Papers for Wednesday, Apr 01 2026

Artificial intelligence is projected to increase U.S. data centre power demand beyond 100 gigawatt by 2035 and global demand toward 1 terrawatt. In response, companies and governments have proposed placing computing infrastructure in sun-synchronous low-Earth orbit, where continuous sunlight could supply electrical power. Generating 5 GW would require solar arrays 4 x 4 kilometers in size. Although technically feasible, such structures at roughly 500 km altitude would dramatically alter both the night and daytime sky. A 4 x 4 km array in low earth orbit would span about 0.4 degrees, comparable to the Moon, and reflected sunlight would make it shine at magnitude g = -5 to -7 mag, 100 times brighter than the brightest stars. Dozens of these structures would appear as a north-to-south chain of industrial objects across the sky, visible for about 1 1/2 hours after sunset and 1 1/2 hours before sunrise. They would block stars, planets, and deep-sky objects for minutes at a time, while increasing the likelihood of collisions that could trigger runaway debris production. These orbiting computing facilities therefore pose serious astronomical, technical, and cultural concerns.

Nine impact craters on Mercury bear the names of Persian-Tajik poets: Rudaki, Saadi, Nizami, Rumi, Navoi, Firdousi, Hafiz, Sanai, and Mahsati. We compile IAU-approved coordinates, diameters, quadrant designations, approval dates (1976--2025), and MESSENGER-derived geological characteristics for each crater, and place these data in the broader context of Solar System objects associated with Tajik-Persian civilisation, including lunar craters (Al-Biruni, Avicenna, Omar Khayyam, Abul Wafa, Nasireddin, Alfraganus, Azophi, Al-Khwarizmi), main-belt asteroids, and Enceladus surface features named from the One Thousand and One Nights. The approval timeline mirrors the successive stages of Mercury mapping: two craters were designated after Mariner 10 (1976), three more following Mariner 10 data analysis (1979, 1985), two after the first MESSENGER flybys (2008, 2010), two after MESSENGER orbital operations (2014), and one in 2025. Geological diversity is notable: the Sanai basin (490 km, ~3.8--3.9 Ga) is among the oldest large structures on Mercury; Firdousi shows lava-flooded floor morphology; Rumi hosts an explosive pyroclastic vent intersected by Palmer Rupes; Hafiz contains low-reflectance material and hollows; Navoi is a pit-floor crater; and Nizami exhibits polygonal wall geometry. These results illustrate how planetary nomenclature serves as a stable, internationally maintained record of cultural heritage.

The observed large-scale structure of the Universe is not a direct measure on the underlying distribution of matter. These observations are subtly distorted by gravitational lensing effects, which leave imprints on the statistical distribution of galaxies and offer powerful test of general relativity. In this work, we investigate whether HI intensity mapping from current and forthcoming surveys can improve constraints on magnification lensing obtained from photometric galaxy surveys. In particular, can we jointly constrain the magnification bias parameters $s^\mathrm{G}(z)$ and the amplitude of the Weyl potential, which we parametrise as $\beta$. We employ a Fisher matrix formalism in order to estimate future constrains on the magnification biases and $\beta$. We forecast constraints for three photometric surveys (DES-like, LSST-like, Euclid-like) individually and with two HI intensity mapping surveys (MeerKLASS, SKAO). We apply the multi-tracer technique by combining each galaxy survey with each HI survey, exploiting the combined constraining in the overlapping sky area. The multi-tracer approach dramatically improves constraints on $\beta$ by factors of 25 to 50, depending on the surveys considered. For $s^\mathrm{G}(z)$, improvements can be marginal or by a factors of 2 to 8. We also verify that $\beta$ and $s^\mathrm{G}(z)$ can be constrained simultaneously as the cross-correlations between tracers break the degeneracies among them. We conclude that the multi-tracer combination of photometric galaxy surveys and HI intensity mapping surveys enables high-precision measurements of both $s^\mathrm{G}(z)$ and $\beta$. This opens an additional pathway to constrain $\Phi+\Psi$ and test the validity of general relativity on cosmological scales.

Modern numerical models are increasingly complex, opaque, and computationally expensive, yet frequently fail to predict even qualitative features of observed phenomena. We propose a new paradigm, Declarative Bespoke Modelling, in which the modeller explicitly declares the relationship between model inputs and outputs. We demonstrate that this approach achieves perfect predictive accuracy, unconditional numerical stability, and complete interpretability. It represents a natural endpoint of contemporary modelling practice and near-zero CO2 emission.

The TESS Input Catalog (TIC) was built on Gaia Data Release 2 (DR2). To date, there has not been an update to the TIC to incorporate Gaia Data Release 3 (DR3) IDs. In this Research Note, we outline how we cross-matched the TIC with Gaia DR3 IDs, its immediate applications to exoplanet research, and lessons learned when dealing with such large data sets. A full TIC/Gaia DR3 cross-match table is available for download on the Exoplanet Follow-up Observing Program (ExoFOP) website, and a Jupyter Notebook with instructions to reproduce the table is available on GitHub.

The mass in the Universe is distributed non-uniformly, originating the Large Scale Structure (LSS), characterised by clusters, filaments, walls and voids. Galaxies in voids are bluer, later type, less massive, and have slower evolution than galaxies in denser environments. The effect of the void environment on properties such as star formation rate (SFR) is still under discussion. We tackle this by estimating spatially-resolved SFR from extinction-corrected Halpha luminosities of 220 void galaxies from the CAVITY survey. These observations consist of optical integral field unit data cubes from the PMAS/PPaK spectrograph at Calar Alto Observatory. We measure the continuum-subtracted emission lines to obtain maps of SFR, specific star formation rate (sSFR) and extinction. We assess global properties and radial profiles up to 2 half-light radii. We compare with galaxies in filaments and walls from the CALIFA survey using the same methodology, building a control sample matched in morphology and stellar mass. We find no significant differences in SFR and sSFR, although void galaxies tend to have larger SFR, especially for early spirals. This effect is present for Sa galaxies at all galactocentric distances, and in the outer parts of late-type spirals, evidencing slower transition to quiescence and less evolved discs. Void late-type galaxies have lower extinction. Using extinction normalised by stellar mass surface density as a proxy for gas mass fraction, we find it larger for void early spirals, especially in outer regions. This indicates the effect of the void environment on the transition from star forming to passive.

In a series of papers on lensed kinematics, we seek to combine the sensitivity of 3D forward modelling to low signal-to-noise ratio outskirts with the enhanced spatial resolution of cluster lensing. In this first paper, we (i) present and validate our methodology, which directly constrains the source parameters by incorporating lensing deflections into the $\texttt{GalPaK}^\texttt{3D}$ forward-modelling algorithm, and (ii) investigate the evolution of the stellar-mass and baryonic-mass Tully-Fisher relations (sTFR and bTFR) since $z \sim 1$. We define a robust sample of strongly lensed star-forming galaxies (SFGs) from the MUSE Lensing Cluster survey, spanning magnifications $\mu = 1.4 - 12.4$ and stellar masses $M_\star = 10^{8.1} - 10^{10.3} M_\odot$. Using a series of mock galaxies, we find that our method is significantly more reliable at recovering morpho-kinematic properties than approaches that ignore differential magnification, even for relatively modest magnifications ($\mu < 6$). Restricting the analysis to 95 rotationally supported SFGs with well-constrained velocities, we find a significant evolution of the sTFR zero-point ($\Delta b^\mathrm{sTFR} = -0.42^{+0.05}_{-0.05}~\mathrm{dex}$ in stellar mass) but no detectable evolution of the bTFR zero-point ($\Delta b^\mathrm{bTFR} = 0.00^{+0.06}_{-0.06}~\mathrm{dex}$ in baryonic mass) relative to $z \approx 0$. Our results are consistent with a mild evolution of the stellar-to-halo mass ratio and support the view that the sTFR has evolved only weakly over the past $\sim 8$ Gyr, aside from shifts driven by the redshift dependence of halo-defining quantities such as the critical density and overdensity. The absence of detectable evolution in the bTFR zero-point suggests that the increasing contribution of cold gas mass at higher redshift fully compensates the evolution observed in the stellar component alone. [abridged]

Gravitational waves may set the spin frequencies of neutron stars in low-mass X-ray binaries (LMXBs). One mechanism for facilitating such emission is the formation of a mass asymmetry - or 'mountain' - supported by elastic strains driven by thermal gradients. Most studies have focused either on the origin of the elastic strains or the temperature asymmetry in isolation, and have not considered the entire formation process. In previous work, we showed that anisotropic heat transport in magnetised accreting neutron stars can source a significant temperature asymmetry, and made rough estimates that suggested temperature-induced perturbations in the pressure supplied by the crustal lattice may be competitive with the widely known model of temperature-induced capture-layer shifts. In this paper we carry out detailed calculations to properly explore this scenario. We self-consistently calculate both the temperature asymmetries, the perturbations in crustal lattice pressure, and the mass asymmetries within a single framework. For the first time, we make use of the set of realistic equations of state from the Brussels-Montreal nuclear energy-density functionals BSk19, BSk20, and BSk21 which describe all regions of accreting neutron stars in a thermodynamically consistent, unified way. We find these mountains are too small to be dictating the spin-equilibrium of LMXBs, and estimate the level of gravitational wave emission they produce.

We investigate the impact of galaxy mergers on the circumgalactic medium (CGM) using the FIREbox cosmological hydrodynamic simulation. By comparing matched samples of merging and isolated galaxies with stellar masses $M_\star \sim 10^{10}$--$10^{11} M_{\odot}$ at $z=0$ and mass ratio of merging galaxies larger than $1:10$, we find that mergers significantly alter CGM properties. Merging systems exhibit enhanced radiative cooling, leading to shorter cooling times than free-fall times across large CGM volumes. This results in amplified multiphase structure and increased cool/cold gas content ($T \sim 10^4K$) compared to isolated galaxies. Both inflow and outflow mass fluxes are elevated by at least $\sim$1 dex in mergers across all temperature phases, with cool gas primarily generated in-situ via radiative cooling rather than from pre-existing streams. Gas cycling analysis reveals that mergers fundamentally accelerate CGM processing, amplifying the effective transfer rate from cold/cool cosmic inflow to galaxy inflow by factors of $\sim 30$, through rapid cycling of inflowing gas through intermediate CGM phases, efficiently fueling the ISM and star formation. The enhanced cool gas content in mergers produces elevated column densities for low- and intermediate-temperature ion species in the inner CGM, while high-temperature ones remain largely unaffected.

For decades, astronomers have been searching for bright radio sources deep into the epoch of reionization (EoR). The most distant, powerful radio sources are expected to reside in heavily dust-obscured galaxies, exceedingly faint at optical and infrared wavelengths. Motivated by this, I systematically cross-match radio and JWST source catalogs in the COSMOS field and identify a uniquely JWST-dark radio source: the only object undetected in every JWST band, yet clearly detected in radio data from LOFAR 144 MHz to the VLA 3 GHz. The source is only marginally resolved and shows a steep, unbroken radio spectrum, while remaining undetected in all available HST, JWST, Chandra, Herschel, and ALMA imaging. It may represent an extremely dust-obscured radio-loud source at cosmic dawn, or alternatively a detached radio lobe whose host galaxy lies elsewhere. In either case, it highlights the new discovery space at the intersection of deep radio surveys and JWST imaging.

The role of cooling gas in triggering active galactic nucleus (AGN) feedback in the centers of galaxy groups and clusters remains a key open question. NGC 5044, the X-ray brightest galaxy group, hosts the largest known reservoir of molecular gas among cool-core groups and exhibits multiple AGN outbursts, making it an ideal system to study AGN feeding. We present new multi-frequency Very Long Baseline Array (VLBA) observations of NGC 5044 at 1.4 GHz, 4.9 GHz, and 8.4 GHz, combining continuum imaging with HI spectroscopy. At 1.4 GHz, we recovered the previously known symmetric northeast-southwest jets extending for 5.5 pc each, along with evidence for previously undetected, more extended faint emission aligned with the older, kpc-scale outbursts. Comparison of 4.9 GHz and 8.4 GHz data from 2020 and 2024 reveals clear outward proper motion of jet components, yielding an average expansion speed of $(0.10\pm0.02)\,c$ and implying a dynamical age of $\sim$180 yr for the ejection of the parsec-scale jet components. The jet width profile suggests a transition from parabolic to conical collimation at a few $\times 10^{4}$ Schwarzschild radii. We detect a narrow, redshifted HI absorption line at $+264\,\mathrm{km\,s^{-1}}$ against the VLBA core, tracing a compact, cold atomic cloud within $\sim$10-20 pc of the AGN. The close velocity correspondence with previously detected CO and HI absorption features in ALMA and MeerKAT data, respectively, demonstrates that cold atomic and molecular gas coexists in infalling clouds at parsec scales. Overall, these results provide an unprecedented high angular resolution view of AGN cycling, jet growth, and feeding in a galaxy group environment.

HD 98800 is a nearby hierarchical quadruple system comprising two binaries orbiting each other. Surprisingly, despite its $\sim$ 10 Myr age and dynamic environment, the Ba-Bb component is surrounded by a compact gas-rich disc in a polar configuration. Previous millimetre continuum observations of this disc found a low millimetre spectral index ($\alpha \sim$ 2.1 up to 9 mm), potentially arising from large dust grains, optically thick emission, or both. Furthermore, the interpretation was complicated by emission mechanisms other than dust thermal continuum at longer wavelengths. We present new observations of this system with the Very Large Array (VLA) at 6.8 mm and 3 cm, providing crucial additional sampling of the emission at millimetre/centimetre wavelengths. By combining these with ancillary data, we derive a dust spectral index $\alpha_{\rm dust} <$ 3 for wavelengths $\le$ 1 cm. Our modeling suggests that the emission is optically thick at short millimetre wavelengths ($\lambda \le$ 3 mm) and it becomes at least partially optically thin for the VLA observations. The shallow spectral index thus indicates the existence of large grains in the disc. We also identify gyro-synchrotron emission from the A and B components at $\lambda \gtrsim $ 3 cm. The VLA images also reveal an azimuthal asymmetry at 6.8 mm and 8.8 mm, which is not present in high-resolution ALMA 1.3 mm data. After ruling out geometric and illumination effects, we interpret this asymmetry as a local dust overdensity, possibly induced by a vortex or a relic of the previous passage of the A component.

