Papers for Thursday, Mar 27 2025

In addition to planets and other small bodies, stellar systems will likely also host exozodiacal dust, or exozodi. This warm dust primarily resides in or near the habitable zone of a star, and scatters stellar light in visible to NIR wavelengths, possibly acting as a spatially inhomogeneous fog that can impede our ability to detect and characterize Earth-like exoplanets. By improving our knowledge of exozodi in the near term with strategic precursor observations and model development, we may be able to mitigate these effects to support a future search for signs of habitability and life with a direct imaging mission. This white paper introduces exozodi, summarizes its impact on directly imaging Earth-like exoplanets, and outlines several key knowledge gaps and near-term solutions to maximize the science return of future observations.

From the scale-free nature of gravity, the structure in the universe is expected to be self-similar on large scales. However, this self-similarity will eventually break down due to small-scale gas physics such as star formation, AGN and stellar feedback as well as non-linear effects gaining importance relative to linear structure formation. In this work we investigate the large-scale matter flows that connect collapsed structures to their cosmic environments specifically for their agreement with self-similarity in various properties. For this purpose we use the full power of the hydrodynamical cosmological simulation suite Magneticum Pathfinder to calculate the in- and outflow rates for haloes on a large range of masses and redshifts. We find a striking self-similarity across the whole mass range and cosmic epochs that only breaks in the outflowing regime due to the different outflow driving mechanisms for galaxies vs. galaxy clusters. Geometrical analysis of the patterns of in vs. outflow demonstrate how the inflows organize into anisotropic filaments driven by the tidal environment, while the outflows are isotropic due to their thermal nature. This also manifests in the thermal and chemical properties of the gas: While the inflowing gas is pristine and colder, encountering the accretion shocks and entering the influence region of AGN and stellar feedback heats the gas up into a diffuse, metal enriched and hot atmosphere. Overall the differences between outflowing and infalling gas are enhanced at the galaxy cluster scale compared to the galaxy scale due to the accretion shocks that reach out to large radii for these objects. An individual study of the gas motions in the outskirts of one of the most massive clusters in the simulations illustrates these results: Gas found in the outer hot atmosphere at z=0 falls in and is completely enriched early before being shock heated and expanding.

As discussed in a number of recent papers, cosmological stasis is a phenomenon wherein the abundances of multiple cosmological energy components with different equations of state remain constant for an extended period despite the expansion of the universe. One of the most intriguing aspects of the stasis phenomenon is that it can give rise to cosmological epochs in which the effective equation-of-state parameter $\langle w \rangle$ for the universe is constant, but differs from the canonical values associated with matter, radiation, vacuum energy, etc. Indeed, during such a stasis epoch, the spatial average of the energy density of the universe evolves in precisely the same manner as it would have evolved if the universe were instead dominated by a perfect fluid with an equation-of-state parameter equal to $\langle w \rangle$. However, as we shall demonstrate, this equivalence is broken at the level of the perturbations of the energy density. To illustrate this point, we consider a stasis epoch involving matter and radiation and demonstrate that within this stasis background the density perturbations associated with a spectator matter component with exceedingly small energy density exhibit a power-law growth that persists across the entire duration of the stasis epoch. This growth can potentially lead to significant enhancements of structure at small scales. Such enhancements are not only interesting in their own right, but may also provide a way of observationally distinguishing between a stasis epoch and an epoch of perfect-fluid domination -- even if the universe has the same equation of state in both cases.

In this Letter, we shed light on the evolutionary phase of HD 144812, a Galactic yellow supergiant showing infrared excess that is typically expected for evolved stars undergoing enhanced mass-loss activity. We present high-resolution spectroscopy of the star in the $H-$ and $K-$band acquired with the GRating INfrared Spectrometer (IGRINS) and further explore multi-band imaging of the wider field of view from the ultraviolet to the radio regime. The IGRINS data reveal several lines from the hydrogen series and iron in a double-peaked emission and we here suggest, that HD 144812 is orbited by a disk-hosting companion. Furthermore, we report emission in the CO band heads of the star that is modeled to arise from a circum-stellar/binary disk (or ring) of ejected gas. The latter consists of material that is expected to have been dredged up from the core of the star to its surface during a prior phase as a red supergiant (RSG). These findings together suggest that HD 144812 is a rare, post-RSG star in a binary system, encouraging further investigation on the effect that the stellar encounters have on triggering instabilities and driving the evolution of the primary star shortly prior to the supernova event.

The development line of bolometric corrections within the brief history of photometry was described from the perspective of the Kuhnian philosophy of science. The luminous efficiency and heat index were two previous concepts to imply visual and bolometric brightness difference of a star, which was mainly suggested and used as auxiliary tools for calibrating stellar temperature scales before the term ``bolometric correction'' (BC) was also introduced for the same purpose by Kuiper in 1938, as $BC = M_{\rm bol} - M_{\rm V} = m_{\rm {bol}} - V$. Despite its ill-posed nature imposing no zero-point constant ($C_2=0$) for the BC scale and $L_{\rm V} = L \times 10^{BC/2.5}$, if $BC>0$, $L_{\rm V}$ is unphysical, for the luminosity of a star from which ``BC of a star must always be negative,'' ``the bolometric magnitude of a star ought to be brighter than its $V$-magnitude,'' and ``the zero point of bolometric corrections are arbitrary'' (paradigms) were extracted. The newest of the first three definitions of BC was accepted and used throughout the century. Therefore, the part of the development line of BC before Kuiper could be considered a prescience period. The rest could be named the normal science period in which astrophysicists work under the three paradigms. The rise of BC as a concept, how the ill-posed definition BC emerged/used, how inconsistencies (paradigms) of BC developed, and how the Resolution B2 of the General Assembly of the International Astronomical Union imposing $C_{\rm bol} = 71.197\,425\,\ldots$ mag, and $C_2>0$, for the zero-point constants of the $M_{\rm {Bol}}$ and BC scales resolve the long-lasting problems were discussed. Generalized new definition of BC implying $L_{\rm V}=L \times 10^\frac{({\rm BC}-C_2)}{2.5}$ were given to replace $L = L_{\rm V} \times 10^{BC/2.5}$.

Using a sample of 166 projected quasar pairs we investigate the influence of active galactic nuclei on the circumgalactic medium (CGM) of the quasar host galaxies probed using strong Mg II absorption (i.e., $W_{2796}\ge 1\dot{A}$) at impact parameters ($D$) $<$100 kpc. The foreground quasars are restricted to the redshift range $0.4 \leq z \leq 0.8$ and have median bolometric luminosity and stellar mass of $10^{45.1} erg~s^{-1}$and $10^{10.89} M_\odot$ respectively. We report detections of Mg II absorption in 29 cases towards the background quasar and in 4 cases along the line of sight to the foreground quasars. We do not find any difference in the distribution of $W_{2796}$ and covering fraction ($f_c$) as a function of $D$ between quasar host galaxies and control sample of normal galaxies. These results are different from what has been reported in the literature, possibly because: (i) our sample is restricted to a narrow redshift range, (ii) comparative analysis is carried out after matching the galaxy parameters, (iii) we focus mainly on strong Mg II absorption and (iv) our sample lacks foreground quasars with high bolometric luminosity (i.e., $L_{bol}>10^{45.5}$ erg s$^{-1}$). Future studies probing luminous foreground quasars, preferably at lower impact parameters and higher equivalent width sensitivity is needed to consolidate our findings.

Although all Type II supernovae (SNe) originate from massive stars possessing a hydrogen-rich envelope, their light curve morphology is diverse, reflecting poorly characterised heterogeneity in the physical properties of their progenitor systems. Here, we present a detailed light curve analysis of a magnitude-limited sample of 639 Type II SNe from the Zwicky Transient Facility Bright Transient Survey. Using Gaussian processes, we systematically measure empirical light curve features (e.g. rise times, peak colours and luminosities) in a robust sampling-independent manner. We focus on rise times as they are highly sensitive to pre-explosion progenitor properties, especially the presence of a dense circumstellar medium (CSM) shed by the progenitor in the years immediately pre-explosion. By correlating our feature measurements with physical parameters from an extensive grid of STELLA hydrodynamical models with varying progenitor properties (CSM structure, $\dot M$, $R_{CSM}$ and $M_{ZAMS}$), we quantify the proportion of events with sufficient pre-explosion mass-loss to significantly alter the initial light curve (roughly $M_{CSM} \geq 10^{-2.5} M_{\odot}$) in a highly complete sample of 377 spectroscopically classified Type II SNe. We find that 67 $\pm$ 6\% of observed SNe in our magnitude-limited sample show evidence for substantial CSM ($M_{CSM} \geq 10^{-2.5} M_{\odot}$) close to the progenitor ($R_{CSM} <10^{15}$ cm) at the time of explosion. After applying a volumetric-correction, we find 36$^{+5}_{-7}$\% of all Type II SN progenitors possess substantial CSM within $10^{15}$ cm at the time of explosion. This high fraction of progenitors with dense CSM, supported by photometric and spectroscopic evidence of previous SNe, reveals mass-loss rates significantly exceeding those measured in local group red supergiants or predicted by current theoretical models.

An analytic expression for the frequencies of standing waves in stars, applicable to any radial order n, is derived from ray-tracing equations by the mean of Wigner-Weyl calculus. A correction to previous formulas currently employed in asteroseismology is identified as the Berry phase, which accounts for the vectorial nature of wave propagation in stars. Accounting for this quantity significantly improves upon previous laws for low n modes of the Sun, and we show that the Berry phase is indeed present in the available observational data of solar modes. This phase is due to inhomogeneities of the medium.

The quadrupole Kozai mechanism, which describes the hierarchical three-body problem in the leading order, is shown to be equivalent to a simple pendulum where the change in the eccentricity squared equals the height of the pendulum from its lowest point: $e_{\text{max}}^2-e^2=h=l\left(1-\cos{\theta}\right)$. In particular, this results in useful expressions for the KLC period, and the maximal and minimal eccentricities in terms of orbital constants. We derive the equivalence using the vector coordinates $\boldsymbol{\alpha}=\textbf{j}+\textbf{e}, \boldsymbol{\beta}=\textbf{j}-\textbf{e}$ for the inner Keplerian orbit, where $\textbf{j}$ is the normalized specific angular momentum, and $\textbf{e}$ is the eccentricity vector. The equations of motion for $\boldsymbol{\alpha}$ and $\boldsymbol{\beta}$ simplify to $\dot{\boldsymbol{\alpha}}=2\partial_{\boldsymbol{\alpha}} \phi \times \boldsymbol{\alpha}$ and $\dot{\boldsymbol{\beta}}=2\partial_{\boldsymbol{\beta}} \phi \times \boldsymbol{\beta}$, where $\phi$ is the normalized averaged interaction potential and are symmetric to replacing $\boldsymbol{\alpha}$ and $\boldsymbol{\beta}$ for the KLC quadratic potential. Their constraints simplify to $\boldsymbol{\alpha}^2=\boldsymbol{\beta}^2=1$, and they are distributed uniformly and independently on the unit sphere for a uniform distribution in phase space (with a fixed energy).

