Papers for Monday, Mar 31 2025

Making an unambiguous detection of lensed gravitational waves is challenging with current generation detectors due to large uncertainties in sky localisations and other inferred parameter distributions. However, in the case of binary neutron star (BNS) mergers this challenge can be overcome by detecting multiple images of its lensed kilonova counterpart, simultaneously confirming the lensing nature of the event and locating it precisely - further enabling a wealth of lensed multimessenger science. Such a strategy demands answers to two key problems: 1) How can candidate lensed BNS events be identified fast enough to ensure the lensed kilonova is still detectable? 2) What is the most economical observing strategy on telescope time for following up candidate lensed events to discover lensed kilonovae? This article will discuss solutions to both points, specifically: how GW detections of progenitors in the $\sim$ 2.5 to 5 $M_\odot$ black hole "mass gap" can be interpreted as candidate lensed BNS events, giving evidence for lensing from just a single detection, and will present a strategy that can actively be employed for follow-up of such events in the O4 run of LVK and beyond.

Recent studies of gas kinematics at high redshift have reported disky systems which appear to challenge models of galaxy formation, but it is unclear whether they are representative of the underlying galaxy population. We present the first statistical sample of spatially resolved ionised gas kinematics at high redshift, comprised of $272$ H$\alpha$ emitters in GOODS-S and GOODS-N at redshifts $z\approx3.9-6.5$, observed with JWST/NIRCam slitless spectroscopy and imaging from JADES, FRESCO and CONGRESS. The sample probes two orders of magnitude in stellar mass ($\log (M_{\star}[\mathrm{M}_{\odot}])\approx8-10$) and star formation rate ($\text{SFR}\approx0.3-100\thinspace M_{\odot}/$yr), and is representative down to $\log(M_{\star}[\mathrm{M}_{\odot}])\approx 9$. Using a novel inference tool, $\texttt{geko}$, we model the grism data to measure morphological and kinematic properties of the ionised gas, as probed by H$\alpha$. Our results are consistent with a decrease of the rotational support $v/\sigma_0$\ and increase of the velocity dispersion $\sigma_0$ with redshift, with $\sigma_0\approx100$ km/s and $v/\sigma_0\approx1-2$ at $z\approx3.9-6.5$. We study the relations between $\sigma_0$, and $v/\sigma_0$, and different star formation tracers and find a large scatter and diversity, with the strongest correlations between $\sigma_0$ and SFR and SFR surface density. The fraction of rotationally supported systems ($v/\sigma_0>1$) slightly increases with cosmic time, from $(36\pm6)\%$ to $(41\pm6)\%$ from $z\sim 5.5$ to $z\sim 4.5$, for galaxies with masses $9<\log(M_{\star}[\mathrm{M}_{\odot}])<10$. Overall, disks do not dominate the turbulent high-redshift galaxy population in the mass range probed by this work. When placed in the context of studies up to cosmic noon, our results are consistent with a significant increase of disk-like systems with cosmic time.

In the Fuzzy Dark Matter (FDM) scenario, the dark matter is composed of an ultra-light scalar field with coherence length and wave interference on astrophysical scales. Scalar fields generically have quartic self-interactions that modify their dispersion relation and the associated evolution of density perturbations. We perform the first dedicated analysis of the role of wave interference on this evolution due to self-interactions in FDM and vice versa, developing a perturbative treatment applicable at early times and then comparing against a suite of fully nonlinear benchmark simulations, varying the dark matter density, interaction strength, and fiducial momentum scale. We explicitly simulate the limit where this momentum scale is relatively high compared with the scale of the simulation volume, applicable to cases where the dark matter is initially ``warm" due to causal constraints on a post-inflationary production or in virialized halos and other ``thermalized" cases with initially cold production. We find that in such scenarios, density perturbations are unable to grow on the expected self interaction time scale because of interference effects, instead saturating on the much shorter de Broglie crossing time, with a dependence on the sign of the interaction. Finally, we comment on the implications of our results for astrophysical systems such as high-density ultra-faint dwarf galaxies where wave interference plays an important role.

We have not yet observed the epoch at which disc galaxies emerge in the Universe. While high-$z$ measurements of large-scale features such as bars and spiral arms trace the evolution of disc galaxies, such methods cannot directly quantify featureless discs in the early Universe. Here we identify a substantial population of apparently featureless disc galaxies in the Cosmic Evolution Early Release Science (CEERS) survey by combining quantitative visual morphologies of $\sim 7,000$ galaxies from the Galaxy Zoo JWST CEERS project with a public catalogue of expert visual and parametric morphologies. While the highest-redshift featured disc we identify is at $z_{\rm{phot}}=5.5$, the highest-redshift featureless disc we identify is at $z_{\rm{phot}}=7.4$. The distribution of Sérsic indices for these featureless systems suggests that they truly are dynamically cold: disc-dominated systems have existed since at least $z\sim 7.4$. We place upper limits on the featureless disc fraction as a function of redshift, and show that up to $75\%$ of discs are featureless at $3.0<z<7.4$. This is a conservative limit assuming all galaxies in the sample truly lack features. With further consideration of redshift effects and observational constraints, we find the featureless disc fraction in CEERS imaging at these redshifts is more likely $\sim29-38\%$. We hypothesise that the apparent lack of features in a third of high-redshift discs is due to a higher gas fraction in the early Universe, which allows the discs to be resistant to buckling and instabilities.

The Bullet Cluster (1E 0657-56) is a key astrophysical laboratory for studying dark matter, galaxy cluster mergers, and shock propagation in extreme environments. Using new JWST imaging, we present the highest-resolution mass reconstruction to date, combining 146 strong lensing constraints from 37 systems with high-density (398 sources arcmin$^{-2}$) weak lensing data, without assuming that light traces mass. The main cluster's mass distribution is highly elongated (NW-SE) and consists of at least three subclumps aligned with the brightest cluster galaxies. The subcluster is more compact but elongated along the E-W direction, with a single dominant peak. We also detect a possible mass and ICL trail extending from the subcluster's eastern side toward the main cluster. Notably, these detailed features are closely traced by the intracluster light, with a modified Hausdorff distance of $19.80 \pm 12.46$ kpc. Together with multi-wavelength data, the complex mass distribution suggests that the merger history of the Bullet Cluster may be more complex than previous binary cluster merger scenarios.

Source inference for deterministic gravitational waves is a computationally demanding task in LISA. In a novel approach, we investigate the capability of Gaussian Processes to learn the posterior surface in order to reconstruct individual signal posteriors. We use GPry, which automates this reconstruction through active learning, using a very small number of likelihood evaluations, without the need for pretraining. We benchmark GPry against the cutting-edge nested sampler nessai, by injecting individually three signals on LISA noisy data simulated with Balrog: a white dwarf binary (DWD), a stellar-mass black hole binary (stBHB), and a super-massive black hole binary (SMBHB). We find that GPry needs $\mathcal O(10^{-2})$ fewer likelihood evaluations to achieve an inference accuracy comparable to nessai, with Jensen-Shannon divergence $D_{\scriptscriptstyle \mathrm{JS}} \lesssim 0.01$ for the DWD, and $D_{\scriptscriptstyle \mathrm{JS}} \lesssim 0.05$ for the SMBHB. Lower accuracy is found for the less Gaussian posterior of the stBHB: $D_{\scriptscriptstyle \mathrm{JS}} \lesssim 0.2$. Despite the overhead costs of GPry, we obtain a speed-up of $\mathcal O(10^2)$ for the slowest cases of stBHB and SMBHB. In conclusion, active-learning Gaussian process frameworks show great potential for rapid LISA parameter inference, especially for costly likelihoods, enabling suppression of computational costs without the trade-off of approximations in the calculations.

Hydrogen-poor superluminous supernovae (SLSNe) are among the most energetic explosions in the universe, reaching luminosities up to 100 times greater than those of normal supernovae. Detailed spectral analysis hold the potential to reveal their progenitors and underlying energy sources. This paper presents the largest compilation of SLSN photospheric spectra to date, encompassing data from ePESSTO+, the FLEET search and all published spectra up to December 2022. The dataset includes a total of 974 spectra of 234 SLSNe. By constructing average phase binned spectra, we find SLSNe initially exhibit high temperatures (10000 to 11000 K), with blue continua and weak lines. A rapid transformation follows, as temperatures drop to 5000 to 6000 K by 40 days post peak, leading to stronger P-Cygni features. These averages also suggest a fraction of SLSNe may contain some He at explosion. Variance within the dataset is slightly reduced when defining the phase of spectra relative to explosion, rather than peak, and normalising to the population's median e-folding time. Principal Component Analysis (PCA) supports this, requiring fewer components to explain the same level of variation when binning data by scaled days from explosion, suggesting a more homogeneous grouping. Using PCA and K-Means clustering, we identify outlying objects with unusual spectroscopic evolution and evidence for energy input from interaction, but find not support for groupings of two or more statistically significant subpopulations. We find Fe II {\lambda}5169 lines velocities closely track the radius implied from blackbody fits, indicating formation near the photosphere. We also confirm a correlation between velocity and velocity gradient, which can be explained if all SLSNe are in homologous expansion but with different scale velocities. This behaviour aligns with expectations for an internal powering mechanism.

Dust is a key galaxy component together with gas, stars, and central supermassive black holes, playing a crucial role in stellar and galaxy evolution. Hence, it is critical to understand galaxies' dust content and properties across cosmic time in order to better understand how galaxies evolve. In addition to photometric constraints on the absorption of blue light and its re-emission at infrared (IR) wavelengths, the detailed dust grain properties can be explored spectroscopically via Polycyclic Aromatic Hydrocarbon (PAH) emission bands in the mid-IR. The new SPHEREx space telescope will conduct an all-sky spectrophotometric survey of stars and galaxies at wavelengths of 0.75-5 ${\mu}$m, making it ideal for studying the widespread presence of the 3.3 ${\mu}$m PAH emission across entire galaxy populations out to z~0.4. In the present paper, we performed realistic simulations of galaxy spectra to investigate the capability of SPHEREx to study PAH emission in galaxies up to z=0.4. We find that for the all-sky survey, the PAH 3.3 ${\mu}$m emission band flux can be measured to an accuracy of 30% at log(M/$M_\odot$)>9.5 and Star Formation Rate (SFR)>1 $M_\odot$ yr$^{-1}$ at z=0.1, log(M/$M_\odot$)>10.5 and SFR>10 $M_\odot$ yr$^{-1}$ at z=0.2-0.3, and log(M/$M_\odot$)>11 and SFR>100 $M_\odot$ yr$^{-1}$ at z=0.4. In the deep SPHEREx fields, a factor of ~10 deeper sensitivity limits can be reached. Overall, SPHEREx will enable the measurement of the 3.3 ${\mu}$m PAH band emission in a several hundred thousand galaxies across the sky. Given that PAH emission originates from interactions between small dust grains ("nano grains") and ultraviolet radiation from young stars, these measurements will provide a population study of the smallest dust grains and radiation properties in massive galaxies in the nearby Universe.

