ASASSN-20mq during its rebrightening outburst. Thanks to the continuous coverage of TESS, we find the broken-powerlaw rise of the outburst light curve in V748 Hya and PNV J19030433$-$3102187, previously found in only one WZ Sge-type DN observed by Kepler. Early superhumps appeared when the system reached $\simeq40$% of the outburst peak flux. No orbital modulation from a hot spot is detected before and after this. This non-detection of orbital humps on the early rise of V748 Hya constrains that the corresponding mass transfer rate should be below $\simeq1\times10^{16}$ g s$^{-1}$, disfavouring an enhancement of a mass transfer rate by an order of magnitude or larger, even if it occurs. The contentious TESS observations also confirm the coexistence of early and ordinary superhumps during their transition and $\leq$2-cycle duration of stage A--B superhump transition in V748 Hya.

The spectral energy distributions (SEDs) of certain BL Lac objects (BL Lacs) exhibit an additional hard $\gamma$-ray component in the TeV energy range that surpasses the predictions of the one-zone leptonic jet model. The origin of this excess emission remains unclear. In this study, we selected five BL Lacs whose SEDs display a very hard intrinsic spectrum in the TeV band and successfully reproduced their broadband SEDs using a two-zone lepto-hadronic model. Within this framework, the emission observed in the optical, X-ray, GeV $\gamma$-ray, and sub-TeV $\gamma$-ray bands is modeled using the synchrotron and synchrotron self-Compton radiation processes of the relativistic electrons in the jets. Meanwhile, the TeV excess is attributed to $\gamma$-ray emission resulting from the photomeson ($p\gamma$) process via $\pi^0$ decay occurring within advection-dominated accretion flows (ADAFs). This scenario requires a hard proton spectrum with a spectral index of $p \sim 1.6-1.7$ and a cutoff energy ranging from 30 to 90 TeV, as well as a relatively large ADAF radius. Such hard proton spectra suggest that the dominant acceleration mechanisms are likely magnetic reconnection and/or stochastic acceleration processes within ADAFs. Additionally, the emission from the cascaded electrons results in a bump in the keV--MeV band; however, it is overwhelmed by the jet emission. Although the hadronuclear ($pp$) process cannot be entirely ruled out, it would necessitate an even harder proton spectrum and a higher cutoff energy compared to the $p\gamma$ process, making it a less favorable explanation for the observed TeV excess.

In this paper, we explain the recently reported a nHz-band gravitational-wave background from NANOGrav 15-year through the merger of binary super-massive black holes with masses of $10^9 M_{\odot}$ formed by the growth of primordial black holes. When a primordial black hole accretes at a high accretion rate, it emits a large number of high-energy photons. These heat the plasma, causing high-redshift cosmological 21cm line emission. Since this has not been detected, there is a strict upper bound on the accretion rate. We have found that with the primordial black hole abundance $10^{-14} \lesssim f_{\rm PBH} \lesssim 10^{-12}$ and the mass $1 M_{\odot} \lesssim m_{\rm PBH} \lesssim 10^3 M_{\odot}$, we successfully fit the nHz band gravitational wave background from NANOGrav 15-year while avoiding the 21 cm line emission. We propose that future observations of the gravitational wave background and the cosmological 21cm line can test this scenario.

Solar filaments are cool and dense plasma structures suspended in the solar corona against gravity. We present observations of a quiescent filament eruption that occurs on 13 July 2015. The eruption is associated with a two-ribbon GOES B8.9 class flare. Photospheric magnetic flux cancellation is present below the filament during days. This builds up a flux rope which progressively rises until it gets unstable, first leading to a confined eruption and pre-flare brightenings, then to an ejection which starts $\approx$ 20 min later with the flare onset. An interesting feature of this event is the presence of a large circular brightening formed around the erupting region. This brightening is produced due to interchange reconnection of the ejected magnetic configuration with the surrounding open magnetic field. This null-point topology is confirmed by a potential-field extrapolation. The EUV loops located on the southern side of the filament eruption first contract during the null-point reconnection, then expand as the flux rope is ejected. The associated CME has both a classical flux rope shape and plasma ejected along open field lines on the flux rope side (a trace of interchange reconnection). Finally, we set all this disparate observations within a coherent framework where magnetic reconnection occurs both below and above the erupting filament.

Most of the physical information about astrophysical objects is obtained via the analysis of their electromagnetic spectra. Observed data coupled with radiation transfer models in physical conditions representative of stars, planets, kilonovae, and ISM, yield constrains on their physical structure, gas flow dynamics at the surface, mass loss, and detailed chemical composition of the systems. All these core astrophysical parameters are just as reliable as the physical quality of the models that are employed for simulations of radiation transfer. Recent advances in multi-D transfer modeling with Non-Local Thermodynamic Equilibrium (NLTE) in inhomogeneous time-dependent systems revealed systematic shortcomings of canonical models. Owing to major complexities of solving coupled multi-frequency RT equations in 3D geometry, a number of approximations have been introduced. This review presents an overview of the physical problem, standard solutions, and recent methodological advances. We also provide an overview of main results in the area of 3D NLTE radiation transfer and its applications to modeling diverse astrophysical environments, including FGKM type- and OBA-type stars, multi-epoch spectra of kilonovae, and atmospheres of rocky and gaseous exoplanets.

Dynamic processes in the accretion flow near black holes produce X-ray flux variability, sometimes quasi-periodic. Determining its physical origin is key to mapping accretion geometry but remains unresolved. We perform a novel phase-resolved analysis on a newly discovered quasi-periodic oscillation (QPO) in the active galactic nucleus 1ES 1927+654. For the first time in a supermassive black hole (SMBH), we detect a unique `U'-shaped QPO lag-energy spectrum and observe coronal spectral variability over the QPO phase. We find that the QPO is adequately explained by plasma resonant oscillations within a corona. Modeling of QPO spectral properties and reverberation mapping reveal that the corona is contracting and confined to only a few gravitational radii regions near the SMBH, consistent with theoretical predictions for a decreasing QPO period of near 10 minutes. These results present the first observational evidence for an oscillating and contracting compact corona around an SMBH.