We introduce the rapidly emerging field of multi-messenger gravitational lensing - the discovery and science of gravitationally lensed phenomena in the distant universe through the combination of multiple messengers. This is framed by gravitational lensing phenomenology that has grown since the first discoveries in the 20th century, messengers that span 30 orders of magnitude in energy from high energy neutrinos to gravitational waves, and powerful "survey facilities" that are capable of continually scanning the sky for transient and variable sources. Within this context, the main focus is on discoveries and science that are feasible in the next 5-10 years with current and imminent technology including the LIGO-Virgo-KAGRA network of gravitational wave detectors, the Vera C. Rubin Observatory, and contemporaneous gamma/X-ray satellites and radio surveys. The scientific impact of even one multi-messenger gravitational lensing discovery will be transformational and reach across fundamental physics, cosmology and astrophysics. We describe these scientific opportunities and the key challenges along the path to achieving them. This article is the introduction to the Theme Issue of the Philosophical Transactions of The Royal Society A on the topic of Multi-messenger Gravitational Lensing, and describes the consensus that emerged at the associated Theo Murphy Discussion Meeting in March 2024.

The evolution of quiescent galaxies is driven by numerous physical processes, often considered to be related to their stellar mass and environment over cosmic time. Tracing their stellar populations can provide insight into the processes that transformed these galaxies into their observed quiescent state. In particular, higher-redshift galaxies exhibit more pronounced relative age differences. At early stages, even small differences in age remain significant, whereas as galaxies evolve, these differences become harder to detect in the local Universe. The COSMOS Wall is a structure at z ~ 0.73 that contains a large variety of environments, from rich clusters down to field-like regions. This sample offers a great opportunity to study the effect of the environment on the quiescent galaxy population. Leveraging high-quality spectroscopic data from the LEGA-C survey, and photometric data from the COSMOS2020 catalogue, we performed a full-index and photometry fitting of 74 massive quiescent galaxies, deriving their mass-weighted ages, metallicities, and star formation timescales. We characterised the environment in three subsamples: X-ray and non-X-ray groups and a field subsample. We find a decreasing trend in mass-weighted age with increasing environmental density, with galaxies groups > 1 Gyr older than those in the field. Conversely, we do not find any significant difference in stellar metallicity between galaxies in X-ray and non-X-ray groups, while we find galaxies with 0.15 dex higher metallicities in the field. Our results indicate that, at z ~ 0.7, the environment plays a crucial role in shaping the evolution of massive quiescent galaxies, noticeably affecting both their mass-weighted age and star formation timescale. These results support faster quenching mechanisms, at fixed stellar mass, in the dense X-ray-detected groups compared to the field.

Gravitationally lensed Gamma-ray bursts (GRBs) offer critical advantages over other lensed sources. They can be detected via continuously operating detectors covering most of the sky. They offer extremely high time resolution to determine lensing delays and find short-time delays accurately. They are detectable across most of the visible Universe. However, they are also rare and frequently poorly localized. In this paper, we review searches for gravitational lensing in GRBs and comment on promising avenues for the future. We note that the highly structured jets in GRBs can show variations on sufficiently small scales that, unlike lensing of most transient sources, gravitational lensing in gamma-ray bursts may not be achromatic. Such behavior would weaken the stringent requirements for identifying lensed bursts but would also make robust identification of lensing more challenging. A continuously running search that could identify candidate lensed events in near real-time would enable afterglow searches with current and near-future wide-field optical/IR surveys that could yield the first unambiguous detection of a lensed GRB. The new generation of sensitive X-ray and gamma-ray detectors, such as the Einstein Probe and SVOM, will complement Swift and significantly enhance the number of well-localized gamma-ray and X-ray transients. Tuned strategies could dramatically improve the probability of observing a lensed GRB.

Accurate measurements of stellar positions and velocities are crucial for studying galactic and stellar dynamics. We aim to create a Cartesian catalog from {\it Gaia} DR3 to serve as a high-precision database for further research using stellar coordinates and velocities. To avoid the negative parallax values, we select 31,129,169 sources in {\it Gaia} DR3 with radial velocity, where the fractional parallax error is less than 20\% ($0 < \sigma_\varpi/\varpi < 0.2$). To select the most accurate and efficient method of propagating mean and covariance, we use the Monte Carlo results with $10^7$ samples (MC7) as the benchmark, and compare the precision of linear, second-order, and Monte Carlo error propagation methods. By assessing the accuracy of propagated mean and covariance, we observe that second-order error propagation exhibits mean deviations of at most 0.5\% compared to MC7, with variance deviations of up to 10\%. Overall, this outperforms linear transformation. Though Monte Carlo method with $10^4$ samples (MC4) is an order of magnitude slower than second-order error propagation, its covariances propagation accuracy reaches 1\% when $\sigma_\varpi/\varpi$ is below 15\%. Consequently, we employ second-order error propagation to convert the mean astrometry and radial velocity into Cartesian coordinates and velocities in both equatorial and galactic systems for 30 million {\it Gaia} sources, and apply MC4 for covariance propagation. The Cartesian catalog and source code are provided for future applications in high-precision stellar and galactic dynamics.

This paper outlines the Radio Science Experiment (RSE) proposed for the RAMSES mission to asteroid (99942) Apophis, which will undergo a close Earth encounter in April 2029. This event provides a unique opportunity to study the asteroid's physical and dynamical changes under strong tidal forces. The experiment leverages a combination of Earth-based radiometric measurements, optical imaging, and inter-satellite links between the RAMSES mothercraft and deployable subcraft in proximity to Apophis. Using high-precision Doppler and optical navigation data, the RSE aims to estimate the asteroid's mass, gravity field, and spin state with unparalleled accuracy, furthering our understanding of near-Earth asteroid evolution and internal structure. Simulation results show the robustness of the proposed mission scenario, highlighting the critical role of multi-probe configurations and novel inter-satellite link technologies in achieving accurate gravity science results.

Ever since the Planck satellite measured the the cosmic microwave background (CMB) down to arcminute angular scales the mismatch between the CMB-inferred value of the Hubble constant and the value inferred from the distance ladder (i.e., the Hubble tension) has been a growing concern and is currently at the $\sim 6 \sigma$ level. There are a handful of proposed mechanisms operating in the early universe which have shown some promise in resolving the Hubble tension. These mechanisms are expected to leave a measurable impact on the smallest scale CMB anisotropy, deep in the damping tail. Using current CMB data, baryonic acoustic oscillation data, and the luminosities of type Ia supernovae as a baseline, we compute the predicted small-scale CMB power spectra for a characteristic set of these models. We find that near-future CMB data should be able to detect some but not all of the investigated models.

We present $4-12$ GHz in-band spectral energy distributions with accompanying 6 GHz and 10 GHz imaging results for a volume-complete sample ($<40$ Mpc) of hard X-ray selected active galactic nuclei (AGNs) observed with the Karl G. Jansky Very Large Array (VLA) in its A-array configuration. Despite expectations, only 12 out of 25 of these targets have been detected by the Very Long Baseline Array (VLBA) at milliarcsecond resolution in our previous studies, and we aim to understand the nature of why the circumnuclear radio emission resolves away at the subparsec spatial scales. We find that the sources not detected by the VLBA are also the faintest sources observed with the VLA. We explore the spectral structure derived from the nuclear emission and measure a mean spectral index of $\langle\alpha\rangle=-0.69$ with a scatter of $\sigma_\alpha=0.18$ for the sources not detected by the VLBA, indicative of optically thin synchrotron emission. The 12 sources detected by the VLBA primarily have flat ($-0.5\leq\alpha\leq0.0$) or inverted ($\alpha>0$) spectral indices. Nine of the sources have statistically significant curvature, with only one that was not detected by the VLBA. In NGC~3079, we model an approximately flat spectrum for the excess emission observed by the VLA that is likely produced entirely beyond parsec spatial scales.

Increasing data volumes from scientific simulations and instruments (supercomputers, accelerators, telescopes) often exceed network, storage, and analysis capabilities. The scientific community's response to this challenge is scientific data reduction. Reduction can take many forms, such as triggering, sampling, filtering, quantization, and dimensionality reduction. This report focuses on a specific technique: lossy compression. Lossy compression retains all data points, leveraging correlations and controlled reduced accuracy. Quality constraints, especially for quantities of interest, are crucial for preserving scientific discoveries. User requirements also include compression ratio and speed. While many papers have been published on lossy compression techniques and reference datasets are shared by the community, there is a lack of detailed specifications of application needs that can guide lossy compression researchers and developers. This report fills this gap by reporting on the requirements and constraints of nine scientific applications covering a large spectrum of domains (climate, combustion, cosmology, fusion, light sources, molecular dynamics, quantum circuit simulation, seismology, and system logs). The report also details key lossy compression technologies (SZ, ZFP, MGARD, LC, SPERR, DCTZ, TEZip, LibPressio), discussing their history, principles, error control, hardware support, features, and impact. By presenting both application needs and compression technologies, the report aims to inspire new research to fill existing gaps.

We have created a new image analysis pipeline to reprocess images taken by the Near Earth Asteroid Tracking survey and have applied it to ten nights of observations. This work is the first large-scale reprocessing of images from an asteroid discovery survey in which thousands of archived images are re-calibrated, searched for minor planets, and resulting observations are reported to the Minor Planet Center. We describe the software used to extract, calibrate, and clean sources from the images, including specific techniques that accommodate the unique features of these archival images. This pipeline is able to find fainter asteroids than the original pipeline.