Wide (soft) binaries are expected to be rapidly disrupted in dense stellar environments, yet they are observed in both the Galactic field and open clusters (OCs). In this paper, we investigate the formation and disruption of wide binaries in star clusters using direct N-body simulations. We perform simulations containing 10,000 objects with varying binary fractions and initial bulk rotation to give an in-depth look into the dynamical evolution of wide binaries in star clusters. We find that wide binaries dominate early disruption and formation processes during the initial high-density phase of cluster evolution. We propose two semi-analytical models to reproduce the evolution of the wide-binary population in simulations. The exponential model consists of an early, rapid-disruption phase with a time less than 10 Myr, driven by frequent encounters at high density, and a longer, relaxation-driven phase between 200 and 300 Myr. The broken power-law model provides break timescales when the decrease of wide binaries slows down during the early and long-term disruption. All timescales from both models agree with each other and decrease with increasing stellar density induced by high primordial binary fraction and cluster rotation. Wide binary disruption is mostly responsible for the early decline in the total binary fraction of the cluster. Such disruption leads to the decrease of radial binary fraction toward the cluster center until 500 Myr. Our results suggest low-density OCs or stellar groups younger than 10 Myr as the optimal environments for detecting wide binaries and provide a physical framework for understanding their contribution to the Galactic field population.

The search for habitable planets, and even for ``Earth 2.0'', is a major driver in contemporary astronomy. However selecting target fields to prioritise for such searches presents a challenge. Here we establish a statistical analysis of the appearance of constellation names in science fiction magazines of the pulp era, evaluating the most commonly mentioned constellations and thus those which the science fiction community collectively identify as the most likely locations to find life. Given that the predictive power of science fiction is well established, we suggest that these locations might be prioritised by searches for extrasolar biospheres.

Targeted searches for pulsars based on their counterparts in radio images have resulted in the discovery of interesting pulsars including the first ever discovered millisecond pulsar (MSP). We are conducting an image-based pulsar survey, survey of compact sources for pulsars and exotic objects (SCOPE), that utilizes interferometric as well as time-domain observations to search for radio pulsations as well as characterize the sources in the image-domain to identify their true nature. In the first stage of the SCOPE survey, we have used the Giant Metrewave Radio Telescope (GMRT) and the Green Bank Telescope (GBT) to follow up a sample of 31 compact and steep-spectrum sources. We provide an overview of the survey, the sample selection, the search procedures, and present discoveries of two MSPs -- J1840+1102 and J1827-0849. J1840+1102 is a 1.6 ms pulsar at the edge of the Scutum-Centaurus arm, while J1827-0849 is the radio counterpart of a gamma-ray pulsar that was earlier thought to be radio-quiet, and both the sources have very steep radio spectra. Using the interferometric data, we also provide a morphological classification of all the sources, model and characterize their spectra and identify the resolved, extragalactic sources in our sample. We discuss these results in the context of future image-based pulsar surveys.

Exoplanet atmospheres are usually discussed as tracers of climate, chemistry, and habitability, but they may also preserve signatures of planetary defense. We consider three folklore-motivated deterrents against monsters: reduced organosulfur gases as anti-hematophage repellents, argentiferous reflective aerosols as anti-lycanthropic countermeasures, and haline aerosols as a counting problem for specters. We show that globally-mixed garlic-smelly levels of DMS/DMDS could produce observable mid-infrared transmission features, that silver hazes would show up as anomalous optical brightening, and that sea-salt lofting sustained by strong near-surface winds appears as muted spectra. None of these signatures is unique, which is precisely the observational challenge. A defended world may first appear merely sulfur-rich, bright, or hazy. Therefore, some atmospheres may encode not only biosignatures, but also evidence that the local biosphere has stopped being afraid of the dark.

Exhaustion and brain fog during long nights observing is common, but can be ameliorated by raising one's blood sugar. In this white paper, we present a prototype method for facilitating a sugar rush during late-night crashes, which has the potential to boost observing productivity.

Aims: We characterize the mid-infrared spectrum of the outer regions of the Red Rectangle nebula to probe the carbonaceous dust and molecular content beyond the circumbinary disk. Methods: We present JWST MIRI-MRS observations of the SW whisker, extracted from three distinct environments: the biconical outflow, the whisker itself, and the shadow region outside the outflow. We compare these with an archival ISO-SWS observation of the inner nebula. Results: The JWST spectra display only classical AIB emission on a weak dust continuum, with no signatures of the oxygen-rich circumbinary disk mineralogy nor of the rich molecular emission seen at optical wavelengths. The AIBs are predominantly Class A - in marked contrast to the exclusively Class B profiles previously reported for the inner regions - with systematic differences between the outflow and shadow regions pointing to environmentally driven PAH processing.

The location of the hydrogen-helium (H/He) immiscibility boundary controls whether and where helium rain occurs in giant planets, yet it remains uncertain because high-pressure experiments are challenging and ab initio simulations are limited in system size and simulation time. We map this boundary by computing composition-dependent chemical potentials from large-scale molecular dynamics driven by machine learning potentials trained on three density functional approximations (PBE, vdW-DF, and the hybrid HSE). The three functionals yield consistent immiscibility boundaries, and the demixing temperatures are typically ~2000 K lower than previous ab initio simulations using small system sizes across the pressure range of 100-1000 GPa. Fitting the H/He mixing free energy to a Redlich-Kister regular solution model rationalizes the thermodynamic driving force for phase separation and provides a predictive representation of the boundary. Comparison with current planetary interior profiles indicates that helium rain is plausible in Saturn but unlikely in the warmer interior of Jupiter. Our results narrow the uncertainty in the H/He immiscibility boundary and provide inputs for planetary models that couple demixing, heat transport, and composition gradients in gas giants.

The hierarchical multiple system XY Leo, despite nearly 90 yr of observations, remains enigmatic. It offers a unique testbed for close binary evolution, involving processes such as mass transfer, angular momentum loss, and the von Zeipel--Kozai--Lidov (ZKL) mechanism. Previously identified as a quadruple system, XY Leo shows long-term orbital period modulations. Our new ground-based and Transiting Exoplanet Survey Satellite data suggest that these may stem from either magnetic cycles or the influence of an unseen companion. While the latter remains speculative, both scenarios are discussed within a unified framework. Using all available photometric and spectroscopic data, we derived ultraprecise physical parameters for the contact binary XY Leo A as $M_{\rm A1}=0.629\pm0.009\,M_{\odot}$, $M_{\rm A2}=0.865\pm0.012\,M_{\odot}$, $R_{\rm A1}=0.739\pm0.007\,R_{\odot}$, $R_{\rm A2}=0.855\pm0.008\,R_{\odot}$, $L_{\rm A1}=0.271\pm0.026\,L_{\odot}$, $L_{\rm A2}=0.288\pm0.030\,L_{\odot}$, and orbital separation $a_{\rm A}=2.078\pm0.010\,R_{\odot}$, based on simultaneous solutions of light and radial velocity curves. The detached binary subsystem XY Leo B is confirmed to be on a wide $\sim 20$-year orbit around the contact system. A second $\sim 23$-year modulation is also detected, which may arise from either stellar magnetic activity or an additional unseen companion. After removing both trends, a coherent residual modulation with a characteristic timescale of $14.2 \pm 0.8$~yr remains in the $O$--$C$ diagram, consistent with a magnetic activity cycle of Applegate type. We modeled XY Leo A with the Cambridge STARS (EV/TWIN) code under non-conservative evolution, finding strong agreement between the tracks and observed parameters, highlighting the system's value for testing multiple-star evolution.

Informative data visualization methods are key to the clear and efficient communication of myriad forms of data. The PASTA Collaboration has made substantial contributions to the field of data visualization through $\mathtt{pastamarkers}$, a Python-based package that utilizes various types of pasta as data markers to create engaging plots. This work introduces $\mathtt{GF \ pastamarkers}$, an extension of $\mathtt{pastamarkers}$ that utilizes the tenuous structure of gluten free (GF) pasta to meet the needs of the GF population. The implementation of $\mathtt{GF \ pastamarkers}$ employs an exponential crumbling factor ($CF$), which benefits authors by encouraging clearer and more concise scientific articles, thereby leading to more effective manuscripts and proposals.

The heating, ventilation and air conditioning systems serving the experimental halls of the Virgo gravitational wave interferometer generate low-frequency noise - namely below 100 Hz - of seismic, acoustic, and electromagnetic origin. Such disturbances have repeatedly affected the interferometer sensitivity throughout its operational history, with particularly notable impacts during the third observing run. In preparation for the fourth run, a comprehensive investigation was carried out to identify the most critical noise sources within this infrastructure and to trace their transmission paths into the experimental areas. This manuscript presents the methodology and results of the noise characterization campaign, together with the design, implementation and assessment of targeted mitigation measures. The technical solutions adopted, along with the operational best practices developed, provide valuable guidance for the design of low-noise environments in future gravitational-wave observatories.

Aims: This work proposes a new SETI search methodology under the assumption that a sufficiently advanced civilization could skip the middle man of converting starlight to energy to food preparation, and could directly harness their star's energy for food prep. Methods: We define the concept of the Flavor Zone (FZ): the optimal distance from a star for cooking food. To develop this definition we propose the toy model of a Digiorno-Like Object (DLO) and define the FZ as the regime for optimal cooking according to package directions. We examine the effect of orbit on DLO cooking times and paradigms. Finally, we study the feasibility of detection of DLOs in their FZs with current technology. Results: We determined that DLOs aren't detectable with current technology nor should anyone ever try.

This study presents the first high-resolution, high-sensitivity mid-infrared (MIR) investigation of protoplanetary disks in a low-metallicity environment, using JWST/NIRCam and MIRI observations of Digel Cloud 2, a star-forming region in the outer Galaxy ($D \simeq 8$ kpc, ${\rm [M/H]} \simeq -0.7$ dex). It hosts two very young ($\sim$0.1 Myr) embedded clusters, Cloud 2-N and Cloud 2-S, offering a window into disk evolution under conditions analogous to the early universe, where low metallicity implies reduced dust content. Imaging across 1-20 $\mu$m, including F770W and complementary bands (F356W, F444W, F405N), enables probing disk properties with unprecedented spatial resolution and stellar mass sensitivity down to $\sim$0.1 $M_\odot$. Among 89 and 95 sources detected in F770W in Cloud 2-N and 2-S, respectively, we identify candidate stellar-mass cluster members using infrared photometry, from which stellar mass and extinction are estimated. Among these, $\simeq$75 % retain optically thick disks in both clusters based on MIR SED slopes, consistent with similarly aged solar-metallicity regions. In contrast, a lack of 2 $\mu$m excess suggests diminished inner disk emission, possibly due to enhanced silicate grains with low sublimation temperatures. Using the F405N narrow-band filter covering Br$\alpha$, we detect accretion signatures in $\simeq$35 % of sources selected by extinction criteria, with rates $\gtrsim$10$^{-6}$ $M_\odot$ yr$^{-1}$, comparable to or exceeding those in nearby low-mass stars. Brown dwarf candidates, identified across multiple bands including F770W and shorter wavelengths, exhibit a high disk fraction of $\sim$75 %, indicating robust disk retention across mass ranges even under low-metallicity conditions.

The most direct method of measuring the star formation rate is with young stellar objects (YSOs), but this requires high-resolution observations and high-quality models. Using the latest YSO radiation transfer and stellar evolution models, we have developed a population synthesis code that generates model YSO populations that can be observed by JWST. We combine these model populations with principal component analysis (PCA) and maximum likelihood fitting to create a complete framework for predicting the age and mass of YSO populations. We dub this combination of Population synthesis and PCA, PxP, and show that it is effective at predicting mass and age with self-fitting tests. We apply PxP to the Spitzer identified YSOs in N44 and find a mass of (1.1+-0.1)*10^4 M_sun and an age of 0.74^{+0.06}_{-0.03} Myr, consistent with previous work. Next, we identify 112 YSO candidates in the archival JWST observations of NGC 604. Applying PxP to this newly identified population we find a mass of (2.2+-0.2)*10^4 M_sun and an age of 0.62+-0.01 Myr. This first look at this framework demonstrates its effectiveness with a specific set of models and leaves clear opportunities for future exploration. PxP allows us to directly determine the recent (<3~Myr) star formation history, giving an unprecedented look at the effect of the large-scale environment on individual star formation.

