Floquet engineering has emerged as a powerful route to dynamically control band structure and topology in quantum materials, but most implementations rely on externally imposed laser fields that are power intensive, difficult to integrate into devices, and weakly coupled to the electronic system. We propose and analyze an alternative paradigm in which a self-generated cavity field Floquet-dresses the electronic bands and produces a geometric Hall response in an electrically driven cavity material system. We consider a semiconductor layer embedded in a cavity and coupled to external leads and a bath of acoustic phonons, where dc pumping leads to the buildup of a coherent intracavity field through light-matter coupling. We determine the resulting nonequilibrium steady state self-consistently and show that, above threshold, the coupled system settles into a stable time-periodic limit cycle with a field amplitude set by the cavity quality factor and dissipation. This emergent periodic field Floquet-dresses the electronic bands and modifies the anomalous Hall response of a material with broken time-reversal symmetry. We demonstrate that the resulting Hall conductivity can be directly probed via in-plane dc transport measurements. Our work establishes a route to self organized Floquet band reconstruction and geometric transport without external laser illumination, highlighting cavity driven steady states as a platform for electrically controlled nonequilibrium phases.

Under the rapid solidification conditions of laser powder bed fusion (LPBF), solute trapping manifests in an element-specific manner, altering nonequilibrium partitioning, constitutional undercooling, and grain selection behavior in multicomponent alloys. Here, we elucidate the mechanisms by which element-specific solute trapping governs nucleation behavior and grain structure evolution during LPBF demonstrated on a SS316L. This requires quantitative description of nonequilibrium multicomponent thermodynamics and grain evolution across broad LPBF solidification conditions, which is achieved through a CALPHAD-informed Gaussian Process Regression (GPR)-assisted Phase-Field (PF) approach. The predicted transitions in grain morphology and grain size are validated against EBSD measurements under multiple LPBF processing conditions. Results demonstrate that increasing solidification rate drives a composition-dependent transition from solute diffusion-controlled nucleation to solute trapping-controlled grain growth, where nonequilibrium solute redistribution intensified by solute trapping suppresses equiaxed grain formation despite high cooling rates. Quantitative decomposition of multicomponent undercooling further reveals distinct element-specific sensitivities to solute trapping, where C, Cr, and Mo remain dominant contributors to the overall undercooling, while the undercooling contribution of low-partitioning elements such as S and P are strongly suppressed relative to their equilibrium values under rapid solidification conditions. These results reveal how element-specific solute trapping governs grain selection in multicomponent alloys, providing a mechanistic basis for alloy design under nonequilibrium solidification conditions.

Despite their large abundance, it is still unknown whether and under what conditions rocky planets around M dwarf stars can host atmospheres. This open question motivated the on-going Rocky Worlds DDT survey focused on searching for atmospheres on relatively low-temperature rocky exoplanets by systematically probing for the presence of day-night heat redistribution and CO2 absorption through JWST/MIRI 15 $μ$m eclipse observations. Here we present the analysis of the first full data set from this survey, consisting of four observations of the warm Earth-size exoplanet GJ 3929 b, with a planetary mass of 1.75+0.44-0.45 M$_\oplus$ and instellation flux of 17.3+/-0.7 S$_\oplus$. In our analysis, we include two previously unpublished eclipse observations and find an overall eclipse depth of 118+/-22 ppm and a dayside surface brightness temperature of 641+59-64 K. This is marginally lower than the eclipse depth of 160+26-27 ppm previously reported based on only the first two observations. While the full data set remains consistent with bare rock scenarios, it also leaves more room for thin atmosphere scenarios. Only thick CO2 atmospheres without thermal inversion remain ruled out at greater than 3$σ$. We also continue with lessons-learned in robustly analyzing these kind of high-precision JWST/MIRI 15 $μ$m eclipse observations. Notably, we find that the Frame Normalized Principal Component Analysis (FN-PCA) method appears more robust against the choice of extraction aperture size, which otherwise can have a significant impact on the inferred eclipse depth and scientific conclusions when using a standard polynomial baseline detrending method.

Ultra-hot Jupiters (UHJs; $T_{\rm eq} \gtrsim 2000$ K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b ($T_{\rm eq} \approx 2600$ K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR$>$4) signals from H$_2$O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of $\approx$0.2 dex, retrieving a solar atmospheric metallicity ([M/H]$_\odot$ $= 0.07^{+0.17}_{-0.13}$ $\approx 1.2\times$ solar), a C/O ratio (C/O $= 0.65^{+0.08}_{-0.08}$) consistent with solar value (C/O $=$ 0.59), an enhanced refractory abundance ([R/H]$_\odot$ $= 0.40^{+0.23}_{-0.17} \approx 2.5\times$ solar; $\approx 3.8\times$ stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V]$_\odot$ $= 0.36^{+0.11}_{-0.09}$ $\approx 2.3\times$ solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H$_2$O or H$_2$O-CO snowlines (at 68$\%$ confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68$\%$ confidence). The Mg/Fe is also found to be consistent with stellar value at 95$\%$ confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.