Motivated by JWST observations of dense, clumpy and clustered high redshift star formation, we simulate the hierarchical assembly of nine $M_{\mathrm{cl}}=10^6 M_\odot$ star clusters using the BIFROST N-body code. Our low metallicity models ($0.01Z_\odot$) with post-Newtonian equations of motion for black holes include evolving populations of single, binary and triple stars. Massive stars grow by stellar collisions and collapse into intermediate mass black holes (IMBHs) up to $M_\mathrm{\bullet}\sim6200 M_\odot$, stellar multiplicity boosting the IMBH masses by a factor of $2$--$3$. The IMBHs tidally disrupt (TDE) $\sim50$ stars in $10$ Myr with peak TDE rates of $\Gamma\sim10^{-5}$ yr$^{-1}$ per cluster. These IMBHs are natural seeds for supermassive black holes (SMBHs) and the hierarchical assembly frequently leads to $>2$ SMBH seeds per cluster and their rapid mergers ($t<10$ Myr). We propose that a gravitational wave (GW) driven merger of IMBHs with $1000 M_\odot \lesssim M_\bullet \lesssim 10000 M_\odot$ with comparable masses is a characteristic GW fingerprint of SMBH seed formation at redshifts $z>10$, and IMBH formation in similar environments at lower redshifts. Massive star clusters provide a unique environment for the early Universe GW studies for the next-generation GW observatories including the Einstein Telescope and the Laser Interferometer Space Antenna.

Proxima Centauri (Cen) has been the subject of many flaring studies due to its proximity and potential to host habitable planets. The discovery of millimeter flares from this M dwarf with ALMA has opened a new window into the flaring process and the space-weather environments of exoplanets like Proxima b. Using a total of ~50 hours of ALMA observations of Proxima Cen at 1.3 mm (233 GHz), we add a new piece to the stellar flaring picture and report the first cumulative flare frequency distribution (FFD) at millimeter wavelengths of any M dwarf. We detect 463 flares ranging from energies 10$^{24}$ erg to 10$^{27}$ erg. The brightest and most energetic flare in our sample reached a flux density of 119 $\pm$ 7 mJy, increasing by a factor of 1000x the quiescent flux, and reaching an energy of 10$^{27}$ erg in the ALMA bandpass, with t$_{1/2}$~16s. From a log-log linear regression fit to the FFD, we obtain a power law index of $\alpha_\mathrm{FFD}$ = 2.92 $\pm$ 0.02, much steeper than $\alpha_\mathrm{FFD}$ values (~2) observed at X-ray to optical wavelengths. If millimeter flare rates are predictive of flare rates at extreme-UV wavelengths, the contribution of small flares to the radiation environment of Proxima b may be much higher than expected based on the shallower power-law slopes observed at optical wavelengths.

Stellar occultations by asteroids observed from several stations are routinely used to reconstruct the asteroid's sky-plane projections. Together with the asteroid's shape model reconstructed from photometry, such occultations enable us to precisely determine its size and reveal details of its shape. When reducing occultation timings, the usual assumption is that the star has a negligible angular diameter compared to the asteroid, so it is modeled as a point source. The occultation of Betelgeuse (alpha Orionis) by asteroid (319) Leona on 12 December 2023 was a rare exception - the apparent angular diameter of the star was $\sim 50$ mas, about the same as that of the asteroid. This work aimed to reconstruct the shape and spin model of asteroid Leona. Then, the projection of that model for the time of the occultation can be computed, which is necessary to interpret the occultation timings and infer valuable information about Betelgeuse itself. We collected available photometric data of Leona, carried out new observations, and reconstructed a unique convex shape model. Using three other occultations observed in 2023, we scaled this convex model. We also reconstructed an alternative nonconvex model with the same spin parameters and size but showing some surface details that explain better one of the occultations. We confirmed the tumbling rotation state of Leona and uniquely determined the rotation period $P_\psi = 1172.2 \pm 0.3$ h and the precession period $P_\phi = 314.27 \pm 0.02$ h. The volume-equivalent diameter determined by occultations is $59.1 \pm 0.9$ km. The reconstructed shape model of Leona enabled us to compute its sky-plane projection for the time of the Betelgeuse occultation. A reliable shape model can be used to interpret the observed occultation of Betelgeuse by Leona.

We report an extremely tight, linear relation between ${\rm H\alpha}$ and [O III] line fluxes in logarithm, discovered using a large sample of low and mid-resolution spectra (totaling 563) obtained by the James Webb Space Telescope (JWST) NIRSpec instrument in three widely separated extragalactic fields. While a certain correlation between ${\rm H\alpha}$ and [O III] is expected for star forming galaxies, such a log-linear and tight (dispersion of $\sim$0.1 dex) and trend is hard to explain because dust reddening would skew any intrinsic relation between the two. Furthermore, another surprising finding emerges from investigating the dust reddening properties of these galaxies. We find that the classic method of using the Balmer decrements under the standard Case B assumption does not work: a high fraction ($\sim$40\%) of our objects have ${\rm H\alpha}$/${\rm H\beta}$ line ratios even smaller than the canonical Case B ratio of 2.86. Such a high fraction of non-Case B Balmer decrements is also present in other JWST and ground-based spectroscopic studies, but the universal applicability of the Case B assumption was not questioned until recently. The mysterious ${\rm H\alpha}$--[O III] correlation and the high fraction of non-Case B Balmer decrements, which may or may not be related, should be further investigated to put our spectral analysis onto a more solid footing.

The non-grey picket-fence model predicts more accurately the temperatures in low-density regions compared to semi-grey models. This study investigates how the vertical mixing and convection fluxes modify the picket-fence model. The usual radiative-convective-equilibrium (RCE) is now extended to radiative-convective-mixing-equilibrium (RCME). The temperature profile, characterized by an increase with pressure in the upper region and an inversion in the lower, is influenced by Rosseland opacity, spectral bands, and chemical composition. The atmosphere consists of five distinct layers: a pseudo-adiabatic zone shaped by mixing flux, two convective layers driven by convective flux with a smaller adiabatic gradient, and two radiative layers. In scenarios with lower Rosseland opacity, vertical mixing significantly reduces the width of temperature inversion, counteracting the cooling effect of the convective layers and driving the deep convective layer inward. The convective flux lowers the upper temperature and expands the upper convective layer. In the low-Rosseland-opacity five-band model, these fluxes significantly cool the mid-atmosphere when temperature increases with pressure, enlarging the pseudo-adiabatic region. Without TiO/VO, the pseudo-adiabatic region shrinks, indicating that TiO/VO enhances the mixing effect. Moreover, less mixing intensity is essential to maintain a stable five-layer structure. Therefore, future studies of chemical equilibrium with multi-frequency atmospheric opacity should clearly define the constraints on vertical mixing.

We present the analysis of the multi-phase gas properties in the Seyfert II galaxy NGC 424, using spatially resolved spectroscopic data from JWST/MIRI, part of the Mid-InfraRed Activity of Circumnuclear Line Emission (MIRACLE) program, as well as VLT/MUSE and ALMA. We trace the properties of the multi-phase medium, from cold and warm molecular gas to hot ionised gas, using emission lines such as CO(2-1), H2 S(1), [OIII]5007, [NeIII]15, and [NeV]14. These lines reveal the intricate interplay between the different gas phases within the circumnuclear region, spanning approximately 1.4x1.4 kpc^2, with a resolution of 10 pc. Exploiting the multi-wavelength and multi-scale observations of gas emission we model the galaxy disc rotation curve from scales of a few parsec up to 5 kpc from the nucleus and infer a dynamical mass of 1.09\pm0.08x10^10 M_{\odot} with a disc scale radius of 0.48\pm0.02 kpc. We detect a compact ionised outflow with velocities up to 10^3 km/s, traced by the [OIII], [NeIII], and [NeV] transitions, with no evidence of cold or warm molecular outflows. We suggest that the ionised outflow might be able to inject a significant amount of energy into the circumnuclear region, potentially hindering the formation of a molecular wind, as the molecular gas is observed to be denser and less diffuse. The combined multi-band observations also reveal, in all gas phases, a strong enhancement of the gas velocity dispersion directed along the galaxy minor axis, perpendicular to the high-velocity ionised outflow, and extending up to 1 kpc from the nucleus. Our findings suggest that the outflow might play a key role in such enhancement by injecting energy into the host disc and perturbing the ambient material.

Torques from asymmetric dust structures (so-called dust-void and filamentary structures) formed around low-mass planets embedded in a non turbulent dust-gas disk can exceed the torques produced by the gas disk component, then governing the planet's orbital dynamics. Here, we investigate how these structures (hence the dust torque) change when the effect of turbulent dust diffusion and dust feedback are included, and the direct implications on the migration of Earth-like planets. Using the \textsc{Fargo3D} code, we perform 2D and 3D multifluid hydrodynamic simulations, focusing on a non-migrating planet with the mass $M_p=1.5\,M_\oplus$ in 2D and on migrating planets with $M_p\in[1.5,12]\,M_\oplus$ in 3D. We vary the $\delta$-dimensionless diffusivity parameter in the range $[0,3\times10^{-3}]$ and consider three different Stokes numbers $\mathrm{St}=\{0.04,0.26,0.55\}$, which are representative of the gas, transitional and gravity-dominated regimes, respectively. In our 2D models, we find that turbulent diffusion of dust prevents the formation of the dust-void and filamentary structures when $\delta>3\times10^{-4}$. Otherwise, dust structures survive turbulent diffusion flow. However, dust and total torques become positive only in transitional and gravity-dominated regimes. In our 3D models, we find that the dust-void is drastically modified and the high-density ring-shaped barrier delineating the dust-void disappears if $\delta\gtrsim10^{-4} $, due to the effect of dust turbulent diffusion along with the back-reaction of the dust. For all values of $\delta$, the filament in front of the planet is replaced by a low-density trench. Remarkably, as we allow the planets to migrate, the evolving dust-void can drive either runaway migration or outward (inward) oscillatory-torque migration. Our study thus suggests that low-mass Earth-like planets can undergo runaway migration in dusty disks.

Early B-type stars ($M_i=8-15$ M$_\odot$) are frequently in multiple systems, as evidenced by spectroscopic campaigns in the Milky Way (MW) and the Large Magellanic Cloud (LMC). Previous studies have shown no strong metallicity dependence in the close-binary (a>10 au) fraction or orbital-period distributions between the MW's solar metallicity (Z$_\odot$) and that of the LMC (Z=0.5 Z$_\odot$). However, similar analyses in more metal-poor environments are still scarce. We focus on 309 early B-type stars (luminosity classes III-V) from the Binarity at LOw Metallicity campaign in the Small Magellanic Cloud (SMC, Z=0.2 Z$_\odot$) using VLT/FLAMES multi-epoch spectroscopy. By applying binary detection criteria consistent with previous works, we identify 153 stars (91 SB1, 59 SB2, 3 SB3) exhibiting significant radial-velocity (RV) variations, resulting in an observed multiplicity fraction of $f^{obs}_{mult}=50\pm3\%$. Using Monte Carlo simulations to account for observational biases, we infer an intrinsic close-binary fraction of $f_{mult}=80\pm8\%$. A Markov chain Monte Carlo analysis of the peak-to-peak RV distribution ($\Delta{\rm RV}_{\rm max}$) confirms a high multiplicity fraction of $f_{mult}=78\pm5\%$. These findings suggest a possible anti-correlation between metallicity and the fraction of close B-type binaries, with the SMC multiplicity fraction significantly exceeding previous measurements in the LMC and MW. The enhanced fraction of close binaries at SMC's low metallicity may have broad implications for massive-star evolution in the early Universe. More frequent mass transfer and envelope stripping could boost the production of exotic transients, stripped supernovae, gravitational-wave progenitors, and sustained UV ionising flux, potentially affecting cosmic reionisation. Theoretical predictions of binary evolution under metal-poor conditions will provide a key test of our results.