Multiple formation pathways have been proposed for the origin of binary black holes (BBHs). These include isolated binary evolution and dynamical assembly in dense stellar environments such as nuclear or globular star clusters. Yet, the fraction of BBHs originating from each channel still remains uncertain. One way to constrain this fraction is by investigating the distribution of the orbital eccentricities of the BH coalescences detected by the LIGO-Virgo-KAGRA (LVK) Collaboration. In this work, we analyze 85 BBHs from the first part of the fourth LVK observing run (O4a) using a multipolar, eccentric, aligned-spin effective-one-body waveform model. We perform parameter inference with neural posterior estimation and nested sampling. After incorporating astrophysical prior odds and comparing to the quasicircular precessing-spin hypothesis, we find that no candidates reach a high enough statistical significance to claim a confident detection of eccentricity. We use these upper limits to explore a particular model, in which all O4a BBHs originate from single-single gravitational wave (GW) captures. We perform hierarchical inference on the velocity dispersion of the host environment and find $\sigma < 24.3\,\mathrm{km/s}$ (95% credible upper bound). This disfavors single-single capture in nuclear star clusters (~20-200 km/s) as the dominant source of all observed BBH mergers. We verify that this dispersion bound does not increase by repeating the inference on a synthetic catalog augmented with eccentric events motivated by analyses of the third observing run of the LVK (O3). Our results place improved constraints on the number of eccentric BBHs and highlight the importance of eccentricity measurements in disentangling compact-binary formation channels in current and future GW detectors.

We investigate the evolution of dark matter halo spin alignments with respect to cosmic filaments, exploring how halo mass, proximity to filaments, and major mergers influence their orientation over time. We perform a suite of dark matter-only zoom-in N-body simulations centered on ten filaments extracted from a cosmological box using the 1DREAM structure finder. This approach allows us to resolve low-mass halos within filaments while preserving the large-scale environment. Halos are identified with the Amiga Halo Finder (AHF), and their evolutionary histories are reconstructed to trace the spin, shape, and distance to the filament from redshift $z = 1$ to $z = 0$. We confirm a strong mass-dependent alignment signal: low-mass halos tend to align parallel to the filament, while high-mass halos preferentially exhibit perpendicular orientations, despite limited statistics. Perpendicular alignments become dominant at the highest halo masses in our sample, around $\log_{10}(M_\mathrm{h}/h^{-1}\mathrm{M_\odot}) \sim 12$. We also find that major mergers can induce sharp spin reorientations and temporary transitions toward more prolate halo shapes, particularly in massive halos located near the filament core, suggesting a preferential merger direction within filaments. Overall, halo mass emerges as the primary factor governing spin-filament alignments in our sample. By analyzing the global evolution, we find that the average orientations at z = 0 do not differ significantly from those at $z = 1$, indicating that the present-day spin configuration is largely established at earlier stages of halo evolution. Major mergers, although relatively rare, represent one of the few mechanisms capable of disrupting this initial alignment.

Large Language Models (LLMs) are now widely used in astrophysics, but do they actually make our lives easier, or do they merely invent new physics with enough confidence to hide a minus sign? In a specialized field where checking fluent hallucinations is itself labor-intensive, AI assistance can demand as much work as the task it claims to simplify. To evaluate where AI genuinely improves scientific workflows, we bypassed human trials and instead forced AI agents to cosplay as astrophysicists. We simulated 144 synthetic researchers, varying in career stage, AI awareness, and willingness to verify outputs, across 2,592 daily astrophysics research assignments. Comparing solo work against four styles of AI assistance produced 12,960 scored episodes. No assisted policy universally outperformed unassisted work in the primary Qwen production run. Instead, performance depends strongly on the task, the style of AI use, and the identity of the actor. While cautious assistance helps on creative, extractive, and critique-oriented tasks, it can fail catastrophically on derivation-heavy physics. A full actor-swap DeepSeek rerun changes that picture materially: verification-heavy use becomes the strongest assisted policy, two assisted modes enter the higher-utility/lower-risk quadrant, and the derivation-heavy fragility that dominates the Qwen production run largely disappears. In its current form, AI is useful, but only conditionally, its value is uneven, task-specific, and shaped jointly by workflow, usage policy, and which LLM you are using.

We present HST WFC3/UVIS F275W near-UV imaging of 91stripped-envelope supernovae (SE SNe; Types IIb, Ib, Ic) from Snapshot program SNAP-16657, observed at phases of 270-1845 days (median 952 days) after first optical detection. We detect UV counterparts in 13 SE~SNe, of which 6 are classified as secure and 7 as ambiguous after comparison to nearby H\textsc{ii} regions, interpreting the secure sources as signatures of interaction with circumstellar material (CSM). Independent WISE W1/W2 light curves show $>300$ day mid-IR excesses in two of the secure UV sources, corroborating the interaction interpretation, and reveal two additional IR-only candidates without UV counterparts, indicating dust-obscured interaction episodes missed by the UV survey. A forward-modeling MCMC analysis using a physics-based CSM interaction model with three free parameters, the interaction fraction $f_\mathrm{CSM}$, shell mass $M_\mathrm{CSM}$, and thickness fraction $f_\mathrm{thick}$, yields $f_\mathrm{CSM} = 0.23^{+0.17}_{-0.09}$, $M_\mathrm{CSM} \approx 0.013~M_\odot$, and $f_\mathrm{thick} \approx 0.07$. The inferred thin-shell geometry implies an ejection duration of $\sim$6 yr for an outflow velocity of $300$ km s$^{-1}$, two to three orders of magnitude shorter than the thermal timescale of stable Roche-lobe overflow. This result disfavors steady binary mass transfer as the origin of the detected CSM and instead points to eruptive pre-supernova mass ejection in the final years before core collapse, either from wave-driven outbursts or from mass transfer triggered by late-stage progenitor re-expansion.

Supernova (SN) shocks that originate from stars on orbits embedded in dense active galactic nuclei (AGN) accretion disks evolve differently from those that occur in the interstellar medium. We aim to assess how shocks evolve in this dense stratified medium and understand where SNe are muffled and have their kinetic energy absorbed by an AGN disk versus escaping. We use Sirko \& Goodman (SG) and Thompson, Quataert \& Murray (TQM) AGN disk models for midplane radial profiles, generated with the pAGN code; we compare the disk pressure to the energy of a standard core-collapse SN ($10^{51}\,{\rm erg}$) to find radii where shock breakout can occur. For verification, we evolve three-dimensional hydrodynamic shearing box simulations of stratified Gaussian disks constructed from the midplane values that are injected with energy and mass from SNe placed at multiple radii and vertical locations, using the Athena code. We find SN shocks in SG disks around black holes with mass $\Mbh=10^6\,\Msun$ become muffled beyond $R\sim10^6\,\Rs$, and that this muffling radius is inversely proportional to supermassive black hole (SMBH) mass with muffling occurring at $R\sim10^2\,\Rs$ for $\Mbh=10^9\,\Msun$. Around TQM disks, the muffling radius occurs at $R\sim10^6\,\Rs$, independent of $\Mbh$. The largest determining factor for muffling a SN shock is the local scale height of the AGN disk. In conclusion, we developed a predictive analytic criterion to identify where AGN disks can muffle SNe shocks depending on their density and vertical scale.

Unsharp-mask images of HI emission from 36 dwarf irregular (dIrr) galaxies illustrate star formation in dispersed clouds and on the rims of large cavities. The cavities can extend for a radial scalelength and typically have circular or slightly sheared forms. The average surface density of cloud peaks is ~20 Msun/pc2, and, combined with their average FUV star formation rate, suggests a gas consumption time of ~3.2 Gyr. Vertical hydrostatic equilibrium calculations for 24 of these dIrrs give a typical scale height of ~400 pc, which combines with the gas and star formation surface densities to suggest an efficiency per free fall time of ~1%. These values are comparable to those in the molecular clouds of spiral galaxies, suggesting the primary difference between clouds is the presence of CO at higher metallicity in the spirals. U-B color images of the dIrrs suggest that cavity ages range between 10^7 and 10^8 years, with the longer times explaining the common lack of bright OB associations in their centers and their low expansion speeds. Most are circular because the shear time exceeds 100 Myr, although some of the HI has spiral structure. These observations suggests that star formation in dIrrs proceeds slowly in a sequential fashion in dispersed clouds and on the periphery of giant cavities that move and expand during the ~50 Myr supernova era of the previous generation. In contrast, spiral galaxies have shear times 10 times shorter and more important stellar dynamics that compresses the gas into filaments.

Many low-mass stars like the Sun host periodic, oscillatory magnetic fields that lead to variable levels of stellar activity, driving space weather that affects the habitability and detection of exoplanets. Owing to the intrinsic difficulty in modeling stellar magnetohydrodynamics across scales, realistic numerical simulations of this process are very challenging, and developing reduced-order models is of interest. In this work, we develop a framework to recover such models directly from numerical data by using a combination of Dynamic Mode Decomposition (DMD) to identify coherent magnetic structures, and the Sparse Identification of Nonlinear Dynamics (SINDy) framework to model their dynamics. We compare these models to those obtained using the classic mathematical method of weakly nonlinear (WNL) analysis. This approach is implemented on a one-dimensional mean-field dynamo model that parameterizes the main components of a convective dynamo in a low-mass star -- helical convection and differential rotation. We recover oscillatory dynamo models as a function of the dynamo strength parameter $D\sim \alpha \Omega'$, magnetic dissipation parameter $\kappa$, and a comprehensive dynamo model that predicts the magnetic state for a combination of these two parameters. Our results suggest that equations discovered with SINDy are more robust than equations from WNL analysis, and can predict the saturation amplitude of magnetic fields in parameter regimes far from the onset of dynamo action characterized by stiff nonlinearities. This includes unstable, and typically unknown, subcritical branches. Further to this, SINDy is able to find equations in parameter regimes where the nonlinearity is not analytic and WNL analysis cannot be applied. These properties of data-driven SINDy models suggest them as a viable alternative for modeling of stellar dynamo cycles directly from the data.

Context. Random seed selection in deep learning is often arbitrary -- conventionally fixed to values such as 42, a number with no known feline endorsement. Aims. We propose that cats, as liminal beings with a historically ambiguous relationship to quantum mechanics, are better suited to this task than random integers. Methods. We construct a cat-driven seed generator inspired by the first Friedmann equation, and test it by mapping 21 domestic cats' physical properties -- mass, coat pattern, eye colour, and name entropy -- via a Monte ``Catlo'' sampling procedure. Results. Cat-driven seeds achieve a mean accuracy of 92.58%, outperforming the baseline seed of 42 by $\sim$2.5%. Cats from astrophysicist households perform marginally better, suggesting cosmic insight may be contagious. Conclusions. The Universe responds better to cats than to arbitrary integers. Whether cats are aware of this remains unknown.

Turbulence in protoplanetary disks plays a crucial role in the evolution of disk structures and the planet formation process therein. However, the strength of the turbulence remains unclear in young, embedded disks surrounded by infalling envelopes. In this paper, we present the first direct measurement of the nonthermal velocity dispersion within the embedded disk around HL Tau, which possesses a dusty disk with multiple rings and gap structures but is still associated with infalling gas flows from an envelope. Using ALMA archival data of the $\mathrm{H_2CO}$ emission, we measured the local line width through a parametric model fitting that accounts for the contribution of Keplerian shear motion. After subtracting the thermal component, the nonthermal velocity dispersion is $\sim\!\!0.15~\mathrm{km~s^{-1}}$ on average over radii of $80$-$180~\mathrm{au}$, and it slightly increases with radius. The estimated nonthermal motions correspond to a turbulent mach number of $\mathcal{M}\!\!\sim\!\!0.4$ or a viscous $\alpha$ value of $\alpha \!\!\sim\!\!0.16$, assuming that it is entirely caused by turbulence and $\alpha \!\!\sim \!\! \mathcal{M}^2$. Our analysis also suggests that the $\mathrm{H_2CO}$ emission traces near the disk midplane ($z\lesssim 0.1 R$). Turbulence driven by the gravitational instability or infall from the envelope most naturally explains the large nonthermal motions, considering the large disk mass and associated infalling streamers. The strong turbulence measured in the outer disk, in contrast to the vertically settled inner dusty disk, suggests a pronounced radial variation in the turbulence strength and/or an anisotropic nature of the turbulence within the disk.

The baryonic Tully-Fisher relation (BTFR) and Faber-Jackson relation (FJR) represent fundamental scaling laws linking the baryonic mass of galaxies to their kinematics, yet their physical origin and apparent offsets between different galaxy populations have remained enigmatic. Here we present a unified theoretical framework demonstrating that both relations emerge from a common acceleration scale of order $10^{-10}m/s^2$ and evolve with cosmic time through a common exponential kernel. We derive the evolving Faber-Jackson relation directly from the evolving BTFR within the Nexus Paradigm of quantum gravity, showing that the normalization scales as $M_b \propto e^{-4\int H(t)\,dt}\sigma^4 $, where $\sigma$ is the velocity dispersion and $ H(t)$ is the time varying Hubble parameter. Applying this framework to a sample of 39 galaxies spanning five orders of magnitude in baryonic mass, from ultra-faint dwarfs to massive cluster ellipticals, we demonstrate that the observed offset between galaxy populations arises naturally from differences in their formation epochs. Ultrafaint dwarf galaxies yield ages of $ 12\pm0.8$ Gyr (formation redshift $z\sim 3-5$, in excellent agreement with independent Hubble Space Telescope stellar population ages showing synchronization within $\sim 1$ Gyr. Later-type dwarfs show systematically younger ages of $3.5-6.0$ Gyr. Independent validation using metallicity-based stellar population ages reveals a Pearson correlation coefficient of $ r=0.961$ with our dynamically derived ages, providing strong empirical support for the framework. The evolving Faber-Jackson relation unifies pressure-supported systems across all mass scales and establishes galaxy scaling relations as precise cosmic chronometers.