We present new results on the spatial structure and kinematics of Lya and several far-UV metallic ions in the circumgalactic medium of Keck Baryonic Structure Survey galaxies using foreground/background galaxy pairs with angular separations < 30". Keck/KCWI and Keck/LRIS spectra of 736 background galaxies with z_bg = 2.58 +/- 0.38 probe sightlines through 1033 foreground galaxies (z_fg = 2.03 +/- 0.36) at projected distances 8 < D_tran/kpc < 250. For each ion, we measure equivalent widths (W_lambda) as a function of D_tran and find W_lambda ~ D_tran^(-gamma) with 0.3 < gamma < 0.6. Higher ionization species (C IV) decrease less rapidly and extend to larger D_tran compared to low ions (O I, C II, Si II). Splitting the pair sample into subsets based on foreground galaxy properties, we find W_lambda(C IV) exhibits a strong dependence on stellar mass (M_star) and a weaker dependence on star formation rate. Similarly, W_lambda(Lya) increases with M_star, albeit with more scatter. In 2D, we map the excess Lya and C IV absorption as functions of line-of-sight velocity and D_tran. The Lya velocity centroid varies with D_tran; at D_tran < 50 kpc, Lya emission from the foreground galaxy affects the Lya absorption feature measured in the background galaxy spectrum, resulting in a net blueshifted absorption profile. We construct a two-component model to fit the observed Lya map. The best fit suggests approximately half of the excess Lya absorption arises from a decelerating outflow component with initial velocity v_out ~ 750 km/s; the remainder is associated with a component centered on the galaxy systemic redshift with a D_tran-independent 1D velocity dispersion of sigma_v ~ 220 km/s, consistent with the average foreground galaxy circular velocity.

The OVI 1032, 1038 A line is a key probe of cooling gas in the circumgalactic medium (CGM) of galaxies, but has been observed to date primarily in absorption along single sightlines. We present deep HST ACS-SBC observations of the compact, massive starburst Makani. Makani hosts a 100 kpc, [OII]-emitting galactic wind driven by two episodes of star formation over 400 Myr. We detect OVI and Ly$\alpha$ emission across the [OII] nebula with similar morphology and extent, out to r ~ 50 kpc. Using differential narrow-band imaging, we separate Ly$\alpha$ and OVI and show that the OVI emission is comparable in brightness to [OII], with $L_{OVI} = 4\times10^{42}$ erg/s. The similar hourglass morphology and size of [OII] and OVI implicate radiative cooling at $T = 10^{5.5}$ K in a hot-cold interface. This may occur as the $T > 10^7$ K CGM -- or the hot fluid driving the wind -- exchanges mass with the $T \approx 10^4$ K clouds entrained in (or formed by) the wind. The optical/UV line ratios may be consistent with shock ionization, though uncertain attenuation and Ly$\alpha$ radiative transfer complicate the interpretation. The detection of OVI in Makani lies at the bleeding edge of the UV imaging capabilities of HST, and provides a benchmark for future emission-line imaging of the CGM with a wide-area UV telescope.

We present the JWST NIRSpec PRISM 0.7-5.3 micron spectra of Albiorix and Siarnaq and the NIRSpec G235H/G395M 1.7-5.3 micron spectra of Phoebe, the three largest Saturnian irregular satellites. The irregular satellites of the giant planets are thought to be captured planetesimals from the same population as Kuiper belt objects. They are emplaced inside Saturn's Hill sphere during the giant-planet instability described by the Nice Model, and are thus valuable tracers of Kuiper belt surface evolution. Phoebe's JWST spectrum matches the global average from Cassini VIMS, and by comparing the spectrum to the library of Kuiper belt object spectra from JWST, we demonstrate Phoebe's compositional similarity to water-rich KBOs. On the smaller Albiorix and Siarnaq, we observe a broad 3 micron O-H band but do not see a Fresnel peak or the 1.5/2.0 micron features characteristic of H$_2$O ice. We posit that after capture, the frequent high-velocity collisions between smaller irregular satellites sublimate the water ice, while the much larger Phoebe is resistant to disruption and retains its water ice. We suggest that the presence of CO$_2$ on the smaller satellites, despite the lack of water ice, indicates later formation of CO$_2$ on these surfaces through irradiation of organic compounds.

The Nuclear Spectroscopic Telescope Array (NuSTAR) enables detailed high-energy X-ray observations from 3--79 keV, but its performance can be constrained by telemetry saturation when observing bright sources, leading to reduced effective exposure times. In this study, we investigate the use of serendipitous stray light (SL) observations to infer properties of an X-ray bright source in comparison to focused data. Our case study is performed on the neutron star (NS) low-mass X-ray binary (LMXB) GX 340+0, a prominent Z source, where we execute a spectral analysis comparing 25 SL and 7 focused NuSTAR observations. Our findings demonstrate that SL observations can significantly enhance long-term temporal coverage; detecting variations in the thermal components of the system across the baseline of the mission, which could not be inferred from focused observations alone.

This work presents the first optical imaging catalogue of resolved Galactic nova remnants. It compiles images from proprietary observations carried out at the Nordic Optical Telescope and public archives using different telescopes and instruments. The catalogue includes images spanning from 1950 to 2024 of 66 novae out of the more than 550 novae detected to date. Diffuse emission from a nova shell is detected in 45 sources, with another 16 sources been stellar and five more been barely resolved. We used the catalogue to introduce a main morphological classification of the nova remnants (R - round, E - elliptical, B - bipolar, A - asymmetric, I - irregular, S - stellar, and G - barely resolved) with secondary features (s - smooth, c - clumpy, m - mixed, f - filaments, t - tails, m - multiple shells, e - equatorial brightness enhancement). Resolved nova remnants are mostly round (27%) or elliptical (56%), with very few bipolar or with equatorial brightness enhancement (13%). Most nova remnants are younger than 150 yr, with about 80% of nova remnant detection rate among those younger than 60 yr. The physical size of nova remnants increases with age at a rate of 0.0725 pc per century up to a median value of 0.03 pc. This relationship seems to apply even to the few known ancient nova shells with ages up to a few millennia. The aspect ratio of nova remnants can be described by a Gaussian distribution with a standard deviation $\sigma$ of 0.18 from round morphologies (major to minor axes ratio of unity).

Deneb, the prototype Alpha Cygni variable, is a bright A2 Ia supergiant which shows irregular variability with a 12-day quasi-period, presumed to be caused by pulsations. At the 2023 AAVSO Annual Meeting we discussed radial velocity and photometry data from several sources showing that the 12-day variations begin abruptly at an arbitrary phase, damp out after several cycles, and resume at intervals of around 75 days. Additional data with more frequent time sampling and longer time series were needed to verify the existence and precision of the 75-day interval. We have identified additional data sets and have intensified ground-based observing programs. Here we present analysis of 1) an 8.6-year photometric data set from the Solar Mass Ejection Imager; 2) BRITE Constellation light curves from six observing seasons of 60 to 180 days each, 2014-2021; 3) 4.6 years of radial velocity data from Morrison; 4) 1.4 years of radial velocity data from Eaton; and 5) additional V-band photometry from the AAVSO Photoelectric Photometry (PEP) section. Examining the SMEI data set, we find a most common 100 to 125 day interval between `pulsation' resumptions. These resumptions sometimes skip intervals. We also find sudden large excursions in brightness and radial velocity which are distinct from the `pulsation' resumptions and may or may not be data artifacts. We point out changes in the average level of Deneb's radial velocity which appear to be real given the accuracy of the measurements but are not explained.

This chapter provides a detailed overview of Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, located in the dense Galactic Center region approximately 8 kpc from Earth. Despite its relatively low activity compared to more luminous active galactic nuclei, Sgr A* has provided invaluable insights into black hole physics due to its proximity, enabling high-resolution observations of stellar orbits, gas dynamics, and variable emissions. In addition, Sgr A* illustrates how supermassive black holes influence galaxy evolution through energy feedback and matter redistribution. Early identification as a compact radio source and subsequent measurements of stellar orbits confirmed Sgr A* as a black hole with a mass near 4 million solar masses. Observations of stars moving on tight, short-period orbits around the black hole have allowed direct tests of general relativity, such as gravitational redshift and orbital precession, under the influence of extreme gravitational fields. Sgr A* displays variability across the electromagnetic spectrum, with flares in radio, infrared, and X-rays revealing complex interactions in the accretion flow, while outflows redistribute energy into the surrounding environment. Together, Sgr A* and its environment offer a crucial window into the behavior of galactic nuclei.

The planned NASA Habitable Worlds Observatory (HWO) flagship mission aims to image and spectroscopically characterise 25 Earth-size planets in the habitable zones of their stars. However, one giant planet in the habitable zone can ruin your whole day. Recent work has examined the current state of our knowledge on the presence or absence of such objects in samples of likely HWO targets, and that knowledge has been found wanting; even Saturn-mass planets remain undetectable in many of these systems. In this work, we present simulations assessing the degree to which new campaigns of high-cadence radial velocity observations can ameliorate this woeful state of affairs. In particular, we highlight the value of moderate-precision but highly flexibly-scheduled RV facilities in aiding this necessary HWO precursor science. We find that for a subset of Southern HWO stars, 6 years of new RVs from the Minerva-Australis telescope array in Australia can improve the median detection sensitivity in the habitable zones of 13 likely HWO targets to $\sim$50 Earth masses, an improvement of $\sim$44%.

As the only moon in the solar system with a thick atmosphere, Titan is a compelling and enigmatic world containing a complex organic haze. Polycyclic aromatic hydrocarbon (PAH) molecules are believed to play an essential role in the formation of Titan's aerosols and haze layers. The existence of PAHs in Titan's upper atmosphere has been revealed by the detection of the 3.28-micron emission band with Cassini's Visual and Infrared Mapping Spectrometer (VIMS). However, there is little knowledge about the identity, composition, size and abundance of PAH molecules in Titan's atmosphere. Due to its unprecedented sensitivity and spectral coverage and resolution, the advent of the James Webb Space Telescope (JWST) could possibly enable a full characterization of the chemical makeups of Titan's aerosols. In particular, with a much better spectral resolution than Cassini's VIMS, JWST's Near Infrared Spectrograph (and Mid Infrared Instrument) could enable the spectral bands to be better resolved, potentially providing crucial information about which PAHs are really present in Titan's upper atmosphere. To facilitate JWST to search for and identify Titan's PAH molecules, we are performing a systematic study of the photophysics of PAHs in Titan's upper atmosphere. As a pilot study, here we report the infrared emission spectra of vibrationally excited cyanonapthalenes and their ions which are composed of two fused benzene rings and one nitrile (-CN) group. The calculated emission spectra will help JWST to quantitatively determine or place an upper limit on the abundances of cyanonapthalenes in Titan's upper atmosphere.