Magnetic field generation in giant planets and rapidly rotating stars produces a diverse range of field geometries, from large-scale dipole-dominated configurations to complex, small-scale multipolar structures. Earlier dynamo studies have suggested that multipolar solutions tend to arise when rotational effects become less dominant. We investigate the strength of non-dipolar magnetic fields generated in systems dominated by rotation. 40 three-dimensional, spherical-shell dynamo simulations were carried out using the MagIC code, primarily made up of bistable pairs - simulations with the same control parameters that can settle in both a dipolar and non-dipolar steady-state regime. We use this suite of models to test how their magnetic field strength scales with heat flux and velocity. Our dynamo simulations produce magnetic fields with morphologies that fall on the two distinct branches, dipolar or non-dipolar, yet have very similar convective velocities. The strength of the dipole component differs by an order of magnitude between the two regimes, when scaled as a function of driving power. However, their non-dipolar magnetic field strengths are very similar. We conclude that when attempting to predict the magnetic field strength of rapidly rotating planets and stars, one cannot assume that it will have a dipole-dominated geometry. In particular, the amplitude of the dipole component is expected to be an order of magnitude smaller in the non-dipolar regime.

The W50 nebula powered by the microquasar SS 433 is a unique laboratory for exploring several fundamental astrophysical phenomena. This study presents observations from NuSTAR and XMM-Newton, concentrating on the western lobe of W50. Detection of hard non-thermal X-ray emission is reported, extending up to approximately 30 keV. This emission originates from a compact, knotty area referred to as the "Head", located at approximately 17 arcmin (equivalent to 26.5 pc at an assumed distance of 5.5 kpc) to the west of SS 433, and characterized by a power-law spectrum with a hard photon index of 1.55 +/- 0.07 (0.5-30 keV). Moving westward from SS 433, the photon index gradually steepens, ultimately reaching a photon index of 2.10 +/- 0.05 in the "w2" region centered at approximately 35 arcmin or approximately 56 pc from SS 433. The distinct hard X-ray knots observed serve as clear markers for sites of particle acceleration within the western jet. The synchrotron radiation from the "Head" region implies equipartition magnetic field strength B of approximately 15 microG. Notably, these properties (western "Head" location, unusually hard spectral index, inferred magnetic field, and spectral evolution away from SS 433) are very similar to what has been observed in the eastern lobe, supporting a symmetric jet-driven origin. Finally, the broadband spectral energy distribution (SED) and X-ray morphology are modeled using semi-analytic jet models, exploring different jet velocity and magnetic field configurations. The results favor a scenario in which in-situ particle acceleration and synchrotron emission dominate, with implications for understanding particle transport, jet dynamics, and W50's role as a Galactic PeVatron.

We compute 95% confidence-level upper limits on the dark matter annihilation cross section and decay rate from both total-intensity and polarized synchrotron emission in five extragalactic targets: M31, the Large Magellanic Cloud (LMC), the Draco and Sculptor dwarf spheroidal galaxies, and the Coma cluster. Using Planck maps at 30, 44, and 70 GHz, we solve the diffusion-loss equation for dark-matter-produced electrons and positrons numerically with DRAGON and integrate the resulting synchrotron emission along the line of sight with HERMES, computing both total-intensity and polarized-intensity maps for each target with target-specific magnetic-field, gas, and radiation-field environments. The 30 GHz channel yields the most stringent constraints in all cases, and limits on annihilation or decay into $e^+e^-$ are stronger than those for $b\bar{b}$ due to the harder injected spectrum. For most targets the total-intensity and polarized limits are broadly comparable; the LMC is an exception, where Faraday depolarization in the turbulent disk suppresses the polarized signal relative to total intensity, making total intensity the primary estimator. Our results are robust against the choice of flux estimator and coordinate uncertainty. This work demonstrates that microwave polarimetry provides a complementary and largely independent probe of dark matter synchrotron emission in extragalactic targets.

The nearby star-forming dwarf galaxy Sextans A offers a unique window into galaxy evolution in the early Universe, owing to its extremely low metallicity (about 1-7% Zsun). Recent JWST imaging of Sextans A spanning 1-21 micron enables a detailed characterization of its dusty stellar populations and interstellar medium. In this work, we compare the observed JWST color-magnitude distributions of evolved stars with stellar evolution and dust-formation models to characterize the properties of the asymptotic giant branch (AGB) population, including progenitor mass, formation epoch, metallicity, and dust production. Evolutionary tracks for 0.8-7 Msun stars with metallicity Z=10^-3 provide good agreement with the overall distribution of AGB stars in Sextans A. More than 90% of the AGB population occupies a nearly vertical sequence in the color-magnitude diagrams, corresponding to stars spanning a wide range of masses and ages but exhibiting little or no circumstellar dust. This sequence appears to be dominated by oxygen-rich (M-type) AGB stars and reveals that the F444W flux is a robust luminosity diagnostic. A small subset of sources displays strong infrared excesses and is dominated by carbon stars descending from 1.25-1.5 Msun progenitors that formed about 2-3 Gyr ago and are currently in the final AGB phases. Their MIRI colors imply very low metallicities, consistent with estimates from the red giant branch morphology (about 1-2% Zsun). Finally, we show that the JWST/NIRCam F277W-F444W color serves as an effective proxy for the dust production rate, with models predicting rates up to 10^-7 Msun/yr for the reddest sources in Sextans A.