We report new branching fraction measurements for 156 ultraviolet and optical transitions of Gd II. These transitions range in wavelength (wavenumber) from 2574 to 6766 Angstroms (38838 - 14777 cm-1) and originate in one odd-parity and 11 even-parity upper levels. Nine of the 12 levels, accounting for 126 of the 156 transitions, are studied for the first time. Branching fractions are determined for three levels studied previously for the purpose of comparison. The levels studied for the first time are high lying, ranging in energy from 36845 to 40774 cm-1. The branching fractions are determined from emission spectra from two different high-resolution spectrometers. These are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5% to 30%. Comparison is made to experimental and theoretical transition probabilities from the literature where such data exist. Abundances derived from these new log(gf) values for 21 Gd II lines in two metal-poor stars yield results consistent with previous studies, and they demonstrate that the new log(gf) values can be used in stellar abundance analysis as a self-consistent extension of previous work.

Double-peaked emission lines are observed in a few percent of active galactic nuclei (AGN) and allow the determination of properties of the line-emitting region, known as the broad-line region (BLR). We investigate the structure and kinematics of the BLR in the Seyfert galaxy NGC 4593 through an analysis of the NIR line blend of Ca II 8498, 8542, 8662 and O I 8446 observed in a 2019 VLT/MUSE spectrum. We perform a detailed decomposition of the near-infrared Ca II triplet and O I 8446 blend, extracting clean profiles of Ca II 8498, 8542, 8662 and O I 8446. We then fit Ca 8662 with a relativistic elliptical line-emitting disk model. The line profiles are double-peaked with a full width at half maximum (FWHM) of approx. 3700 km/s and exhibit a redward asymmetry with a red-to-blue peak ratio of 4:3. The Ca ii triplet lines have an intensity ratio of 1:1:1 and show no evidence of a central narrow or intermediate-width component. The profiles of Ca II and O I are remarkably similar, suggesting a common region of origin. Given the 1:1:1 ratio of the Ca II triplet, this region is likely a high-density emission zone, and the Ca II 8662 profile is well described by a mildly eccentric, low-inclination relativistic disk with minimal internal turbulence. The profile represents one of the clearest kinematic signatures of a relativistic disk observed in BLR emission lines to date. The double-peaked profiles of the NIR Ca II triplet and O I 8446 in NGC 4593 represent the first detection of double-peaked Ca II and O I 8446 in a non-transient AGN spectrum. The minimal intrinsic turbulence -- the lowest value reported for an AGN emission line to date -- and absence of narrow or intermediate-width components in Ca II 8662 make it a powerful diagnostic tool of BLR structure and kinematics. Further investigations of the profiles of Ca II and O I in other AGN are warranted to better constrain BLR properties.

Some stars orbiting supermassive black holes (SMBH) are expected to undergo a gravitational-wave (GW)-driven inspiral and initiate mass transfer on nearly circular orbits. However, the stability and duration of such phases remain unexplored. In this work, we focus on the evolution of a low-mass, radiative-envelope subgiant star being stripped by an SMBH. We find that such systems can undergo a long-lasting, stable mass-transfer phase, even if none of the angular momentum of the transferred material returns to the orbit to counterbalance the GW-driven decay. We show an example where a 2 Msun subgiant is stripped before entering the LISA band and loses almost its entire hydrogen envelope. The remaining helium core undergoes a prolonged GW-driven inspiral, becoming a loud LISA source. If formed in our galaxy, the system would be detectable for several hundred thousand years, ultimately reaching extreme signal-to-noise ratios of a million. Hydrogen shell flashes in the residual envelope cause temporary radial expansions of the stripped star. As a result, a few additional phases of rapid mass transfer occur at orbital periods of 20 - 30 hours. Eventually, the core possibly undergoes circular partial tidal disruption at an orbital period of ~10 minutes, corresponding to a GW emission frequency of a few mHz. We estimate a chance of about 1% that such a detectable LISA source exists in our own galactic center. The loud final GW transient may lead to a few detections reaching as far as ~1 Gpc, including, e.g., the Abell clusters.

Recent high-dispersion spectroscopy from ground-based telescopes and high-precision spectroscopy from space observatories have enabled atmospheric observations of substellar objects, such as brown dwarfs and hot gaseous exoplanets, with sufficient precision to make ambient gas differences in molecular line broadening a significant factor. In this paper, we experimentally measured the pressure broadening of methane in a high-temperature hydrogen-helium background atmosphere in the H band, which had not been previously measured. The experiment used glass cells, inserted in a tube furnace, filled with methane in a hydrogen-helium background atmosphere or pure methane gas. Spectra were obtained at four temperatures ranging from room temperature to 1000 K, in the wavelength range 1.60-1.63 $\mu$m, using a tunable laser, yielding eight high-resolution spectra in total. A full Bayesian analysis was performed on the obtained spectra, using the differentiable spectral model ExoJAX and the Hamiltonian Monte Carlo for inferring a large number of parameters, allowing us to infer the H2/He pressure broadening for 22 transitions mainly in the R-branch of the 2$\nu_3$ band. As a result, we found a temperature exponent of approximately 0.27 and a reference width at 296 K of around 0.040 for $ J_{lower} $ = 13-20. This temperature dependency is much milder than that provided by the molecular database ExoMol, yielding a line width approximately 5-45% smaller than ExoMol at 296 K, but similar at 1000 K. Our results suggest the need for further accumulation of experimental data for spectral analysis of substellar objects with hydrogen-helium atmospheres.

The dark and dynamic parts of the Galaxy, including the bulk shape and movement of the Galactic Bulge and characteristics of dark compact object populations, such as a hypothetical population of primordial black holes (PBHs), are difficult to study directly by their very nature, but are critical to our understanding of the universe. Fortunately, all of these mysteries can be uniquely studied via gravitational microlensing, a method of astronomical detection that traces mass and dynamics as opposed to light. Using the OGLE-IV microlensing survey bulge fields, we apply a Bayesian hierarchical model to jointly infer properties of the Galaxy, the characteristics of compact objects, and and test PBHs with an extended mass distribution as a test PBHs as a viable explanation of dark matter, extending work focused on the Small and Large Magellanic Clouds, both with much lower event-rates. We infer a preference within the data for a lower patternspeed in the galactic model and a wider mass spectrum for compact objects. When adding a PBH component to the favored astrophysical model from our initial investigations, we find a Bayes factor of $\ln\mathcal{B} = 20.23$ preferring the PBH model. Upon further investigation of these results, we find the critical feature in the PBH model to be the velocity distribution, which is fundamentally different than the velocity distribution of astrophysical objects and uniquely able to explain a large number of low parallax, low timescale microlensing events. Noting that this effect is not unique to PBHs, we consider the implications of these results as applied to a hypothetical population of PBHs and discuss alternative explanations, including a variety of other possible astrophysical and survey or analysis systematics.

The kinematics of star-forming galaxy populations at high redshifts are integral to our understanding of disk properties, merger rates, and other defining characteristics. Nebular gas emission is a common tracer of galaxies' gravitational potentials and angular momenta, but is sensitive to non-gravitational forces as well as galactic outflows, and thus might not accurately trace the host galaxy dynamics. We present kinematic maps of young stars from rest-ultraviolet photospheric absorption in the star-forming galaxy CASSOWARY 13 (a.k.a. SDSS J1237+5533) at $z=1.87$ using the Keck Cosmic Web Imager, alongside nebular emission measurements from the same observations. Gravitational lensing magnification of the galaxy enables good spatial sampling of multiple independent lensed images. We find close agreement between the stellar and nebular velocity fields. We measure a mean local velocity dispersion of $\sigma = 64\pm12$ km$\,$s$^{-1}$ for the young stars, consistent with that of the H II regions traced by nebular C III] emission ($52\pm9$ km$\,$s$^{-1}$). The $\sim20$ km$\,$s$^{-1}$ average difference in line-of-sight velocity is much smaller than the local velocity width and the velocity gradient ($\gtrsim 100$ km$\,$s$^{-1}$). We find no evidence of asymmetric drift nor evidence that outflows bias the nebular kinematics, and thus conclude that nebular emission appears to be a reasonable dynamical tracer of young stars in the galaxy. These results support the picture of star formation in thick disks with high velocity dispersion at $z\sim2$, and represent an important step towards establishing robust kinematics of early galaxies using collisionless tracers.

Tomography is a powerful technique for recovering the three-dimensional (3D) density structure of the global solar corona. In this work, we present an improved tomography method by introducing radial weighting in the regularization term. Radial weighting provides balanced smoothing of density values across different heights, helping to recover finer structures at lower heights while also stabilizing the solution and preventing oscillatory artifacts at higher altitudes. We apply this technique to reconstruct the 3D electron density of Carrington Rotation (CR) 2098 using two weeks of polarized brightness (pB) observations from the inner coronagraph (COR1) onboard spacecraft-B of the twin Solar Terrestrial Relations Observatory (STEREO), where the radial weighting function is taken as the inverse intensity background, calculated by averaging all the pB images used. Comparisons between density distributions at various heights from the tomography and magnetohydrodynamics (MHD) simulations show good agreement. We find that radial weighting not only effectively corrects the over-smoothing effect near the inner boundary in reconstructions using second-order smoothing but also significantly improves reconstruction quality when using zeroth-order smoothing. Additionally, comparing reconstructions for CR 2091 from single-satellite data with that from multi-viewpoint data suggests that coronal evolution and dynamics may have a significant impact on the reconstructed density structures. This improved tomography method has been used to create a database of 3D densities for CRs 2052 to 2154, based on STEREO/COR1-B data, covering the period from 08 January 2007 to 17 September 2014.

We present a comprehensive study of bar structures in the local Universe using data from the DESI Legacy Imaging Surveys. Through isophotal analysis of 232,142 galaxies, we identify bars and classify them into strong and weak categories based on normalized bar length, using a threshold of 0.4. We find a total bar fraction of 42.9%, rising to 62.0% in disk galaxies, with strong barred galaxies accounting for 30.0%. For barred galaxies in our sample, deprojected bar lengths are measured both in absolute terms and normalized by galaxy size. Most bars are found to have absolute lengths of 3-7 kpc, and normalized bar lengths concentrated around a median value of 0.4. Bar ellipticity mainly ranges from 0.2 to 0.6, with a median value of 0.3. Our analysis reveals a bimodal distribution of bar fractions with respect to galaxy color, with weak bars in our classification being more prevalent in intermediate-color systems. With respect to stellar mass, strong bars also present a bimodal distribution, while weak bars are distributed uniformly. Normalized bar length remains relatively stable across stellar masses, while absolute bar length positively correlates with stellar mass. Cross-validation with visual classifications from GZD catalog confirms a bar identification accuracy of 93%. These results validate our automated method for bar identification and measurement, demonstrating its reliability. Our findings underscore the importance of bars in galaxy evolution and highlight the potential of upcoming wide-field surveys to deepen our understanding of barred galaxies.

