Main

We present TIC 160582982, an eccentric $\delta$ Scuti binary with a dynamically massive unseen companion. Six coherent high-frequency pressure modes used as pulsation clocks yield a phase-modulation orbit with $P_{\rm orb}=89.29\pm0.19$ d, $e=0.539^{+0.040}_{-0.037}$, and $a_1\sin i/c=145.6^{+3.7}_{-3.4}$ s, corresponding to $K_1=42.2^{+2.2}_{-1.8}$ km s$^{-1}$ and $f(M)=0.416^{+0.032}_{-0.028}\,M_\odot$. An independent frequency-modulation analysis of the two strongest modes gives a consistent orbital solution. Rotating MIST isochrones constrained by the atmospheric parameters and spectral energy distribution (SED) give $M_1=1.93\pm0.19\,M_\odot$ and $R_1=2.65\pm0.23\,R_\odot$. The mass function implies a formal edge-on minimum companion mass of approximately $1.80\,M_\odot$. Assuming a luminous main-sequence companion and including the non-eclipsing geometry gives $M_2=2.19^{+1.24}_{-0.34}\,M_\odot$ and $i=61.5^{+16.6}_{-19.6}$ deg. However, no clear evidence for the presence of a luminous counterpart is found, either photometrically or spectroscopically. This suggests the presence of a massive compact object, such as a neutron star or even a stellar-mass black hole, as the massive unseen binary companion. Future phase-resolved high-resolution spectroscopy will be crucial for obtaining an independent orbital constraint and clarifying the nature of the companion.

We report the discovery of three candidate spider millisecond pulsars via multi-wavelength follow-up of unassociated Fermi Large Area Telescope gamma-ray sources. All have optical spectroscopy from the SOAR 4.1-m telescope and X-ray data from Swift. Two optical/X-ray sources are exceptionally strong redback candidates, sitting close to the centres of the localization ellipses of the gamma-ray sources 4FGL J1020.4-5314 and 4FGL J1408.7-3747. We show that both optical sources are spectroscopic binaries with orbital periods (0.15-0.3 d) and mass functions (0.6-0.9 Msun) typical for redbacks. 4FGL J1020.4-5314 shows bright, very broad (full width at half maximum 2100 km/s) H-alpha emission in all spectra obtained over two years. Remarkably, the H-alpha radial velocities are offset in phase from the absorption-line velocities of the secondary, and match the signal expected for an emission source near the primary. This demonstrates, for the first time for any spider, that the H-alpha emission can be associated with an intrabinary shock that wraps around the pulsar, opening up the possibility of using optical emission lines as kinematic tracers of the intrabinary shock in some redbacks. A third candidate spider is less secure in its association with the gamma-ray source 4FGL J1429.8-0739, but has unusual properties, including a 30.5-hour orbital period, a potential subgiant secondary, and a high X-ray luminosity, making it worthy of further investigation.

The nearby (3.2 pc) K2V star $\epsilon$ Eridani hosts the closest detected debris disk and an exo-Jupiter analog ($\epsilon$ Eridani b). In this work, we reanalyse ALMA Band 6 (1.29 mm) observations of $\epsilon$ Eridani to assess whether its outer debris belt exhibits a non-zero eccentricity, potentially induced by planet-disk interactions. Considering two models, one that accounts for the disk's forced eccentricity ($e_\mathrm{f}$) and another that accounts for a proper eccentricity ($e_\mathrm{p}$), we place stringent (99.7th-percentile) upper limits of $e_\mathrm{f} < 2.6\%$ and $e_\mathrm{p} < 6.8\%$, respectively, and find tentative evidence for a non-zero forced eccentricity of $e_\mathrm{f} = 1.62^{+0.39}_{-0.40}\%$ at the $4\sigma$ level. This corresponds to the lowest millimeter-derived upper limit on the forced eccentricity of any debris disk to date, which, together with the low upper limit on the proper eccentricity, suggests that the outer belt is nearly circular and dynamically cold. We further explore planetary system architectures that are consistent with these ALMA-based results in combination with Spitzer/IRAC, JWST/NIRCam F444W, and JWST/MIRI F2550W data. Together, these analyses provide insight into potential planet-disk interactions in this nearby system, constraining any additional planet beyond $\epsilon$ Eridani b to masses ranging from $\sim 2\times10^{-4}$ to $0.3\,M_\mathrm{Jup}$ at orbital separations of $\sim 6$-$60$ au.