Neutrinos enter cosmology in different ways and are constrained by distinct observational probes across different epochs: as a relativistic species at high redshift, as a massive but clustering-suppressing component at low redshift, and as a particle physics observable in laboratory experiments. Low (verging on negative) bounds on neutrino mass from galaxy surveys motivate exploration of models where neutrinos may couple to dark energy, causing their mass to vary over cosmic evolution. If the coupling involves an inverse phase transition (symmetry broken, rather than restored, as neutrinos become nonrelativistic) this can tame instabilities in neutrino growth, appear as a lower neutrino mass in galaxy surveys, and add extra suppression to the matter power spectrum. We find that the late-time decoupling shuts down the fifth force and inhibits the excessive growth of neutrino perturbations, thereby eliminating linear-regime instabilities. The model may potentially address the Hubble tension via an early dark energy component localized around the time of recombination.

We present a detailed molecular line analysis of one of the most chemically rich cores in the ALMAGAL sample, the high-mass core~9 in the AG318.9477-00.1960 clump (AG318-c9), located at a heliocentric distance of \sim 10.4\,\rm kpc. We further assessed whether the emission of selected COMs, that is, ethylene glycol ((CH_2OH)_2; EG), glycolaldehyde (CH_2(OH)CHO; GA), and methyl formate (CH_3OCHO; MF), can be used to trace the innermost regions of hot molecular cores (HMCs). We analysed ALMA Band~6 observations (\sim 217-221GHz). Spectral line identification and local thermodynamic equilibrium modelling were performed using the software MADCUBA. We derived the physical parameters, including the column density (N), excitation temperature (Tex), velocity, line width, and molecular abundances relative to H_2, for all detected species. The chemical inventory of AG318-c9 was compared with that of the HMC G31.41+0.31 (G31). In addition, we performed a pixel-by-pixel analysis of EG, GA, and MF to generate spatially resolved N and Tex maps and corresponding radial profiles.

The James Webb Space Telescope (JWST) has detected an unexpectedly large number of galaxies at redshifts $z\geq 10$ compared to the predictions of the standard $Λ$CDM model. One of possible explanations is the presence of an excess (bump) in the power spectrum of perturbations at the mass scale of these galaxies, which is about $10^{10}M_\odot$. This excess simultaneously shifts the epoch of cosmic reionization to significantly earlier times, in contradiction with observations. Here we show that this defect of the bump model can be avoided if the perturbation spectrum has a cutoff (suppression) at smaller scales, which can be realized by lowering the amplitude of the primordial perturbation spectrum or by considering warm dark matter. With a cutoff present, fewer low-mass halos form and, consequently, fewer stars producing ionizing UV radiation. We also derive the halo merger-rate distribution in the presence of a bump using the extended Press--Schechter (EPS) theory, and verify this distribution against direct $N$-body simulations. Based on this distribution, and under the assumption that mergers trigger starbursts, we compute the UV luminosity function of early galaxies and demonstrate its agreement with available observational data. In the model under consideration, the fraction of early galaxies forming via the monolithic mechanism (through a single large-scale collapse) is significantly increased in comparison with the standard $Λ$CDM model, and the first stars appear directly in halos with masses $\geq10^8M_\odot$. We refer to such stars with primordial chemical composition as ``Population~IV stars,'' to distinguish them from the evolutionary different stellar populations.

Understanding the chemistry related to the early stages of star formation is of great importance, as it is linked to the beginnings of the most complex chemistry in the interstellar medium. In this context, we investigate the chemical behaviour of simple cyano-bearing molecules and formylium ions isotopologues in a sample of massive infrared-quiet molecular cores. Using archive ALMA Band 7 data of 37 early molecular cores embedded in ATLASGAL clumps, we obtain abundances of HC$_{3}$N, H$^{13}$CN, HN$^{13}$C, H$^{13}$CO$^+$, and HC$^{17}$O$^+$. We used various statistical methods, including hierarchical clustering, to analyse the correlations between molecular abundances, ratios and temperature. We find that HN$^{13}$C, H$^{13}$CO$^{+}$, and HC$^{17}$O$^{+}$ abundances correlate positively with kinetic temperature, suggesting temperature-driven chemical regulation in young massive cores. A similar trend is observed for H$^{13}$CN, although the limited number of detections prevents a definitive conclusion. HC$_3$N abundances show no dependence on temperature within the 40-100 K range, suggesting a chemical steady state between gas-phase production and grain-surface depletion. Similarly, the H$^{13}$CN/HN$^{13}$C ratio, measured in only six regions, suggests no correlation with temperature, differing from findings at lower temperatures. Using a hierarchical clustering method based on abundance ratios, novel in astrochemistry, we identified chemically distinct core groups that align with thermal conditions. Additionally, we provide HC$^{17}$O$^+$ detections for 28 cores-a significant expansion of existing literature-and find evidence that H$^{13}$CO$^{+}$ transitions may have higher optical depths than commonly assumed. These results are important because characterizing the chemical state of early star-forming stages is essential for understanding the onset of the most complex chemistry.