Fast radio bursts (FRBs) are a type of highly-polarized, millisecond-duration electromagnetic pulses in the radio band, which are mostly produced at cosmological distances. These properties provide a natural laboratory for testing the extreme Faraday effect, a phenomenon in which two different propagation modes of a pulse separate after passing through a dense, highly ionized, and magnetized medium. We derive the critical condition (e.g., rotation measure) for the extreme Faraday effect to occur in FRBs, which exceeds the currently observed maximum value but remains within the theoretically predicted range. Some new features of FRBs (in particular, radio bursts with much shorter durations) after undergoing the extreme Faraday effect are predicted, such as sudden sign reversals of circular polarization, conspicuous frequency drifting, and emergency of extremely high circular polarization degrees. A potential application of this effect in FRBs is that, by comparing morphological differences of the two separated twin modes, one can identify the variations of plasma properties over extremely short timescales along the propagation path. Therefore, if this effect is found with future observations, it would provide a new tool for probing dense, magnetized environments near FRB sources.

Utilizing the PHOENIX synthetic spectra, we investigated the impact of spectral resolution on the calculation of $S$-indices. We found that for spectra with a resolution lower than $\approx$30,000, it is crucial to calibrate $S$-indices for accurate estimations. This is especially essential for low-resolution spectral observations. We provided calibrations for several ongoing or upcoming spectroscopic surveys such as the LAMOST low-resolution survey, the SEGUE survey, the SDSS-V/BOSS survey, the DESI survey, the MSE survey, and the MUST survey. Using common targets between the HARPS and MWO observations, we established conversions from spectral $S$-indices to the well-known $S_{\rm MWO}$ values, applicable to stars with [Fe/H] values greater than $-$1. These calibrations offer a reliable approach to convert $S$-indices obtained from various spectroscopic surveys into $S_{\rm{MWO}}$ values and can be widely applied in studies on chromospheric activity.

The direct imaging of Earth-like planets in solar neighbors is challenging. Both transit and radial velocity (RV) methods suffer from noise due to stellar activity. By choosing a typical configuration of an X array interferometer, we used theoretical formulas to calculate the intrinsic Poisson noise and the noise of stellar activities. Assuming a fixed array with no rotation and ignoring other systematic and astrophysical noises, we considered a single active region on a stellar disk, including both spots and flares with different parameters, for instance, the position, size, and temperature of the active regions. Then we simulated the S/N of Earth-like planets in HZ around G dwarf stars (solar-like) and M dwarfs (Proxima-like), with different stellar activities in the mid-infrared (MIR) band ( 7-12 $\mu$m). The noise attributed to stellar activity has much less influence than the Transit and RV method when detecting Earth-like planets around both G and M dwarfs. I.e. Stellar activity can hardly influence the detection of Earth-like planets around G dwarf stars. However, detecting Earth-like planets around M dwarfs, which are usually more active, can be significantly hindered. We also analyzed the uncertainty of the planet's location due to the deduced S/N. Consequently, we have determined the possibility of mistaking a planet in the HZ as being outside the HZ based on an erroneous S/N measurement. Selecting quiescent target stars or monitoring the light curves of stars would be a helpful way to get rid of contaminates associated with violent stellar activities.

We present updated constraints on the parameters of an axion dark energy model, for which we took into account the properties of its characteristic potential and its full cosmological evolution. We show that the values of the axion parameters appear sufficiently constrained by the data, including the latest DESI DR1, and are consistent with the theoretical expectations of a field mass $m_a$ in the ultralight regime $\log (m_a c^2/\mathrm{eV}) \simeq -32.6$, and an effective energy scale $f_a$ close to the reduced Planck energy $\log (f_a/M_\mathrm{Pl}) \simeq -0.22$. Our results also support the idea of dynamical dark energy, although Bayesian evidence still favors the phenomenological dark energy model $w_0w_a$ over the axion dark energy, with the Bayes factor indicating moderate and weak strength of the evidence, respectively, when the models are compared to the cosmological constant $\Lambda$. However, the results suggest that axion dark energy remains a well-motivated model and may even become more competitive compared to other options with the help of upcoming DESI data.

We present a summary of the in-orbit performance of the soft X-ray imaging telescope Xtend onboard the XRISM mission, based on in-flight observation data, including first-light celestial objects, calibration sources, and results from the cross-calibration campaign with other currently-operating X-ray observatories. XRISM/Xtend has a large field of view of $38.5'\times38.5'$, covering an energy range of 0.4--13 keV, as demonstrated by the first-light observation of the galaxy cluster Abell 2319. It also features an energy resolution of 170--180 eV at 6 keV, which meets the mission requirement and enables to resolve He-like and H-like Fe K$\alpha$ lines. Throughout the observation during the performance verification phase, we confirm that two issues identified in SXI onboard the previous Hitomi mission -- light leakage and crosstalk events -- are addressed and suppressed in the case of Xtend. A joint cross-calibration observation of the bright quasar 3C273 results in an effective area measured to be $\sim420$ cm$^{2}$@1.5 keV and $\sim310$ cm$^{2}$@6.0 keV, which matches values obtained in ground tests. We also continuously monitor the health of Xtend by analyzing overclocking data, calibration source spectra, and day-Earth observations: the readout noise is stable and low, and contamination is negligible even one year after launch. A low background level compared to other major X-ray instruments onboard satellites, combined with the largest grasp ($\Omega_{\rm eff}\sim60$ ${\rm cm^2~degree^2}$) of Xtend, will not only support Resolve analysis, but also enable significant scientific results on its own. This includes near future follow-up observations and transient searches in the context of time-domain and multi-messenger astrophysics.

The neutral hydrogen (HI) signal is a crucial probe for astrophysics and cosmology, but it is quite challenging to measure from raw data because of bright foreground contaminants at radio wavelengths. Cross-correlating the radio observations with large-scale structure tracers (LSS) could detect faint cosmological signals since they are not correlated with the foreground, but exquisite component separation procedures must be performed to reduce the variance induced by the foreground. In this work, we adopt the lensing of the cosmic microwave background (CMB) as the LSS tracer and investigate the cross-correlation of CMB lensing and HI observations at the post-reionization epoch. We use simulations to study lensing and HI cross-correlations in the context of next-generation CMB and intensity mapping experiments. We investigate the impact of the component separation based on linear combinations of the HI observations at different frequencies and estimate the signal-to-noise ratios for the cross-correlation measurements in different scenarios.

The origin of radio emission in radio-quiet (RQ) AGN remains a long-standing mystery. We present a detailed study of the cm to sub-mm emission from the nucleus of the nearby prototypical RQ Seyfert 2 galaxy, NGC 1068. We analyse observations between 4.5-706 GHz using $e$-MERLIN, VLA and ALMA. We restricted all data used for imaging to a matching $uv-$range of 15$-$3300 k$\lambda$, to ensure that all data sampled the same spatial scales. All images were restored with a $\sim$ 0.06$''$ beam. To derive the spectral energy distribution (SED), we fit synchrotron, free-free, dust and coronal component models to these data. We report that the sub-mm excess between $\sim$ 200-700 GHz is consistent with synchrotron emission from a compact and optically thick corona with a radius $R_\mathrm{c}\approx 70\pm5 \,R_\mathrm{g}$, a fraction of $\sim$\,$10\pm2$% of the energy density in the form of non-thermal electrons, and a magnetic field strength $B\approx 148$ G. The luminosity of the corona is roughly consistent with -- though higher than -- the expected from mm--X-ray correlations derived in recent studies of RQ AGN. This difference is likely due to the corona SED peaking at ($\approx$550 GHz). Between 10 and $\sim$ 200 GHz, the SED is dominated by free-free emission. High angular resolution observations at frequencies below 5 GHz are needed to constrain a putative optically thin synchrotron component and the amount of free-free absorption.

Very Long Baseline Interferometry (VLBI) provides the finest angular resolution of all astronomical observation techniques. However, observations with Earth-based instruments are approaching fundamental limits on angular resolution. These can only be overcome by placing at least one interferometric element in space. In this paper, several concepts of spaceborne VLBI systems are discussed, including TeraHertz Exploration and Zooming-in for Astrophysics (THEZA) and the Black Hole Explorer (BHEX). Spaceborne VLBI telescopes have some of the most demanding requirements of any space science mission. The VLBI system as a whole includes globally distributed elements, each with their own functional constraints, limiting when observations can be performed. This necessitates optimisation of the system parameters in order to maximise the scientific return of the mission. Presented is an investigation into how the impact of the functional constraints of a spaceborne VLBI telescope affect the overall system performance. A preliminary analysis of how these constraints can be minimised through optimisation of the spacecraft configuration and operation is also provided. A space-based VLBI simulation tool (spacevlbi) has been developed to model such missions and its capabilities are demonstrated throughout the paper. It is imperative that the functional constraints are considered early in the design of the future space-based VLBI systems in order to generate feasible mission concepts and to identify the key technology developments required to mitigate these limitations.

A search for $\gamma$-ray emission from SNRs in the Large Magellanic Cloud (LMC) based on the detection of concentrations in the arrival direction Fermi-LAT images of photons at energies higher than 10 GeV found significant evidence for 9 of these sources. This analysis was based on data collected in the time window since August 4 2008 to August, 4 2020 (12 years). In the present contribution, we report results of a new search extended using a 15-year long (up to August, 4 2023) data set and to a broad energy range (higher than 4 GeV). The longer baseline and the softer energy lower limit are required to further understand the relation between the X-ray and gamma ray SNRs in the LMC, and to investigate the completness of the sample at low luminosities. Two different methods of clustering analysis were applied: Minimum Spanning Tree (MST), and the combination of Density-Based Spatial Clustering of Applications with Noise (DBSCAN) and DENsity-based CLUstEring (DENCLUE) algorithms. We confirm all previous detections and found positive indications for at least 8 new clusters with a spatial correspondence with other SNRs, increasing thus the number of remnants in LMC candidate or detected in the high energy $\gamma$-rays to 16 sources. This study extends previous analyses of $\gamma$-ray emission from SNRs in the LMC by incorporating a longer observational baseline and a broader energy range. The improved dataset and advanced clustering techniques enhance our understanding of the connection between X-ray and $\gamma$-ray SNRs, providing new insights into their high-energy properties, and contributing to assessing the completeness of the sample at lower luminosities.