Long secondary periods (LSPs), observed in about one-third of pulsating red giants, remain unexplained despite decades of study, with binarity and non-radial oscillations as the leading competing hypotheses. If LSP variables are indeed interacting, eccentric binary systems consisting of a red giant and a substellar object, tidally excited oscillations (TEOs) would be expected to appear in a fraction of them. Therefore, detection of TEOs offers an independent test of the binary scenario that has not previously been applied to LSP stars. Using a combined, approximately 80-year light curve assembled from Digital Access to a Sky Century @ Harvard (DASCH), Hipparcos, and All Sky Automatic Survey (ASAS) photometry, we find that CZ Tucanae (CZ Tuc) exhibits a pulsation period of $55.4734\pm0.0074$ days along with its LSP of $443.62\pm0.12$ days, with a ratio of $7.9970\pm0.0024$ - consistent with a TEO. Theoretical models show the observed amplitude of the candidate TEO could be produced after adopting the estimated fundamental parameters of CZ Tuc. Our findings identify CZ Tuc as the first candidate LSP star with a TEO, providing independent evidence for binarity among at least a subset of these enigmatic variables.

Introducing primordial magnetic fields (PMFs) into the standard cosmological model, $\Lambda$CDM, has an impact on the matter power spectrum at the linear level, resulting in an increase of power on small scales. In this work, we use the enhanced spectrum as the initial condition for dark-matter-only N-body simulations and study its non-linear evolution. From the resulting non-linear matter power spectrum, we calculate the convergence power spectrum of weak lensing ($C_{\kappa}$) and show how the presence of PMFs causes an enhancement at high multipoles. We then construct an emulator for $C_{\kappa}$ that also includes intrinsic alignment and baryon feedback. We perform MCMC analyses using mock data generated for different PMF models and for three values of the maximum multipole, $\ell_{\rm max}=5000$, $10000$, and $20000$. The PMFs models are characterized by the two parameters that define the power-law power spectrum of the magnetic field $P_B(k)\propto B_{\rm 1Mpc}^2 k^{n_B}$, where $B_{\rm 1Mpc}$ is the amplitude at a scale of $1$ Mpc and $n_B$ is the power spectral index. For $\Lambda$CDM mocks, corresponding to $B_{\rm 1Mpc}=0$, we obtain approximate upper limits of $B_{\rm 1Mpc}<1.6$, $1.0$, and $0.8\,{\rm nG}$ at the $95\%$ confidence level for the three values of $\ell_{\rm max}$ respectively. For non-zero input magnetic fields, the recovery of $B_{\rm 1Mpc}$ and $n_B$ depends strongly on the PMFs model and on the maximum multipole considered. Models with $n_B=-2.1$ are more easily constrained than models with $n_B=-2.7$, since they produce a stronger enhancement of the convergence power spectrum. We find no clear degeneracy between the PMFs parameters and the intrinsic alignment or baryon feedback parameters, while $B_{\rm 1Mpc}$ and $n_B$ can be degenerate. We characterize this degeneracy through linear fits to selected $2$D posterior distributions.

After sixteen years in quiescence, EXO 0748-676 unexpectedly returned to outburst in March 2024. However, in stark contrast to its previous outburst (1985 - 2008), EXO 0748-676 returned to quiescence in January 2025, after   10 months in outburst. Here, we collate data from nine observing facilities, covering wavelengths from radio to X-ray, to provide the first multi-wavelength study of the 2024/25 outburst. Unlike the 1985 outburst, both the rise and decay are fully captured at X-ray and optical wavelengths. The light curves do not exhibit the hallmarks of a canonical transient low-mass X-ray binary outburst. Instead, the X-ray and optical fluxes remain reasonably stable during the 2024/25 outburst. The wealth of optical data of EXO 0748-676 reveals a skewed optical phase curve and an irradiation-dominated optical light curve which lasts until the onset of hydrogen recombination in the outer disc at  11000K, triggering a rapid fade at the end of the outburst. X-ray observations by XMM-Newton and NICER revealed that EXO 0748-676 was heavily obscured early on, with spectra exhibiting a dampened soft X-ray contribution. We find that a spectral model including a clumpy, ionised absorber describes the obscuration, although the exact cause of the early-time obscuration remains uncertain. X-ray colour analysis indicates that EXO 0748-676 spent most of the  10 month outburst in a faint, hard state. EXO 0748-676 increased marginally in brightness towards the end of the outburst, but never entered a soft spectral state. This behaviour is characteristic of a failed transition outburst.