The cosmic chronometer (CC) method provides a direct measurement of the expansion history, $H(z)$, from the differential ages of passively evolving galaxies. However, most CC analyses rely on high-quality spectroscopy to select passive galaxies, measure age-sensitive spectral features, and control stellar-population systematics. We build on existing works that use the D4000 spectral break as a proxy for measuring galaxy ages and apply it to a photometry-selected galaxy sample from VIPERS PDR2 in the range $0.5 \le z \le 0.8$. Our goal is to extend the scope of the standard CC framework to photometric surveys. To achieve this, we first select a massive and passive galaxy sample using rest-frame colors and mass. Second, we design a Bayesian framework to infer full galaxy age posteriors in fine redshift bins, using a D4000-age-metallicity grid from stellar population synthesis (SPS) models. We also marginalize over metallicity, using a Gaussian metallicity prior to break the D4000-age-metallicity degeneracy. Subsequently, we derive age-difference posteriors between redshift bins by convolving their age posteriors to propagate the non-Gaussian features correctly. Finally, using the median and errors extracted from the differential age posteriors, we calculate the weighted average $H(z)$ over our selected redshift range. We obtain $H(z=0.65)=93.68\pm28.27\,{\rm (stat.)}\pm10.67\,{\rm (syst.)}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, which is consistent with existing spectroscopic CC measurements and with the Planck $Λ$CDM prediction at the same redshift. This result provides a proof of concept for extending direct $H(z)$ measurements from cosmic chronometers to photometric and spectro-photometric surveys, where larger samples can compensate for lower spectral resolution, provided that passive-galaxy selection, metallicity priors, and stellar-population systematics are carefully controlled.

The role of stellar chromospheres in the chemistry, mass loss, and evolution of cool evolved stars remains poorly understood. We present high-resolution ultraviolet spectra of the nearby Mira-type AGB star R~Leo obtained with STIS on board the \textit{Hubble Space Telescope}. We focus on two strong chromospheric diagnostics, the Mg\,\textsc{ii} h \& k resonance lines and the C\,\textsc{ii}] 2325\,Å multiplet, and model their formation with the NLTE radiative-transfer code RH using phase-dependent hydrodynamic atmospheric structures that include pulsation-driven shocks. The observed C\,\textsc{ii}] multiplet ratios imply an electron density of order $10^9\,\mathrm{cm^{-3}}$. The RH contribution functions show that the C\,\textsc{ii}] emission is strongly localized in a compact shock-heated shell at the first temperature peak of the model atmosphere, near $R\simeq1.8~R_{\rm phot}$, where $T\sim10^4$\,K and the local electron density is a few $10^8\,\mathrm{cm^{-3}}$. In contrast, the Mg\,\textsc{ii} h \& k lines probe a more extended region ($R< 16~R_{\rm phot}$), with the line cores forming at greater radial distances than the wings. The Mg\,\textsc{ii} h line is reproduced more reliably than the k line, which is more strongly affected by circumstellar and interstellar absorption. As an additional low-opacity kinematic check, the semi-forbidden Al\,\textsc{ii}] $\lambda2669$ line shows a projected stellar-rest-frame blueshift of $\sim6~{\rm km~s^{-1}}$, consistent with shock-related motions expected in Mira atmospheres. Overall, the compact C\,\textsc{ii}] formation region, the extended Mg\,\textsc{ii} contribution functions, and the strong phase dependence of the synthetic Mg\,\textsc{ii} profiles support a picture in which pulsation-driven shocks shape the ultraviolet chromospheric emission lines in Mira variable stars.