This work present the results of a multi-epoch observational study of the blazar S5\,1803+784, carried out from 2019 to 2023. The analysis is based on simultaneous data obtained from the Swift/UVOT/XRT, ASAS-SN, and Fermi-LAT instruments. A historically high $\gamma$-ray flux observed for this source on march 2022 ($\mathrm{2.26\pm0.062)\times10^{-6}~phcm^{-2}s^{-1}}$. This study investigates the $\gamma$-ray emission from a blazar, revealing a dynamic light curve with four distinct flux states: quiescent and high-flux by using the Bayesian Blocks (BB) algorithm. A potential transient quasi-periodic signal with an oscillation timescale of $\sim$411 days was identified, showing a local significance level surpassing 99.7$\%$ from the Lomb-Scargle Periodogram (LSP) and Damped Random Walk (DRW) analysis and exceeds 99.5$\%$ from the Weighted Wavelet Z-Transform (WWZ) analysis. The observed QPO was confirmed through an autoregressive process (AR(1)), with a significance level exceeding 99$\%$, suggesting a potential physical mechanism for such oscillations involves a helical motion of a magnetic plasma blob within the relativistic jet. Log parabola modeling of the $\gamma$-ray spectrum revealed a photon index ($\alpha_\gamma$) variation of 1.65$\pm$0.41 to 2.48$\pm$0.09 with a steepening slope, potentially indicative of particle cooling, changes in radiative processes, or modifications in the physical parameters. The $\alpha_\gamma$ of 2.48$\pm$0.09 may hint at an evolutionary transition state from BL\,Lac to FSRQ. A comparative analysis of variability across different energy bands reveals that Optical/UV and GeV emissions display greater variability compared to X-rays. Broadband SED modeling shows that within a one-zone leptonic framework, the SSC model accurately reproduces flux states without external Compton contributions, highlighting magnetic fields crucial role.

We examine the eccentricity distribution(s) of radial velocity detected exoplanets. Previously, the eccentricity distribution was found to be described well by a Beta distribution with shape parameters $a=0.867, b=3.03$. Increasing the sample size by a factor of 2.25, we find that the CDF regression method now prefers a mixture model of Rayleigh + Exponential distributions over the Beta distribution, with an increase in Bayesian evidence of $\Delta\ln{Z}\sim 77$ ($12.6\,\sigma$). Using PDF regression, the eccentricity distribution is best described by a Gamma distribution, with a Rayleigh + Exponential mixture a close second. The mixture model parameters, $\alpha = 0.68\pm0.05, \lambda=3.32\pm0.25, \sigma =0.11\pm0.01$, are consistent between methods. We corroborate findings that exoplanet eccentricities are drawn from independent parent distributions when splitting the sample by period, mass, and multiplicity. Systems with a known outer massive companion provide no positive evidence for an eccentricity distribution distinct from those without. We quantitatively show M-dwarf hosted planets share a common eccentricity distribution with those orbiting FGK-type stars. We release our python code, eccentriciPy, which allows bespoke tailoring of the input archive to create more relevant priors for particular problems in RV planet discovery and characterisation. We re-characterised example planets using either traditional Beta, or updated priors, finding differences for recovery of low-amplitude multi-signal systems. We explore the effects of a variety of prior choices. The accurate determination of small but non-zero eccentricity values has wide-ranging implications for modelling the structure and evolution of planets and their atmospheres due to the energy dissipated by tidal flexing.

Different cosmological probes, such as primary cosmic microwave background (CMB) anisotropies, CMB lensing, and cosmic shear, are sensitive to the primordial power spectrum (PPS) over different ranges of wavenumbers. In this paper, we combine the cosmic shear two-point correlation functions measured from the Subaru Hyper Suprime-Cam (HSC) Year 3 data with the Planck CMB data, and the ACT DR6 CMB lensing data to test modified shapes of the PPS at small scales, while fixing the background cosmology to the flat $\Lambda$CDM model. We consider various types of modifications to the PPS shape: the model with a running spectral index, the tanh-shaped model, the Starobinsky-type modification due to a sharp change in the inflaton potential, the broken power-law model, and the multiple broken power-law model. Although the HSC cosmic shear data is sensitive to the PPS at small scales, we find that the combined data remains consistent with the standard power-law PPS, i.e., the single power-law model, for the flat $\Lambda$CDM background. In other words, we conclude that the $S_8$ tension cannot be easily resolved by modifying the PPS within the $\Lambda$CDM background.

The James Webb Space Telescope (JWST) has revealed a population of active galactic nuclei (AGNs) that challenge existing black hole (BH) formation models. These newly observed BHs are overmassive compared to the host galaxies and have an unexpectedly high abundance. Their exact origin remains elusive. The primary goal of this work is to investigate the formation of massive BH seeds in dense Population III (Pop III) star clusters. Using a cosmological simulation of Pop III cluster formation, we present models for the assembly and subsequent evolution of these clusters. The models account for background gas potential, stellar collisions and associated mass loss, gas accretion, stellar growth, their initial mass function (IMF), and subsequent star formation. We conduct $N$-body simulations of these models over a span of 2 million years. Our results show that BHs of $> 400$ M$_\odot$ are formed in all cases, reaching up to $\sim 5000$ M$_\odot$ under optimistic yet reasonable conditions and potentially exceeding 10$^4$ M$_\odot$ provided that high accretion rates of 10$^{-3}$ M$_\odot$ yr$^{-1}$ onto the stars can be sustained. We conclude that massive BHs can be formed in Pop III stellar clusters and are likely to remain within their host clusters. These BHs may experience further growth as they sink into the galaxy's potential well. This formation channel should be given further consideration in models of galaxy formation and BH demographics.

Radio observation of the large-scale structure (LSS) of our Universe faces major challenges from foreground contamination, which is many orders of magnitude stronger than the cosmic signal. While other foreground removal techniques struggle with complex systematics, methods like foreground avoidance emerge as effective alternatives. However, this approach inevitably results in the loss of Fourier modes and a reduction in cosmological constraints. We present a novel method that, by enforcing the non-negativity of the observed field in real space, allows us to recover some of the lost information, particularly phase angles. We demonstrate that the effectiveness of this straightforward yet powerful technique arises from the mode mixing from the non-linear evolution of LSS. Since the non-negativity is ensured by mass conservation, one of the key principles of the cosmic dynamics, we can restore the lost modes without explicitly expressing the exact form of the mode mixing. Unlike previous methods, our approach utilizes information from highly non-linear scales, and has the potential to revolutionize the analysis of radio observational data in cosmology. Crucially, we demonstrate that in long-baseline interferometric observations, such as those from the Square Kilometre Array (SKA), it is still possible to recover the baryonic acoustic oscillation (BAO) signature despite not directly covering the relevant scales. This opens up potential future survey designs for cosmological detection.

On December 27, 2024, Juno's JIRAM infrared experiment observed an unprecedented volcanic event on Io's southern hemisphere, covering a vast region of ~ 65,000 square km, near 73°S, 140°E. The total power output is estimated between 140 and 260 TW, potentially the most intense ever recorded, surpassing the brightest eruption at Surt in 2001 (~80 TW). Within that region, only one hot spot was previously known (Pfd454). This feature was earlier estimated to cover an area of 300 square km with a total power output of 34 GW. JIRAM results show that the region produces a power output of 140-260 TW, over 1,000 times higher than earlier estimates. Three adjacent hot spots also exhibited dramatic power increases: P139, PV18, and an unnamed feature south of the main one that surged to ~1 TW, placing all of them among the top 10 most powerful hot spots observed on Io. A temperature analysis of the features supports a simultaneous onset of these brightenings and suggests a single eruptive event propagating beneath the surface across hundreds of kilometers, the first time this has been observed on Io. This implies a connection among the hotspots' magma reservoirs, while other nearby hotspots that have been known to be active in the recent past, such as Kurdalagon Patera, appear unaffected. The simultaneity supports models of massive, interconnected magma reservoirs. The global scale of this event involving multiple hotspots and covering several hundred thousand square km should be considered in the future models of the lithosphere and interior of Io.

We present 3D radiation hydrodynamics simulations of common-envelope (CE) evolution involving a 12 solar mass red supergiant donor and a 3 solar mass companion. Existing 3D simulations are predominantly adiabatic, focusing strongly on low-mass donors on the red giant and asymptotic giant branches. However, the adiabatic assumption breaks down once the perturbed CE material becomes optically thin or when entering a longer-timescale evolutionary phase after the dynamical plunge-in. This is especially important for high-mass red supergiant donors, which have short thermal timescales, adding significant uncertainty in understanding how massive binary stars evolve into gravitational-wave sources, X-ray binaries, stripped-envelope supernovae, and more. We compare our radiation hydrodynamics simulations with an adiabatic simulation from Paper I that is otherwise identical, finding that radiative diffusion strongly inhibits CE ejection. The fraction of ejected mass is roughly half that of the adiabatic case when recombination energy release is not included. Almost no material is ejected during the dynamical plunge-in, and longer-timescale ejection during the slow spiral-in is suppressed. However, the orbital separation reached at the end of the dynamical plunge-in does not differ significantly. The large amount of remaining bound mass tentatively supports the emerging view that the dynamical plunge-in is followed by a non-adiabatic phase, during which a substantial fraction of the envelope is ejected and the binary orbit may continue to evolve.

[Abridged] SFGs are the dominant population in the faint radio sky, corresponding to flux densities at 1.4 GHz $< 0.1$ mJy. A panchromatic approach is essential for selecting SFGs in the radio band and understanding star formation processes over cosmic time. Semi-empirical models are valuable tools to effectively study galaxy formation and evolution, relying on minimal assumptions and exploiting empirical relations between galaxy properties and enabling us to take full advantage of the recent progress in radio and optical/near-infrared (NIR) observations. In this paper, we develop the Semi-EMPirical model for Extragalactic Radio emission (SEMPER) to predict radio luminosity functions and number counts at 1.4 GHz and 150 MHz for SFGs. SEMPER is based on state-of-the-art empirical relations and combines the redshift-dependent galaxy stellar mass functions obtained from the recent COSMOS2020 catalogue, which exploits deep near-infrared observations, with up-to-date observed scaling relations, such as the galaxy main sequence and the mass-dependent far-infrared/radio correlation across cosmic time. Our luminosity functions are compared with recent observational determinations from several radio telescopes, along with previous semi-empirical models and simulations. Our semi-empirical model successfully reproduces the observed luminosity functions at 1.4 GHz and 150 MHz up to $z\sim 5$ and the most recent number count statistics from radio observations in the LoTSS deep fields. Our model, based on galaxies selected in the NIR, naturally predicts the presence of radio-selected massive and/or dust-obscured galaxies already in place at high redshift ($z\gtrsim3.5$), as suggested by recent results from JWST. Our predictions offer an excellent benchmark for upcoming updates from JWST and future ultra-deep radio surveys planned with the SKA and its precursors.