Classical Cepheids are among the most important distance calibrators and play a crucial role in the calibration as the first rung of the extragalactic distance ladder. Given their typical age, they also constitute an optimal tracer of the young population in the Galactic disc. We aim to increase the number of available DCEPS with high-resolution spectroscopic metallicities, to study the galactocentric radial gradients of several chemical elements and analyse the spatial distribution of the Galactic young population of stars in the Milky Way disc. We performed a complete spectroscopical analysis of 136 spectra obtained from three different high-resolution spectrographs, for a total of 60 DCEPs. More than half have pulsational periods longer than 15 days, up to 70 days, doubling the number of stars in our sample with P>15d. We derived radial velocities, atmospheric parameters and chemical abundances up to 33 different species. We present an updated list of trusted spectroscopic lines for the detection and estimation of chemical abundances. We used this new set to revisit the abundances already published in the context of the C-MetaLL survey and increase the number of available chemical species. For the first time (to our knowledge), we present the estimation of abundances for Dysprosium, as well as a systematic estimation of Erbium, Lutetium and Thorium abundances. We calculate a galactic radial gradient for [Fe/H] with a slope of $-0.064\pm0.002$, in good agreement with recent literature estimation. The other elements also exhibit a clear negative radial trend, with this effect diminishing and eventually disappearing for heavier neutron-capture elements. Depending on the proposed spiral arms model present in several literature sources, our most external stars agree on tracing either the Perseus, the Norma-Outer or both the Outer and the association Outer-Scutum-Centaurus (OSC) arms.

A key task in cosmology is to test the validity of general relativity (GR) at cosmological scales and, therefore, to distinguish between dark energy and modified gravity (MG) as the driver of the late-time cosmic acceleration. The decay rate ($DR$) of cosmological gravitational potential, being sensitive to gravity and being immune to various astrophysical uncertainties, enables GR tests independent to other structure growth probes. Recently we have measured $DR$ at $0.2\leq z\leq 1.4$, combining the DR9 galaxy catalog from the DESI imaging surveys and Planck cosmic microwave background maps \citep{arXiv:2411.12594}. Here we use this measurement to test gravity, and restrict the analysis to one-parameter extensions to the standard $\Lambda$CDM cosmology. We consider four one-parameter MG parameterizations. One is $f(a)=\Omega_m^\gamma(a)$. The other three adopt the gravitational slip parameter $\eta=1$ and consider variations in the effective gravitational constant $G_{\rm eff}/G$ with the parameterization $\Sigma(a)=\Sigma_\Lambda \Omega_\Lambda(a)/\Omega_\Lambda$, $\Sigma(a)=\Sigma_1 a$ or $\Sigma(a)=\Sigma_2 a^2$. We find $\gamma=0.47^{+0.22}_{-0.15}$, consistent with the GR prediction $\gamma\simeq 0.55$. We also find $\Sigma_\Lambda=0.018^{+0.052}_{-0.053}$, $\Sigma_1=0.020^{+0.065}_{-0.062}$, and $\Sigma_2=0.027^{+0.067}_{-0.069}$, fully consistent with the GR case of $\Sigma=0$, regardless of parameterizations of $\Sigma(a)$. The constraining power is already competitive, while a factor of 2 further improvement is expected for the upcoming full-sky galaxy surveys.

We investigated a volume-limited sample of LAMOST main-sequence stars with masses from 0.25 to 1 $M_{\odot}$ and distances of 150-350 pc to explore how the stellar initial mass function (IMF) varies with metallicity. We corrected the spectroscopic selection function by comparing the stellar number densities with the photometric ones at the same colour and magnitude. From these corrected number density distributions, we derived IMFs for each metallicity sub-samples. Fitting a broken power-law function in each IMF with a fixed break point at 0.525 $M_{\odot}$, we found the power-law indices increase with [Fe/H] for both mass regimes: $\alpha_1$ (mass $\leq$ 0.525 $M_{\odot}$) rises from 0.54 $\pm$ 0.21 to 1.40 $\pm$ 0.07 and $\alpha_2$ (mass>0.525 $M_{\odot}$) grows from 1.40 $\pm$ 0.16 to 1.86 $\pm$ 0.04 as [Fe/H] varies from -1 to +0.5 dex. It demonstrates that low-mass stars make up a larger fraction in metal-rich environments than in metal-poor ones. We performed simulations to assess the impact of unresolved binaries on the IMF power-law indices. After correction, the binary-adjusted $\alpha$ values retained a similar metallicity-dependent trend. Furthermore, by examining the IMF of the aggregate sample, we found the corrected indices ($\alpha_{\rm{1,corr}} = 1.48 \pm 0.03$ , $\alpha_{\rm{2,corr}} = 2.17 \pm 0.03$) are consistent with Kroupa's IMF values ($\alpha_1 = 1.3 \pm 0.5$ and $\alpha_2 = 2.3 \pm 0.3$). Finally, we verified the robustness of our results by testing different break points and mass bin sizes, confirming that the IMF's dependence on [Fe/H] remains consistent.

Thanks to a recent observation with XMM-Newton, we discovered periodic pulsations at P= 9.6652 +/- 0.0002 s in a new ultraluminous X-ray source (ULX) in the galaxy NGC 4631. This source, dubbed as X-8, shows one of the largest spin-up rates ever observed, dP/dt = (-9.6 +/- 0.5)*1E-8 s/s. These findings indicate that the compact object is a neutron star, and X-8 is a new member of the pulsating ULX class. The 0.3-10 keV luminosity of X-8 is ~3.4E39 erg/s, and its X-ray spectrum can be described by an absorbed disk blackbody or a cut-off power law, similar to what is observed in other pulsating ULXs. We discuss two possible causes for the large spin-up rate: Doppler shift from orbital motion of the neutron star and intrinsic spin-up due to accretion torque. This new ULX pulsar adds a key source to the small known population, and will enable future studies to better constrain the physical mechanisms responsible for their super-Eddington luminosities.

In our alternative theory, built around the coincidence of experimental and theoretical data, three "free" parameters -- the magnetic field in the tachocline of the order of ~10^7 G (see Fig.(A.1) and Eq.(A17) in V. D. Rusov et al. (2021)), the axion mass ma ~3.2*10^{-2} eV (see Eq. (11) in V. D. Rusov et al. (2021)), and the asymmetric dark matter (ADM) in the Universe with mADM ~5 GeV ((see V. D. Rusov et al. (2021); A. C. Vincent et al. (2016)) -- give a complete solution to the problem of the theory of magnetic flux tubes in strong fields with 11-year variations of axion-origin photons, which are caused by and anticorrelated to the 11-year variations in density of ADM, gravitationally captured on the Sun.