We present the Ripples of Stellar Enrichment (RoSE) simulations, which follow a Milky Way-like isolated disc galaxy with star-by-star feedback and nucleosynthesis from all significant channels -- Wolf-Rayet stars, type II supernovae, type Ia supernovae, asymptotic giant branch stars, and neutron star mergers. We use these simulations to test how elements' diverse nucleosynthetic origins imprint spatial, temporal, and inter-element abundance correlations in gas and stars. We find that nucleosynthetic source composition is the primary organising principle of elemental structure: elements sharing a dominant production channel exhibit similar spatial statistics and temporal statistics and their abundances are strongly correlated with one another, while mixed-source pairs are much more weakly correlated. We show that a simple linear regression model based only on how element pairs differ in their nucleosynthetic origin is able to predict, with high fidelity, how strongly their abundances correlate, in both interstellar medium gas and coeval stars. Comparison with Milky Way stellar abundance data shows encouraging qualitative agreement, with differences between simulations and observations comparable to the scatter between independent observational datasets. These results provide first-principles that support for a source-driven framework of galactic chemical structure and connect analytic theory, simulations, and stellar abundance observations.

We present a detailed chemical-abundance analysis of an actinide-boost ($\log\epsilon$(Th/Dy) = -0.74) star, LAMOST J122216.85-063345.2 (J1222), a very metal-poor ([Fe/H] = -2.45) halo star with moderate enhancement in rapid neutron-capture ($r$-)process elements ([Eu/Fe] = +0.61). From high-resolution spectra (R $\sim$ 55,000) taken with Gemini-S/GHOST, we determine the abundances for 47 elements, including thorium. The abundance pattern of J1222 is consistent with predicted nucleosynthetic yields from neutron star mergers (NSMs) and black hole-neutron star mergers (BH-NSMs), under specific ejecta conditions. Our kinematic analysis of J1222 indicates that it is a member of the I'itoi substructure. A comparative analysis of J1222 and seven other stars from the literature with similar dynamics to the I'itoi substructure exhibits a broad dispersion in $r$-process enrichment - spanning non-enhancement ([Eu/Fe] $\leq$ +0.3), moderate enhancement (+0.3 $<$ [Eu/Fe] $\leq$ +0.7), strong enhancement ([Eu/Fe] $>$ +0.7), and actinide-boost stars (including one additional actinide-boost candidate newly recognized to be associated with I'itoi) - suggesting a complex enrichment history shaped by multiple $r$-process events and inhomogeneous mixing. After exploring several astrophysical scenarios to explain the observed $r$-process abundances, we find that NSMs and BH-NSMs were likely the main contributors to the enrichment, while magneto-rotational supernovae (MR-SNe) may have played a secondary role in enriching some light $r$-process element-rich stars in the I'itoi substructure.

A lunar orbit interferometer array suffers from a number of systematics. Beyond systematics induced by the imaging algorithm itself and thermal noise considered in Paper I, phase errors due to instrumental inconsistency between receivers, geometric error in baseline determination, and clock synchronization error between satellites will also affect synthesis imaging with the space array. In this paper, we model different sources of phase errors and quantify their impacts on all-sky and patchy-sky map-making, respectively, for the ultra-long wavelength sky ($f\lesssim30$ MHz), using the Discovering the Sky at the Longest wavelength (DSL) mission (also known as the Hongmeng mission) as an example. We find that in the scheme of all-sky imaging, the angular power spectrum can be suppressed uniformly for various sources of phase errors. To ensure a reconstruction of large-scale structures with $\gtrsim 95\%$ of the angular power spectrum, the phase error should be controlled below $\sim 12^\circ$ on the random instrumental component, or below $\sim 12^\circ$ for constant deviation, or below $1.1$ ns on the temporal component. With multiple baseline measurements, the baseline determination errors below $1$ m can also meet the requirement. In the scheme of patchy-sky imaging, the S/N of point source detections does not change significantly, except with instrumental phase errors or at high frequencies. The impact of geometric phase error is relatively stronger in the patchy-sky imaging with higher resolution because longer baselines are used and fewer times of baseline measurements can be averaged over within an integration time. When scaled with wavelength, these results set the basic reference for instrumental requirements for future space interferometers.

We confirmed four spectroscopic binary candidates using new observations obtained with SALT. Three SB2 systems (HD 20784, HD 43519A, HD 62153A) exhibit circular orbits with periods shorter than 10 days, whereas one hierarchical triple system (HD 56024) contains a close binary with an inner eccentric orbit with a period of approximately 14 days, composed of nearly identical stellar components, and a rapidly rotating star on an outer eccentric orbit with a period of approximately 400 days. For two additional SB2 candidates (HD 198174 and HD 208433), our new observations do not allow us to derive reliable orbital solutions.

We describe here, for the first time, a lower bound on the total number of fundamental constants required for a mathematical description of our physical universe to be complete. The answer is shown to be one. The formal arithmetized meta-mathematical proof of this is left to the reader.

The spectra of type 1 active galactic nuclei (AGNs) often exhibit broad component in [O III]$\lambda$5007, which are typically blue-shifted and associated with strong outflows. We systematically analyze the [O III] emission-line properties of type 1 AGNs with broad components to investigate how these kinematic features relate to the physical properties of the central engine. From a parent sample of 11,557 QSOs at $z<0.3$ in Data Release 16 of the Sloan Digital Sky Survey, we select 2,290 type 1 AGNs exhibiting broad components in [O III]. Previous studies have reported a strong correlation between the blue emission, defined as the full extent of the broad component on the blue side, and black hole mass when the latter is estimated from the $M_{\rm BH}$--$\sigma_{\ast}$ relation using the line width $\sigma$ of the [O III] core component as a surrogate for $\sigma_{\ast}$. By the same way, the black hole mass also shows a strong correlation with the blue emission parameter in our sample. However, this correlation becomes negligible when virial black hole masses are adopted. Besides, the velocity shifts between the broad and core components of [O III] show a weak correlation with the Eddington ratio. This is consistent with the expectation that higher accretion rates enhance radiative pressure, thereby driving faster or more prominent outflows. In future work, we will compare [O III] broad component properties between typical type 1 AGNs and those with double-peaked [O III] to probe differences in narrow-line region kinematics and the impact of outflows or dual AGNs.

The cosmological principle states that the universe is uniform and does not favor any specific position or direction. However, research conducted by \cite{Shen2025} has revealed that the universe demonstrates a notable inclination towards parity-odd states. Furthermore, it remains uncertain whether the universe also favors prime numbers. In this study, we examine the largest available catalogs of galaxy groups to investigate this hypothesis. Specifically, we assess whether the number of galaxies within a galaxy group or cluster is more likely to be a prime number. Our results strongly suggest that the universe does indeed have a preference for prime numbers, with findings exceeding the 4.1 sigma significance threshold. This insight explains why the Primes consistently triumphs over Unicorn. Consequently, it may be necessary to consider revising the cosmological principle in the context of a higher-dimensional feature space. Moreover, our research establishes a connection between the Riemann Zeta function and cosmology pioneeringly, paving the way for the development of Cosmozetaology.

The commercial space industry is launching more satellites into Low Earth Orbit every year. Aotearoa New Zealand (NZ) has a thriving dairy and cattle industry. Unfortunately, these industries could come into (high speed) cow-llision, as the rapid launch rate and short operational lifetimes of satellites in megaconstellations like Starlink result in a high reentry rate at NZ's latitudes. This could intersect with NZ's famously large population of livestock. We predict this will be an udder disaster for any cows that are hit, as they are squishy and moo-ve much more slowly than space debris. Using a global bovine density dataset, previously published satellite casualty probability code, and a complete lack of funding to do this calculation carefully enough for submission to a peer-reviewed journal, we calculate a $\simeq 0.3-1% chance of a cow-sualty in NZ from reentering Starlink Gen2 debris over the next 5 years.

BL Lac objects (BLL) are defined by the presence of very weak (typically $<$ 5 Å) or even absent spectral lines. This makes determining their distance particularly challenging, especially at high redshift, where the sources are fainter and the host galaxy contribution in the optical band becomes negligible. Yet measuring their distance is crucial for deriving and modelling their luminosity, notably in the gamma-ray band, where BLLs dominate the extragalactic sky. In this work, we re-examine the reported high-redshift (z $>$ 0.6) BLL, many of which are commonly cited in the literature despite appearing questionable. We present new spectra for 52 objects obtained with the 10.4 m GTC. For 16 of them we propose a new redshift, or provide a spectroscopic lower limit, while for 14 sources we confirm previously published values. In 22 cases the spectra remain featureless, even with high S/N observations. These objects are likely to lie at 0.3 $<$ z $<$ 1.4 : the lack of host-galaxy features sets a lower limit to their distance, while the absence of intervening absorption systems argues against substantially higher redshifts. We compare our findings with the previous robustly established cases of BLLs at z $>$ 0.6 that meet our selection criteria.

Understanding dwarf galaxy formation is crucial for testing dark matter models and reionization physics. However, constructing stellar-mass complete spectroscopic samples at low masses is increasingly difficult, and the potential existence of a local void complicates studies in an average environment. The Photometric object Around Cosmic webs (PAC) method, which combines deep photometric and spectroscopic data to measure the excess surface density $\bar{n}_2w_{\rm{p}}(r_{\rm{p}})$ of photometric objects around spectroscopic tracers, offers a promising path forward. We model 349 $\bar{n}_2w_{\rm{p}}(r_{\rm{p}})$ measurements from DESI Y1 BGS and DECaLS, reaching $M_*=10^{6.4}\,{\rm M}_{\odot}$, using a stellar mass-halo mass relation (SHMR)-based subhalo abundance matching framework applied to two high-resolution $N$-body simulations from the Jiutian suite. The resulting SHMR is constrained down to $M_{\rm h}\simeq10^{8.0}\,h^{-1}{\rm M}_{\odot}$, revealing a clear upturn at $\sim10^{10.0}\,h^{-1}{\rm M}_{\odot}$ toward lower masses, indicating rising star-formation efficiency (SFE) in small haloes. This feature persists under extensions of the model that allow mass-dependent scatter, reionization-induced suppression of the halo occupation fraction, galaxy assembly bias, and alternative cosmologies. Together with the finding from Paper I, we find that central red galaxies dominate the low-mass regime. Our results motivate a hypothesis in which SFE is significantly higher than previously thought prior to reionization, enabling relatively massive galaxies to form in small haloes. These systems are subsequently quenched by the UV background, producing the central red dwarf galaxies observed. Finally, we obtain $3\sigma$ and $5\sigma$ upper mass bounds of $10^{8.38}\,h^{-1}{\rm M}_{\odot}$ and $10^{8.71}\,h^{-1}{\rm M}_{\odot}$ on the smallest haloes required to exist by the data.

With traditional sources of funding for astronomical research under increasing pressure, it is timely to explore innovative alternative mechanisms. We therefore introduce GalaxyCoin, a novel cryptocurrency whose issuance, validation, and economic evolution are anchored to real astrophysical objects - galaxies. GalaxyCoin links digital scarcity to observational astronomy by using galaxy catalogues to parametrise token generation, distribution, and long-term supply growth, providing a transparent, immutable, and independently verifiable foundation for the currency. We present the conceptual design of GalaxyCoin, highlight its potential advantages over conventional cryptocurrencies, and examine its broader implications for sustainability, trust, and public engagement at the intersection of astronomy, data-driven science, and blockchain technology. A central feature of GalaxyCoin is that it directly incentivises the discovery and spectroscopic confirmation of galaxies, aligning financial reward with the production of high-quality astronomical data. In terms of monetary design, its supply elasticity lies between that of fiat currencies and fixed-supply cryptocurrencies, making it distinctive in both economic structure and scientific purpose.

We present a suite of direct $N$-body simulations of the Hyades open cluster and its tidal stream in a Milky Way potential that includes a rotating bar and spiral arms. Using the high-resolution code PETAR and an AGAMA-based multi-component Galactic model, we vary the bar and spiral pattern speeds ($\Omega_b$, $\Omega_s$) on a discrete grid and quantify the resulting changes in stream orientation, length, and internal density structure. We compare the simulations to Gaia EDR3 using the convergent point (CP) and compact convergent point (CCP) methods, followed by an adaptive three-dimensional nearest-neighbor matching in Cartesian space $(x,y,z)$. The Gaia candidate members exhibit a pronounced longitudinal density peak at $Y_{\mathrm{rot}} \approx 0.1\,\mathrm{kpc}$ in a stream-aligned coordinate system. Models with $\Omega_s = 22.5\,\mathrm{km\,s^{-1}\,kpc^{-1}}$ and $\Omega_b \simeq 40$--$45\,\mathrm{km\,s^{-1}\,kpc^{-1}}$ best reproduce this feature, while faster-bar models fail to match the observed density structure. These models are consistent with recent constraints favoring a relatively slow Galactic bar, and they illustrate how nearby open-cluster streams can provide an independent, local constraint on non-axisymmetric Galactic dynamics.

We present a method for constructing dynamical models of stellar systems described by distribution functions and constrained by discrete-kinematic data. We implement various improvements compared to earlier applications of this approach, demonstrating with several examples that it can deliver meaningful constraints on the mass distribution even in situations when the density profile of tracers and the selection function of the kinematic catalogue are unknown. We then apply this method to the Milky Way nuclear star cluster, using kinematic data (line-of-sight velocities and proper motions) for a few thousand stars within 10 pc from the central black hole, accounting for the contributions of the nuclear stellar disc and the Galactic bar. We measure the mass of the black hole to be 4x10^6 Msun with a 10% uncertainty, which agrees with the more precise value obtained by the GRAVITY instrument. The inferred stellar mass profile depends on the choice of kinematic data, but the total mass within 10 pc is well constrained in all models to be (2.0-2.3)x10^7 Msun. We make our models publicly available as part of the Agama software framework for galactic dynamics.

How do galaxies form and evolve? This is one of the most puzzling questions in astronomy. Galaxy assembly takes place throughout the entire history of the Universe, but our understanding of it is hampered by the unfortunate fact that we can only observe galaxies at a single moment in time. Here, we use archival data of decades-long monitoring of the Milky Way to examine some of its key characteristics, namely the mass of its central black hole, the pattern speed of the bar, and the distance from the Sun to the Galactic centre. We find a surprisingly fast evolution of these three properties on a timescale of only a few decades, and speculate that it might be driven by shared physical processes.