This paper studies photometric and spectropolarimetric variability of HD210684 in order to derive its magnetic properties, rotational period, evolutionary stage, and global stellar parameters. The Discrete Fourier Transform is used to measure frequencies and amplitudes of periodic signals present in light curves of HD210684. Evolution models are calculated with MESA, while roAp type pulsations are simulated with GYRE. The values of $T_{eff}$, log(g), $v\sin{i}$, and radial velocity (RV) are derived from the best fit of Balmer line profiles using FITSB2. The Least Square Deconvolution (LSD) method is applied to available Stokes I&V spectra to measure the mean longitudinal magnetic field <Bz> and RV. Detailed analysis of photometric variability reveals rotational modulation with period P=5.02188$\pm$0.00005d and splitting of high-overtone pulsations that corresponds to the same rotational period. Derived <Bz> measurements also show periodic variability with P=5.02188d, but this variability appears to be different from the one predicted by a centred magnetic dipole model. We have determined the inclination angle between the line of sight and the rotation axis to be $i = 31^{\circ} \pm 2^{\circ}$, and the angle between the rotation and magnetic dipole axes as $β= 77^{\circ} \pm 3^{\circ}$. Simulations of stellar pulsations constrain $\log T_{eff}$<3.85 and show that our best fitting model depends on whether the observed modes are $\ell = 1$ or $\ell =2$. Considering the derived value of $β$, we prefer the best fit model with $\ell =2$ mode, which predicts that HD210684 lies on the main sequence with an age of approximately 1.45Gyr. The best fit of Balmer line profiles has resulted in higher values of $T_{eff}$ and log(g) for spectra acquired at rotational phases $φ$= 0.14 - 0.39 suggesting visibility of an area with higher surface temperature.

RAMSES is an adaptive mesh refinement (AMR) astrophysical simulation code that generates high-resolution multiscale data. However, its native binary output format is not directly compatible with standard visualization tools, making efficient analysis challenging. We present Chhavi, an open-source Python tool that converts RAMSES outputs into the VTKHDF format for direct use in visualization platforms such as ParaView. The tool reconstructs the AMR hierarchy, preserves key physical fields including density, pressure and velocity, and organizes them into a structured representation suitable for multi-resolution visualization. The conversion is validated using the three-dimensional Sedov blast wave test case. Quantitative evaluation through radial profile comparison and Lin's concordance correlation coefficient demonstrates strong agreement between the original and converted datasets, confirming both physical and structural fidelity. Chhavi provides a scalable bridge between RAMSES simulation outputs and modern visualization workflows, supporting efficient and reproducible analysis in computational astrophysics.

Interplanetary coronal mass ejections (ICMEs) carry magnetic clouds (MCs), large-scale structures with average radial widths about a fifth of an astronomical unit at Earth's orbit. ICMEs display substructures in white light images and reveal rich dynamics across many spatial scales when directly measured by spacecraft. A spacecraft encounter with an ICME can result in smoothly rotating MC intervals or less organised magnetic obstacle (MO) ones. We investigate how the interplay of expansion, turbulence, and internal cloud dynamics affects magnetic cloud properties, which are reflected in the plasma signatures measured by spacecraft. We perform high-resolution 2.5D MHD simulations of a magnetic flux rope cross-section, which is embedded in the turbulent, expanding solar wind with the expanding box model. We probe the local plasma properties, and thus the flux rope signatures and angular coherence, with virtual spacecraft. Our simulations reproduce clear and stable MC signatures when the flux rope core is intercepted by virtual spacecraft. Disordered MO signatures appear at the edges of the flux rope, and are attributed to both expansion and turbulent transport. We vary some key physical parameters of the flux rope and the environment to understand their effect on the observed coherence and signatures. The pace of the expanding flow controls the angular extent of MC signatures, whereas the intensity of interplanetary turbulence controls how asymmetric and distorted the flux rope appears at 1 AU. The geometry of spacecraft encounters determines whether MC or MO signatures are observed. The presence of a magnetic structure which can result in MO signatures is strongly controlled by the flux rope's initial/early magnetic configuration: MO signatures can only be observed when the axial flux rope field is spatially not well confined by the rope's own magnetic tension, and disappear otherwise.

Lunar impact flashes provide a direct means of estimating the flux of centimetre-sized meteoroids impacting the lunar surface. However, 25-60 frames per second imaging typical of most monitoring programs limit the ability to resolve the rapid temporal evolution of the impact process, while the integration of Earthshine background restricts the detection of faint flashes. In this work, we present high-speed observations of lunar impact flashes captured at 200 and 250 FPS using the Zadko Telescope in Western Australia. We resolve the light curves of four confirmed events, revealing complex morphologies, some of which are not well modelled by simple exponential decays. One event was simultaneously detected by a second observer using a 50 FPS system, revealing a significantly faster brightness drop in the high-speed data that cannot be explained by spectral differences alone, indicating temporal integration of the vapour plume and subsequent ejecta. Our data also indicates that the initial flash intensity (representing the vapour plume) exhibits significantly less variance across events than the total luminous energy. Furthermore, we found no statistical correlation between the initial luminous energy and the total integrated energy of the flashes in this data, suggesting that the physical mechanism driving the initial vapour expansion may be physically decoupled from the longer-duration glow driven by the cooling ejecta. High temporal resolution combined with high sensitivity are therefore essential for accurately characterising the physical properties of the impactor and distinguishing the initial vapour plume from the subsequent incandescent cooling phase, although a significantly larger dataset is required to definitively constrain these mechanisms.