Spectra have been obtained with multi-fibre instrument 2dF on the Anglo-Australian Telescope of 89 candidate main sequence stars in the globular cluster M55 (NGC 6809). Radial velocities and Gaia proper motions confirm 72 candidates as cluster members. Among these stars one stands out as having a substantially stronger G-band (CH) than the rest of the member sample. The star is a dwarf carbon star that most likely acquired the high carbon abundance ([C/Fe] approx 1.2 +/- 0.2) via mass transfer from a 1-3 Msun binary companion (now a white dwarf) during its AGB phase of evolution. Interestingly, M55 also contains a CH-star that lies on the cluster red giant branch -- the low central concentration/low density of this cluster presumably allows the survival of binaries that would otherwise be disrupted in denser systems. The existence of carbon stars in six other globular clusters is consistent with this hypothesis, while the origin of the carbon-enhanced star in M15 (NGC 7078) is attributed to a merger process similar to that proposed for the origin of the carbon-rich R~stars.

We investigate the evolution of star clusters containing intermediate-mass black hole (IMBH) of $300$ to $5000\ \mathrm{M}_\odot$, focusing on the formation and evolution of IMBH-stellar mass black holes (SBHs; $M_{\rm BH} \lesssim 10^2\ \mathrm{M}_\odot$) binaries. Dense stellar systems like globular clusters (GCs) or nuclear star clusters offer unique laboratories for studying the existence and impact of IMBHs. IMBHs residing in GCs have been under speculation for decades, with their broad astrophysical implications for the cluster's dynamical evolution, stellar population, GW signatures, among others. While existing GW observatories such as the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) target binaries with relatively modest mass ratios, $q \lesssim 10$, future observatories such as the Einstein Telescope (ET) and the Laser Interferometer Space Antenna (LISA) will detect intermediate-mass ratio inspirals (IMRIs) with $q > 10$. This work explores the potential for detecting IMRIs adopting these upcoming telescopes. For our experiments, we perform multiple direct $N$-body simulations with IMBHs utilizing Nbody6++GPU, after implementing the GW merger schemes for IMBHs. We then study the statistical properties of the resulting IMRIs, such as the event rates and orbital properties. Assuming that IMRIs with a signal-to-noise ratio $S/N > 8$ are detectable, we derive the following detection rates for each observatory: $\lesssim 0.02\mathrm{yr}^{-1}$ for aLIGO, $\sim 101 - 355 \mathrm{yr}^{-1}$ for ET, $\sim 186 - 200 \mathrm{yr}^{-1}$ for LISA, $\sim 0.24 - 0.34 \mathrm{yr}^{-1}$ for aSOGRO, and $\sim 3880 - 4890 \mathrm{yr}^{-1}$ for DECIGO. Our result confirms the capability of detecting IMRIs with future GW telescopes.

Long-period variables (LPVs) are high-luminosity red giants or supergiants with pulsation periods ranging from days to years. Many LPVs in the Large Magellanic Cloud (LMC) and Galactic Bulge (BLG) have been continuously observed over a time span of 26 years by the Optical Gravitational Lensing Experiment (OGLE) survey. Using OGLE-IV data, we applied Gaussian Processes with kernels tailored for solar-like oscillations to extract two global asteroseismic parameters: the frequency of maximum power (numax) and the large frequency separation (Dnu), for LPVs with primary mode periods (P1) between 10 and 100 days in the LMC and BLG. We found that the numax-Dnu relation for LPVs in this work aligns with that of lower-luminosity Kepler red giants, confirming that the pulsations of these LPVs are likely solar-like. We found that numax and Dnu can serve as luminosity indicators. Compared to P1, numax and Dnu exhibit significantly tighter correlations with the absolute magnitude in the 2MASS K_s band (M_{K}), with corresponding scatter of 0.27 mag and 0.21 mag, respectively. Using the calibrated numax-mk and Dnu-mk relations for LPVs in the LMC, we determined the M_{K} values for individual stars in the BLG. By accounting for extinction, we further calculated the distances to 4,948 BLG stars. The peak of the resulting distance distribution corresponds to an estimated distance to the Galactic center of approximately 9.1 kpc, which appears to be overestimated, suggesting that the seismic luminosity relation calibrated from the LMC may not be directly applicable to BLG stars.

JWST reveals numerous high-z galaxies and Supermassive Black Holes (SMBHs), suggesting that stars and SMBH seeds formation at $z \gtrsim 10$ may be more efficient than previously derived. One popular SMBH seed scenario is the Direct Collapse Black Holes (DCBHs) formed in pristine atomic-cooling halos irradiated by nearby galaxies. Therefore, the efficient star formation likely facilitates the formation of DCBH. We calculate the first critical $k_{\rm H_2}-k_{\rm H^-}$ curves for DCBH formation under the influence of X-ray radiation using the one-zone model. We then build the UV luminosity function consistent with JWST observations and incorporate it into the model that calculates the DCBH-triggering probability. We confirm that enhanced star formation promotes the DCBH formation. However, the DCBH abundance $n_{\rm DCBH}$ is significantly influenced by the X-ray radiation that is also related to star formation. Since the 21 cm global spectrum is also X-ray dependent, the 21 cm absorption depth $\delta T_b^{\rm trough}$ at Cosmic Dawn encodes the DCBH abundance information. We provide a tentative trend in the $n_{\rm DCBH}$ - $\delta T^{\rm trough}_{\rm b}$ relation, which could be a useful guide. In our fiducial model, if $\delta T_b^{\rm trough}\gtrsim -100$ mK, then the DCBH is rather rare; if $-150~{\rm mK} \lesssim \delta T_b^{\rm trough}\lesssim -100$ mK, $ n_{\rm DCBH} \sim \mathcal{O}(10^{-2}-10^{-3})$ cMpc$^{-3}$ (comoving $\rm Mpc^{-3}$), consistent with the HST/JWST observed SMBHs abundance at $z\gtrsim 6$; if $\delta T_b^{\rm trough}\lesssim -150$ mK, $n_{\rm DCBH}$ can largely exceed $\mathcal{O}(10^{-2})$ cMpc$^{-3}$. The 21 cm global spectrum observations will help to constrain the DCBH abundance.

If sub-GeV Dark matter(DM) annihilates to the charged particles such as $e^+ e^-$, $\mu^+ \mu^-$, or $\pi^+ \pi^-$, it generates an additional source of electrons and positrons in the cosmic ray (CR) population within our Milky Way. During propagation, these secondary electrons and positrons undergo reacceleration processes, boosting their energies to the GeV scale. Observatories like AMS-02 can detect these high-energy particles, enabling constraints on the properties of sub-GeV DM. By analyzing AMS-02 electron and positron data, the 95\% upper limits on the DM annihilation cross-section have been established in the range of $10^{-28}$ to $10^{-27}$ cm$^3\,$s$^{-1}$, corresponding to DM masses ranging from 100 MeV to 1 GeV. Meanwhile, MeV telescopes will provide complementary constraints on DM properties by detecting photon emissions from such annihilation processes. Notably, the sensitivity of future MeV gamma-ray observatories is projected to approach or match the constraints derived from CR data.

We present the result of two binary classifier ensembled neural networks to identify catastrophic outliers for photo-z estimates within the COSMOS field utilizing only 8 and 5 photometric band passes, respectively. Our neural networks can correctly classify 55.6% and 33.3% of the true positives with few to no false positives. These methods can be used to reduce the errors caused by the errors in redshift estimates, particularly at high redshift. When applied to a larger data set with only photometric data available, our 8 band pass network increased the number of objects with a photo-z greater than 5 from 0.1% to 1.6%, and our 5 band pass network increased the number of objects with a photo-z greater than 5 from 0.2% to 1.8%.

We present the design methodology and characterization of a superconducting magnetic bearing (SMB) system for the polarization modulator in the SAT-LF, one of the small aperture telescopes (SATs) in the Simons Observatory (SO) that is sensitive at 30/40 GHz frequency bands. SO is a ground-based cosmic microwave background (CMB) polarization experiment, with the SATs specifically aiming to search for primordial parity-odd polarization anisotropies at degree scales. Each SAT is equipped with a cryogenic, continuously rotating half-wave plate (HWP) as a polarization modulator to mitigate atmospheric $1/f$ noise and instrumental systematics. The HWP system employs an SMB, consisting of a ring-shaped magnet and superconductor, to achieve a 550 mm clear aperture and stable 2 Hz rotation at a temperature of around 50 K. One challenge for the HWP system in the SAT-LF is the large 35 kg load on the SMB due to the thicker HWP than in previous telescopes. Since the SMB stiffness is critical for maintaining the alignment of the HWP in the telescope, we developed a method to quantitatively predict the stiffness using finite element simulations with the so-called H-formulation. We evaluated the stiffness for various geometries of the magnet and superconductor, thereby optimizing their dimensions. The prediction is in excellent agreement with experimental measurements of the fabricated SMB, demonstrating a $\sim$5\% accuracy. We also demonstrated that the SMB achieves sufficiently low friction-induced heat dissipation, measured at 0.26 W when rotating at 2 Hz. The design methodology and the implementation of the SMB demonstrated here not only provides an enabling technology for the SO SAT-LF, but also is a crucial stepping stone for future CMB experiments that make use of HWP polarization modulators.

A sample of 312 low-frequency peaked BL Lacertae objects (LBLs) and 694 flat spectrum radio quasars (FSRQs) with the parameters both redshift and $\gamma$-ray photon spectral index ($\Gamma _\gamma$) is compiled from the active galactic nuclei (AGNs) Catalog Data Release 2 (4LAC-DR2) from Fermi-LAT. The multi-wavelength data of the sample sources are downloaded from the Space Science Data Center (SSDC), and then match the corresponding gamma-ray data from 4FGL-DR2. The synchrotron radiation peak frequency and Compton dominance (CD) parameters of the sources are obtained by using a log-parabolic to fit the average-state multi-wavelength spectral energy distribution. A support vector machine (SVM) in the $\log L_\gamma$-$\Gamma_\gamma$ frame is utilized to delineate the optimal boundary between FSRQs and LBLs sources. The 1$\sigma$ position of the Gaussian fitting on the histograms of the $\Gamma_\gamma$, $\log \nu^{syn}_{peak}$, and CD parameter distributions are also introduced. In the criterion, 25 FSRQ candidates are selected from LBL sample sources. The optical spectral identification result confirms that 8 out of 13 candidate sources available with the optical spectral data exhibit the relationship of $EW > 5 \mathring{\mathrm{A}}$.

The Herbig Ae/Be star HD190073 is one of the very few magnetic Herbig Ae/Be stars for which close low-mass companions have been reported. Previously published magnetic field measurements indicated an annual change in the field configuration. We aim to study in detail the spectral and magnetic variability of this star and characterise its magnetosphere for the first time. Newly acquired and archival spectropolarimetric observations are combined to determine a more precise magnetic period and to constrain the geometry of the magnetic field. The variability of hydrogen line profiles is studied using dynamical spectra. Archival X-shooter observations of the He I 10830 ang triplet are used to characterise its variability over the rotation cycle. Further, we carry out 2D magnetohydrodynamical simulations of the magnetosphere using the Nirvana code. From the spectropolarimetric observations, we determine for HD190073 a magnetic period P=51.70 d. We estimate a magnetic obliquity angle 82.9 degr and a dipole strength 222 G. Our dynamical spectra constructed for the hydrogen line profiles observed during 2011 clearly reveal a ringlike magnetospheric structure appearing at the rotation phase of best visibility of the positive magnetic pole. These spectra present the first snapshot of a magnetosphere around a Herbig Ae/Be star. 2D MHD simulations involving nonisothermal gas show that the magnetosphere is compact, with a radius of about $3\,R_*$, and that the wind flow extends over tens of $R_*$. With a reported radius of the accretion disk of 1.14 au around HD190073, the distance between the star and the disk is about 25 $R_*$. The detection of a magnetosphere around HD190073, and the possible presence of lower-mass companions at different distances, make this system a valuable laboratory for studying the magnetic interaction between the host star, its companions, and the accretion disk.