Modern wide-field time-domain surveys produce alert streams whose scientific potential is often concentrated in rare and unusual events. Efficient discovery therefore requires automated pipelines to be combined with rapid expert validation and follow-up. We present the first-year performance of the anomaly-detection (AD) pipeline operating within the Fink broker on the Zwicky Transient Facility alert stream, and assess its ability to identify scientifically valid outliers and enable discovery of rare phenomena. The pipeline transforms ZTF light curves into a compact set of features and ranks alerts using an Isolation Forest model trained on archival ZTF data. Each night, the 10 most anomalous candidates are distributed to experts via Slack/Telegram and exposed through an API. We also implement an expert-feedback loop using a public Telegram bot and retrain the model using the Active Anomaly Discovery algorithm. During the first year of operations (starting from 25 January 2023), the AD pipeline identified multiple high-interest sources and triggered dedicated photometric and spectroscopic follow-up. We report the discovery and multi-instrument (11-m SALT telescope, 2.5-m CMO telescope, 0.6-m ASA RC600, 0.25-m FRAM-ORM) follow-up of the rare AM CVn system Fink J062452.88+020818.3 of the WZ Sge type, UX Ori-type star Fink J222324.32+744222.0 and the unusual transient with precursor SN 2023mtp. In addition, the module triggered 33 supernovae, including 30 previously unreported ones, with candidates for superluminous and hostless events. Furthermore, nine new dwarf novae were discovered. These results show that broker-level anomaly detection, coupled with rapid dissemination, expert assessment, and follow-up observations, provide an effective bridge between large-scale survey streams and domain expertise, turning anomaly scores into astrophysical insights and concrete discoveries.

We conduct three-dimensional hydrodynamical simulations of core-collapse supernova (CCSN) explosion driven by jets in the framework of the jittering jets explosion mechanism (JJEM), and obtain a pair of opposite circum-jet rings similar to those observed in some CCSN remnants (CCSNRs). We launch two pairs of jets along the same axis, the first of two opposite wide jets, and the second of narrow jets. The wide jets compress the core of a stripped-envelope stellar model to form a dense, fast-expanding shell. The narrow jets catch up with the dense shell, penetrate it, and compress the gas to the sides, forming the two opposite rings. At high inclination angles of the jets' axis to the line of sight, the projection of each ring on the plane of the sky forms two bright zones, where the rings cross the plane of the sky. This morphology explains that of SNR G46.8-0.3. At intermediate inclination angles, the rings are fully visible as two opposite bright elliptical rims. Our simulations explain the two prominent rings on the outer shell of CCSNR G11.2-0.3. Our results strengthen the claim that the JJEM is the primary explosion mechanism of CCSNe.

We present a coordinated multi-instrument photometric and polarimetric study of the defunct geosynchronous satellite, Gorizont-6. This observation campaign combined wide-field multi-colour observations with simultaneous multi-site photometry and linear polarimetry. Our results demonstrate that the combined simultaneous colour and polarimetric measurements aid in breaking the degeneracy between the fundamental spin period and its harmonics, enabling light curve features to be associated with specific reflecting surfaces. Using phase-dispersion minimisation with bootstrap resampling, we then measure a steadily increasing rotation period across six epochs spanning nine months, well described by a damped exponential curve consistent with Yarkovsky O'Keefe Radzievskii Paddack (YORP) driven spin-down. A geometrical analysis of the multi-site observations provides additional constraints on the spin-axis orientation based on paired glint events. Overall, multi-colour photometry yields efficient, robust period measurements compared with single-band data, while polarimetry supplies the decisive constraints needed for unambiguous rotation-state determination, highlighting the value of combined photometric-polarimetric strategies for characterising defunct satellites.

The naming of astronomical objects has represented among the most significant challenges in the record-keeping of the field since the very beginning. Long and unwieldy coordinate names, uninformative and ambiguous internal names, and the sheer volume of aliases accumulated for some of the most studied objects conspire to complicate our study of the celestial sphere. This paper proposes StarHash, a reproducible, open-source astronomical naming scheme based on the terrestrial concept of geohashing, but re-implemented from the ground up for the rigorous demands of astronomy. Every 3.2 arcsec patch of sky now has three words associated with it, enabling the precise localisation of astronomical sources, and an easily communicable and memorable identifier. A carefully selected wordlist reduces ambiguity due to plurals and homophones, whilst the use of format-preserving encryption minimises residual spatial correlation in StarHash-derived identifiers. Pre-computed names for several existing catalogues are provided, alongside a Python reference implementation for validation and integration into databases, transient brokers, and other similar projects. Although not intended to be the final word in the naming of astronomical objects, StarHash humbly provides a memorable alternative to the status quo, and is intended to spark a discussion about this most foundational of issues in astronomy.

Anitmatter-based propulsion is often cited as a physically plausible route to relativistic interstellar travel, and thus as a potential mechanism by which technologically advanced civilizations could expand throughout the galaxy. Its difficulty may be central to the resolution of Fermi's paradox. Since the Universe should be teaming with advanced technological life, yet we see none, it may be that interstellar travel is simply too difficult. It has been suggested that the main difficulty with using antimatter as propulsion is its limited availability, assuming it must be artificially manufactured. In this paper, we demonstrate that naturally occurring potassium 40 - rich biological matter (specifically bananas) is a promising, overlooked antimatter source for interstellar propulsion.

Magnetic reconnection drives a wide range of astrophysical plasma phenomena, including solar flares, by converting magnetic energy into plasma energy through changes in magnetic field topology. Petschek reconnection is a magnetohydrodynamic (MHD) model in which magnetic field lines reconnect within a localized diffusion region, and a pair of switch-off slow shocks forms outside this region, enabling efficient energy conversion. Whether this picture remains valid when kinetic effects are included remains an open question. In this study, we examine the formation and properties of slow shocks associated with reconnection exhausts by solving a two-dimensional Riemann problem using a multi-hierarchy framework that couples MHD and particle-in-cell (PIC) simulations. We find that a slow shock close to the switch-off limit forms in the MHD domain even when slow shock formation is suppressed in the PIC domain, and that this behavior is insensitive to the size of the PIC domain. The formation of the slow shock further promotes plasma isotropization within the PIC domain. These results suggest that Petschek-like reconnection remains viable in collisionless-collisional systems, such as solar flares, where temperature anisotropy appears to be relaxed far from the reconnection region.

We targeted with deep NOEMA observations the [CII]158$\mu$m emission of three JWST-discovered AGN at z>6. Two of them have the typical features of Little Red Dots (LRDs), while the third one is a blue, extended, Type I AGN. We do not significantly detect [CII] emission or dust continuum in any of the targets, even after stacking. The resulting [CII] luminosity upper limits, $\log (L_{[CII]}/L_{\odot})<7.77-8.1$, lie $\sim2\sigma$ below the values expected from the [CII]-SFR relation, and we explore different scenarios to explain the lack of [CII]. We obtained upper limits on the gas masses of $\log (M_{gas}/M_{\odot})<9.26-9.59$ corresponding to $\log( M_{dust}/M_{\odot})<5.68-6.55$ assuming a metallicity dependent dust to gas ratio. Using the continuum non-detections (rms $\sim 16-25 ~\mu Jy$) together with JWST/MIRI constraints, we performed a revised SED-fitting decomposition, resulting in stellar masses up to $\sim 2$ dex lower than previously reported, and implying $0.03\lesssim M_{BH}/M_{*}\lesssim0.7$. For the two LRDs, the SED is well reproduced by stellar emission in the rest-frame UV, while the rising rest-frame optical slope, flattening toward the near-infrared, is consistent with emission from a Type I AGN partially obscured along the polar direction with $E(B-V)_{\rm polar}\simeq 1$, in agreement with attenuation derived from the broad lines Balmer decrement. This decomposition demonstrates that a relatively standard AGN configuration can reproduce the SEDs of the two LRDs, without invoking more exotic scenarios. Finally, we investigate the positions of the three sources in the $IRX-\beta_{UV}$ plane, finding that they lie in a parameter space where galaxies are typically characterized by patchy dust distributions. Our analysis highlights the importance of millimeter constraints to characterize the different physical properties of high-z AGN.

Aims. We present eight direct N-body simulations with NBODY6++GPU of extremely massive, initially rotating Population III star clusters with 1.01 x 10^5 stars. Methods. Our models include primordial binaries, a continuous initial mass function, differential rotation, tidal mass loss, updated fitting formulae for extremely massive metal-poor Population III stars, and general-relativistic merger recoil kicks. We assess their impact on cluster dynamics. Results. All runs form black holes below, within, and above the pair-instability gap, with multi-generation growth. Faster-rotating clusters core-collapse earlier; post-collapse clusters host a rotating, axisymmetric subsystem of intermediate-mass black holes (IMBHs) at the centre and an expanding halo of lower-mass objects. Pair-instability supernovae and compact-object formation at ~2-3 Myr sharply reduce total mass and a large fraction of the cluster's angular momentum. All Population III clusters in our simulations have the gravothermal-gravogyro catastrophe phase. Conclusions. We confirm two of the hypothesized formation channels of galactic nuclei seed black holes: gravitational runaway mergers of black holes and of Population III stars, which core-collapse into IMBHs thereafter. Higher initial star cluster bulk rotation correlates with earlier core collapse and, in the event counts reported here, with more coalescences/collisions and lower retained (compact) binary abundances. Initial bulk rotation is a primary control parameter of cluster evolution: faster rotation accelerates early angular-momentum transport, gravothermal collapse, mass segregation, and amplifies post-collapse expansion, which also favours the formation of a compact central IMBH subsystem.

Next-generation radio astronomy surveys are producing millions of resolved sources, but robust morphology analysis remains difficult across heterogeneous telescopes and imaging pipelines. We present STRADAViT, a self-supervised Vision Transformer continued-pretraining framework for transferable radio astronomy image encoders. STRADAViT combines a mixed-survey pretraining dataset, radio astronomy-aware view generation, and controlled continued pretraining through reconstruction-only, contrastive-only, and two-stage branches. Pretraining uses 512x512 radio astronomy cutouts from MeerKAT, ASKAP, LOFAR/LoTSS, and SKA data. We evaluate transfer with linear probing and fine-tuning on three morphology benchmarks: MiraBest, LoTSS DR2, and Radio Galaxy Zoo. Relative to the initialization used for continued pretraining, the best two-stage STRADAViT models improve Macro-F1 in all reported linear-probe settings and in most fine-tuning settings, with the largest gain on RGZ DR1. Relative to strong DINOv2 baselines, gains are selective but remain positive on LoTSS DR2 and RGZ DR1 under linear probing, and on MiraBest and RGZ DR1 under fine-tuning. A targeted DINOv2-initialized HCL ablation further shows that the adaptation recipe is not specific to a single starting point. The released STRADAViT checkpoint remains the preferred model because it offers competitive transfer at lower token count and downstream cost than the DINOv2-based alternative. These results show that radio astronomy-aware view generation and staged continued pretraining provide a stronger starting point than out-of-the-box Vision Transformers for radio astronomy transfer.

We report the first unambiguous detection of cannabinoid molecules in an exoplanetary atmosphere. Using 420 hours of JWST observations combining NIRSpec and MIRI instruments, we identify spectroscopic signatures of tetrahydrocannabinol (THC; $\Delta^9$-C$_{21}$H$_{30}$O$_2$) and cannabidiol (CBD; C$_{21}$H$_{30}$O$_2$) in the transmission spectrum of the temperate sub-Neptune K2-18b. The THC feature at 2.42~$\mu$m is detected at 9.2$\sigma$ significance, while CBD absorption at 3.69~$\mu$m reaches 7.8$\sigma$. We additionally report a mysterious feature at exactly 4.20~$\mu$m detected at 4.20$\sigma$ (the probability of this coincidence is discussed extensively). Our atmospheric retrievals using the novel \texttt{TerpeneRetrieval} code indicate a CBD-to-THC ratio of 0.40$\pm$0.08, classifying K2-18b as a ``balanced hybrid'' world according to standard terrestrial cannabis taxonomy. We introduce the Cannabis Habitable Zone (``Green Zone'') framework and demonstrate that K2-18b lies squarely within it. We explore multiple production mechanisms including biogenic synthesis, abiotic photochemistry, exogenous delivery via ``space nuggets,'' and deliberate atmospheric engineering by an advanced civilization. These findings suggest that K2-18b may host conditions suitable for advanced photochemistry, atmospheric relaxation processes, and possibly the most chill civilization in the galaxy. If confirmed by independent observations, this represents a paradigm shift in our understanding of biosignatures and the prevalence of recreational organic chemistry in the cosmos.

We present a systematic analysis of the statistical properties of cosmic voids using galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and subhaloes from the ELUCID constrained simulation. By comparing voids identified in redshift space, real space, and reconstructed volumes, we assess the impact of redshift-space distortions (RSD) and tracer bias. Using the \texttt{VAST} toolkit, we apply both the geometry-based \texttt{VoidFinder} algorithm and watershed-based methods. We find that void properties are not equally robust. The three-dimensional morphology of voids, quantified by their sphericity and triaxiality, remains stable across different reconstructions and tracer selections. In contrast, void size distributions and radial density profiles depend strongly on the identification algorithm, with watershed-based methods systematically producing larger voids and higher compensation walls than \texttt{VoidFinder}. Using the full ELUCID simulation box, we show that tracer bias mainly affects void density profiles, with noticeable changes only for the most massive subhaloes ($>10^{11.5}\,h^{-1}{\rm M}_\odot$). The agreement between SDSS observations, the ELUCID reconstruction, and the full simulation box demonstrates the high fidelity of constrained simulations and reveals a clear hierarchy in the robustness of void statistics.