In addition to comprehensive surveys of the Milky Way bulge, disk, and halo, the Apache Point Galactic Evolution Experiment (APOGEE) project observed seven dwarf spheroidal satellites (dSphs) of the Milky Way: Carina, Sextans, Sculptor, Draco, Ursa Minor, Bootes 1, and Fornax. APOGEE radial velocities, stellar parameters, and Gaia EDR3 proper motions are used to identify member stars in the vicinity of each dwarf. To properly analyze the abundance patterns of these galaxies, a novel procedure was developed to determine the measurable upper limits of the APOGEE chemical abundances as a function of the effective temperature and the spectral signal-to-noise ratio. In general, the APOGEE abundance patterns of these galaxies (limited to [Fe/H] $>$ -2.5) agree with those found in high-resolution optical studies after abundance offsets are applied. Most of the galaxies studied have abundance patterns that are distinctly different from the majority of stars found in the MW halo, suggesting that these galaxies contributed little to the MW halo above [Fe/H] $>$ -2.0. From these abundance patterns, we find that these dSphs tend to follow two types of chemical evolution paths: episodic and continuous star formation, a result that is consistent with previous photometric studies of their star formation histories. We explore whether mass and/or environment have an impact on whether a galaxy has an episodic or continuous star formation history, finding evidence that, in addition to the galaxy's mass, proximity to a larger galaxy and the cessation of star formation may drive the overall shape of the chemical evolution.

Ultra-hot Jupiters (UHJs) in close orbits around early-type stars provide natural laboratories for studying atmospheric escape and star-planet interactions under extreme irradiation and wind conditions. The near-ultraviolet (NUV) regime is particularly sensitive to extended upper atmospheric and magnetospheric structures. We investigate whether star-planet interactions in the WASP-189 system could plausibly account for the early ingress feature suggested by NUV transit fitting models. We analyzed three NUV transits of WASP-189b observed as part of the Colorado Ultraviolet Transit Experiment (CUTE), which employs a 6U CubeSat dedicated to exoplanet spectroscopy. To explore whether the observed transit asymmetry could plausibly arise from a magnetospheric bow shock (MBS), we performed magnetohydrodynamic (MHD) simulations using representative stellar wind velocities and planetary atmospheric densities. During Visit 3, we identified an approximately 31.5-minute phase offset that is consistent with an early ingress. Our MHD simulations indicate that with a wind speed of 573 km s-1 and an upper atmospheric density of about 4.6e-11 kg m-3, a higher-density zone due to compression can form ahead of the planet within five planetary radii where the fast-mode Mach number falls below ~0.56, even without a MBS. Shock cooling and crossing time estimates suggest that such a pileup could produce detectable NUV absorption. Our results indicate that while MBS formation is feasible for WASP-189b, low stellar-wind speeds favor NUV-detectable magnetic pileups over classical bow shocks and enhance the potential detectability of early-ingress signatures.

We present a study of the high-temperature spectral component in meteor fireballs, with a particular focus on neutral hydrogen at 656.28 nm and ionised silicon doublet at 634.71 nm and 637.14 nm. By analysing spectra from the European Fireball Network (EN) that exhibit H$\alpha$ and Si~II emissions, we investigated the relationship between H and Si abundances across different meteoroid types. The plasma temperature of the high-temperature component remains independent of meteor velocity. This allows us to directly compare relative intensities of volatile hydrogen with less volatile silicon in bodies with different velocities. Our results confirmed that the H/Si value remains largely independent of meteor velocity. We show a positive correlation with photometric mass for cometary meteoroids, suggesting that larger bodies better preserve their volatile content, namely hydrogen. This correlation persists across the meteor showers, showing a physical process related to volatile preservation rather than specific parent body composition. Our data suggest that the abundance of hydrogen in large cometary meteoroids is not only higher than in CI chondrites, but is also comparable to or higher than the measured abundances in small particles of dust from Halley's comet, depending on the assumed plasma conditions. This work brought new constraints on the distribution and preservation of volatile elements in Solar System bodies and new insights into the potential delivery mechanisms of water to Earth. The prevalence of hydrogen in larger cometary meteoroids supports models where comets could be significant contributors to Earth's volatile inventory.

In this study, we conduct a comparative analysis of observations carried out on the exoplanet HAT-P-25 b at the Sharjah Astronomical Observatory (SAO). We have employed two distinct filters, namely, the Luminoso (L) and Visual (V) filters. Our research aims to discern any variations in transit depth or exoplanet size resulting from the use of these different filters. The primary focus of this study is to determine the exoplanet's size relative to its host star using the transit method. The application of different filters was expected to introduce subtle variations in size, influenced by factors such as the exoplanet's atmosphere. Notably, our findings reveal that the exoplanet's size appears larger when observed through the L filter compared to the V filter. Throughout the analytical process, we employed the TRASCA model to determine the transit depth for each epoch. Fixed parameters, including the orbital period of the exoplanet (P, measured in days) and the transit duration (measured in minutes), were utilized in these calculations. Our results indicate that the transit depths observed with the L filter were greater than those with the V filter, measuring 0.0238 magnitudes and 0.0200 magnitudes, respectively. These values deviate from the reference result of 0.0204 magnitudes.

The approaches to searching for axion-like signals based on pulsars include observations with pulsar timing arrays (PTAs) and pulsar polarization arrays (PPAs). However, these methods are limited by observational uncertainties arising from multiple unknown and periodic physical effects, which substantially complicate subsequent data analysis. To mitigate these issues and improve data fidelity, we propose the Artificial Pulsar Polarization Arrays (APPA): a satellite network comprising multiple pulsed signal transmitters and a dedicated receiver satellite. In order to constrain the axion-photon coupling parameter $g_{a\gamma}$, we generate simulated observations using Monte Carlo methods to investigate APPA's sensitivity via two complementary approaches: Bayesian analysis and frequentist analysis. Simulations indicate that for axion mass $m_{a}\sim\mathcal{O}\big(10^{-22}-10^{-19}\big)$ eV, APPA yields a better upper limit on $g_{a\gamma}$ (at the 95\% confidence level) than conventional ground-based observations and achieves better detection sensitivity.