We report the results obtained with a XMM-Newton observation, performed in April 2023, of the poorly known Galactic Be X-ray binary pulsar 4U 0728-25. It was revealed at a flux level (not corrected for the absorption) $f_{\rm X}$(0.2-12 keV) = 1.7$\times 10^{-11}$ erg cm$^{-2}$ s$^{-1}$, which implies an unabsorbed source luminosity $L_{\rm X} \simeq 1.3 \times 10^{35}$ erg s$^{-1}$: this is the minimum luminosity ever observed for this source. We measured a pulse period $P_{\rm spin}$ = 103.301(5) s, a value $\simeq $ 0.15 % longer than that estimated in 2016 with AstroSat. The pulse profile shows a broad single peak at all energies, with a limited energy dependence and a small increase in the pulsed fraction with energy. The time-averaged EPIC spectrum can be described equally well by four different emission models, either with a single non-thermal component (a partially covered power law or a cut-off power law), or with a thermal component in addition to the non-thermal one (a black body plus a power law, or a collisionally ionised gas plus a cut-off power law). All of them provided an equally good fit and, in the case of the power-law plus black-body model, the thermal component is characterized by a high temperature ($kT_{\rm BB} \simeq$ 1.5 keV) and a small size ($R_{\rm BB} \simeq$ 240 m), comparable with that of the neutron-star polar caps. A spectral variability along the pulse phase is present, which suggests a flux variation of the black-body component. These results show that, for its luminosity level, flux variabilty over long time scales, and spectral properties, 4U 0728-25 is very similar to most of the persistent Be X-ray binaries. Therefore, it can be considered a member of this class of sources.

WISEA J181006.18-101000.5 (WISE1810) is the nearest metal-poor ultracool dwarf to the Sun. It has a low effective temperature and has been classified as extreme early-T subdwarf. However, methane, the characteristic molecule of the spectral class T, was not seen in the previous low-resolution spectrum. Using the 10.4-m Gran Telescopio Canarias, we collected a high-quality JHK-band intermediate-resolution R~5000 spectrum of WISE1810, in which a 17+/-6 ppm of methane is clearly detected, while carbon monoxide is absent. Based on customly computed ATMO2020++ model, we estimated an effective temperature of 1000+/-100 K, a high surface gravity of log g = 5.5+/-0.5 dex, a carbon abundance [C/H]=-1.5+/-0.2 dex, inferring [Fe/H]=-1.7+/-0.2 dex. Potassium is not seen in our data, and the upper limits of pseudo-equivalent width of J-band atomic lines are at least 25 to 60 times weaker than those measured from solar-metallicity early-T counterparts. We measured a heliocentric radial velocity of -83+/-13 km/s, inferring that WISE1810 is more likely a thick disk member.

Observations of the line-of-sight component of emitter velocities in galaxies are valuable for reconstructing their 2D velocity fields, albeit requiring certain assumptions. A common one is that radial flows can be neglected in the outer regions of galaxies, while their geometry can be deformed by a warp. A specular approach assumes that galactic discs are flat but allows for the presence of radial flows. This approach enables the reconstruction of 2D velocity maps that encompass both the transversal and radial velocity fields. Through the study of velocity fields in toy disc models, we find that the presence of warps is manifested as a dipolar correlation between the two velocity components obtained by assuming a flat disc. This shows that the analysis of angular velocity anisotropies provides an effective tool for breaking the degeneracy between warps and radial flows. We have applied these findings to the analysis of velocity fields of the galaxies from the THINGS sample and M33. Many of these galaxies exhibit such a dipolar correlation, indicating the presence of warps. However, we have found that the warp alone cannot explain all variations in the velocity field, suggesting that intrinsic perturbations are common. Furthermore, we have observed that the spatial distribution of the line-of-sight velocity dispersion may correlate with both velocity components providing independent evidence of non-trivial velocity fields. These findings offer a robust approach to reconstructing the velocity fields of galaxies, allowing us to distinguish between the presence of warps and complex velocity structures assessing their relative amplitude.

$\require{mediawiki-texvc}$Galactic outflows shape galaxy evolution, but their mass, energy, and momentum transfer remain uncertain. High-resolution spectroscopy can help, but systematic discrepancies hinder model interpretation. In this study, we evaluate the performance of semi-analytical line transfer (SALT) and empirical partial covering models (PCMs) to recover the properties of outflows in the FIRE-2 simulation suite from synthetic Si II lines (1190 $Å$, 1193 $Å$, 1260 $Å$, 1304 $Å$, 1527 $Å$). When applicable, we assess each model's ability to recover mass, energy, and momentum outflow rates, as well as radial density and velocity profiles, column densities, and flow geometries. We find that the PCM underestimates column densities by 1.3 dex on average in the range $15 < \log N\ [\text{cm}^{-2}] < 17$ with dispersion 1.3 dex. We attribute this bias to instrumental smoothing. Since the PCM underestimates column densities, it also underestimates flow rates, though its predictions are independent of radius, with a dispersion of 0.55 dex. We detect no bias in the SALT estimates of the column density with dispersion 1.3 dex. When the velocity and density field obey power laws, SALT can constrain the mass, momentum, and energy outflow rates to 0.36 (0.63), 0.56 (0.56), and 0.97 (0.80) dex at $0.15(0.30)R_{\text{vir}}$, respectively. However, certain profiles in FIRE-2 fall outside the SALT framework, where the model breaks down. We find that SALT effectively tracks the flow geometry, capturing the temporal evolution of the photon escape fraction that is out of phase with the star formation rate, fully consistent with hydrodynamic simulations. We advocate for integral field unit spectroscopy to better constrain flow properties.

The nature of the elusive dark matter can be probed by comparing the predictions of the cold dark matter framework with the gravitational field of massive galaxy clusters. However, a robust test of dark matter can only be achieved if the systematic uncertainties in the reconstruction of the gravitational potential are minimized. Techniques based on the properties of intracluster gas rely on the assumption that the gas is in hydrostatic equilibrium within the potential well, whereas gravitational lensing is sensitive to projection effects. Here we attempt to minimize systematics in galaxy cluster mass reconstructions by jointly exploiting the weak gravitational lensing signal and the properties of the hot intracluster gas determined from X-ray and millimeter (Sunyaev-Zel'dovich) observations. We construct a model to fit the multi-probe information within a common framework, accounting for non-thermal pressure support and elongation of the dark matter halo along the line of sight. We then apply our framework to the massive cluster Abell 1689, which features unparalleled multi-wavelength data. In accordance with previous works, we find that the cluster is significantly elongated along the line of sight. Accounting for line-of-sight projections, we require a non-thermal pressure support of $30\text{-}40\%$ at $r_{500}$ to match the gas and weak lensing observables. The joint model retrieves a concentration $c_{200}\sim7$, which is lower and more realistic than the high concentration retrieved from weak lensing data alone under the assumption of spherical symmetry ($c_{200}\sim15$). Application of our method to a larger sample will allow us to study at the same time the shape of dark matter mass profiles and the level of non-thermal pressure support in galaxy clusters.

Cosmic birefringence (CB) is the rotation of the photons' linear polarisation plane during propagation. Such an effect is a tracer of parity-violating extensions of standard electromagnetism and would probe the existence of a new cosmological field acting as dark matter or dark energy. It has become customary to employ cosmic microwave background (CMB) polarised data to probe such a phenomenon. Recent analyses on Planck and WMAP data provide a hint of detection of the isotropic CB angle with an amplitude of around $0.3^\circ$ at the level of $2.4$ to $3.6\sigma$. In this work, we explore the LiteBIRD capabilities in constraining such an effect, accounting for the impact of the more relevant systematic effects, namely foreground emission and instrumental polarisation angles. We build five semi-independent pipelines and test these against four different simulation sets with increasing complexity in terms of non-idealities. All the pipelines are shown to be robust and capable of returning the expected values of the CB angle within statistical fluctuations for all the cases considered. We find that the uncertainties in the CB estimates increase with more complex simulations. However, the trend is less pronounced for pipelines that account for the instrumental polarisation angles. For the most complex case analysed, we find that LiteBIRD will be able to detect a CB angle of $0.3^\circ$ with a statistical significance ranging from $5$ to $13 \, \sigma$, depending on the pipeline employed, where the latter uncertainty corresponds to a total error budget of the order of $0.02^\circ$.

We report the analysis of a planetary microlensing event AT2021uey. The event was observed outside the Galactic bulge and was alerted by both space- (Gaia) and ground-based (ZTF and ASAS-SN) surveys. From the observed data, we find that the lens system is located at a distance of 1 kpc and comprises an M-dwarf host star of about half a solar mass, orbited by a Jupiter-like planet beyond the snowline. The source star could be a metal-poor giant located in the halo according to the spectral analyses and modelling. Hence, AT2021uey is a unique example of the binary-lens event outside the bulge that is offered by a disc-halo lens-source combination.

This work builds on a recently developed self-consistent synchronization model of the solar dynamo which attempts to explain Rieger-type periods, the Schwabe/Hale cycle and the Suess-de Vries and Gleissberg cycles in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. We start again from the basic concept that the spring tides of the three pairs of the tidally dominant planets Venus, Earth and Jupiter excite magneto-Rossby waves at the solar tachocline. While the quadratic action of the sum of these three waves comprises the secondary beat period of 11.07 years, our main focus is now on the action of the even more pronounced period of 1.723 years. We show that this term excites dynamo vacillations with periods that are typical for the quasi-biennial oscillation (QBO). While bimodality of the sunspot distribution is shown to be a general feature of synchronization, it becomes most strongly expressed under the influence of the QBO. This may explain the observation that the solar activity is relatively subdued when compared to that of other sun-like stars. We also discuss anomalies of the solar cycle, and subsequent phase jumps by 180 degrees. In this connection it is noted that the very 11.07-yr beat period is rather sensitive to the time-averaging of the quadratic functional of the waves and prone to phase jumps of 90 degrees. On this basis, we propose an alternative explanation of the observed 5.5-year phase jumps in algae-related data from the North Atlantic and Lake Holzmaar that were hitherto attributed to optimal growth conditions.

Gravitationally lensed quasars have served as a powerful tool for studying the composition of dark matter (DM) in lensing galaxies. In this work, we propose a novel method to investigate stellar-mass primordial black holes (PBHs) by using the microlensing effect of strongly lensed Type Ia supernovae (SNe Ia). Using the parameters of the lensed quasar system PG 1115+80, such as convergence, shear, and stellar/dark matter fractions, we generate microlensing magnification maps. A uniform brightness disk model is applied to these maps to evaluate the microlensing amplitude at different stages of the supernova explosion. We extend this analysis by employing the strong lensing parameters derived from the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) to create extensive image datasets of lensed SNe Ia. Utilizing these datasets and the Kolmogorov-Smirnov (KS) test, we compare two models: (1) the fiducial model, where galaxies are composed of stars and smooth DM, and (2) the alternative model, where galaxies consist of stars and compact DM, specifically PBHs. Our preliminary analysis predicts that at least 60 image datasets are required to distinguish these two scenarios at a 95 percent confidence level. Additionally, by incorporating the Strong Lensing Halo model-based mock catalogs (SL-Hammocks), which provide more realistic and precise image data, we refine our prediction to assess the data requirements for distinguishing cases where PBHs constitute fractions x of the total dark matter mass. Our findings indicate that 50, 55, and 65 image datasets, corresponding to compact dark matter fractions of 100 percent, 50 percent, and 25 percent (denoted by x), are necessary to distinguish between the specific models.