CARMENES consists of two high-resolution spectrographs located at the Calar Alto 3.5m telescope, covering the wavelength range from 520nm to 1710 nm. The original Fabry-Perot (FP) units have been essential to track and remove instrumental drift while also improving the wavelength solution provided by the hollow cathode lamps. In this paper we present the second-generation FP unit that has begun operation at Calar Alto in April 2024. It features drastically improved temperature stabilization, additional temperature monitoring, and enhanced optomechanics. Temperature stabilization is improved through better vacuum vessel design, thermal shielding and improved thermal control. The temperature is now monitored with Pt-100 sensors inside the vacuum vessel, one of which is used to drive the temperature control. The new purpose-built optomechanics allow for an improved alignment procedure leading to higher line contrast. The etalon coatings now cover a broader wavelength range, the optics have been upgraded, and the fibers have been updated to an octagonal shape. In laboratory measurements with a Fourier transform spectrometer we compare the FP radial velocity (RV) drift to that of an iodine cell. In a two hour binning we achieve an RMS of the differential RVs of 6cm/s. The new FP unit has already been successfully integrated at CARMENES, with first calibration data indicating improved RV precision.

How much does the wind affect the path of meteorite falls? We finely model the lower ~30 km of the atmosphere using Weather Research and Forecasting open source tools at 1 km spatial resolution. Models initialised at different times give different results, which can be used as a proxy for uncertainty. We find that in most cases the differences on the ground positions are significant: median shift for a 1 kg meteorite is 143 m, doubling to 307 m for a 10 g rock, though these vary by over an order of magnitude between events. The differences wind model choice makes on the ground are significantly larger than the typical uncertainty on meteoroid state vector obtained from bright flight observations of the fireball (<100 m), and should be taken into account when predicting meteorite free-fall path to the ground. Unsurprisingly the cases where we see the largest differences coincide with documented extreme weather events. We also find that high spatial resolution models (1 vs. 3 km) tend to perform better. We have successfully used these models to guide field teams to the location of 12 fallen meteorites after fireball observations. We release as open data 1107 models we have calculated for 302 meteorite fall events and spacecraft re-entries around the world.

Magneto-Rossby waves in the solar tachocline are currently being discussed as a potential cause of the quasi-biennial oscillation (QBO). By analyzing sequences of ground-level enhancement (GLE) events and S-flares, the dominant period of the QBO was recently shown to be close to 1.723 years, which is the dominant beat between the periods of the two-planet spring tides of Venus, Earth and Jupiter. We improve upon this model by taking into account the dependence of the three tidally-triggered magneto-Rossby waves on the actual strength of the toroidal field at the tachocline, which we infer from the averaged monthly sunspot number. When optimizing the parameters of this magnetic-field dependence, the correlation of the tidal-forcing function with the 109 extreme solar events reaches values of up to 0.8. This is much higher than the corresponding value for the field-independent tidal forcing function (appr. 0.4), and also higher than the correlation with the sunspot number (appr. 0.56). Based on this improved model, we discuss some interesting parallels between the Carrington event of 1859 and the clustering of strong solar events in summer and autumn 1989. We also make some cautious forecasts for the remainder of cycle 25.

Mixed modes are observed in many low-mass evolved stars. They provide information about core rotation rates of these stars, which are lower than predicted by stellar evolution models. The mixed modes themselves have been invoked as an angular momentum transport mechanism, but estimating their transport efficiency requires knowledge of their amplitudes. We constrain, for the first time, the mixed mode amplitudes in 2D hydrodynamical simulations of a $1.3M_\odot$ red giant using the code \textsc{music}. We perform two simulations with outer radial truncations at fractional radii $r_o/r_\star = 0.90$ and $r_o/r_\star = 0.98$. We compare the modes in the simulation with those found using both \textsc{gyre} and a \textsc{dedalus} eigenvalue solver. Excellent frequency agreement is found for all p-dominated modes, with minor discrepancies for g-dominated modes, especially in the frequency range $[60, \ 240]\ μ\mathrm{Hz}$. We find excellent eigenfunction agreement for all modes except those in this frequency range. According to empirical predictions the largest kinetic energies are located around $ν_{\mathrm{max}} = 312.8\ μ\mathrm{Hz}$, but in both simulations the modes with frequencies $ν<50\ μ\mathrm{Hz}$ have the largest kinetic energies. In the simulation with $r/r_\star = 0.98$, the simulated modes have extrapolated surface velocities comparable to the empirical predictions, with highest surface velocities in a bell-shaped curve peaking around $ν= 700 \ μ\mathrm{Hz}$. The extrapolated surface velocities of the low frequency modes are small, and thus hard to observe, but their large kinetic energies deeper in the interior could significantly impact angular momentum transport, which has not yet been investigated.