FUV radiation from massive stars launch photoevaporative winds from the outer regions of protoplanetary discs around other stars, removing gas and dust. Observations have identified a relation between the median dust disc mass and the external UV field strength. Here we use disc evolutionary models to explore how this relation evolves over time, and with respect to other stellar and disc properties. We find that the slope for the relationship $\lambda_{\rm UV}$ flattens over time as populations age, possibly explaining the differences seen between the L1641-N and L1641-S clusters in Orion A. We determine that $\lambda_{\rm UV}$ depends on the stellar mass where more massive stars exhibit steeper gradients than their lesser counterparts, in agreement with the differences seen between Herbig and T Tauri stars. Additionally, the strength of the mechanism for angular momentum transport, either viscosity or MHD disc winds, is found to significantly affect $\lambda_{\rm UV}$ with stronger $\alpha$ values reducing $\lambda_{\rm UV}$ due to more material accreting on to the central stars in weaker UV environments. Estimates of $\lambda_{\rm UV}$ from observations of L1641 place preliminary constraints on $\alpha$ to be between $10^{-3.5}$--$10^{-2.5}$, consistent with literature estimates. Further observations in different regions and better classifications of stellar masses will allow us to place stringent constraints on disc evolution properties, improving our understanding of how protoplanetary discs evolve.

Coagulation of dust particles in protoplanetary disks is the first step on the journey to the formation of planets. The surface free energy (SFE) of the dust particles determines the effectiveness of particles sticking to each other after collision, as well as the critical collision velocity above which fragmentation will occur. Studies of SFE have focused on the simplest silicate, silica, usually at standard temperature and pressure. However, protoplanetary dust grains have a wide variety of mineralogical compositions, temperatures, and a low-pressure environment lacking in water vapor. We perform molecular dynamics simulations using a ReaxFF-type potential of the SFE of silica, albite, and anorthite at temperatures ranging from 30 to 700 K in a true vacuum. We find that the SFE drops by tens of percent with increasing temperature or shifting to more complex silicate compositions. More dramatically, we find that the values of the SFE in a vacuum are two orders of magnitude higher than those usually measured in terrestrial laboratories. Our results confirm previous work that suggests that hydroxylation by monolayers of water produces this reduction in SFE in experiments. The coagulation of dust grains thus appears to depend critically on the cleanliness of their surfaces, as well as their temperature and composition.

The Euclid Quick Data Release 1 (Q1) encompasses 30 million sources across 63.1 square degrees, marking the beginning of petabyte-scale data delivery through Data Release 1 (DR1) and subsequent releases. Systematic exploitation of such datasets requires extracting millions of source-specific cutouts, yet standard tools like Astropy's Cutout2D process sources individually, creating bottlenecks for large catalogues. We introduce Cutana, a memory-efficient software tool optimised for batch processing in both local and cloud-native environments. Cutana employs vectorised NumPy operations to extract cutout batches simultaneously from FITS tiles, implements automated memory-aware scheduling, and supports both Zarr and FITS output formats with multiple common normalisation schemes (asinh, log, zscale). Cutana outperforms Astropy in all tested Q1 subset scenarios achieving near linear scaling and processing thousands of cutouts per second. On just four worker threads, Cutana can process all of Q1 in under four hours. The tool includes an ipywidget interface for parameter configuration and real-time monitoring. Integration with ESA Datalabs is underway for the Euclid DR1 release, with open-source release pending ESA open-source licensing processes.

The VERITAS Collaboration recently reported the detection of very-high-energy (VHE) gamma-ray emission from the prototypical radio quasar 3C273. The temporal and the spectral properties of this component do not appear compatible with the extrapolation of the beamed blazar-like emission of the inner, pc-scale jet. We explore the possibility that the VHE component is produced in the jet at kpc scale through the inverse Compton emission of a population of ultra-high energy electrons (with Lorentz factor $\gamma\sim 10^8$). In the model these electrons are accelerated through the shear acceleration mechanism, and they also account for the still puzzling X-ray emission of knots detected by {\it Chandra} in the large-scale jets of several powerful quasars (including 3C273). In our scenario the VHE component can be interpreted as the integrated emission from the two brightest knots of the 3C273 jet. We speculate that the decay of the emission on the timescale of $\sim 3$ years could be accounted for by the scenario if the VHE radiation is produced in some compact regions in the downstream flow of a recollimation shock.

Recent results from the Dark Energy Spectroscopic Instrument (DESI) support the dynamical dark energy. Intriguingly, the data favor a transition of the dark energy equation of state across $w=-1$, a hallmark of the Quintom scenario. In this paper, we consider a different approach to the dynamical nature of dark energy by investigating its interaction with ordinary matters, specifically the Chern-Simons (CS) interaction with photons. In cosmology, this interaction rotates the polarized plane of the cosmic microwave background (CMB) photons, which induces non-zero polarized TB and EB power spectra. We forecast this measurement with the Ali CMB Polarization Telescope (AliCPT) experiment. We take the best-fit value of the isotropic rotation angle from Planck data as our fiducial input. We project that 11 module-year (modyr) of observations will yield an improved detection sensitivity with a significance $\sim 5\sigma$, given a calibration precision of $0.1^\circ$ in the polarization angle. We also forecast AliCPT's sensitivity to the amplitude of a scale invariant spectrum of the anisotropic polarization rotation field. With $50$~modyr of observations, the large-aperture configuration is expected to reach $\sigma_{A_{\mathrm{CB}}}\sim10^{-2}$, offering a sixfold improvement over the small-aperture design and enabling competitive tests of spatial fluctuations in the dark energy field.

We present a comprehensive study on the physical and chemical structures of a chemically rich bipolar outflow in a high-mass star forming region IRAS 16272$-$4837 (SDC335), utilizing high-resolution spectral line data at 1.3 mm and 3 mm dual-bands from the ALMA ATOMS and QUARKS surveys. The high-velocity jet is enveloped by a lower-velocity outflow cavity, containing bright knots that show enhanced molecular intensities and elevated excitation temperatures. Along the outflow, we have identified 35 transitions from 22 molecular species. By analyzing the spatial distribution and kinematics of these molecular lines, we find that the molecular inventory in the outflow is regulated by three processes: (i) direct entrainment from the natal molecular core by the outflow; (ii) shock-induced release of molecules or atoms from dust grains; and (iii) thermal desorption and gas-phase reactions driven by shock heating. These results confirm that outflows are not only dynamical structures but also active chemical factories, where entrainment, shocks, and thermal processing jointly enrich the molecular content. Our findings confirmed that outflow chemistry has multi-origin nature, and provide critical insights into chemical evolution during high-mass star formation.