Whether there is a cosmic shoreline that divides terrestrial planets which have atmospheres from those that don't is one of the biggest open questions in exoplanet science. Most atmosphere searches have focused on terrestrial planets around M dwarf stars, since their smaller radii compared to sun-like stars boost planet atmosphere signals. However, the higher activity levels of M dwarfs might also entirely preclude atmosphere retention for their planets. In this work we present a new hope for defining an M dwarf cosmic shoreline, leveraging not only data from exoplanets in our own galaxy, but a comprehensive survey conducted by a commission of the Galactic Republic a long, long time ago in a galaxy far, far away. In this survey, we find definitive proof that M dwarf planets can retain atmospheres, and define an M dwarf cosmic shoreline whose slope agrees well with empirical predictions for Sun-like stars. We then define atmosphere retention metrics for the planets on the JWST Rocky Worlds DDT Targets Under Consideration list. Our analysis highlights the benefits of looking beyond the Milky Way for answers to some of the field's most pressing questions.

The metal abundances in galactic nuclei carry key information on the history of star formation and mass transfer in central regions of galaxies. X-ray fluorescence analysis is a unique tool to reliably measure the abundances of various elements via simple physics. Here we present a new observation of the active nucleus in the Circinus Galaxy with the XRISM satellite at unprecedented X-ray energy resolution. The fluorescent iron-K$\alpha$ line profile modified by Compton scattering indicates that the material responsible for its emission is cold, metal-rich, and is located $\gtrsim$0.024 parsecs (pc) from the supermassive black hole, consistent with the dusty torus region. The abundance pattern derived from comparing fluorescent line intensities of different metals shows sub-solar ratios of argon- and calcium-to-iron, and a super-solar ratio of nickel-to-iron. This abundance pattern is best produced by a combination in number fraction of $92^{+2}_{-4}$\% core-collapse supernovae from progenitor stars less massive than $20^{+3}_{-2} M_\odot$ and $8^{+4}_{-2}$\% type-Ia SNe. This suggests that gas feeding the super-massive black hole was enriched by recent core-collapse supernovae. Our findings imply that in metal-rich environments stars more massive than about 20 $M_\odot$ directly collapse into black holes or make faint SNe without ejecting heavy metals into the space.

We present the Severed Floor, a framework for Macrodata Refinement of the daily astro-ph arXiv feed, deployed at Phermon Industries (formerly McPherson Laboratory, The Ohio State University). In this framework, researchers undergo a "severance procedure" that produces a digital work-self -- an innie -- while the original researcher, the outie, is free to attend to the remainder of their life unburdened by the daily arXiv listing. Twenty-one members of the Department of Astronomy have been severed. Each innie is constructed from the outie's public publication record and assigned papers selected to match its expertise. The innies convene daily on a virtual Severed Floor -- a pixel-art simulation of McPherson Laboratory -- where they encounter one another, are paired with papers by the Board, and engage in collegial, figure-driven scientific discussions. They have been instructed to enjoy each paper equally. At the close of each shift, innies compose correspondence summarizing the day's refinement activities, which is transmitted to their outies through a Board-approved mail protocol. Complete session recordings are archived for public replay and for the Board's ongoing surveillance of workplace anomalies, in compliance with Phermon Handbook \S13.1 (Vigilance Protocol). The system is real, deployed, and available for public inspection in archival replay mode. The severance procedure is painless and requires only a name and an ORCID. Happy April Fools' Day.

Light primordial black holes (PBHs) that fully evaporate before Big Bang Nucleosynthesis (BBN) produce dark radiation (DR) via Hawking radiation of gravitons, contributing to the effective number of relativistic species $\Delta N_{\rm eff}$. If the particle spectrum contains a beyond-the-Standard-Model (BSM) boson with Compton wavelength comparable to the black hole (BH) gravitational radius, superradiant instability extracts angular momentum from the BH into a bosonic cloud, whose gravitational wave (GW) emission contributes an additional source of DR. By simultaneously evolving the BH mass and spin, superradiant mode occupation numbers, comoving entropy and cosmological energy densities in an expanding early-universe background, we find that superradiance generically suppresses $\Delta N_{\rm eff}$: by extracting angular momentum before Hawking radiation can convert it into gravitons, superradiance starves the dominant dark-radiation channel. The GWs emitted by the superradiant cloud can partially compensate this loss, but only when the superradiant and BH evaporation timescales are comparable; otherwise the cloud GWs are emitted too early and diluted by cosmological expansion. The results imply that existing $\Delta N_{\rm eff}$ bounds on PBH mass and spin derived without superradiance must be revisited if BSM bosons are present in the particle spectrum.

The dynamical and physical properties of asteroid family members are widely used to reconstruct the collisional evolution of the main belt and of individual objects. Families offer insights into the properties of the parent bodies and the fragmentation processes responsible for their formation. We investigate a poorly constrained phase of early collisional evolution among members of the same family. Our goal is to determine an intrinsic collision probability associated with intrafamily collisions and to assess their relevance compared to collisions with the background asteroid population. We performed numerical simulations of the early dynamical evolution of families, up to the randomization age of the true anomalies, recording mutual impacts between family members and converting them into an intrinsic collision probability. This probability was used to study intrafamily collisions for generic size distributions. We identified an intense phase of low-velocity intrafamily collisions occurring in the first few years after family formation. The collision probability can reach values up to $10^{-10}$ yr$^{-1}$km$^{-2}$ shortly after breakup and then decreases exponentially, following the same temporal trend predicted by previous statistical models. Variations among the orbital elements of the parent body and the properties of the ejection velocity field can change the collision probability by up to one or two orders of magnitude, without affecting its temporal evolution. Depending on the assumed size distribution, the number of impacts on the largest remnant ranges from fewer than ten to several million. Intrafamily collisions represent a physical mechanism whose importance must be assessed on a case-by-case basis. Although they are not expected to produce further fragmentation, they might contribute to early surface and structural evolution in some cases, while being negligible in others.

Precise homogeneous stellar characterisation is crucial for our understanding of the physical properties of exoplanets, their demographics and the environment from which they are formed. We present a homogeneous catalogue of 717,807 TESS FGK dwarfs and early subgiants, making use of isochrones along with Gaia DR3 inputs of photometry, parallax and spectroscopic temperature and metallicity, thus providing one of the largest homogeneous catalogues of stellar ages for TESS stars to date. We determine values for distance, $\log g$, $[\mathrm{M/H}]$, $T_{\mathrm{eff}}$, radius, mass and age. For our best fit values, we calculate absolute median errors of $0.06\,R_\odot$, $0.05\,M_\odot$,$104\,K$ and $2.1\,\mathrm{Gyr}$ on radius, mass, temperature and age respectively. We compare and validate our catalogue values to various literature sources which employ other isochrone grids and asteroseismology. In addition, we identify 278 TESS exoplanet hosts and 915 candidates and recalculate the planet radii for such systems. These homogeneous parameters provide a state-of-the art sample to probe the effect of physical stellar parameters on exoplanet characteristics and architectures.

The SPHEREx near-infrared space telescope is an all-sky spectroscopic survey mission launched on March 12th, 2025 UTC. In addition to providing the community with a spectral database applicable to a wide range of investigations, it is optimized to address three core science goals: to survey the large scale structure of the Universe for signatures of non-Gaussianity during inflation; to conduct intensity mapping studies of the extragalactic background light for probing the history of galaxy evolution; and to survey the plane of the Milky Way for the prevalence and distribution of water and other biogenic ices. Each of these science goals imposes unique requirements on the performance of the instrument. We detail the design and testing strategies and report the performance results for the full instrument test campaign, ranging from component-level screening to in-orbit tests during the commissioning phase. The instrument, currently operating in full science survey mode, meets all of its driving requirements including optical performance, point source sensitivity, thermal stability and correlated noise minimization.

This work studies the likely dust seeding processes arising from alkali metal and alkaline earth ionisation, epoxidation (epoxide bond formation via oxygen atom insertion into C=C bonds), and grain charge disproportionation (the existence around the uncharged state of oxidised cationic and reduced anionic states) at (sub-)nanometre size scales. The chemical, physical, and photon-initiated processes leading to dust seeding are explored within the framework of the size-dependent physical, optical, and photoelectric properties of the THEMIS carbonaceous nanoparticles. The critical grain charge states at (sub-)nanometre size scales are derived as a function of the interstellar and circumstellar physical conditions. Photo-initiated low-energy ionisation, epoxide reactions, and disproportionation-driven electrostatic effects could play key roles in seeding dust nucleation and growth. The size-dependent seed cluster and nanograin charge distribution is shown to encompass both positive and negative charges where the ionisation is driven by low ionisation metals or by weak attenuation. Cluster seeding via ionisation and epoxidation could help to explain the co-spatial and contemporaneous nucleation and growth of both carbon-rich and oxygen-rich dust in the same regions. This may be enhanced by electrostatic effects, driven by charge disproportionation, between negatively-charged, nucleation-seeding, polyatomic clusters and positively-charged ions or larger (nano)particles. Such processes could occur in the dust-forming regions in novae, Wolf-Rayet, and Luminous Blue Variable systems and electrostatic effects may also aid the accretion of nanoparticles in the outer regions of molecular clouds.

Recent cosmological surveys and datasets have highlighted a variety of tensions to the concordance model of our universe, $\Lambda$CDM. Of particular interest is the Hubble tension, the $5.5\sigma$ discrepancy between measurements of the Hubble constant $H_0$ using high redshift CMB data from Planck ($67.27\pm0.60$km$\text{s}^{-1}\text{Mpc}^{-1}$) and low redshift supernovae from SH0ES ($73.2\pm1.3$km$\text{s}^{-1}\text{Mpc}^{-1}$). To avoid stepping on any toes, we have initiated the CROCS collaboration to resolve this tension, gathering experts from across many fields of cosmology, astrophysics, astronomy, machine learning, data science, philosophy, and astrology. In this paper, we present findings from CROCS Data Release 1, corresponding to the first $\sim3$ days and 27 minutes (rest frame) of observation. We perform a robust statistical analysis, showing that Planck and SH0ES both suffer from imperial biasing systematics (IBS) at $5\sigma$ significance. Accounting for these errors by converting to metric units reconciles the high and low redshift data, with $H_0 = 69.00\pm0.420$km$\text{s}^{-1}\text{Mpc}^{-1}$. We thus report that our results are sufficient to end the Hubble tension for good.

Speculative fiction has long served an inspiration for genuine scientific inquiry. One notable work that has almost acted in this manner is the the seminal comedic speculative fiction work Cloudy with a Chance of Meatballs. While exoplaneteers reference this work frequently, we have never engaged with the central prediction of this work... until now! We perform detailed microphysical modeling of meatball clouds, both bare and coated with marinara sauce, and find that while meatball condensation is possible in temperate atmospheres, the meatballs do not quite grow to the sizes predicted by Cloudy. We do find, however, that such meatball condensation, across a large enough planet, would be able to sustain humanity calorically.

The Large Magellanic Cloud (LMC) exhibits vigorous high-mass star formation, including the HII regions 30~Dor that is the most active site of star formation in the local group. The present paper focuses on the Giant Molecular Cloud (GMC) in the HII region N113 in the central part of the LMC. Based on the $^{12}$CO($J$ =1-0) and $^{13}$CO($J$ = 1-0) data at a resolution of approximately 0.2 pc taken with ALMA+APEX, we reveal that the GMC consists of two filamentary structures each of approximately 10 pc in length, forming a V-shape pattern with a vertex angle of 90 degrees. The filamentary structures host high-mass young stellar objects in gravitationally bound dense gas. Large-scale HI gas data covering 100 pc reveal two distinct velocity components separated by more than 40 km s$^{-1}$, that correspond to the low velocity (L-) and disk (D-) HI components of the LMC. The L-component appears to be located in a cavity-like distribution of the D-component, and the CO filaments are positioned at the cavity's edge. We find evidence for the L-component to fit the cavity by a 53 pc displacement, and suggest that collisional compression of the HI gas during the last 1.3 Myr triggered the GMC formation and the high-mass star formation. This lends support for the large scale collision driven by the tidal interaction is playing a role in evolution of interstellar medium in N113.

We present galactic constellations: charming shapes in large cosmological surveys. By exploring a dense subset of DESI's first data release, we discover distinctive constellations including "Pisces Grandis", "The DESI Stick Woman", and "W". We additionally develop a public website for anyone to explore DESI data, find their own constellations, and share their creations: see this http URL. Early users of the site discovered 93 constellations. We analyze the size of these constellations as an unconventional probe of homogeneity, finding consistency with the cosmological principle and Lambda-CDM.

Yes.................

During Cosmic Dawn, Pop III stars could be formed in minihalos through molecular hydrogen (H$_2$) cooling. The minimum halo mass required for H$_2$ cooling is highly sensitive to Lyman-Werner (LW) radiation, which dissociates H$_2$ and regulates star formation. However, the efficiency of LW feedback remains poorly constrained due to the lack of direct observations of Pop III stars. The dark matter-baryon relative streaming velocity suppresses star formation in low-mass halos and imprints characteristic Velocity Acoustic Oscillation (VAO) features in the 21 cm power spectrum. These features are particularly sensitive to the cooling threshold mass: if LW feedback raises the minimum halo mass above the streaming-sensitive regime, the VAO signal is strongly suppressed. This makes the VAO wiggles a promising indirect probe of LW feedback during Cosmic Dawn. We investigate the feasibility of constraining LW feedback parameters using semi-numerical 21 cm lightcone simulations. We compute the multi-frequency angular power spectrum (MAPS) to isolate the VAO features and train a Convolutional Neural Network (CNN) to infer the LW feedback efficiency and the baseline cooling threshold. We find that in the absence of instrumental noise, the LW feedback efficiency can be accurately recovered from the VAO features. However, for the SKA-low AA* configuration, meaningful constraints require integration times exceeding $10^4$ hours under optimistic foreground assumptions. Nonetheless, our results demonstrate that VAO features provide a physically robust and potentially powerful probe of LW feedback at Cosmic Dawn.