Aims. We investigated the potential of using Hepsilon to diagnose small-scale energetic phenomena such as Ellerman bombs, UV bursts, and small-scale flares. Our focus is to understand the formation of the line and how to use its properties to get insight into the dynamics of small-scale energetic phenomena. Methods. We carried out a forward modeling study, combining simulations and detailed radiative transfer calculations. The 3D radiative magnetohydrodynamic simulations were run with the Bifrost code and included energetic phenomena. We employed a Markovian framework to study the Hepsilon multilevel source function, used relative contribution functions to identify its formation regions, and correlated the properties of synthetic spectra with atmospheric parameters. Results. Ellerman bombs are predominantly optically thick in Hepsilon, appearing as well-defined structures. UV bursts and small flares are partially optically thin and give rise to diffuse structures. The Hepsilon line serves as a good velocity diagnostic for small-scale heating events in the lower chromosphere. However, its emission strength is a poor indicator of temperature, and its line width offers limited utility due to the interplay of various broadening mechanisms. Compared to Halpha, Hepsilon exhibits greater sensitivity to phenomena such as Ellerman bombs, as its line core experiences higher extinction than the Halpha wing. Conclusions. Hepsilon is a valuable tool for studying small-scale energetic phenomena in the lower chromosphere. It provides more reliable estimates of velocities than those extracted from wing emission in Halpha or Hbeta. Maps of Hepsilon emission show more abundant energetic events than the Halpha counterpart. Our findings highlight Hepsilons potential to advance our understanding of dynamic processes in the solar atmosphere.

I present the results of echelle spectroscopy of a bright HII region in the irregular galaxy IC4662 and their comparison with results from long-slit spectroscopy of the same region. All observations were obtained with the standard spectrographs of the SALT telescope: (1) low and medium spectral resolution spectrograph RSS (R~800) and (2) echelle spectrograph HRS (R=16000-17000). In both types of data the intensities of most of the emission lines were measured and abundances of oxygen and N, Ne, S, Ar, Cl and Fe were determined as well as physical parameters of the \ion{H}{ii} region. The chemical abundances were obtained from both types of data with the Te-method. Abundances calculated from both types of data agree to within the cited uncertainties. The analysis of the echelle data revealed three distinct kinematic subsystems within the studied \ion{H}{ii} region: a narrow component (NC, $\sigma ~ 12$~km/s), a broad component (BC, $\sigma ~ 40$~km/s), and a very broad component (VBC, $\sigma ~ 60-110$~km/s, detected only in the brightest emission lines). The velocity dispersion dependence on the ionisation potential of elements showed no correlation for the NC, indicating a well-mixed turbulent medium, while the BC exhibited pronounced stratification, characteristic of an expanding shell. Based on a detailed analysis of the kinematics and chemical composition, it was concluded that the BC is associated with the region surrounding a Wolf-Rayet star of spectral type WN7-8. The stellar wind from this WR star interacts with a shell ejected during an earlier evolutionary stage (either as a red supergiant or a luminous blue variable, LBV), which is enriched in nitrogen. These findings highlight the importance of high spectral resolution for detecting small-scale (~25 pc) chemical inhomogeneities and for understanding the feedback mechanisms of massive stars in low-metallicity environments.

There remains debate over whether the accretion disk survives or is entirely disrupted after the nova eruption. In our previous paper, Muraoka et al. (2024, PASJ, 76, 293) have photometrically demonstrated that the surviving accretion disk was expanded close to the L1 point during the optical plateau stage and then drastically shrank to the tidal truncation radius after the optical plateau stage ended. To approach the clarification of the physical mechanism that drives these structural changes, we have then conducted systematic analyses of the spectral evolution of the narrow emission line components in optical over 22 d following the optical peak during the 2022 nova eruption of U Scorpii (U Sco). Additionally, we present its optical spectrum in quiescence 794 d after the 2022 nova eruption. We find that the single-peaked narrow components of H$\alpha$ and He II 4686 appeared almost simultaneously between roughly days 6 and 8, preceding the onset of the disk eclipses observed after day 11. This finding suggests that the nova wind near the binary system may be the primary origin of these narrow components and even remained active several days after the nova eruption with a velocity of approximately 1000 km s$^{-1}$, likely driving the expansion of the accretion disk until the end of the optical plateau stage. While the contribution of the rotating accretion disk might be dominated by that of the nova wind in the H$\alpha$ line profile, the outward surface flow from the expanded disk might also contribute to these narrow features during the optical plateau stage, making the single-peaked narrow line profiles more pronounced.

In this work, we investigate a joint fitting approach based on theoretical models of power spectra associated with density-field reconstruction. Specifically, we consider the matter auto-power spectra before and after baryon acoustic oscillation (BAO) reconstruction, as well as the cross-power spectrum between the pre- and post-reconstructed density fields. We present redshift-space models for these three power spectra at the one-loop level within the framework of standard perturbation theory (SPT), and perform a joint analysis using three types of power spectra, and quantify their impact on parameter constraints. When restricting the analysis to wavenumbers $k \leq 0.2\,h\,\mathrm{Mpc}^{-1}$ and adopting a smoothing scale of $R_{\mathrm{s}} = 15\,h^{-1}\,\mathrm{Mpc}$, we find that incorporating all three power spectra improves parameter constraints by approximately $11\%\text{--}16\%$ compared to using only the post-reconstruction power spectrum, with the Figure of Merit (FoM) increasing by $10.5\%$. These results highlight the advantages of leveraging multiple power spectra in BAO reconstruction, ultimately enabling more precise cosmological parameter estimation.

Context: Orbiting matter misaligned with a spinning black hole undergoes Lense-Thirring precession, due to the frame-dragging effect. This phenomenon is particularly relevant for type-C QPOs observed in the hard states of low-mass X-ray binaries. However, the accretion flow in these hard states is complex, consisting of a geometrically thick, hot corona surrounded by a geometrically thin, cold disk. Recent simulations have demonstrated that, in such a truncated disk scenario, the precession of the inner hot corona slows due to its interaction with the outer cold disk. Aims: This paper aims to provide an analytical description of the precession of an inner (hot) torus in the presence of accretion torques exerted by the outer (cold) disk. Methods. Using the angular momentum conservation equation, we investigate the evolution of the torus angular momentum vector for various models of accretion torque. Results: We find that, in general, an accretion torque tilts the axis of precession away from the black hole spin axis. In all models, if the accretion torque is sufficiently strong, it can halt the precession; any perturbation from this stalled state will cause the torus to precess around an axis that is misaligned with the black hole spin axis. Conclusions: The accretion torque exerted by the outer thin disk can cause precession around an axis that is neither aligned with the black hole spin axis nor perpendicular to the plane of the disk. This finding may have significant observational implications, as the jet direction, if aligned with the angular momentum axis of the torus, may no longer reliably indicate the black hole spin axis or the orientation of the outer accretion disk.

We present the largest visually selected sample of extended ($>$60 arcsec) radio-loud active galactic nuclei (RLAGN) to date, based on the LOw-Frequency Array Two-Metre Sky Survey second data release (LoTSS DR2). From the broader LoTSS DR2 dataset with spectroscopic classifications, we construct a subsample of 2828 RLAGN with radio luminosities greater than $10^{23}~\mathrm{W~Hz^{-1}}$ at $z<0.57$. These RLAGN are further classified by optical emission-line properties into high-excitation and low-excitation radio galaxies, enabling a detailed emission-line analysis. Our subsample is also morphologically classified into Fanaroff \& Riley centre- and edge-brightened (FRI/FRII) sources, wide- and narrow-angle tail (WAT and NAT) sources, head-tail (HT) sources, and relaxed double (RD) sources. For these classifications, we utilize data from the Very Large Array Sky Survey (VLASS) to assist with the classification, taking advantage of its 2.5 arcsec resolution which is sensitive to structures below 30 arcsec. This resolution allows us to identify compact cores and hotspots, facilitating the identification of remnant and restarted RLAGN candidates. We investigate the relationship between emission-line and radio properties in RLAGN, analyzing mid-infrared data, host galaxy mass, and core prominence. These analyses uncover the complex relationship between these factors and the underlying accretion mechanisms. Our findings emphasize that no single property can fully constrain the accretion mode in RLAGN, highlighting the necessity of multi-dimensional approaches to reveal the processes driving RLAGN behaviour.

This article discusses strong nuggets (SNs) which means strong interaction condensed matter clusters with a mass of about $10^6\,$g. They may originate from the early universe, supernova, pulsar merger event, and so on. Depending on the equation of state, the SNs could be stable and even be one of the candidates for dark matter. In order to detect SNs which hitting the Earth or the Moon at a non-relativistic velocity, a new messenger, the acoustic array, is analysed. The results of the calculations show that the impact signal of an SN can be detected at a distance of about 30 kilometers from the nugget's trajectory. By using microphone boxes, hydrophones or seismographs to construct an array in the bedrock, ocean or on the Moon, it is possible to reconstruct the velocity, mass, and interacting cross section of SNs, and then constrain also the nature of supra-nuclear matter. The acoustic array can also be used for distributed acoustic sensing of meteorites or earthquakes. The sonar localisation system on the proposed High-energy Underwater Neutrino Telescope (HUNT) is suggested as a pathfinder for acoustic array detection.

The problem of the formation of exoplanets in inclined orbits relative to the equatorial plane of the parent star or the main plane of the protoplanetary disk can be solved by introducing a smaller inclined disk. However, the question of the nature of such an internal disk remains open. In the paper, we successfully tested the hypothesis about the formation of an inclined inner disk in a protoplanetary disk near a T Tau type star as a result of a gas stream falling on it. To test the hypothesis, three-dimensional gas-dynamic calculations were performed taking into account viscosity and thermal conductivity using the PLUTO package. In the course of the analysis of calculations, it was shown that a single intersection of the matter stream with the plane of the disk cannot ensure the formation of an inclined disk near the star, while a double intersection can. In addition, in the case of a retrograde fall of matter, the angle of inclination of the resulting inner disk is significantly greater. An analysis of the observational manifestations of this event was also carried out: the potential change in the brightness of the star, the distribution of optical thickness in angles, the evolution of the accretion rate. It is shown that the decrease in brightness can reach up to $5^m$, taking into account scattered light, and such a decrease in brightness will last several decades. In addition, a sharp increase in the accretion rate by two orders of magnitude could potentially trigger an FU Ori-like outburst.