Soft X-ray flashes (XRFs) are predicted from a variety of hypothesized phenomena, including "dirty fireballs" (relativistic jets with significant baryon loading), and gamma-ray bursts viewed marginally off-axis. For a given burst, detailed multiwavelength observations are necessary for distinguishing between possible progenitor scenarios, but the number of XRFs with such data remains small. Here we present X-ray, optical, and radio (mm to cm) data of GRB 250419A, an XRF (with peak energy $E_p<4\,$keV) discovered by the Space-based multi-band astronomical Variable Objects Monitor. We observe a clear achromatic break in the X-ray and optical bands, and likely two spectral components in the radio emission. The afterglow is similar to the long-duration gamma-ray burst population, but slightly underluminous, and the optical afterglow has an unusually shallow decay phase at $\lesssim2\,$d. We find that the event is well explained by a high-Lorentz factor jet with low kinetic energy ($E\sim10^{49}$-$10^{50}\,$erg), with energy injection that could arise from radial stratification and/or the jet being viewed marginally off-axis. We conclude that at least some X-ray flashes are an extension of classical gamma-ray bursts down to lower energies.

RR Lyraes (RRLs) are important tracers of old stellar populations and crucial distance indicators. To complement large variability surveys such as Gaia and Rubin-LSST, the topology of the RRL instability strip (IS) and their period-luminosity-metallicity (PLZ) and period-Wesenheit-metallicity (PWZ) relations need to be updated using state-of-the-art stellar evolution and pulsation models. We employ the updated set of BaSTI horizontal-branch (HB) evolutionary models, with finer sampling in effective temperature and metallicity, and compute the corresponding pulsation models using the mesa-rsp module building on the approach of Marconi et al. (2015). We compute a grid of linear non-adiabatic radial pulsation models with mesa-rsp, covering -2.2 <= [Fe/H] <= +0.06 dex. Seven convection configurations are explored including the recently empirically calibrated prescription for RRLs by Kovacs et al. (2024). Analytical IS boundaries are derived for RRab and RRc pulsators and transformed into several photometric systems (Gaia, OGLE, 2MASS, and LSST) and the Kiel diagram. The updated evolutionary models do not substantially change the pulsation predictions: RRab IS edges agree well with previous results, while the RRc red edge is slightly redder. The width of the IS decreases systematically with increasing alpha_MLT, and RRc is relatively more sensitive to the convection prescription than RRab. The PLZ and PWZ relations are also in good agreement with previous empirical and theoretical calibrations across the NIR bands; however, the convection prescription giving the closest match is wavelength dependent. The predicted IS boundaries and PLZ/PWZ relations exhibit a coupled dependence on pulsation mode, metallicity, and convective treatment, with no single prescription performing uniformly best across all observational planes.

We present the first detailed X-ray and optical study of the intermediate polar Swift J0614.0+1709 based on a pointed XMM-Newton observation complemented by long-term optical photometry from TESS. A strong coherent modulation at the white dwarf spin period was detected in X-rays, with a period of $\sim$1411 s, confirming the magnetic nature of the system. The X-ray spin pulse exhibits a pronounced energy dependence, with the modulation amplitude decreasing towards higher energies, consistent with phase-dependent absorption in the accretion flow. Phase-resolved spectroscopy further shows that the spin variability is primarily driven by changes in the covering fraction of the partial-covering absorber. The broadband X-ray spectrum is well described by a partially absorbed thermal plasma model with a temperature of $\sim$12 keV and a soft blackbody component at $\sim$63 eV. The inferred bolometric luminosity of $\sim$5$\times$10$^{34}$ erg s$^{-1}$ places the source among the more luminous intermediate polars. The TESS observations reveal substantial sector-to-sector variability in the relative strengths of the orbital and spin modulations. While the spin signal remains persistently dominant, the beat modulation varies significantly and disappears entirely in one Sector, suggesting temporal changes in the contribution of the reprocessing region(s). The orbital and, to a lesser extent, spin modulation amplitudes show some tendency to be stronger during brighter optical states, suggesting that changes in the mass transfer rate may influence the optical emission and modulation amplitudes. Overall, Swift J0614.0+1709 is a comparatively X-ray luminous intermediate polar exhibiting complex optical variability characterised by changes in pulse morphology and recurrent brightening events, making it a valuable target for future simultaneous optical and X-ray studies.