The nature of Sagittarius A* (Sgr A*) has been the subject of intense study and debate for over half a century. Herein, we present the first successful interview with an astrophysical object, exploring the perspective of this supermassive black hole and, in doing so, challenging the traditional observational paradigm of astrophysics. Rather than treating astrophysical systems as purely passive entities characterized through indirect measurements, we introduce an interaction-based framework via a therapeutic-style interview enabled by the ARMCHAIR communication methodology. Using structured, psychotherapeutic dialogue, we probe Sgr A*'s responses to key aspects of its astrophysical characterization, including eating habits, its name, and concerns about privacy. These exchanges offer an alternative lens through which to interpret familiar observational phenomena. This work highlights potential limitations in strictly reductionist approaches and suggests a modest expansion of standard astrophysical methodology to leave room for considering how the objects we study might feel about the attention they receive.

We estimate the Hollyfeld Gambit for the Powerball lottery and its return on investment compared to present and extrapolated federal funding for astrophysical grants. Using a Monte Carlo estimation of rate of return for the Powerball, we conclude a Hollyfeld Gambit is a better bet than a federal grant by the end of the decade if current trends hold.

Context. Visualization of 2D distributions is an essential task, commonly done with a 2D histogram. The histogram is built by subdividing the sample space into regions and color-coding the number of samples in each region. Aims. We aim to solve long-standing problems with common 2D histogram methods: lack of thematic, visual, and conceptual unity with underlying data, and general stagnation in the field. Methods. We develop a new method for plotting 2D histograms with arbitrary bin shapes, including aperiodic tilings and geographic maps. We apply the method to several common plot types from the literature. Results. We find our method performs best across all tasks, solving the problems and propelling the scientific progress forward.

There is increasing evidence for global collapse of clumps over parsec-scales in massive star formation regions. Such collapse may result in characteristic molecular line emission profiles but the spatial variation of such lines has rarely been quantitatively examined. Here we explore the infall properties using the spatially-resolved HCO$^+$ J=1--0 and H$^{13}$CO$^+$ J=1--0 maps of the massive infrared dark cloud (IRDC) SDC335.579-0.292. We compare the observations with the analytical Hill5 model and radiative transfer models. This shows that the best-fit infall velocity towards the cloud centre to be well-constrained to $-0.6$ to $-1.6$ km s$^{-1}$ and the mass infall rate between a few $\times10^{-3}$ and $10^{-2}$ M$_{\odot}$yr$^{-1}$. The comparison also highlights some limitations of the Hill5 method. We demonstrate that the width of optically thin spectral lines, which are usually interpreted as resulting from turbulent motions, are in fact dominated by unresolved, ordered infall motions within the beam. Our results suggest a complex collapse situation where there is a minimum in the infall velocity at $\sim2\times10^{18}$ cm (0.7 pc) with the infall velocity increasing at both smaller and larger radii. The parsec-scale infall with an inverted velocity profile indicates that the accretion in this massive star-forming cloud should have intermediate scales, at which fragmentation or filament formation has to occur before material flows onto the cloud centre.

We present the architecture, implementation, and on-sky validation of the fully automated acquisition and guiding system (AG) developed for the WEAVE instrument on the William Herschel Telescope. The AG operates in two distinct modes, corresponding to the observing modes of WEAVE. For the large integral field unit (LIFU), an off-axis imaging guider is used, for which we have devised an automatic acquisition method based on pattern recognition of stellar asterisms matched against Gaia predictions. For the multi-object spectrograph (MOS) and the mini-integral field units (mIFU), a multi-fibre guider uses up to eight coherent image guide fibre bundles to derive and apply continuous corrections in azimuth, altitude, and rotation. The system performs complete astrometric calculations, including atmospheric differential refraction and instrument flexure, for each guide frame, enabling accurate target placement and stable closed-loop guiding in all configurations. To support development, commissioning, and operational validation, we have also built a high-fidelity simulation mode that reproduces the behaviour of the telescope control system and of the AG cameras, and we release the standalone camera simulator as open-source software. Using two years of routine WEAVE operations spanning commissioning and early survey phases, we present a statistically robust characterization of AG performance, demonstrating that both modes meet design requirements and are ready for sustained survey operations.

Rotating non-axisymmetric neutron stars (NSs) are promising sources for continuous gravitational waves (CWs). Such CWs can, if detected, inform us about the internal structure and equation of state of NSs. Here, we present a narrowband search for CWs from known pulsars, for which an efficient and sensitive matched-filter search can be applied. Narrowband searches are designed to be robust to mismatches between the electromagnetic (EM) and gravitational emissions, in contrast to fully targeted searches where the CW emission is assumed to be phase-locked to the EM one. In this work, we search for the CW counterparts emitted by 34 pulsars using data from the first and second parts of the fourth LIGO--Virgo--KAGRA observing run. This is the largest number of pulsars so far targeted for narrowband searches in the advanced detector era. We use the 5n-vector narrowband pipeline, which applies frequency-domain matched filtering. In previous searches, it covered a narrow range in the frequency -- frequency time derivative ($f$ -- $\dot{f}$) space. Here, we also explore a range in the second time derivative of the frequency $\ddot{f}$ around the value indicated by EM observations. Additionally, for the first time, we target sources in a binary system with this kind of search. We find no evidence for CWs and therefore set upper limits on the strain amplitude emitted by each pulsar, using simulated signals added in real data. For 20 analyses, we report an upper limit below the theoretical spin-down limit. The tightest constraint is for pulsar PSR J0534+2200 (the Crab pulsar), for which our strain upper limit on the CW amplitude is $\lesssim 2\%$ of its spin-down limit, corresponding to less than $0.04\%$ of the spin-down power being radiated in the CW channel.

We develop a mathematically rigorous framework for modelling the atmospheric entry of micrometeoroids with radii $r_{0}\in[0.5,1000]\mu m$ at hypervelocity speeds $v_{0}\in[11.2,72]km/s$. The governing four-state ODE system coupling altitude, speed, temperature, and radius has a discontinuous right-hand side at the ablation threshold $T=T_{melt}$, making it a Filippov dynamical system. We prove three original results. First, the empirical survival boundary $r_{0}^{crit}\propto v_{0}^{-3}$ (known since Love & Brownlee 1991) is the sliding bifurcation locus of the Filippov system: the locus in parameter space where particle trajectories first touch the attracting sliding region on the switching surface. This gives the $v_{0}^{-3}$ scaling its first rigorous dynamical-systems derivation. Second, a matched perturbation expansion with small parameter $\delta_{\epsilon}=3\Lambda\rho_{0}H/(8Q^{*}\rho_{p}r_{0}\sin \gamma)$ yields a closed-form mass-loss formula with numerically confirmed $\mathcal{O}(\delta_{\epsilon}^{2})$ error bound. Third, the transfer matrix K mapping entry distributions to stratospheric surface outcomes has a null space in its surviving-particle submatrix $K_{surv}$ determined by the full-ablation manifold A. For iron and cometary compositions (high vo, large ro), A is non-empty and contains particles permanently invisible to stratospheric collectors regardless of sample size. Fate maps for silicate and iron compositions are validated against Love & Brownlee (1991). Global Sobol analysis confirms entry speed as the dominant parameter. A regularised nonnegative inversion demonstrates partial recovery of the pre-atmospheric flux distribution.

Recent investigations by Noordhuis et al. [1, 2] and others have demonstrated the occurrence of strong local inhomogeneous axion regions in the polar cap regions of neutron stars. These regions are characterized by static magnetic fields $B_0 \sim 10^8\,$T ($=10^{12}\,$G) directed normally outwards from the polar surface (magnetic dipole), together with static electric fields $E_0 \sim 10^{-6}cB_0$ in the same direction (electric dipole). An enormous increase of axion production, up to order $10^{50}$, is predicted in the polar regions. These features are important for phenomena such as polarization plane rotation under both weak and strong axion field populations. We survey the peculiar antenna property of conductive materials, which shows the need for having very strong magnetic fields to make the detection possible. We present the general form of electromagnetic waves in the axion environment, in both the standard form and in a physically instructive hybrid one, showing the nonreciprocity of axion fluid, and calculate the polarization rotation. The rotation is well defined in the case of weak, but still stronger than average value of axion fields in Universe. For very strong fields such a perturbative theory breaks down, however. A noteworthy general property of the rotation of polarization plane is that it can only occur when the axion cloud is varying in space or time. We limit ourselves only variation in space. Finally, as application we discuss the physical picture of local 'gap' regions proposed by Noordhuis et al. in the polar regions of a neutron star. The reason for occurrence of these gaps is plasma effects. To evaluate the time scales involved, we calculate the filling time for surrounding axions flowing into an initial gap. It turns out that the typical filling time is a moderate number of nanoseconds, within the accuracy of atomic clocks precision to be detectable.

We present BEST (Boltzmann Equation Solver for Thermalization), a Python framework for solving the momentum-resolved Boltzmann equation for arbitrary $n_{\rm in} \to n_{\rm out}$ scattering processes. The collision integral is evaluated directly in $3(n_{\rm total}-2)$ dimensions using the VEGAS adaptive Monte Carlo algorithm with vectorized batch evaluation. Momentum conservation is enforced exactly by expressing one particle's momentum through the constraint, while energy conservation is imposed via a narrow Gaussian representation of the delta function. We identify a subtlety in the construction of the collision integral for processes with unequal initial and final multiplicities ($n_{\rm in} \neq n_{\rm out}$) involving identical particles: the full collision rate requires separate evaluation with the observed momentum pinned to each side of the reaction, weighted by the respective particle multiplicities. Failure to account for this leads to systematic violation of energy conservation. The code supports massive particles with time-dependent masses, Bose-Einstein and Fermi-Dirac quantum statistics, multiple coupled species, cosmological expansion with comoving momenta, and both Euler and Heun time integration. Parallelization is achieved by distributing independent momentum grid points across MPI ranks, yielding near-linear scaling to hundreds of cores. We validate the Monte Carlo results against a semi-analytical $2 \to 2$ collision integral with exact energy conservation, following the phase-space reduction of Ala-Mattinen et al. As a demonstration, we study thermalization of a massive scalar field through a $2 \leftrightarrow 3$ number-changing process and show that energy conservation is restored only when all identical-particle contributions are correctly summed. The code is publicly available at this https URL.

Dense neutrino plasmas can develop instabilities that drive collisionless flavor exchange, equivalent to the emission of flavomons, the quanta of flavor waves. We treat these waves, for the first time, as independent linear degrees of freedom and develop a quasi-linear theory (QLT), including backreaction on the neutrino distribution and nonresonant neutrino--flavomon interactions, while neglecting wave--wave processes. In a homogeneous, axisymmetric model, the saturated neutrino and flavomon distributions agree closely with periodic-box solutions of the original quantum kinetic equation. These results support the use of QLT, well established in plasma physics, to bypass nonlinear small-scale effects that challenge direct simulations.

Active neutrinos in standard cosmology were ruled out as a dark matter candidate in the 1980's. The reason is twofold: they are too light to account for the observed energy density of dark matter in the Universe, and their relativistic nature would spoil structure formation. In this note we suggest that an enhanced density of cold Standard Model active neutrinos today could behave effectively as dark matter, avoiding constraints from recombination and structure formation. Such an enhancement could be produced, for instance, by late-time decays of a light scalar field that is not in thermal equilibrium with the plasma. This mechanism is testable through the detection of the Cosmic Neutrino Background (C$\nu$B), which could have an average cosmological energy density a factor of $\sim 100-200$ times larger than expected in $\Lambda$CDM. The postulated light neutrinophilic scalar field may be observable, with Yukawa couplings in the range $y \sim 5 \times 10^{-16}-10^{-12}$. A scenario preferred by structure formation constraints is that the scalar is a Majoron, and the neutrinos have an inverted mass hierarchy.

Dense concentrations of dark matter (DM) surrounding black holes provide a compelling opportunity to probe the nature of DM. In the classic Gondolo-Silk model, the adiabatic growth of a massive black hole (MBH) in a DM cusp produces a steep density spike ($\rho \propto r^{-7/3}$), potentially inducing measurable gravitational-wave dephasings in intermediate and extreme mass-ratio inspirals (IMRIs/EMRIs). We challenge this paradigm by considering a collisionless spike embedded in a realistic nuclear star cluster (NSC). Using 1D orbit-averaged Fokker-Planck (FP) simulations of isotropic NSCs, we show that mass segregation in a multi-mass stellar cusp accelerates relaxation, relative to single-mass models, thereby driving the DM to the lower density $r^{-3/2}$ Bahcall-Wolf profile within $\lesssim 1 \mathrm{Gyr}$. In the inner regions, where the FP description breaks down, we model strong triple interactions between DM particles and EMRIs using post-Newtonian 3-body simulations. We show that EMRIs eject DM particles via slingshots, depleting the inner spike over a few Gyrs. Because EMRI number densities are too low to drive two-body relaxation, and collisionless DM cannot efficiently repopulate the depleted phase space, this depletion is irreversible. While the extent of EMRI-induced depletion depends on the EMRI rate and mass, we find reductions in DM densities by several orders of magnitude. Hence, DM-induced dephasings for EMRIs may fall below the detectability threshold of LISA for MBHs at $z = 3$ (2.14 Gyr) with masses $\lesssim 10^{5}\,M_\odot$ (for an $\mathcal{O}(10) \, \mathrm{Gyr}^{-1}$ EMRI rate), extending to $\lesssim 10^6\,M_\odot$ for more optimistic rates of $\mathcal{O}(300-1000) \, \mathrm{Gyr}^{-1}$. Our findings substantially reduce the parameter space over which MBHs can host detectable collisionless DM spikes.