We demonstrate that the properties of eccentric gravitational wave (GW) signals enhance the detectability of GW phase shifts caused by environmental effects (EEs): The signal-to-noise ratio (SNR) of EEs can be boosted by up to $\ell_{\rm max}^{1 - n}$ with respect to corresponding circular signals, where $\ell_{\rm max}$ is the highest modeled eccentric GW harmonic and $n$ is the frequency scaling of the GW dephasing prescription associated to the EE. We investigate the impact on a population level, adopting plausible eccentricity distributions for binary sources observed by LIGO/Virgo/Kagra (A+ and A\# sensitivities), as well as Cosmic Explorer (CE) and the Einstein Telescope (ET). For sources in the high eccentricity tail of a distribution ($e \gtrsim 0.2$ at 10 Hz), phase shifts can systematically be up to $\ell_{\rm max}^{1 - n}$ times smaller than in a corresponding circular signal and still be detectable. For typical EEs, such as Roemer delays and gas drag, this effect amounts to SNR enhancements that range from $10^2$ up to $10^5$. For CE and ET, our analysis shows that EEs will be an ubiquitous feature in the eccentric tail of merging binaries, regardless of the specific details of the formation channel. Additionally, we find that the joint analysis of eccentricity and phase shift is already plausible in current catalogs if a fraction of binaries merge in AGN migration traps.

The atmospheres of massive O-type stars (O stars) are dynamic, turbulent environments resulting from radiatively driven instabilities over the iron bump, located slightly beneath the stellar surface. Here, complex radiation hydrodynamic processes affect the structure of the atmosphere as well as the formation of spectral lines. In quantitative spectroscopic analysis, the effects of these processes are often parametrized with ad hoc techniques and values. This work is aimed at exploring how variation of basic atmospheric parameters affects the dynamics within the subsurface turbulent zone. We also explore how this turbulence relates to absorption lines formed in the photosphere for a broad range of O stars at solar metallically. The work in this paper centers around a grid of 2D, radiation-hydrodynamic O-star atmosphere and wind simulations, where the turbulent region is an emergent property of the simulation. For each of the 36 models in the grid, we derived the turbulent properties and correlated them to an estimate of turbulent line broadening imposed by the models' velocity fields. Our work suggests that the subphotospheric turbulent velocity in O-stars scales approximately with the square of the Eddington arameter, $\Gamma_{\rm e}$. We also find a linear correlation between subphotospheric turbulent velocity and the line broadening of several synthetic photospheric absorption lines. Radiation carries more energy than advection throughout the atmosphere for all models in the grid; however, for O-type supergiants, the latter can account for up to 30 \% of the total flux at the peak of the iron bump.

We introduce a noise-aware extension to the parametric maximum-likelihood framework for component separation by modeling correlated $1/f^\alpha$ noise as a harmonic-space power law. This approach addresses a key limitation of existing implementations, for which a mismodelling of the statistical properties of the noise can lead to biases in the characterization of the spectral laws, and consequently biases in the recovered CMB maps. We propose a novel framework based on a modified ridge likelihood embedded in an ensemble-average pipeline and derive an analytic bias correction to control noise-induced foreground residuals. We discuss the practical applications of this approach in the absence of true noise information, leading to the choice of white noise as a realistic assumption. As a proof of concept, we apply this methodology to a set of simplified, idealized simulations inspired by the specifications of the proposed ECHO (CMB-Bh$\overline{a}$rat) mission, which features multi-frequency, large-format focal planes. We forecast the $95 \%$ upper limit on the tensor-to-scalar ratio, $r_{95}$, under a suite of realistic noise scenarios. Our results show that for an optimistic full sky observation, ECHO can achieve $r_{95}\leq 10^{-4}$ even in the presence of significant correlated noise, demonstrating the mission's capability to probe primordial gravitational waves with unprecedented sensitivity. Without degrading the statistical performance of the traditional component separation, this methodology offers a robust path toward next-generation B-mode searches and informs instrument design by quantifying the impact of noise correlations on cosmological parameter recovery.

Coronal mass ejections (CMEs) are a major driver of space weather. To assess CME geoeffectiveness, among other scientific goals, it is necessary to reliably identify and characterize their morphology and kinematics in coronagraph images. Current methods of CME identification are either subjected to human biases or perform a poor identification due to deficiencies in the automatic detection. In this approach, we have trained the deep convolutional neural model Mask R-CNN to automatically segment the outer envelope of one or multiple CMEs present in a single difference coronagraph image. The empirical training dataset is composed of 10^5 synthetic coronagraph images with known pixel-level CME segmentation masks. It is obtained by combining quiet coronagraph observations, with synthetic white-light CMEs produced using the GCS geometric model and ray-tracing technique. We found that our model-based trained Mask R-CNN infers segmentation masks that are smooth and topologically connected. While the inferred masks are not representative of the detailed outer envelope of complex CMEs, the neural model can better differentiate a CME from other radially moving background/foreground features, segment multiple simultaneous CMEs that are close to each other, and work with images from different instruments. This is accomplished without relying on kinematic information, i.e. only the included in the single input difference image. We obtain a median IoU=0.98 for 1.6*10^4 synthetic validation images, and IoU=0.77 when compared with two independent manual segmentations of 115 observations acquired by the COR2-A, COR2-B and LASCO C2 coronagraphs. The methodology presented in this work can be used with other CME models to produce more realistic synthetic brightness images while preserving desired morphological features, and obtain more robust and/or tailored segmentations.

FU Ori outbursts are thought to play an important role in stellar assembly and the evolution of protoplanetary disks. However, the progenitor young stellar objects are largely uncharacterized. We obtained a low-resolution optical spectrum of HBC 722 before its FU Ori outburst as part of a survey of young stellar objects in the North America Nebula. The spectrum yields a spectral type of M3.3$\pm$0.4, which when combined with archival photometry allows us to measure the stellar and accretion properties of a young star prior to its FU Ori outburst. The pre-outburst accretion rate of $7\times10^{-9}$ M$_\odot$ yr$^{-1}$ is high for a protoplanetary disk around an M3-M3.5 star, though about 15,000 times weaker than the accretion rate during the outburst. The pre-outburst variability, inferred from archival B-band photometry, is about a factor 5 with a standard deviation of 0.16 dex and is consistent with variable accretion onto young low-mass stars. The stellar radius is larger than the radius of accreting young stars of similar spectral type by a factor of two. The extinction to HBC 722 is $\sim 1.45\pm0.3$~mag, lower than the 2.5--3.7~mag extinction values measured during the outburst. The u-band photometry plays an especially important role in constraining the veiling at longer wavelengths and therefore also the extinction and photospheric luminosity.