Recent horizon-scale observations of the Sgr A* might open up a new window to study spacetime geometry and accretion matter in the strong-field regime of gravity. Due to the short gravitational timescale for Sgr A*, variable emissions near the galactic center are expected in the observations, including variability in the Sgr A* images and flare motions within ten times gravitational radius. In this paper, we investigate the spatiotemporal auto- and cross-correlations for multiple images of a long-lived corotating hotspot near the black hole. Using the recently developed efficient ray-tracing scheme for point-like sources, we extensively consider multiple images from primary to eighth-order in the correlations. We show that these correlations exhibit a repeated inclined band-like structure in the $\Delta \Phi$-$\Delta t$ plane. And there is a periodic modulation of width of the correlated bands, with the maximum bandwidth increasing with the inclination angles. The point-slope of correlated bands is determined by the lapse in azimuthal angle and time of multiple images, as well as the apparent rotation speed of hotspots. By comparing correlations for lower-order with those for higher-order images, it is found that the fixed points for cross-correlations between lower-order images depend on the orbital configurations of hotspots. It challenges the use of correlations for lower-order images to infer black hole geometries. Additionally, we also examine the influence from hotspot shapes based on semi-analytical formulas. Although the emission shape can significantly influence light curves, it does not change the correlated bands of the correlations.

This study introduces a time-based cleaning method for H.E.S.S. using CT5 in monoscopic mode and presents an optimization workflow for image-cleaning algorithms to enhance telescope sensitivity while minimizing systematic biases. We evaluate three methods - tail-cut cleaning and two flavours of time-based cleaning TIME3D and TIME4D - and find best-cut configurations for two cases: optimal overall sensitivity and minimal energy threshold. TIME3D achieves a $\sim 15\%$ improvement with regard to the standard tail-cut cleaning for $E < 300$ GeV, with a $\sim 200\%$ improvement for the first energy bin (36.5 GeV < E < 64.9 GeV), providing a more stable performance across a wider energy range by preserving more signal. TIME4D achieves a $\sim 20\%$ improvement at low energies due to superior NSB noise suppression, allowing for an enhanced capability of detecting sources at the lowest energies. We demonstrate that using first-order estimations of the performance of a cleaning, such as image size retaining or NSB pixel reduction, cannot provide a full picture of the expected result in the final sensitivity. Beyond expanding the effective area at low energies, sensitivity improvement requires precise event reconstruction, including improved energy and directional accuracy. Enhanced gamma-hadron separation and optimized pre-selection cuts further boost sensitivity. The proposed pipeline fully explores this, providing a fair and robust comparison between different cleaning methods. The method is general and can be applied to other IACT systems like VERITAS, MAGIC. By advancing data-driven image cleaning, this work lays the groundwork for detecting faint astrophysical sources and deepening our understanding of high-energy cosmic phenomena.

The Near-Infrared Spectrometer and Photometer onboard the Euclid space mission has obtained near-infrared (NIR) slitless spectra of millions of objects, including hundreds of ultracool dwarfs. Euclid observations retrieve images and spectra simultaneously. This observing mode marks a new era in the discovery of new objects, such as L- and T-type dwarfs, which can be found from direct identification through the H2O and CH4 absorption bands. NISP spectral resolution (R~450) is enough to classify the objects by the spectral type using known standard templates. Q1 provided more than 4 million NIR spectra in one visit to the Euclid Deep Fields. The large amount of spectra released in these fields allowed us to: a) confirm almost half of the UCD photometric candidates by Zang et al. (2024); b) discover at least 10 new late L- and T-type dwarfs searching directly in the spectra database; and c) spectroscopically confirm one hundred more candidates from a new photometric selection conducted by Zerjal et al. (in prep.). We present a preliminary list of Euclid UCD templates built by the combination of the best spectra from all these searches. We include the first spectral analysis of confirmed UCDs from Q1 data; spectral classifications; determination of effective temperatures; H2O, CH4, and NH3 spectral indices; and measurements of the KI absorption doublet. This paper is a first step in the study of Euclid UCDs and will be improved with each subsequent data release.

Stellar intensity interferometry consists in measuring the correlation of the light intensity fluctuations at two telescopes observing the same star. The amplitude of the correlation is directly related to the luminosity distribution of the star, which would be unresolved by a single telescope. This technique is based on the well-known Hanbury Brown and Twiss effect. After its discovery in the 1950s, it was used in astronomy until the 1970s, and then replaced by direct (``amplitude'') interferometry, which is much more sensitive, but also much more demanding. However, in recent years, intensity interferometry has undergone a revival. In this article, we present a summary of the state-of-the-art, and we discuss in detail the signal-to-noise ratio of intensity interferometry in the framework of photon-counting detection.

In this paper we present a comprehensive study on the properties of the interstellar medium in NGC~1222, a star-forming early-type merging galaxy that forms a triple system, using optical and far-infrared (FIR) spectroscopic, and multiband photometric data. The fit to the spectral energy distribution reveals a high dust content in the galaxy, with a dust-to-stellar mass ratio of $M_\mathrm{dust}/M_\star\sim3.3\times10^{-3}$ that is 40$-$90 larger than the mean value of local S0 galaxies. By comparing the observed optical emission line ratios to shock models, we suggest that a merger-induced shock, which is further supported by the higher-than-average \OI- and \CII-to-PAH ratios, plays a role in heating the gas in NGC~1222. We also show evidence for gas inflow by analysing the kinematic properties of NGC~1222.

We explore transformations of the Friedman-Lemaître-Robertson-Walker (FLRW) metric and cosmological parameters that align with observational data, aiming to gain insights into potential extensions of standard cosmological models. We modify the FLRW metric by introducing a scaling factor, $e^{2\Theta(a)}$ (the cosmological scaling function, CSF), which alters the standard relationship between cosmological redshift and the cosmic scale factor without affecting angular measurements or Cosmic Microwave Background (CMB) anisotropies. Using data from DESI Year 1, Pantheon+ supernovae, and the Planck CMB temperature power spectrum, we constrain both the CSF and cosmological parameters through a Markov Chain Monte Carlo approach. Our results indicate that the CSF model fits observational data with a lower Hubble constant (although it is compatible with the value given by Planck 2018 within 1$\sigma$) and is predominantly dark-matter-dominated. Additionally, the CSF model produces temperature and lensing power spectra similar to those predicted by the standard model, though with lower values in the CSF model at large scales. We have also checked that when fitting a CSF model without dark energy to the data, we obtain a more negative conformal function. This suggests that the CSF model may offer hints about missing elements and opens up a new avenue for exploring physical interpretations of cosmic acceleration.

Violent relaxation (VR) is often regarded as the mechanism leading stellar systems to collisionless meta equilibrium via rapid changes in the collective potential. We investigate the role of chaotic instabilities on single particle orbits in leading to nearly-invariant phase-space distributions, aiming at disentangling it from the chaos induced by collective oscillations in the self-consistent potential. We explore as function of the systems size (i.e. number of particles $N$) the chaoticity in terms of the largest Lyapunov exponent of test trajectories in a simplified model of gravitational cold collapse, mimicking a $N-$body calculation via a time dependent smooth potential and a noise-friction process accounting for the discreteness effects. A new numerical method to evaluate effective Lyapunov exponents for stochastic models is presented and tested. We find that the evolution of the phase-space of independent trajectories reproduces rather well what observed in self-consistent $N-$body simulations of dissipationless collapses. The chaoticity of test orbits rapidly decreases with $N$ for particles that remain weakly bounded in the model potential, while it decreases with different power laws for more bound orbits, consistently with what observed in previous self-consistent $N$-body simulations. The largest Lyapunov exponents of ensembles of orbits starting from initial conditions uniformly sampling the accessible phase-space are somewhat constant for $N\lesssim 10^9$, while decreases towards the continuum limit with a power-law trend. Moreover, our numerical results appear to confirm the trend of a specific formulation of dynamical entropy and its relation with Lyapunov time scales.

This paper presents a comparison of plasma dynamics in Coronal Holes (CHs) and Quiet Sun (QS) through 2.5D MHD flux emergence simulations. The magnetic reconnection between the emerging and the pre-existing flux leads to the formation of cool, dense plasmoids with hot boundaries, and hot & cool jets with velocities $\approx50$ km s$^{-1}$. We perform spectral synthesis in spectral lines probing transition region and coronal temperatures. CHs show reduced intensities, excess upflows (downflows), and widths during the jetting (downflow) period when compared to QS. During the jetting and downflow periods, velocity and line width of the hot spectral lines in CHs show a strong positive correlation with the vertical magnetic field at z = 0, while the intensity of the cooler lines shows a weak correlation, which is not seen in QS. During the jetting period in CH, we find upflows in Si IV to be correlated (anti-correlated) with upflows (downflows) in other lines, and downflows in CH in Si IV to be correlated (anti-correlated) with upflows (downflows) in other lines when compared to QS. During downflow, we find no strong correlation between Si IV and other line velocities. The correlation during the jetting period occurs due to coincident, co-spatial origins of the hot and cool jet, while the lack of correlation during the downflow phase suggests a decoupling of hot and cool plasma. These results demonstrate that flux emergence and reconnection with pre-existing flux in the atmosphere support a unified scenario for solar wind formation and coronal heating.

Understanding and characterising the magnetic activity of M dwarfs is of paramount importance in the search for Earth-like exoplanets orbiting them. Energetic stellar activity phenomena, such as flares or coronal mass ejections, which are common in these stars, are deeply connected with the habitability and atmospheric evolution of the surrounding exoplanets. We present a follow-up of a sample of M dwarfs with strong H$\alpha$ and CaII H and K emission lines identified with J-PLUS photometry in a previous work. We collected low-resolution NOT/ALFOSC and GTC/OSIRIS spectra, measuring the PC3 index for the spectral type determination. We used two-minute-cadence calibrated TESS light curves to identify and characterise multiple flares and to calculate the rotation period of the two active M dwarfs found in our sample. We confirm that the strong emission lines detected in the J-PLUS photometry are caused by transient flaring activity. We find clear evidence of flaring activity and periodic variability for LP 310-34 and LP 259-39, and estimated flare energies in the TESS bandpass between $7.4\times10^{30}$ and $2.2\times10^{33}$ erg for them. We characterised LP 310-34 and LP 259-39 as very rapidly rotating M dwarfs with CaII H and K and H$\alpha$ in emission, and computed a rotation period for LP 259-39 for the first time: $P_{\rm rot}=1.69\pm0.02$ d. This work advocates the approach of exploiting multi-filter photometric surveys to systematically identify flaring M dwarfs, especially to detect episodes of strong CaII H and K line emission, which may have important implications for exoplanetary space weather and habitability studies. Our results reveal that common M dwarfs experience flare events in CaII H and K in addition to well known H$\alpha$ flares.