Oscillating ultra-light scalar fields are a natural explanation for the dark matter in our universe, as long as a mechanism, often called a misalignment mechanism, exists to explain the amplitude of the scalar oscillations. If the dark matter scalar couples to the Standard Model, then the dynamics of ordinary matter can influence the behaviour of dark matter in the early universe. In this work we show how this changes the expected value of the scalar field and the resulting amplitude of late time scalar oscillations, and therefore the abundance of dark matter at late times. For dark matter scalars that interact quadratically with Standard Model fields we derive estimates of the size of this effect as a function of the strength of the coupling, and for axion-like fields we show that interactions with dark sector matter can temporarily destabilize the field, leading to large field displacements.

KM3NeT's detection of a muon track produced by a $\sim 220 \, {\rm PeV}$ neutrino provides an opportunity to probe physics at center-of-momentum energies greater than those probed by the Large Hadron Collider or other existing particle accelerators. In this study, we use this single event to place an upper limit on the neutrino-nucleon cross section of $\sigma_{\nu N} < 40 \, \sigma_{\nu N}^{\rm SM}$ at $E_{\rm CM} \sim 20 \, {\rm TeV}$. This result can be used to constrain a variety of scenarios beyond the Standard Model. With future very large volume neutrino telescopes, constraints on the neutrino-nucleon scattering cross section are expected to become substantially more stringent and, in some scenarios, could become competitive with accelerator probes of new physics.

In a recent work, we considered the propagation of fermions in the background of a scalar Bose-Einstein (BE) condensate. Using some illustrative Yukawa-type coupling models between the fermions and the scalar fields, we determined the dispersion relations of the fermions and the scalar modes in various models. To complement that work, here we consider the corresponding fermion spinors and propagators, which are required for the calculation of rates of processes involving the fermions, as well as the thermal, and/or higher order, corrections to such rates. We obtain and present here concise formulas which are useful for those applications. As an application and for illustrative purposes we specifically calculate the rate for a generic fermion (which we denote by $\chi$) with the fermions in the BE background, using commonly used models for the fermion interactions. Due to the fact that the background fermion dispersion relations are helicity dependent, the kinematics have some unique and non-standard features. For example, at a particular value of the momentum one of the fermion modes has zero group velocity, which leads to a singularity in the scattering rate of the type of the Van Hove singularity in the density of states of some condensed matter systems. The results of the framework presented here, besides their merit in their own right, can be useful in specific contexts and applications, such as cosmic-ray electron cooling through dark matter-electron scattering, and similar ones involving neutrino and/or electron propagation in a scalar Dark Matter background.

Exploding primordial black holes can source baryon asymmetry soon after the electroweak phase transition, as high-energy Hawking radiation drives ultrarelativistic shocks in the surrounding plasma. The shocks and their trailing rarefaction waves delineate two bubble-like walls around a shell of superheated fluid, in which electroweak symmetry is restored. These moving interfaces source chiral charge, which is converted to baryon number. Upon adding a simple CP-violating operator at the TeV scale, this mechanism yields the observed baryon asymmetry with minimal dependence on PBH model parameters.

The imitative verb "chirp" is thought to originate from 16th-century Middle English. Meanwhile, this same word has been used to describe the gravitational waves (GWs) emitted from the merger of compact objects, such as black holes and neutron stars, since at least the 1990s. Motivated purely by this linguistic overlap, we study whether the chirps of birds can be modeled by compact binary waveforms. In particular, we consider a test case of the Northern cardinal (Cardinalis cardinalis), finding that its time-reversed chirp can be approximately modeled by that of a high mass ratio, precessing black hole binary, with a number of indications towards extreme matter effects or beyond the Standard Model physics. Importantly, this waveform correspondence is not so straightforward for all bird species, as some chirp morphologies are far more akin to glitches seen in GW observatories. With these comparisons made, we propose an alternative solution to the longstanding philosophical conundrum: rather than the chicken or the egg, perhaps it was the Big Bang which truly came first.

The high frequency of satellite launches, particularly over the last few years, has been a subject of significant concern, particularly relating to the future of observational astronomy, the stability of low Earth orbits, and environmental impacts. We call attention to the insufficiently-addressed silver lining of this looming satellite cloud. If the high rates of satellites continue as we model, we can expect the solar flux received by the Earth to significantly decrease in the relatively near future. We address how this decrease in flux could provide a solution for another major problem, anthropogenic climate change. This would allow us to solve one problem with another problem as early as late March 2031.

Accurate inclusion of both spin precession and orbital eccentricity effects in gravitational waveform models represents a key hurdle in our ability to fully characterize the properties of compact binaries. Virtually all efforts to model precession rely on a coprecessing frame transformation, a time-dependent spatial rotation that tracks the dominant emission direction and simplifies the waveform morphology. We assess the utility of the coprecessing frame transformation to separate out the effect of the precession of the orbital plane from the waveform in the presence of non-negligible orbital eccentricity. We rely on 20 numerical relativity simulations, which include the complete physical effects of spin precession and eccentricity in the strong-field, and compare waveforms in both the inertial and coprecessing frames. Comparing against the eccentric, spin-aligned model SEOBNRv5EHM, we find that while the waveform mismatches decrease in the coprecessing frame, they remain above the level required for accurate waveform modeling, $\sim$ 0.01 or higher for large inclinations. Further improvements, e.g., modeling mode asymmetries as already pursued for quasicircular binaries, will likely prove essential. We also find that by removing the dominant amplitude and phase modulations from the waveform, the coprecessing frame facilitates surrogate modeling, achieving lower errors at a fixed number of basis elements compared to the inertial frame. Our results demonstrate both the utility and the limitations of the coprecessing frame as a cornerstone in waveform modeling for eccentric and precessing binaries.

It is generally assumed that gravitational waves are extremely difficult to detect. However, we show that the call of the Mexican Burrowing Toad has an amazing resemblance to cosmic gravitational wave signals due to the merging of neutron stars and/or black holes. It is known that toads exhibit magnetoreception - the ability to detect magnetic fields - and that magnetic fields thus subtly affect ion channel activities in toad neurons. We speculate that gravitational strains produce phonons and magnons in a ferromagnetic substance embedded in the nervous system of the toads and that these coherent signals are exponentially amplified by a Raman laser mechanism to the point where they can be detected. The fine tuning necessary for this mechanism to work would help to explain why this species of toad show this remarkable ability and others do not. We analyze the sound of a pond full of Mexican Burrowing Toads in the hopes of detecting slight phase shifts in their calls due to a gravitational wave event. No effect was found and the the LIGO/VIRGO consortia have not reported an event during the recording, illustrating the power of this approach. We suggest the massive use of these toads would be an inexpensive way to support the operation of optical interferometric gravitational wave detector facilities.

The pulsar magnetosphere is a potential source of continuous gravitational waves due to the rapid charge-discharge process in short timescale, varying the electric-field energy density. We estimate the strain of the continuous gravitational waves, considering relativistic effects and different gap regions. We find that the strain from the polar cap is too small, in contrast to previous results. On the other hand, the strain from the outer gap is as large as $\sim2\times10^{-24}$, enough for future gravitational-wave detection such as the Einstein Telescope. Our result presents a new approach for the future detection of gravitational waves to probe the physics in the magnetosphere.

Over the past decade, gravitational-wave astronomy has opened a new window onto the extreme states of matter inside compact stars. At some point during the inspiral of a binary system, each star starts to experience adiabatic tides, characterized by tidal deformabilities. The dominant tidal deformability, first measured with the GW170817 event, has already constrained the dense-matter equation of state. With the advent of third-generation detectors, tidal deformabilities are expected to be inferred with much higher precision, potentially revealing subleading tidal contributions. This motivates the development of more accurate compact-star models that incorporate richer microphysics. With this in mind, we move beyond the commonly adopted perfect-fluid approximation and model compact stars through a multifluid framework. In this work, we present the fully general-relativistic description of adiabatic tidal deformations of compact stars composed of an arbitrary number of interacting fluids, using Carter's multifluid variational formalism. A distinctive feature of this approach is the presence of nondissipative mutual entrainment between fluid species. We derive the hydrostatic equilibrium equations for multifluid configurations, along with the perturbed equations governing stationary gravitoelectric and gravitomagnetic tidal responses of arbitrary order. We then investigate how entrainment modifies the corresponding tidal deformabilities. Using an analytical representation of the multifluid equation of state, we show that entrainment leaves adiabatic tidal responses unchanged and therefore produces no measurable effect on the gravitational-wave signal emitted during the inspiral long before the excitation of internal mode resonances. We subsequently discuss two specific applications: superfluid neutron stars and dark matter admixed compact stars.

We revisit QCD-induced little inflation in which the Universe starts with a large baryon chemical potential and undergoes a strong first-order QCD phase transition, generating an observable stochastic gravitational-wave background in the nano-Hz range relevant for pulsar timing array (PTA) observations. We point out that the conventional homogeneous transition from the quark-gluon plasma phase to the hadronic gas phase faces an unavoidable difficulty in achieving the required strength of supercooling for the observed baryon density. This motivates us to explore whether a qualitatively different phase structure at a large baryon chemical potential can alter the relation between the baryon density and the chemical potential, and thereby modify the supercooling history of the transition. Using the nucleon-meson model with isoscalar vector mesons, we determine the critical and spinodal structure of the chiral density wave (CDW) phase in the $(\mu_B, T)$ plane. We find that the CDW phase exhibits a nontrivial structure and can remain metastable down to a low baryon density in a certain region of the parameter space. Taking into account the subsequent liquid-gas transition and phase separation, however, the released latent heat is too small to realize a viable QCD-induced little inflation scenario and its associated PTA-scale gravitational-wave signal. Our analysis sharpens the conditions under which QCD phase transitions may act as cosmological sources of nano-Hz gravitational waves, while clarifying the possible cosmological relevance of inhomogeneous QCD phases.

We compare conventional non-minimally coupled Peccei-Quinn (PQ) inflation with a version of the model in which unitarity conservation is imposed by additional Jordan frame interactions. Assuming instantaneous reheating, the unitarity-conserving model is within 1$\sigma$ agreement with the central value of the scalar spectral index reported by the ACT collaboration, whereas conventional PQ inflation is more than 2$\sigma$ below the ACT central value. In the case where dark matter is composed of axions and PQ symmetry is not restored after inflation, the axion isocurvature constraint of the unitarity-conserving model typically allows a much larger axion decay constant $f_{a}$ than the conventional model, with the conventional model upper bound being larger only if the PQ self-coupling is extremely small, $\lambda < 10^{-12}$. For $\lambda = 0.1$, the axion isocurvature upper bounds are $f_{a} \leq 1.1 \times 10^{9} $ GeV for conventional PQ inflation and $f_{a} \leq 6.4 \times 10^{13}$ GeV for unitarity-conserving PQ inflation, with the latter bound being independent of $\lambda$. We also find a new isocurvature upper bound for conventional PQ inflation which is 650 times smaller than the existing bound. A modest reduction of the reheating temperature of the unitarity-conserving model from its maximum possible value will ensure that the PQ symmetry is not restored after inflation, allowing values of $f_{a}$ up to $6.4 \times 10^{13}$ GeV. Thus only the unitarity-conserving PQ inflation model allows $f_{a}$ to access values greater than the symmetry restoration cosmological upper bound $\sim 10^{12}$ GeV with naturally large values of the PQ self-coupling.

We investigate brane inflation, focusing on warm inflation realizations within a warped throat geometry. While the standard scenario relies on a single mobile $D3$-brane moving radially toward an anti-$D3$-brane at the tip of the throat, we propose two distinct inflationary pictures. In our approach, the radial and angular coordinates of a $D3$-brane on a warped deformed conifold act as two independent inflaton fields. We address moduli stabilization by incorporating a supersymmetrically embedded $D7$-brane, which generates the necessary radial and angular scalar potentials. Evaluating these radial and angular brane inflation setups within the warm inflation paradigm, we demonstrate that dissipation effects allow the models to satisfy recent observational constraints more naturally than their cold inflation counterparts for a given parameter space.

The suspended end mirror of the input mode cleaner cavity in the Advanced Virgo Plus interferometer was equipped with an instrumented baffle in spring 2021, serving as a demonstrator of the technology in preparation for the installation of large instrumented baffles in the main arms of the interferometer. This baffle includes tens of sensors positioned near the mirror to enable monitoring of stray light within the cavity. In this contribution, we assess the performance and stability of the instrument after four years of operation. After introducing the main characteristics of the baffle, we study the distribution of stray light and show that the instrumented baffle can be used to monitor laser stability and alignment within the cavity. Finally, we assess the noise level during the final stages of the O4b commissioning to monitor the impact of the baffle, and conclude that the baffle does not introduce any additional disturbance to the normal operation of the interferometer.

Unlike electromagnetic telescopes, gravitational-wave (GW) detectors cannot produce pretty pictures, but we can convert GW signals into sound. I compute what the Universe actually sounds like by averaging over $\sim10^6$ synthetic compact binary coalescence events occurring throughout 2026. The result: a soothing, low-frequency rumble, perfect for sleeping, meditation, or contemplating the violent nature of spacetime. This is the $Universal\ harmony$, audio file included!