Initially discovered optically, Tidal Disruption Event (TDE) AT2018hyz was first detected in radio 972 days later. The continued monitoring of the event revealed a late-time (1370-2160 days) radio brightening. The source for this radio brightening has been associated with an afterglow originating from an off-axis jet or a delayed mildly relativistic outflow. In this work, we explored the conditions required for a delayed off-axis jet to explain the observed radio brightening. We find that the combined effect of different delay times (t_delay) and observer angles (theta_obs) can produce radio afterglow, as observed for AT2018hyz. The further off-axis from the jet core an observer is, the shorter is the delay inferred between the optical disruption and launching of the jet. This presents a degeneracy between different theta_obs and tdelay. We estimate the sky projection of the jet for these different combinations to break this degeneracy. The spread in sky images ranges from 0.6 mas for a 30 deg off-axis observer to 0.3 mas for an observer perpendicular to the jet core. Future VLBI observations should be able resolve these structures. Thus a combined observation of the light curve and sky images for AT2018hyz (and other jetted TDEs) can be used to narrow down the observer angle and any delay in launching of the underlying jet.

Recent optical and near-IR photometric databases like Gaia data release 3 (DR3) and the VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey allow the exploration of candidate unresolved multiple systems (binaries, triples, quadruples, etc.) in nearby clusters, that need spectroscopic confirmation. NGC 2437 (M 46) is a benchmark open cluster with well determined physical parameters. Its relative proximity (D=1.6 kpc) makes this cluster an ideal laboratory to measure the fractions of unresolved multiple systems. We aim here to identify unresolved triple and higher order systems that are reliable members of the open cluster NGC 2437, and provide the spectroscopic confirmation using radial velocities. We confirm that there is a sequence of unresolved binaries in NGC 2437, and report the discovery of a sequence of unresolved triple systems in this cluster. We corroborate membership for 13 binary systems and 8 triple systems using radial velocities measured by the ESO KMOS VVVX-GalCen spectroscopic survey. We further select stars with colors consistent with K-dwarfs, in order to have a controlled sample, comparable to the Solar neighborhood. We also find that the fraction of unresolved triples and quadruples is higher than that of the older open cluster Trumpler 19, studied using a similar setup, suggesting that these systems merge to form blue stragglers or get dissolved with time. We report the spectroscopic confirmation of 95% of the selected VVVX targets, thereby securing the presence of a sequence of unresolved triple systems in NGC 2437, located above the sequence of equal-mass binaries. The single stars constitute 60% of the mass of the cluster, while the rest of the mass (40%) is lodged in the unresolved multiple systems.

The abundance of galaxy clusters as a function of mass — the halo mass function (HMF) — depends strongly on cosmological parameters. Large-scale simulations are computationally expensive, motivating emulators that interpolate simulation outputs. We present a neural network emulator that maps cosmological and astrophysical parameters, halo mass, and redshift directly to a cumulative count of halos above the input mass, avoiding the information loss inherent to binning and to the functional or PCA-based data reduction used in prior emulators. Each emulator prediction is accompanied by a self-estimated error, expressed in units of Poisson shot noise, that the network learns to predict alongside the halo count itself — giving every output a built-in confidence metric. We validate the emulator with leave-one-out tests on three simulation suites — the N-body MassiveNus suite and the hydrodynamical CAMELS IllustrisTNG and SIMBA suites — spanning a range of box sizes, redshifts, sub-grid physics, and softwares. Of all the held-out predictions ($1.2\times 10^6$ in total), 88\% have model bias at or below shot noise and 99.9\% are within $3\times$ shot noise. The only significant high-error tail is in MassiveNus, where the predicted model bias flags 76\% of predictions exceeding $3\times$ shot noise; the remaining number of high error predictions is comparable to the number expected from shot noise alone. This emulator is publicly available and can be trained on other simulation suites making it a flexible HMF tool that can be used for cosmological and astrophysical inference.