The coexistence of PAHs and the C$_{60}$ fullerene in different astrophysical environments can give rise to the formation of new complex species denoted as PAH-C$_{60}$ adducts, which may contribute to the infrared (IR) emission observed. These PAH-C$_{60}$ adducts have been previously reported experimentally due to the high reactivity between PAHs and C$_{60}$. From the astrophysical point of view, however, they have not been considered in detail yet. Here we have performed a combined experimental and theoretical study in order to characterize the IR spectra of PAH-C$_{60}$ adducts, including multiple adducts. By using new advanced experimental techniques, we have been able to synthesize some specific PAH-C$_{60}$ adduct isomers, and measured their IR spectra. These experimental data are used to correct their harmonic scaled spectra, as obtained from quantum-chemistry calculations performed at the DFT level under the B3LYP-GD3/6-31+G(d) approach. This way, we simulate the IR ($\sim$3$-$25 $\mu$m) spectra of multiple PAH-C$_{60}$ adducts, composed by a different number of PAH units: mostly one or two units. In addition, the chemical kinetics data available in the literature are used to tentatively estimate the possible order of magnitude of the abundances of these PAH-C$_{60}$ adducts using the available observational data. Essentially, our results reveal a possible strong modification of the IR spectra when astronomically estimated abundances are considered. Several spectral peculiarities are observed, such as a broad $\sim$3.4-3.6 $\mu$m feature, and important modifications in the 6-10 and 12-16 $\mu$m spectral regions together with contributions to the C$_{60}$ features at 7.0 and 18.9 $\mu$m. Interestingly, these PAH-C$_{60}$ adducts lack aliphatic CH bonds, but they display IR features around 3.4 $\mu$m, challenging previous interpretations of this astronomical feature.

Recent cosmological data, including DESI DR2, highlight significant tensions within the $\Lambda$CDM paradigm. When analyzed in the context of General Relativity (GR), the latest DESI data favor a dynamical dark energy (DDE) equation of state, $w(z)$, that crosses the phantom divide line $w=-1$. However, this framework prefers a lower Hubble constant, $H_0$, than Planck 2018, thereby worsening the tension with local measurements. This phantom crossing is a key feature that cannot be achieved by minimally coupled scalar fields (quintessence) within GR. This suggests the need for a new degree of freedom that can simultaneously: (A) increase the best-fit value of $H_0$ in the context of the DESI DR2 data, and (B) allow the crossing of the $w=-1$ line within a new theoretical approach. We argue that both of these goals may be achieved in the context of Modified Gravity (MG), and in particular, Scalar-Tensor (ST) theories, where phantom crossing is a natural and viable feature. We demonstrate these facts by analyzing a joint dataset including DESI DR2, Pantheon+, CMB, and growth-rate (RSD) data in the context of simple parametrizations for the effective gravitational constant, $\mu_G(z) \equiv G_{eff}/G_N$, and the DDE equation of state, $w(z)$. This MG framework significantly alleviates the tension, leading to a higher inferred value of $H_0 = 70.6 \pm 1.7 \, \text{km s}^{-1} \text{Mpc}^{-1}$. We also present a systematic, data-driven reconstruction of the required underlying ST Lagrangian and provide simple, generic analytical expressions for both the non-minimal coupling $F(\Phi) = 1+\xi\Phi^{2}e^{n\Phi}$ and the scalar potential $U(\Phi) = U_{0}+ae^{b\Phi^{2}}$, which well-describe the reconstructed functions.

Very Long Baseline Interferometry (VLBI) provides high angular resolution images and has been used for stellar astrometry for decades. The DYNAMO-VLBA project utilizes the Very Long Baseline Array (VLBA) to study tight binary and multiple pre-main sequence stars, whose components have detectable radio emission and typical separations on the order of milli-arcseconds. Such systems cannot be resolved by Gaia, making VLBI an essential tool for the study of their orbital parameters and, eventually, the determination of their mass. Here, we report VLBA dynamical mass measurements of the individual stars in the S1 system in Ophiuchus and EC\,95 in Serpens. S1 is the most luminous and massive stellar member of the nearby Ophiuchus star-forming region. We find that the primary component, S1A, has a mass of $4.11 \pm 0.10\,M_{\odot}$. This is significantly less than the value of $\sim6\,M_{\odot}$ expected from theoretical models given the location of S1A on the HR diagram. The secondary, S1B, has a mass of $0.831 \pm 0.014\,M_{\odot}$ and is most likely a T Tauri star. In the Serpens triple system EC\,95, we measure the masses of EC\,95A and EC\,95B, finding $2.15\pm0.10$ M$_\odot$ and $2.00\pm0.12$ M$_\odot$, respectively. In this case, the measured masses agree with the location of the stars in the HR diagram for very young 2 $M_\odot$ stars. For the first time, we also estimated the mass of tertiary, EC\,95C, to be 0.26 $^{+0.53}_{-0.46}$ M$_\odot$.

Bayesian inference is central to modern cosmology, yet comprehensive model comparison and tension quantification remain computationally prohibitive for many researchers. To address this, we release $\texttt{unimpeded}$, a publicly available Python library and data repository providing pre-computed nested sampling and MCMC chains. We apply this resource to conduct a systematic analysis across a grid of eight cosmological models, including $\Lambda$CDM and seven extensions, and 39 datasets, including individual probes and their pairwise combinations. Our model comparison reveals that whilst individual datasets show varied preferences for model extensions, the base $\Lambda$CDM model is most frequently preferred in combined analyses, with the general trend suggesting that evidence for new physics is diluted when probes are combined. Using five complementary statistics, we quantify tensions, finding the most significant to be between DES and Planck (3.57$\sigma$) and SH0ES and Planck (3.27$\sigma$) within $\Lambda$CDM. We characterise the $S_8$ tension as high-dimensional ($d_G=6.62$) and resolvable in extended models, whereas the Hubble tension is low-dimensional and persists across the model space. Caution should be exercised when combining datasets in tension. The $\texttt{unimpeded}$ data products, hosted on Zenodo, provide a powerful resource for reproducible cosmological analysis and underscore the robustness of the $\Lambda$CDM model against the current compendium of data.