In 2022, the CHIME/FRB Collaboration reported the detection of FRB 20191221A, an apparent fast radio burst exhibiting a significant periodicity of 217 ms. Recently, this event has been identified as a series of pulses originating from the known Galactic pulsar PSR J0248+6021. The initial misidentification was caused by an unusual calibration problem with the CHIME telescope, coupled with the atypical characteristics of the pulsar's emission. Here, we detail the issues with the calibration and how it led to a many-degree offset in the pointing of the calculated beams. We describe how we verified that this problem has not affected any other FRB localization, including those reported in the Second CHIME/FRB Catalog, and our newly implemented checks to ensure this mispointing problem does not affect future data.

A tidal disruption event (TDE) occurs when a star is torn apart by a supermassive black hole. The resulting UV/optical flare irradiates parsec-scale dust, producing delayed mid-infrared echoes that persist for years. These echoes provide unique calorimetric probes of the total radiated energy and dust geometry.Existing models usually assume static axisymmetric illumination patterns. However, the TDE accretion disk is likely misaligned and undergoes relativistic precession.In this work, we present a theoretical framework for infrared dust echoes from a precessing TDE disk. The precession will lead to highly variable infrared light curves, which can be revealed by high-cadence observations. The overall profile of the infrared light curves shows double-peaked to single-peaked pattern transitions as a result of the changes in the viewing angle or precession angle.The results indicate that infrared echoes are dynamic tracers of the evolving lighting patterns of the central engine.

Context. Non-local thermodynamic equilibrium conditions in the interstellar medium require collisional rate coefficients to model astronomical observations; these are usually determined from theoretical scattering calculations. Aims. The aim of this study is to measure experimentally low-temperature pressure-broadening cross-sections for the H2CO-He system in order to validate the theoretical methodology involved in determining new collisional rate coefficients. Methods. The experiments employed the chirped-pulse in uniform supersonic flow method, and H2CO is generated in situ by 193 nm excimer laser photolysis of tetrahydrofuran in cold He flows. State-of-the-art calculations are performed by computing a new potential energy surface for the H2CO-He system which is subsequently implemented in scattering calculations using the close-coupling method to derive collisional rate coefficients and pressure-broadening cross-sections. Results. Excellent agreement between theory and experiment is obtained, with the calculated values falling within the 95% confidence intervals of the experimental measurements. Such agreement validates the high accuracy of the theoretical data. Conclusions. Helium constitutes about 20% relative to H2 in the interstellar medium. The inclusion of collisional rate coefficients for H2CO with He in radiative transfer modelling leads to variations in the excitation temperature of frequently detected rotational lines of up to 12% in warm regions such as protostars.

Recently, LHAASO detected gamma-ray emission from the pulsar wind nebula (PWN) J1849-0001 extending up to approximately 2 PeV, providing strong evidence for PeV particle acceleration. To explain the origin of this ultra-high-energy emission, we investigate three physical scenarios: a pure leptonic model, a hadronic-dominated model, and a hybrid lepto-hadronic model. We show that while both pure leptonic and hadronic-dominated models can reproduce parts of the multiwavelength spectral energy distribution (SED), neither can simultaneously explain the entire dataset, particularly the PeV tail. The leptonic scenario requires an unrealistically high electron cutoff energy, while the hadronic model underpredicts the highest-energy emission. We therefore propose a hybrid model that combines inverse Compton emission from PWN electrons with hadronic interactions between escaped cosmic rays and a nearby molecular cloud. In this framework, a suppressed diffusion coefficient ($\sim 1\%$ of the Galactic average) is required to confine PeV particles in the source vicinity. This model successfully reproduces the full SED, including the approximately 2 PeV emission. We further calculate the associated neutrino flux, and show the sensitivity of NEON to this source. Our results support the interpretation that evolved PWNe embedded in complex environments can act as Galactic PeVatrons.

Fuzzy dark matter (FDM), often realized as an ultralight scalar field, can suppress the growth of small-scale structures and could be strictly tested with Lyman-$α$ forest measurements. In this work, we constrain both pure and mixed FDM models (PFDM and MFDM) using measurements of the one-dimensional (1D) Lyman-$α$ forest flux power spectrum at $z=5.0$, 4.6, and 4.2. We perform cosmological hydrodynamical simulations with modified initial conditions and construct a two-stage neural network emulator for accurate analysis. The first stage predicts the cold dark matter (CDM) 1D flux power spectrum, while the second stage predicts the MFDM effect relative to the CDM baseline. This construction improves the sensitivity to weak FDM effects, enforces the correct CDM limit, and enables robust interpolation across a broad range of FDM masses and fractions. After marginalizing over the intergalactic medium parameters, we obtain the FDM mass $m_{\mathrm{FDM}}>1.9\times10^{-21}~\mathrm{eV}$ at 95\% credible level for the PFDM model. For the MFDM model, we find the FDM fraction of dark matter $f_{\mathrm{FDM}}<0.07$, $0.12$, and $0.65$ at 95\% credible level for $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})=-23.0$, $-22.0$, and $-21.0$, respectively. When $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})\gtrsim -20$, the current data do not provide an effective upper limit on $f_{\mathrm{FDM}}$.