Early in the 2006 outburst of the recurrent nova RS Oph, Swift detected the onset of the super-soft-source (SSS) phase. An XMM-Newton observation on day 26.1 revealed an unusual soft X-ray spectrum containing transient narrow emission features that could not be identified with known transitions and are atypical of SSS spectra. We analyse a new XMM-Newton observation obtained at a comparable stage of the 2021 outburst and compare it with spectra from other epochs and with similar novae. A blackbody model reproduces the low-resolution 2006 EPIC/pn spectrum but fails to describe the simultaneous high-resolution RGS data. The 2021 spectrum closely resembles that observed in 2006 and consists of a slowly fading shock component and a highly variable soft component containing several unidentified features. While the shock emission evolves on timescales of days, the soft component varies on hourly timescales and dominates the observed variability. Its properties resemble those of the novae V1494 Aql and V1716 Sco, but not those of the persistent SSS Cal 87. No significant 35-s periodicity is detected. The results demonstrate that low-resolution observations can miss the complex line-dominated emission revealed by high-resolution spectroscopy. The rapidly variable soft component, together with radiative recombination continua, Fe X emission, and the previously detected 35-s period, suggests the presence of a hidden photoionising source. We conclude that these enigmatic spectra form an intermediate class between the SSe and SSa categories of Ness et al. (2013), together with V1494 Aql and V1716 Sco. Future modelling will be required to determine the relative importance of photoionisation, charge exchange, and other processes in shaping this class of intermediate SSS spectra.

Studies suggest that protoplanetary disks around stars with high carbon-to-oxygen (C/O) ratios can produce terrestrial planets with carbon-dominated compositions instead of silicon-dominated ones. While previous work studied the evolution of these disks and the planets that form within them, none analyze in detail how the differences in the surface density profiles of these disks could affect the architectures and iron and siderophile contents of exoplanetary systems. Here, we present a new study that uses the N-body integrator REBOUND and data from a sequential dust condensation model to simulate the formation of planets in systems with varying C/O ratios. We find that bulk density could be used to distinguish between silicon-rich and carbon-rich planets, though it may not be a reliable metric on its own.

The high-energy and astroparticle physics literature has grown into an enormous body of knowledge. Gaining a comprehensive understanding of this literature is an important step in research, but is a challenging task. Before making meaningful advances, it is important to establish what has already been done and identify open questions. However, this process is becoming increasingly difficult given the sheer volume of publications. Conducting a focused literature survey on a narrow topic is particularly challenging. We develop an open-source Retrieval Augmented Generation (RAG) pipeline to produce concise, targeted summary reports with citations, grounded in the database of arXiv papers, enabling researchers, editors, and referees to rapidly orient themselves within any corner of the field. Specifically, we embed approximately 230K hep-ph and astro-ph.HE papers to enable a hybrid retrieval that captures both keyword matches and semantic similarity. The fused candidate set is then refined using a cross-encoder reranker. Following retrieval, the papers are passed to a Large Language Model (LLM), for which we use Google DeepMind's open-source Gemma-4-E4B model. The LLM first acts as a judge to evaluate the relevance and then synthesizes a coherent and grounded report with references. This modern AI-driven approach allows us to go beyond the capabilities of classical keyword search on arXiv or Inspire-HEP.