We present KGB-evolution, a relativistic $N$-body simulation code that extends the $k$-evolution code by incorporating an effective field theory parameterization of kinetic gravity braiding, while also including the $k$-essence model as a limiting case. As a first step, we implement the linearized dark energy stress-energy tensor and scalar field equations, providing the groundwork for a future full Horndeski theory extension. We validate KGB-evolution by comparing its power spectra against linear predictions from hi$\_$class, finding excellent agreement on large scales at low redshifts and over all scales at high redshifts. We demonstrate that nonlinear growth of matter and metric perturbations on small scales drives the linearized dark energy field into a nonlinear clustering regime, which in turn feeds back on the growth of cosmic structure. In contrast to the $k$-essence limit, a nonzero braiding considerably amplifies this backreaction, producing a significantly stronger alteration of structure formation in the kinetic gravity braiding model.

We study a system of a self-gravitating condensate, a boson star, formed from scalar ultra-light dark matter (ULDM), with a black hole hosted at its center. We numerically solve the equations of hydrostatic equilibrium in the non-relativistic limit, consistently incorporating the gravitational potential of the black hole, to obtain all possible configurations of this BS-BH system for different boson star masses, interaction types, and black hole masses. We also propose an analytic expression for the density profile and compare it with the numerical results, finding good agreement for attractive interactions and for a finite range of mass ratios between the black hole and boson star. Finally, considering the inspiral of this BS-BH system with a second, smaller black hole, we study the dephasing of gravitational waves due to the presence of the ULDM environment. A Fisher matrix analysis reveals the regions of parameter space of the ULDM mass and self-coupling that future gravitational-wave observatories such as LISA can probe.

Disturbances in gravitational wave (GW) observational data are often caused by non-stationary noise in the detector itself, such as back-scattering of laser stray light into the signal field. Unlike GW signals, non-stationary noise can appear in both the GW-signal quadrature and the orthogonal quadrature, which is usually not measured. Simultaneous sensing of this orthogonal quadrature provides a witness channel that can be used to reconstruct the disturbance in the signal quadrature enabling a subtraction of non-stationary noise. Here, we present the concept of quadrature witness that is compatible with frequency-dependent squeezing, which is already used to simultaneously reduce photon shot noise and photon radiation pressure noise. We demonstrate that implementing this approach in a GW detector could reduce noise caused by loud back-scatter events, thereby improving the overall sensitivity and robustness of GW observatories.

We explore charged black holes in Scalar-Tensor-Vector Gravity (STVG), unveiling their distinctive features across multiple physical domains. Our topological analysis reveals that the STVG coupling parameter $\alpha$ bolsters thermal stability while electromagnetic charge $Q$ weakens it. Using the Gauss-Bonnet theorem, we find that $\alpha$ amplifies light deflection and enlarges shadow silhouettes, with $Q$ generating opposite effects. Our quantum-corrected models with exponential entropy terms pinpoint phase transitions in the microscopic regime, modifying conventional thermodynamic relationships. Calculations of strong gravitational lensing, shadow geometry, and Hawking emission show clear STVG signatures that diverge from Einstein's predictions. Notably, our accretion disk analysis uncovers an intriguing phenomenon: specific combinations of $\alpha$ and $Q$ can produce radiation patterns resembling spinning Kerr black holes, creating potential identification challenges for observers. These findings establish concrete observational tests for STVG theory through next generation astronomical imaging and lensing campaigns. By connecting theoretical predictions to measurable quantities, we outline specific pathways to confirm or constrain STVG using data from current and future space telescopes.

Super-Kamiokande [SK] was upgraded through the addition of gadolinium sulfate to its ultrapure water, initiating the SK-Gd program. This development enables efficient neutron tagging via the large capture cross section of gadolinium, greatly improving the identification of inverse beta decay events, the primary channel for detecting the diffuse supernova neutrino background [DSNB]. The upgrade also enhances sensitivity to galactic and pre-supernova neutrinos, as well as atmospheric neutrino interactions. To realize this capability, extensive work was performed, including the construction and operation of the EGADS demonstrator, the refurbishment of the SK tank, the development of radiopure gadolinium production methods, and the validation of the loading and uniformity of gadolinium in solution. Early SK-Gd operation has demonstrated high neutron-tagging efficiency, reduced backgrounds, and world-leading limits on the DSNB flux. With these advances, SK-Gd now stands at the threshold of discovering the DSNB and opens a wide range of new opportunities in astrophysics and neutrino physics.

According to General Relativity (GR), gravitational waves (GWs) should travel at the speed of light $c$. However, some theories beyond GR predict deviations of the velocity of GWs $c_{\rm gw}$ from $c$, and some of those expect vacuum dispersion. Therefore, probing the propagation effects of GWs by comparing the wave format detectors against the one at emission excepted from GR. Since such propagation effects accumulate through larger distance, it is expected that super-massive black holes binary (SMBHB) mergers serve as better targets than their stellarmass equivalent. In this paper, we study with simulations on how observations on a population of SMBHs can help to study this topic. We simulate LISA observations on three possible SMBHB merger populations, namely Pop\MakeUppercase{\romannumeral 3}, Q3-nod and Q3-d over a 5-year mission. The resulting constraints on the graviton mass are \(9.50\), \(9.33\), and \(9.05 \times 10^{-27} \, \mathrm{eV}/c^2\), respectively. We also obtain the corresponding constraints on the dispersion coefficients assuming different dispersion scenarios. If the electromagnetic wave counterparts of SMBHB merger can be detected simultaneously, the $c_{\rm gw}$ can be constrained waveform-independently to \(\Delta c/c\) to \(10^{-13}-10^{-12}\), corresponding to graviton mass constraints of \(10^{-26}-10^{-24} \mathrm{eV}/c^2\).