We present a detailed 3D photoionization model of the planetary nebula NGC 3132, constrained by the latest observations. Using the MOCASSIN code, the model incorporates integrated and spatially resolved spectroscopy, velocity-resolved line profiles, emission line maps, and photometry, including recent high-quality data from MUSE (VLT) and JWST among others. Based on new data from the SAMFP instrument at SOAR, the three-dimensional density structure of the nebula was obtained by assuming homologous expansion of the surrounding nebular gas. The final fitted model successfully reproduces all key observational constraints available, particularly in terms of the detailed emission line integrated fluxes and ionization structures across different ionic stages. The results of the model show that the progenitor star had a mass of $(2.7 \pm 0.2)M_{\odot}$ and is surrounded by a He poor shell of dust and gas. The abundances of He, C, N, O, and S determined by the model show that the nebula has C/O=$(2.02 \pm 0.28)$ and N/O=$(0.39 \pm 0.38)$ consistent with the progenitor mass found.

The Pierre Auger Observatory, located near the town Malargüe in the province of Mendoza, Argentina, is the largest cosmic-ray detector in existence, covering an area of 3000 km2. The upgraded Observatory, in Phase II of operations, consists of a surface array of 1660 stations combining water Cherenkov, scintillator, and radio detectors. A subset of stations also includes underground muon detectors. Additionally, fluorescence detectors located at four sites overlook the array. The science goals for the enhanced Observatory include the measurement of the properties of ultra-high-energy cosmic rays with large statistics and high sensitivity to the primary composition. The Observatory is also sensitive to photons and neutrinos at the highest energies, allowing it to participate in multi-messenger studies. The Auger Offline Framework provides the tools to perform detailed simulations, using the Geant 4 toolkit, of all components of the Observatory and the analysis of both data and simulated events. It proved to have the flexibility needed to evolve during the lifetime of the Observatory, to accommodate new sub-detectors and, recently, changes to the station readout electronics. A new challenge is interfacing the framework with Machine Learning tools for both the development and execution of neural-network-based algorithms. Independent of the framework, CORSIKA 7 is used to simulate particles, fluorescence light, and radio signals produced by air showers. The production of simulations is coordinated centrally to provide standard libraries for analyses and to optimize the use of computing resources. We will describe the evolution and status of the Offline Framework and the tools used to coordinate the simulation efforts. We will also discuss the challenges of the massive simulation efforts and the resources consumed to provide the simulation libraries required by the Collaboration.

We present 850 $\mu$m polarized continuum observations carried out with the POL-2 polarimeter mounted on the James Clerk Maxwell Telescope (JCMT) towards NGC 7023 located in the Cepheus Flare region. NGC 7023 is a reflection nebula powered by a Herbig Ae Be star HD 200775 and also identified as a hub in the hub-filament cloud, LDN 1172/1174. We detect submillimetre emission well towards the northern (identified as C1) and the eastern region of the reflection nebula. We investigated the polarization structure and the magnetic field (B-field) morphology, which is found to be curved and follows the clump morphology. The comparison of the B-field morphology at the clump scales ($\sim$0.02 pc) with that of the envelope ($\sim$0.5 pc) suggests that the field lines are not preserved from envelope to clump scales, implying that an external factor may be responsible for disturbing the B-field structure. We estimated a magnetic field strength of 179$\pm$50 $\mu$G in the starless core, 121$\pm$34 $\mu$G in the protostellar core with a class I source and 150$\pm$42 $\mu$G in the protostellar core with a class II source using the $N_{2}H^{+}$ (1-0) line observed with 13.7 m single dish radio telescope at Taeduk Radio Astronomy Observatory (TRAO). The stability analysis using these B-field strengths gives magnetically sub-critical values, while the magnetic, gravitational, and outflow kinetic energies are roughly balanced. We also suggest that the reordering of the magnetic field lines could be due to the interaction with the already evolved high-velocity outflow gas around the central star, which hints at the presence of outflow feedback.

It is established that the ultraviolet (UV) and X-ray emissions in active galactic nuclei (AGN) are tightly correlated. This correlation is observed both in low- and high-redshift sources. In particular, observations of large samples of quasars revealed the presence of a non-linear correlation between UV and X-rays. The physical origin of this correlation is poorly understood. In this work, we explore this observed correlation in the framework of the X-ray illumination of the accretion disc by a central source. We have shown in previous works that this model successfully explains the continuum UV/optical time delays, variability, and the broadband spectral energy distribution in AGN. We use this model to produce $150,000$ model SEDs assuming a uniform distribution of model parameters. We compute the corresponding UV ($ 2500~Å $) and X-ray (2 keV) monochromatic luminosities and select only the model data points that agree with the observed UV-to-X-ray correlation. Our results show that the X-ray illumination of accretion disc model can reproduce the observed correlation for a subset of model configurations with a non-uniform distribution of black hole mass ($M_{\rm BH}$), accretion rate ($\dot{m}/\dot{m}_{\rm Edd}$), and power transferred from the accretion disc to the corona ($L_{\rm transf}/L_{\rm disc}$). In addition, our results reveal the presence of a correlation between $M_{\rm BH}$ and $\dot{m}/\dot{m}_{\rm Edd}$, and between $\dot{m}/\dot{m}_{\rm Edd}$ and $L_{\rm transf}/L_{\rm disc}$, to explain the observed X-ray-UV correlation. We also present evidence based on observed luminosities supporting our findings. We finally discuss the implications of our results.

We introduce a comprehensive, custom-developed neural network, the PUREPath-B, that yields a posterior predictive distribution of Cosmic Microwave Background (CMB) B-mode signal conditioned on the foreground contaminated CMB data and informed by the training dataset. Our network employs nested probabilistic multi-modal U-Net framework, enhanced with probabilistic ResNets at skip connections and seamlessly integrates Bayesian statistics and variational methods to minimize the foreground and noise contaminations. During training, the initial prior distribution over network parameters evolves into approximate posterior distributions through Bayesian inference, constrained by the training data. From the approximate joint full posterior of the model parameters, our network infers a predictive CMB posterior during inference and yields summary statistics such as predictive mean, variance of the cleaned map. The predictive standard deviation provides an interpretable measure of per-pixel uncertainty in the predicted mean CMB map. For loss function, we use a linear combination of KL-Divergence loss and weighted MAE-which ensures that maps with higher amplitudes do not dominate the loss disproportionately. Furthermore, the results from the cosmological parameter estimation using the cleaned B-mode power spectrum, along with its error estimates demonstrates our network minimizes the foreground contaminations effectively, enabling accurate recovery of tensor-to-scalar ratio and lensing amplitude.

Stellar mass can enhance the ranking of potential hosts for compact binary coalescences identified by ground-based gravitational-wave detectors within large localisation areas containing even thousands of galaxies. Despite its benefits, accurate stellar mass estimation is often time-consuming and computationally intensive. In this study, we implement four stellar mass estimation methods based on infrared magnitudes and compare them with values estimated with spectral energy distribution fitting from GAMA DR3, revealing strong correlations. We also introduce a method to calibrate the results from these estimation methods to match the reference values. Our analysis of simulated binary black hole events demonstrates that incorporating stellar mass improves the rank of actual hosts ~80 per cent of cases. Furthermore, the improvement is comparable when stellar masses are derived from the tested estimation methods to when they are obtained directly from the simulated galaxy catalogue, demonstrating that simple stellar mass estimates can provide a computationally efficient alternative.

The chiral gravitational wave background (GWB) can be produced by axion-like fields in the early universe. We perform parameter estimation for two types of chiral GWB with the LISA-Taiji network: axion-dark photon coupling and axion-Nieh-Yan coupling. We estimate the spectral parameters of these two mechanisms induced by axion and determine the normalized model parameters using the Fisher information matrix. For highly chiral GWB signals that we choose to analyze in the mHz band, the normalized model parameters are constrained with a relative error less than $6.7\%$ (dark photon coupling) and $2.2\%$ (Nieh-Yan coupling) at the one-sigma confidence level. The circular polarization parameters are constrained with a relative error around $21\%$ (dark photon coupling) and $6.2\%$ (Nieh-Yan coupling) at the one-sigma confidence level.

Using first-principles field-theoretic methods, we investigate neutrino emission from strongly magnetized dense quark matter under conditions relevant to compact stars. We develop a customized approximation that fully accounts for the Landau-level quantization of electron states while neglecting such quantization for quarks. This approach is well-justified in dense quark matter, where the chemical potentials of up and down quarks significantly exceed those of electrons. Our analysis provides a detailed exploration of the influence of strong magnetic fields on neutrino emission, including both the modification of the total emission rate and the emergence of emission asymmetry relative to the magnetic field direction. We further examine the role of temperature in smoothing the oscillatory behavior of neutrino emission as a function of magnetic field strength. Additionally, we study the interplay between the Landau-level quantization of electrons and the Fermi-liquid effects of quarks in modifying the phase space of relevant weak processes. Finally, we briefly discuss the broader implications of magnetic fields on stellar cooling processes and the potential contribution of asymmetric neutrino emission to pulsar kicks.

We propose a dark energy model in which a quintessence field $\phi$ rolls near the vicinity of a local maximum of its potential characterized by the simplest $S$ self-dual form $V(\phi) = \Lambda \ {\rm sech}(\sqrt{2} \, \phi/M_p)$, where $M_p$ is the reduced Planck mass and $\Lambda \sim 10^{-120} M_p^4$ is the cosmological constant. We confront the model with Swampland ideas and show that the $S$-dual potential is consistent with the distance conjecture, the de Sitter conjecture, and the trans-Planckian censorship conjecture. We also examine the compatibility of this phenomenological model with the intriguing DESI DR2 results and show that the shape of the $S$-dual potential is almost indistinguishable from the axion-like potential, $V (\phi) = m_a^2 \ f_a^2 \ [ 1 + \cos(\phi/f_a)]$, with $m_a$ and $f_a$ parameters fitted by the DESI Collaboration to accommodate the DR2 data.