We show that using a Taylor expansion for the dark energy equation-of-state parameter and limiting it to the zeroth and first-order terms, i.e., the so-called Chevallier-Polarski-Linder (CPL) parametrization, instead of allowing for higher-order terms and then marginalizing over them, adds extra information not present in the data and leads to markedly different and potentially misleading conclusions. Fixing the higher-order terms to zero, one concludes that vacuum energy that is currently non-dynamical (e.g., the cosmological constant) is excluded at several $\sigma$ significance as the explanation of cosmic acceleration, even in Dark Energy Spectroscopic Survey (DESI) DR1 data. Meanwhile, instead marginalizing over the higher-order terms shows that we know neither the current dark energy equation of state nor its current rate of change well enough to make such a claim. This issue has become more prominent now with the recent release of high-quality Stage IV galaxy survey data. The results of analyses using simple Taylor expansions should be interpreted with great care.

Cosmic voids are low-mass-density regions on intergalactic scales. They are where cosmic expansion and acceleration are most dominant, important places to understand and analyse for cosmology. This entry summarises theoretical underpinnings of cosmic voids, and explores several observational aspects, statistics and applications of voids. The density profiles, velocity profiles, evolution history and the abundances of voids are shown to encode information about cosmology, including the sum of neutrino masses and the law of gravity. These properties manifest themselves into a wide range of observables, including the void distribution function, redshift-space distortions, gravitational lensing and their imprints on the cosmic-microwave background. We explain how each of these observables work, and summarise their applications in observations. We also comment on the possible impact of a local void on the interpretations of the expansion of the Universe, and discuss opportunities and challenges for the research subject of cosmic voids.

We build a semi-empirical framework of galaxy evolution (dubbed StAGE) firmly grounded on stellar archaeology. The latter provides data-driven prescriptions that, on a population statistical ground, allow to define the age and the star formation history for the progenitors of quiescent galaxies (QGs). We exploit StAGE to compute the cosmic star formation rate (SFR) density contributed by the progenitors of local QGs, and show it to remarkably agree with that estimated for high-$z$ dusty star-forming galaxies which are faint/dark in the NIR, so pointing toward a direct progenitor-descendant connection among these galaxy populations. Furthermore, we argue that by appropriately correcting the observed stellar mass density by the contribution of such NIR-dark progenitors, StAGE recovers a SFR density which is consistent with direct determinations from UV/IR/radio surveys, so substantially alleviating a longstanding tension. Relatedly, we also show how StAGE can provide the average mass and metal assembly history of QGs, and their redshift-dependent statistics. Focusing on the supermassive black holes (BHs) hosted by massive QGs, we exploit StAGE to reconstruct the average BH mass assembly history, the cosmic BH accretion rate density as a function of redshift, and the evolution of the Magorrian-like relationship between the relic stellar and BH masses. All in all, StAGE may constitute a valuable tool to understand via a data-driven, easily expandable, and computationally low-cost approach the co-evolution of QGs and of their hosted supermassive BHs across cosmic times.

Astrophysical radio sources are embedded in turbulent magnetised environments. In the 1 MHz sky, solar radio bursts are the brightest sources, produced by electrons travelling along magnetic field lines from the Sun through the heliosphere. We demonstrate that the magnetic field not only guides the emitting electrons, but also directs radio waves via anisotropic scattering from density irregularities in the magnetised plasma. Using multi-vantage-point type III solar radio burst observations and anisotropic radio wave propagation simulations, we show that the interplanetary field structure is encoded in the observed radio emission directivity, and that large-scale turbulent channelling of radio waves is present over large distances, even for relatively weak anisotropy in the embedded density fluctuations. Tracing the radio emission at many frequencies (distances), the effects of anisotropic scattering can be disentangled from the electron motion along the interplanetary magnetic field, and the emission source locations are unveiled. Our analysis suggests that magnetic field structures within turbulent media could be reconstructed using radio observations and is found consistent with the Parker field, offering a novel method for remotely diagnosing the large-scale field structure in the heliosphere and other astrophysical plasmas.

The Galactic evolution of copper remains poorly understood, partly due to the strong departures from local thermodynamic equilibrium (LTE) affecting Cu I lines. A key source of uncertainty in non-LTE modelling is the treatment of inelastic Cu+H collisions. We present new rate coefficients based on a combined asymptotic LCAO and free electron model approach, which show significant differences from previous calculations. Applying these updated rates to non-LTE stellar modelling, we find reduced line-to-line scatter and improved consistency between metal-poor dwarfs and giants. Our non-LTE analysis reveals a strong upturn in the [Cu/Fe] trend towards lower [Fe/H] < -1.7. We show that this may reflect the interplay between external enrichment of Cu-rich material of the Milky Way halo at low metallicities, and metallicity-dependent Cu yields from rapidly rotating massive stars. This highlights the unique diagnostic potential of accurate Cu abundances for understanding both stellar and Galactic evolution.

Motivated by misaligned discs observed in eccentric orbit Be/X-ray binaries, we examine the evolution of a retrograde disc around one component of an eccentric binary with hydrodynamic simulations, $n$-body simulations and linear theory. Forced eccentricity growth from the eccentric orbit binary causes the initially circular disk to undergo eccentricity oscillations. A retrograde disc becomes more radially extended, more highly eccentric and undergoes more rapid apsidal precession compared to a prograde disc. We find that a retrograde disc can be subject to disc breaking where the disc forms two rings with different eccentricities and longitude of periastrons while remaining coplanar. This could have implications for the lightcurves and the X-ray outbursts observed in Be/X-ray binaries.

The sub-Neptune GJ 1214b has an infamously flat transmission spectrum, likely due to thick aerosols in its atmosphere. A recent JWST MIRI spectroscopic phase curve of GJ 1214 b added to this picture, suggesting a highly reflective and metal-rich atmosphere. Using a 3D General Circulation Model with both photochemical hazes and condensate clouds, we characterize how different aerosol types affect the atmospheric structure of GJ 1214 b and manifest in its spectroscopic phase curve. Additionally, we reanalyze the original GJ 1214 b JWST phase curve. The reanalysis shows a hotter nightside, similar dayside temperature, and a lower, but still elevated, Bond albedo (0.42 +/- 0.11) than the original results. We find that a scenario with both clouds and hazes is most consistent with the JWST phase curve. Reflective clouds or hazes are needed to explain the large Bond albedo, and hazes or a super-solar metallicity help account for the several hundred Kelvin day-night temperature difference measured by the phase curve.

This study examines the mineral composition of volcanic samples similar to lunar materials, focusing on olivine and pyroxene. Using hyperspectral imaging from 400 to 1000 nm, we created data cubes to analyze the reflectance characteristics of samples from samples from Vulcano, a volcanically active island in the Aeolian Archipelago, north of Sicily, Italy, categorizing them into nine regions of interest and analyzing spectral data for each. We applied various unsupervised clustering algorithms, including K-Means, Hierarchical Clustering, GMM, and Spectral Clustering, to classify the spectral profiles. Principal Component Analysis revealed distinct spectral signatures associated with specific minerals, facilitating precise identification. Clustering performance varied by region, with K-Means achieving the highest silhouette-score of 0.47, whereas GMM performed poorly with a score of only 0.25. Non-negative Matrix Factorization aided in identifying similarities among clusters across different methods and reference spectra for olivine and pyroxene. Hierarchical clustering emerged as the most reliable technique, achieving a 94\% similarity with the olivine spectrum in one sample, whereas GMM exhibited notable variability. Overall, the analysis indicated that both Hierarchical and K-Means methods yielded lower errors in total measurements, with K-Means demonstrating superior performance in estimated dispersion and clustering. Additionally, GMM showed a higher root mean square error compared to the other models. The RMSE analysis confirmed K-Means as the most consistent algorithm across all samples, suggesting a predominance of olivine in the Vulcano region relative to pyroxene. This predominance is likely linked to historical formation conditions similar to volcanic processes on the Moon, where olivine-rich compositions are common in ancient lava flows and impact melt rocks.

We explore the massive cluster XMMXCS J2215.9-1738 at z about 1.46 with MUSE and KMOS integral field spectroscopy. Using MUSE spectroscopy we trace the kinematics of the ionized gas using [OII] in the central 500x500 square kpc area of the cluster, which contains 28 spectroscopically identified cluster galaxies. We detect [OII] emission lines in the integrated spectra of 21 galaxies with the remaining seven being passive galaxies. Six of these passive galaxies lie in the cluster central part with a diameter of 200 kpc which contains no star-forming objects, being a place where star-formation in galaxies is quenched. An interesting discovery in this central area of the cluster are three diffuse ionized [OII] gas structures, which we refer as [OII] blobs, extending over areas of hundreds of square kpc. The source of ionization of one of the gaseous structures which displays two prominent filamentary patterns indicating outflow of gas is an active galactic nucleus (AGN). The KMOS data enabled us to use the BPT diagram to identify this object as a type-2 AGN. The other two diffuse ionized oxygen gaseous structures are more enigmatic, being located between the stellar components of passive cluster galaxies; one of these blobs does not have any stellar counterpart in the HST optical and near-infrared data, and the other only a very faint counterpart. Ram-pressure stripping of photo-ionized gas or AGN feedback could be an explanation. Additionally, the galaxy velocity distribution in this high redshift cluster is bimodal indicating that the cluster is unlikely to be fully virialized, and that recent and ongoing merging events producing shocks could provide photo-ionization sources for the two enigmatic [OII] blobs.

Cometary impacts play an important role in the early evolution of Earth, and other terrestrial exoplanets. Here, we present a numerical model for the interaction of weak, low-density cometary impactors with planetary atmospheres, which includes semi-analytical parameterisations for the ablation, deformation, and fragmentation of comets. Deformation is described by a pancake model, as is appropriate for weakly cohesive, low-density bodies, while fragmentation is driven by the growth of Rayleigh-Taylor instabilities. The model retains sufficient computational simplicity to investigate cometary impacts across a large parameter space, and permits simple description of the key physical processes controlling the interaction of comets with the atmosphere. We apply our model to two case studies. First, we consider the cometary delivery of prebiotic feedstock molecules. This requires the survival of comets during atmospheric entry, which is determined by three parameters: the comet's initial radius, bulk density, and atmospheric surface density. There is a sharp transition between the survival and catastrophic fragmentation of comets at a radius of about 150m, which increases with increasing atmospheric surface density and decreasing cometary density. Second, we consider the deposition of mass and kinetic energy in planetary atmospheres during cometary impacts, which determines the strength and duration of any atmospheric response. We demonstrate that mass loss is dominated by fragmentation, not ablation. Small comets deposit their entire mass within a fraction of an atmospheric scale height, at an altitude determined by their initial radius. Large comets lose only a small fraction of their mass to ablation in the lower atmosphere.

Measuring the atmospheric composition of hazy sub-Neptunes like GJ~1214b through transmission spectroscopy is difficult because of the degeneracy between mean molecular weight and haziness. It has been proposed that phase curve observations can break this degeneracy because of the relationship between mean molecular weight (MMW) and phase curve amplitude. However, photochemical hazes can strongly affect phase curve amplitudes as well. We present a large set of GCM simulations of the sub-Neptune GJ~1214b that include photochemical hazes with varying atmospheric composition, haze opacity and haze optical properties. In our simulations, photochemical hazes cause temperature changes of up to 200~K, producing thermal inversions and cooling deeper regions. This results in increased phase curve amplitudes and adds a considerable scatter to the phase curve amplitude--metallicity relationship. However, we find that if the haze production rate is high enough to significantly alter the phase curve, the secondary eclipse spectrum will exhibit either emission features or strongly muted absorption features. Thus, the combination of a white-light phase curve and a secondary eclipse spectrum can successfully distinguish between a hazy, lower MMW and a clear, high MMW scenario.