It is widely believed that Sgr A$^*$, located at the center of our Galaxy, is a supermassive black hole. Recent observations of its shadow and long-term monitoring of the S2 star have provided compelling evidence supporting this hypothesis. These observational advancements also offer valuable opportunities to explore the physical properties of the black hole and its surrounding environment. Since a dark matter halo is expected to exist in the Milky Way and around Sgr A$^*$, investigating the behavior of the Galactic Center black hole embedded in such a halo provides a crucial means to simultaneously probe both black hole physics and dark matter properties. In this work, We develop a black hole metric that incorporates a generalized double power law dark matter halo, and analyze the corresponding null and timelike geodesics to investigate how the halo parameters affect the black hole shadow and the motion of the S2 star. Furthermore, by comparing our theoretical predictions with observational data of the shadow and the S2 orbit, we constrained the dark matter halo parameters. The results of this study provide both theoretical and phenomenological insights into the nature of Sgr A$^*$ and the distribution of dark matter in our Galaxy.

We introduce Accelerated Sequential Posterior Inference via Reuse (ASPIRE), a broadly applicable framework that transforms existing posterior samples and Bayesian evidence estimates into unbiased results under alternative models without rerunning the original analysis. ASPIRE combines normalizing flows with a generalized Sequential Monte Carlo scheme, enabling efficient updates of existing results and reducing the computational cost of reanalyses by 4-10 times. This addresses a growing problem in gravitational-wave astronomy, where events must be repeatedly reanalyzed under different models or physical hypotheses. We show that ASPIRE reproduces full Bayesian results when switching waveform models or adding physical effects such as spin precession and orbital eccentricity. With this statistical robustness, ASPIRE turns repeated reanalyses into fast, reliable updatespaving the way for systematic studies of waveform systematics, scalable reanalyses across large event catalogs, and broadly applicable Bayesian reanalysis across other scientific domains.

Accurate thermal analysis is crucial for modern spacecraft, driving demand for reliable modeling tools. This research advances space thermal modeling by improving the simulation accuracy and efficiency of radiative heat transfer, the dominant mode of heat exchange in space. To this end, we incorporate diffuse reflectivity using the Gebhart method, which computes radiative exchange factors (REFs) from geometric view factors. The view factors, obtained via Monte Carlo ray tracing (MCRT), require post-processing to mitigate statistical errors. Critically, existing correction schemes cannot simultaneously enforce closure and reciprocity for open systems. This research addresses this gap by proposing two novel enforcement methods: (i) a least-squares optimization with non-negativity rectification (NNR) and small positive value avoidance (SPVA), and (ii) an iterative enforcement algorithm. To ensure consistency across different discretization levels, this work also introduces the multi-node surface model relations to formalize the connection between sub-face, face, and node representations of view factors and REFs. A simple case study demonstrates a substantial reduction in mean absolute error (MAE): the least-squares method achieves an 81% MAE reduction, while the iterative method offers the best balance of accuracy (56% MAE reduction) and computational efficiency. A second case study shows that including diffuse reflections decreases the steady-state temperature of a plate by $4^{\circ}C$, reinforcing that reflected radiation reduces net absorption. This work introduces and validates computationally efficient methods for integrating diffuse reflectivity into space thermal analyses and for consistently coupling multi-node surface radiative models. The results enable more accurate and robust thermal predictions for spacecraft systems.

Homodyne Quadrature interferometers (HoQI) are an interferometric displacement sensing scheme proven to have excellent noise performance, making them a strong candidate for sensing and control schemes in gravitational wave detector seismic isolation. Like many interferometric schemes, HoQIs are prone to nonlinear effects when measuring displacements. These nonlinearities, if left unsuppressed, would substantially limit the use cases of HoQIs. This paper first shows a means of measuring and quantifying nonlinearities using a working HoQI and a mechanical resonator. We then demonstrate a method for real-time correction of these nonlinearities and several approaches for accurately calibrating the correction technique. By correcting in real time, we remove one of the biggest obstacles to including HoQIs in upgrades to future gravitational wave detectors. Finally, we discuss how to post correct data from HoQIs, suppressing even further the nonlinearity-induced errors, broadening the appeal of such sensors to other applications where measurement data can be reconstructed after the fact. We demonstrate all of this on a working HoQI system and show the measured suppression of nonlinear effects from each of these methods. Our work makes HoQIs a more broadly applicable tool for displacement sensing.

We present a novel equivalence between scale-dependent gravity and scalar-tensor theories that have only a single scalar field with a canonical kinetic term in the Einstein frame and a conformal coupling to the metric tensor. In particular, we show that the set of well-behaved scale-dependent gravity theories can be fully embedded into scalar-tensor theories in a unique way. Conversely, there are multiple ways to write a scalar-tensor theory as a scale-dependent theory. This equivalence is established both on the level of the actions and on the level of field equations. We find that, in the context of this equivalence, the scale-setting relation $k(x)$ is naturally promoted to a dynamical field, which is made manifest by including a corresponding kinetic term in the scale-dependent action. In addition, we demonstrate that the new equivalence fits well into the framework of existing equivalences involving the aforementioned theories and $f(R)$-gravity. Finally, we apply the equivalence relations to explicit examples from both scale-dependent gravity and scalar-tensor theories.

We present a general formalism linking modified entropy functions directly to a modified spacetime metric and, subsequently, to an effective matter sector of entropic origin. In particular, within the framework of general relativity, starting from the first law of black-hole thermodynamics we establish an explicit correspondence between the entropy derivative and the metric function, which naturally leads to an emergent stress-energy tensor representing an anisotropic effective fluid. This backreaction effect of horizon entropy may resolve possible inconsistencies recently identified in black hole physics with modified entropies. As specific examples, we apply this procedure to a wide class of modified entropies, such as Barrow, Tsallis-Cirto, Renyi, Kaniadakis, logarithmic, power-law, loop-quantum-gravity, and exponential modifications, and we derive the associated effective matter sectors, analyzing their physical properties and energy conditions.

Scalar fields with a global U(1) symmetry often appear in cosmology and astrophysics. We study the spherically-symmetric, stationary accretion of such a classical field onto a Schwarzschild black hole in the test-field approximation. Thus, we consider the relativistic Bondi accretion beyond a simplified perfect-fluid setup. We focus on the complex scalar field with canonical kinetic term and with a generic quartic potential which either preserves the U(1) symmetry or exhibits spontaneous symmetry breaking. It is well known that in the lowest order in gradient expansion the dynamics of such a scalar field is well approximated by a perfect superfluid; we demonstrate that going beyond this approximation systematically reduces the accretion rate with respect to the perfect fluid case. Hence, black holes can provide a way to distinguish a perfect fluid from its ultraviolet completion in form of the complex scalar field.