Fast radio bursts (FRBs) provide a powerful probe of ionized baryons through their dispersion measures (DMs), but the observed signal contains contributions from the intergalactic medium (IGM), circumgalactic (CGM) gas, host galaxies, and source-local environments. In this thesis, I investigate FRB DMs from cosmic-web to source-local scales using cosmological simulations, zoom-in galaxy simulations, and supernova-remnant (SNR) simulations. Using the CROCODILE simulation suite, I study the DM-$z$ relation, baryon distribution, halo contributions, and host-galaxy DMs. AGN feedback redistributes baryons from halo centers into the diffuse CGM/IGM gas, particularly affecting DM contributions from massive foreground halos. From the simulated DM-$z$ relation, I derive diffuse baryon fractions of $f_{\rm diff}=0.865^{+0.101}_{-0.165}$ and $0.856^{+0.101}_{-0.162}$ for the fiducial and NoBH models. Host-galaxy DM contributions range from below 100 pc cm$^{-3}$ in dwarf galaxies to above 1300 pc cm$^{-3}$ in cluster environments. I also model young magnetars embedded in SNRs using one-dimensional hydrodynamical simulations. The dominant time-variable DM component arises from unshocked ejecta, while the shocked region contributes only a minor fraction. Comparisons with FRB 20190520B and FRB 20121102 suggest source-local DM contributions of tens to hundreds of pc cm$^{-3}$. Most models become transparent to GHz radio emission within 70 yr. In contrast, the shocked region dominates the RM contribution and evolution, with the $11\,M_\odot$ single-star model best reproducing the RM evolution of FRB 20121102. These results demonstrate that FRB dispersion measures must be interpreted as multi-component signals spanning a wide range of physical scales, linking the cosmic web, gaseous halos, host galaxies, and compact-object environments

Understanding the stellar spin evolution of young stars is crucial for understanding the evolution of protoplanetary disks and, consequently, the formation of exoplanets. According to stellar spin models, T Tauri stars should evolve toward a spin equilibrium in which the external spin-down torque balances both the external spin-up (accretion) torque and the spin-up due to stellar contraction. A useful reference point along the way to this equilibrium is the "zero-torque state" (ZTS), at which only the external torques cancel out. Recent observations, however, have shown that the spin state of a considerable number of stars is shifted out of the spin equilibrium and the ZTS. We investigate the effects of variable stellar magnetic fields on the stellar spin state of T Tauri stars. [Abstract shortened for arXiv] Temporal variations in the stellar magnetic field can significantly affect the stellar spin state of T Tauri stars. The strength of the effect on the stellar spin state depends on the relation between the timescale of the changing magnetic field, the spin-up timescale, and the viscous timescale of the accretion disk. A developing radiative core on a timescale shorter than the spin-up timescale has a strong effect on the spin state. Stellar magnetic cycles on timescales shorter than the viscous timescale of the inner disk have a weaker effect on the stellar spin state due to a slow back-reaction of the accretion disk. Our results can explain (at least) a part of the stars that are observed out of both states. Further theoretical and observational work is needed to connect accretion, stellar rotation, and magnetic properties in T Tauri stars.

Searches of unassociated gamma-ray sources in the Fermi-LAT catalogues have led to the discoveries of around a fifth of all known millisecond pulsars (MSPs). These searches have almost exclusively been performed at radio frequencies above 300 MHz, where dispersion and scattering in the interstellar medium are less significant. We report on a shallow survey for pulsars targeting 308 unassociated Fermi-LAT sources in archival Murchison Widefield Array (MWA) observations from the Southern-sky MWA Rapid Two-metre (SMART) pulsar survey at 154 MHz. This is the largest radio survey of unassociated Fermi-LAT sources to date, and only the second to be conducted below 300 MHz after a survey with the Low Frequency Array (LOFAR) that discovered three MSPs. Each source was observed for 20 min by digitally beamforming the MWA tile voltages. Searches were then performed using a new pipeline that implements a semi-coherent dispersion removal scheme for MWA data, enabling greater sensitivities to MSPs than is possible with fully-incoherent dispersion removal (e.g. 2-3 times better sensitivity for dispersion measures between 20-40 pc/cm^3). No new pulsars were identified in the survey, which we attribute to insufficient sensitivity. We estimate flux density limits of approximately 30-220 mJy at 154 MHz (or 0.7-5.2 mJy at 1.4 GHz) for a spin period of 2 ms and a duty cycle of 28%. We discuss how the improved instantaneous sensitivity from the Phase III upgrade of the MWA will increase the number of detectable gamma-ray pulsars by ~30% for the same integration time. The semi-coherent search pipeline we have developed will also be useful for searches of supernova remnants, globular clusters, and pulsar candidates identified in imaging surveys, all of which will help to inform the significance of future surveys with SKA-Low.