Seventeen representative samples of volcanic origin were collected from Ecuador (Pichincha Volcano), Iceland (Eyjafjallajökull Volcano), India (Deccan Traps), Hawaii, Kilimanjaro, Mt. Etna, Rwanda (Virunga Mountains), and Uganda (Virunga Mountains). Neutron activation analysis (NAA) was performed to determine the concentration of 33 chemical elements, including 21 trace elements, 20 heavy metals, and 9 rare earth elements: Al, As, Ba, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, Ti, U, Yb, Zn, and Zr. Correlation analysis of the abundance of samples from different islands in the Hawaii archipelago (Kauai, Kilauea, Mauna Loa, and Haleakala) confirmed that the islands were likely formed by two different lava sources. Additionally, the upper limit of iridium was determined in 11 of these samples using Bayesian analysis, which does not support the hypothesis that volcanic activity caused the extinction of the dinosaurs. We also discuss how the abundance of thorium and uranium in lava from different geological formations and depths can contribute to building a better map of natural radioisotope occurrences on Earth, which is important for geoneutrino experiments. A high abundance of rare elements was reported in some of the analyzed locations, indicating potential commercial interest and the possibility of exploring volcanoes as sources of chemical elements used in electronic devices.

Quantum fields can notoriously violate the null energy condition (NEC). In a cosmological context, NEC violation can lead to, e.g., dark energy at late times with an equation-of-state parameter smaller than $-1$ and nonsingular bounces at early times. However, it is expected that there should still be a limit in semiclasssical gravity to how much `negative energy' can accumulate over time and in space as a result of quantum effects. In the course of formulating quantum-motivated energy conditions, the smeared null energy condition has emerged as a recent proposal. This condition conjectures the existence of a semilocal bound on negative energy along null geodesics, which is expected to hold in semiclassical gravity. In this work, we show how the smeared null energy condition translates into theoretical constraints on NEC-violating cosmologies. Specifically, we derive the implied bounds on dark energy equation-of-state parameters and an inequality between the duration of a bouncing phase and the growth rate of the Hubble parameter at the bounce. In the case of dark energy, we identify the parameter space over which the smeared null energy condition is consistent with the recent constraints from the Dark Energy Spectroscopic Instrument (DESI).

We search for signatures of extremely long-baseline oscillations between left- and right-handed neutrinos using the high-energy astrophysical neutrino spectra measured by IceCube. We assume the astrophysical neutrino sources to be distributed in redshift following the star formation rate and use the IceCube all-sky flux measurements from TeV to PeV energies. We find, for the first time, that $\delta m^2$ in the range $2\times 10^{-19}$ to $3 \times 10^{-18}\textrm{eV}^2$ is disfavored at the $3\sigma$ confidence level, while there exists a preference for a $\delta m^2$ of $1.9 \times 10^{-19}\textrm{eV}^2$ at $2.8\sigma$. This preference for quasi-Dirac neutrinos is driven by the tension between cascade and track measurements below $30~\textrm{TeV}$.

Nonlinear tails in black hole perturbations, arising from second-order effects, present a distinct departure from the well-known Price tail of linear theory. We present an analytical derivation of the power law indices and amplitudes for nonlinear tails stemming from outgoing sources, and validate these predictions to percent-level accuracy with numerical simulations. We then perform a perturbative analysis on the dynamical formation of nonlinear tails in a self-interacting scalar field model, wherein the nonlinear tails are sourced by a $\lambda \Phi^3$ cubic coupling. Due to cascading mode excitations and back-reactions, nonlinear tails with $t^{-l-1}$ power law are sourced in each harmonic mode, dominating the late time behavior of the scalar perturbations. In verification, we conducted numerical simulations of the self-interacting scalar model, including all real spherical harmonic (RSH) with $l\leq 4$ and their respective nonlinear couplings. We find general agreement between the predicted and numerical power law indices and amplitudes for the nonlinear tails, with the exception of $l=4$ modes, which display $t^{-4}$ power law instead of the predicted $t^{-5}$. This discrepancy is due to distortion in the source of the tails, which is caused by another nonlinear effect. These results establish nonlinear tails as universal features of black hole dynamics, with implications for gravitational wave astronomy: they may imprint observable signatures in merger remnants, offering novel probes of strong-field gravity and nonlinear mode couplings.

In axion electrodynamics, magnetic fields enable axion-photon mixing. Recent proposals suggest that rotating, conductive plasmas in neutron star magnetospheres could trigger axion superradiant instabilities -- an intriguing idea, given that such instabilities are typically associated with rotating black holes. In this work, we extend these investigations by properly incorporating plasma dynamics, particularly the plasma-induced photon effective mass, which suppresses the axion-photon mixing. Using two toy models for the conductive regions in the magnetosphere and accounting for fluid dynamics in both the frequency and time domain, we show that typical astrophysical plasma densities strongly inhibits the axionic instability. While our results assumes flat spacetime, the conclusions also apply to axion bound states in curved spacetimes, making neutron star superradiance less viable than previously thought. As a byproduct of our work, we provide a detailed description of axion electrodynamics in dissipative plasmas and uncover phenomena such as low-frequency axion "tails" and axion-induced electrostatic fields in dense plasmas.

The transition from the end of inflation to a hot, thermal Universe, commonly referred to as (re)heating, is a critical yet often misunderstood phase in early Universe cosmology. This short review aims to provide a comprehensive, conceptually clear, and accessible introduction to the physics of (re)heating, tailored to the particle physics community. We critically examine the standard Boltzmann approach, emphasizing its limitations in capturing the intrinsically non-perturbative and non-linear dynamics that dominate the early stages of energy transfer. These include explosive particle production, inflaton fragmentation, turbulence, and thermalization; phenomena often overlooked in perturbative treatments. We survey a wide range of theoretical tools, from Boltzmann equations to lattice simulations, clarifying when each is applicable and highlighting scenarios where analytic control is still feasible. Special attention is given to model-dependent features such as (pre)heating, the role of fermions, gravitational couplings, and the impact of multifield dynamics. We also discuss exceptional cases, including Starobinsky-like models and instant (pre)heating, where (re)heating proceeds through analytically tractable channels without requiring full non-linear simulations. Ultimately, this review serves both as a practical guide and a cautionary tale, advocating for a more nuanced and physically accurate understanding of this pivotal epoch within the particle physics community.

We study a massive-photon electrodynamics and magnetohydrodynamics (MHD) in the curved spacetime of Einstein's gravity. We consider a Proca-type photon mass and present equations in terms of electric and magnetic (EM) fields and the vector potential. We present the electrodynamics and MHD in the covariant and ADM formulations valid in general spacetime and in linearly perturbed cosmological spacetime. We present wave equations assuming the metric variations are negligible compared with the field variations. Equations are derived without fixing the temporal gauge condition and the gauge transformation properties of the EM fields and the vector potential are presented. Using the post-Newtonian approximation we show the dark Proca field behaves as dust in the non-relativistic limit under the Klein transformation.

Axions and other very weakly interacting slim (with $m <$ 1 GeV) particles (WISPs) are a common feature of several extensions of the Standard Model of Particle Physics. The search of WISPs was already recommended in the last update of the European strategy on particle physics (ESPP). After that, the physics case for WISPs has gained additional momentum. Indeed, WISPs may provide a new paradigm to explain the nature of dark matter and puzzling astrophysical and particle physics observations. This document briefly summarizes current searches for WISPs and the perspectives in this research field for the next decade, ranging from their theoretical underpinning, over their indirect observational consequences in astrophysics, to their search in laboratory experiments. It is stressed that in Europe a rich, diverse, and low-cost experimental program is already underway with the potential for one or more game-changing discoveries. In this context, it is also reported the role of the EU funded COST Action ''Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments'' (CA21106, this https URL) in coordinating and supporting WISPs searches in Europe, shaping a roadmap to track the strategy to guarantee a European leadership in this field of research. This document has been submitted in March 2025 as an input to the update process of the ESPP.

Indene (C$_9$H$_8$) is the only polycyclic pure hydrocarbon identified in the interstellar medium to date, with an observed abundance orders of magnitude higher than predicted by astrochemical models. The dissociation and radiative stabilization of vibrationally-hot indene cations is investigated by measuring the time-dependent neutral particle emission rate from ions in a cryogenic ion-beam storage ring for up to 100~ms. Time-resolved measurements of the kinetic energy released upon hydrogen atom loss from C$_9$H$_8^+$, analyzed in view of a model of tunneling through a potential energy barrier, provides the dissociation rate coefficient. Master equation simulations of the dissociation in competition with vibrational and electronic radiative cooling reproduce the measured dissociation rate. We find that radiative stabilization arrests one of the main C$_9$H$_8$ destruction channels included in astrochemical models, helping to rationalize its high observed abundance.

The fact that no Hawking radiation from the final stages of evaporating primordial black holes (PBHs) has yet been observed places stringent bounds on their allowed contribution to dark matter. Concretely, for Schwarzschild PBHs, i.e., uncharged and non-rotating black holes, this rules out black hole masses of less than $10^{-15} M_{\odot}$. In this article, we propose that by including an additional 'dark' $U(1)$ charge one can significantly lower the PBHs' Hawking temperature, slowing down their evaporation process and significantly extending their lifetimes. With this, PBHs again become a viable option for dark matter candidates over a large mass range. We will explore in detail the effects of varying the dark electron (lightest dark charged fermion) mass and charge on the evaporation dynamics. For instance, we will show that by allowing the dark electron to have a sufficiently high mass and/or low charge, our approach suppresses both Hawking radiation and the Schwinger effect, effectively extending even the lifespan of PBHs with masses smaller than $10^{-15} M_{\odot}$ beyond the current age of the universe. We will finally present a new lower bound on the allowed mass range for dark-charged PBHs as a function of the dark electron charge and mass, showing that the PBHs' mass can get to at least as low as $10^{-24}M_\odot$ depending on the dark electron properties. This demonstrates that the phenomenology of the evaporation of PBHs is ill-served by a focus solely on Schwarzschild black holes.

In this paper, we investigate the production of Majorana fermionic dark matter (DM) via the Higgs portal, considering both freeze-in and freeze-out mechanisms during and after the post-inflationary reheating phase. We assume that the Universe is reheated through the decay of the inflaton into a pair of massless fermions. Our analysis focuses on how the non-standard evolution of the Hubble expansion rate and the thermal bath temperature during reheating influence DM production. Additionally, we examine the impact of electroweak symmetry breaking (EWSB), distinguishing between scenarios where DM freeze-in or freeze-out occurs before or after EWSB. We further explore the viable DM parameter space and its compatibility with current and future detection experiments, including XENONnT, LUX-ZEPLIN (LZ), XLZD, and collider searches. Moreover, we incorporate constraints from the Lyman-$\alpha$ bound to ensure consistency with small-scale structure formation.