Strong gravitational lensing is a powerful tool for probing the internal structure and evolution of galaxies, the nature of dark matter, and the expansion history of the Universe, among many other scientific applications. For almost all of these science cases, modeling the lensing mass distribution is essential. For that, forward modeling of imaging data to the pixel level is the standard method used for galaxy-scale lenses. However, the traditional workflow of forward lens modeling necessitates a significant amount of human investigator time, requiring iterative tweaking and tuning of the model settings through trial and error. An automated lens modeling pipeline can substantially reduce the need for human investigator time. In this paper, we present \textsc{dolphin}, an automated lens modeling pipeline that combines artificial intelligence with the traditional forward modeling framework to enable full automation of the modeling workflow. \textsc{dolphin} uses a neural network model to perform visual recognition of the strong lens components, then autonomously sets up a lens model with appropriate complexity, and fits the model with the modeling engine, lenstronomy. Thanks to the versatility of lenstronomy, dolphin can autonomously model both galaxy-galaxy and galaxy-quasar strong lenses.

We report the first detection of the X-ray polarisation of the transient black hole X-ray binary IGRJ17091-3624 taken with the Imaging X-ray polarimetry Explorer (IXPE) in March 2025, and present the results of an X-ray spectro-polarimetric analysis. The polarisation was measured in the 2--8 keV band with 5.2$\sigma$ statistical confidence. We report a polarisation degree (PD) of $9.1\pm1.6$ per cent and a polarisation angle of $83^{\circ} \pm 5^{\circ}$ (errors are $1\sigma$ confidence). There is a hint of a positive correlation of PD with energy that is not statistically significant. We report that the source is in the corona-dominated hard state, which is confirmed by a hard power-law dominated spectrum with weak reflection features and the presence of a Type-C quasi-periodic oscillation at $\sim0.2$~Hz. The orientation of the emitted radio jet is not known, and so we are unable to compare it with the direction of X-ray polarization, but we predict the two to be parallel if the geometry is similar to that in Cygnus X-1 and Swift J1727.8-1613, the two hard state black hole binaries previously observed by IXPE. In the Comptonisation scenario, the high observed PD requires a very favourable geometry of the corona, a high inclination angle (supported by the presence of a dip in the light curve) and possibly a mildly relativistic outflow and/or scattering in an optically thick wind.

Young protoplanetary discs are expected to be gravitationally unstable, which can drive angular momentum transport as well as be a potential mechanism for planet formation. Gravitational instability is most prevalent in the outer disc where cooling timescales are short. At large radii, stellar irradiation makes a significant contribution to disc heating and is expected to suppress instability. In this study, we compare two models of implementing irradiation in 2D hydrodynamic simulations of self-gravitating discs: supplying a constant heating rate per unit mass and per unit area of the disc. In the former case, instability is quenched once the stellar irradiation becomes the dominant heating source. In the latter case, we find instability persists under high levels of irradiation, despite large values of the Toomre Q parameter, in agreement with analytic predictions. Fragmentation was able to occur in this regime with the critical cooling timescale required decreasing as irradiation is increased, corresponding to a maximum threshold for the viscosity parameter: $\alpha\sim0.03-0.09$.

Detection of quasi-monochromatic, long-duration (continuous) gravitational wave radiation emitted by, e.g., asymmetric rotating neutron stars in our Galaxy requires a long observation time to distinguish it from the detector's noise. If this signal is additionally microlensed by a lensing object located in the Galaxy, its magnitude would be temporarily magnified, which may lead to its discovery and allow probing of the physical nature of the lensing object and the source. We study the observational feasibility of Galactic microlensing of continuous gravitational wave signals in the point mass lens approximation by discussing the parameter space of the problem as well as by applying a gravitational wave detection method, the Time Domain F-statistic search, to ground-based detectors in the simulated data.

We consider and compare the Bondi and Novikov-Thorne accretion mechanisms in spherically symmetric regular black holes. To do so, we model the dark matter distribution adopting two main approaches. The first takes into account a cosmologically-inspired dark fluid, whose pressure turns out to be constant, whereas the density and equation of state depend on the radial coordinate. The second case employs an exponential dark matter energy distribution that describes the dark matter cloud in the accretion process. Accordingly, we quantify the mass accreted by regular solutions with the above information on the energy-momentum tensor and their luminosity and thermal properties, derived from the background models. Numerical simulations of the accretion processes are then reported, comparing regular black holes with Schwarzschild and Schwarzschild-de Sitter metrics. In so doing, we consider the Hayward, Bardeen, Dymnikova and Fang-Wang solutions, where the addiction of a further parameter determines regularity. Implications and physical consequences of using the Novikov-Thorne and Bondi accretion backgrounds are thus critically discussed in varying the free parameters of each spacetime.

Several small polycyclic aromatic hydrocarbons (PAHs) with closed-shell electronic structure have been identified in the cold, dark environment Taurus Molecular Cloud-1. We measure efficient radiative cooling through the combination of recurrent fluorescence (RF) and IR emission in the closed-shell indenyl cation (C$_{9}$H$_{7}^{+}$), finding good agreement with a master equation model including molecular dynamics trajectories to describe internal-energy dependent properties for RF. We find that C$_{9}$H$_{7}^{+}$ formed with up to $E_{c}=5.85$\,eV vibrational energy, which is $\approx$2\,eV above the dissociation threshold, radiatively cool rather than dissociate. The efficient radiative stabilization dynamics are likely common to other closed-shell PAHs present in space, contributing to their abundance.

We construct a four-dimensional supersymmetric QCD in conformal window with a marginally relevant deformation which triggers the spontaneous breaking of (approximate) scale invariance and the subsequent confinement, generating a mass gap, at an energy scale hierarchically smaller than the Planck scale without fine-tuning. We analyze the finite temperature system and show that the phase transition associated with the breaking of conformal invariance is of the strong first order. When such a phase transition takes place at a temperature of the Universe around the electroweak scale, it generates a stochastic gravitational wave (GW) background probed by future space-based interferometers, while a conformal phase transition in a dark sector at $\mathcal{O}(1)$ GeV generates GWs to explain the reported pulsar timing array signal.

We study axial perturbations of static black holes with primary hair in a family of degenerate higher-order scalar-tensor (DHOST) theories. These solutions possess a scalar charge, fully independent of the mass, leading to a continuous one-parameter deformation of the standard Schwarzschild black hole. Starting from these solutions, we also construct new black holes, solutions of other DHOST theories, obtained via disformal transformations of the metric. In particular, we investigate two specific types of disformal transformations: the first leading to a theory where gravitational waves propagate at the speed of light, the second to a Horndeski theory, where the equations of motion remain second order. The dynamics of axial perturbations can be formally related to the general relativistic equations of motion of axial perturbations in an effective metric. The causal structure of the effective metric differs from that of the background metric, leading to distinct gravitational and luminous horizons. Using a WKB approximation, we compute the quasi-normal modes for the Schrödinger-like equation associated with the effective metric outside the gravitational horizon.

We study the effects of the oscillating axion field present in our environment on the Casimir pressure between two metallic plates. We take into account the finite conductivity of the boundary plates and model the interactions between matter and photons in the Schwinger-Keldysh formalism. This allows us to take into account dissipation in the quantum field description of this open quantum system and retrieve the Lifschitz results for the Casimir interaction between two metallic plates. We then compute the leading correction to the Lifschitz theory in inverse powers of the axion suppression scale and show that the Casimir pressure receives oscillating corrections depending on the product of the axion mass and the distance between the plates. This contribution is repulsive at large distance compared to the axion Compton wavelength as a consequence of the breaking of parity invariance by the axion dark matter background.

We propose a novel cosmological scenario to explain the exceptional KM3-230213A neutrino event reported at an energy scale of $\mathcal{O}(100)$~PeV by the KM3NeT collaboration, along with its associated gravitational wave (GW) signatures. In our framework, ultra high energy neutrinos originate from the decay of a super-heavy sterile neutrino produced via the Hawking evaporation of primordial black holes (PBHs) in the early Universe. Employing an ultraviolet complete type-I seesaw model, we demonstrate that while two sterile neutrinos are responsible for light neutrino masses as required by oscillation data, one sterile neutrino can have an exceedingly feeble coupling, allowing its lifetime to be tuned so that its decay yields a neutrino flux consistent with the observed event. Furthermore, our scenario predicts two distinct GW signatures: one arising from gravitons emitted during PBH evaporation and another from the Bremsstrahlung process during the decay of the sterile neutrino. These complementary signals provide a multi-messenger probe of the underlying physics. Our results thus offer a compelling explanation for the KM3-230213A event and open new avenues for investigating the interplay between high-energy neutrino astronomy and gravitational wave cosmology.

Recent DESI DR2 results provide compelling evidence that the dark energy equation of state evolves from $w<-1$ at high redshift to $w>-1$ today, reinforcing interest in null energy condition (NEC) violation. While NEC violation may be crucial for dark energy and solving the cosmological singularity problem, it generically leads to ghost or gradient instabilities. It is well established in the study of nonsingular cosmology that the effective field theory (EFT) operator $\delta g^{00} R^{(3)}$ enables fully stable NEC violation and represents ``beyond Horndeski'' physics. We investigate its implications in the observable Universe and confirm within the EFT framework that $\delta g^{00} R^{(3)}$ can also stabilize NEC violation in dark energy, as indicated by the latest DESI DR2 BAO observations. Furthermore, our results show that current data already impose a nontrivial constraint on the EFT coefficient $\tilde{m}^2_4$ associated with $\delta g^{00} R^{(3)}$, indicating $\tilde{m}^2_4 \neq 0$ at approximately $2\sigma$. This finding suggests an unexpected possible connection between the primordial Universe and the late observable Universe.

The hypothesis that classical scalar fields could constitute dark matter on galactic and cosmic scales has garnered significant interest. In scenarios where supermassive black holes (SMBHs) form through the accretion of matter onto black hole seeds, a critical question arises: what role does dark matter play in this process? We conduct a numerical investigation into the nonlinear dynamical evolution of black hole shadows and gravitational lensing effects resulting from the accretion of an ultralight, real scalar field onto a non-rotating black hole. The scalar field is minimally coupled to Einstein's gravity, and our simulations focus on wave packets, parameterized by their wave number and width, as they interact with and are accreted by a dynamic black hole. Our results demonstrate significant growth in the apparent horizon, photon ring, and Einstein ring sizes compared to those of a Schwarzschild black hole. These findings suggest that the observed photon ring and black hole shadow in Sgr\,A*, and M87* may be influenced by the gravitational interaction between the black hole and ultralight scalar field dark matter.

Gravitational lensing magnification is maximal around caustics. At these source locations, an incoming wave from a point source would formally experience an infinite amplification in the high-frequency or geometric optics limit. This divergence reflects the break-down of the mathematical formalism, which is regularized by either the finite size of the source or its wavelength. We explore diffraction around caustics and their implications for the distortion of waveforms from point sources, focusing on three types of caustics: point singularities, folds, and cusps. We derive analytical results for the amplitude and phase of the diffracted waves, and compare those against the stationary phase approximation. We then study the observational signatures and detectability of these distortions on gravitational waves. We find that the lensing distortions could be detectable, but that the stationary phase approximation is still a good description of the system even close to the caustic, when the repeated gravitational wave chirps interfere with each other. We also quantify the possibility of distinguishing lensed signals from different caustics by performing Bayesian parameter estimation on simulated signals. Our results demonstrate that the universal distortions due to diffraction around caustics could be used to single out a gravitational wave event as lensed.