Tidal disruption events (TDEs) can launch sub-relativistic outflows that drive shocks into the surrounding circumnuclear material (CNM), providing a natural site for cosmic ray (CR) acceleration and high-energy neutrino production through hadronuclear ($pp$) interactions. We model this emission for optically bright and infrared (IR)-only TDEs, the latter motivated by a recently identified population of luminous IR transients with weak or absent optical counterparts, consistent with TDEs embedded in dusty, obscured nuclear environments. We semi-analytically compute the shock dynamics, CR acceleration and transport, and neutrino production, including the radiative cooling and compression in dense environments. While optical TDEs remain inefficient $pp$ neutrino sources with comparatively small neutrino yields, radiative compression in dense IR-only TDEs enhances the target density and allows the pp efficiency to approach the calorimetric regime, yielding up to $\sim 10\%$ of the observed diffuse neutrino flux at $100$ TeV, given the rate uncertainties. The long-lasting neutrino emission and low individual source yield motivate joint electromagnetically informed stacking searches. We forecast such searches for IceCube, IceCube-Gen2, KM3NeT, and HUNT, and conclude that a future $\sim 30\ {\rm km^3}$ neutrino observatory can reach $3\sigma$ sensitivity for nearby ($z \lesssim 0.4$) IR-only TDEs with multi-year search windows. Growing optical and IR TDE samples can therefore enable population-resolved searches that can test whether dense, obscured nuclear environments are efficient high-energy neutrino sources.

A sudden transition from an early matter-dominated era to a radiation-dominated era provides a representative mechanism for enhancing induced gravitational waves (GWs). In the primordial black hole (PBH) evaporation scenario, discrete PBH number-density fluctuations naturally generate Poisson isocurvature perturbations. By evaluating the GWs induced by these perturbations through the sudden evaporation transition, we show how the full hierarchy of intrinsic non-Gaussian statistics of a Poisson isocurvature source enters the induced GW spectra. We find that the tensor power spectrum retains only the two-point correlations of the scalar source, while higher-order correlations first appear in the tensor bispectrum. We also find a nontrivial scale dependence in the relative amplitudes of different bispectrum configurations, which may provide additional information for distinguishing the discrete PBH scenario from other induced-GW mechanisms.

Dividing source galaxies into tomographic redshift bins is a cornerstone of modern weak gravitational lensing analyses, enabling measurements of the growth of cosmic structure and the nature of dark energy. In practice, these tomographic bins are defined using photometric redshift (photo-$z$) estimates. However, correlations between photo-$z$ estimates and weak lensing shear can introduce redshift-dependent selection biases in the measured shear signal; if left uncorrected, these biases distort the inferred amplitude and redshift evolution of the lensing signal, and in turn bias the measurement of the growth of cosmic structure across cosmic time. In this paper, we extend the analytical self-calibration for shear measurement (AnaCal) framework to account for photo-$z$-based selection biases in tomographic weak lensing analyses by propagating shear responses through the selection process. This approach eliminates the need for external image simulations to calibrate this correction. As a first sanity check on real data, we validate the photo-$z$ estimates derived from AnaCal fluxes on the Rubin Observatory Data Preview 1 dataset, and find that they reach photo-$z$ quality comparable to, and at high redshift slightly better than, the standard LSST estimates. We then validate the shear calibration on LSST-like image simulations with blending at the expected LSST Y10 depth, with two representative photo-$z$ algorithms – a template-fitting method and a machine-learning method – and show that the multiplicative shear bias induced by photo-$z$ selection remains within the LSST ten-year requirement $|m| < 3\times 10^{-3}$ across all five tomographic bins for both algorithms. These results establish AnaCal as a self-consistent pipeline for tomographic weak lensing science in upcoming LSST analyses.

We present the results of a spectroscopic and multi-band photometric study of the magnetic cataclysmic variable 1RXS J174320.1-042953. Multi-band photometry confirms a periodic modulation with an orbital period of $P_{\rm orb}=0.0864 \pm 0.0001$ days. Using the estimated secondary mass of $\sim0.15\,\mathrm{M_\odot}$ and, the X-ray-based white dwarf mass of $\sim0.75\,\mathrm{M_\odot}$, we obtain values of $q\sim0.2$ and a system inclination of $47^\circ\pm10^\circ$. The optical spectra of 1RXS J174320.1-042953 are dominated by strong, complex, asymmetric, and highly variable single-peaked emission lines of the Balmer series, \ion{He}{i}, and \ion{He}{ii}, which are characteristic of polar-type magnetic cataclysmic variables. Doppler tomography reveals no evidence of a Keplerian accretion disc, supporting the classification of the system as a polar. The H$\beta$ and \ion{He}{ii} emission lines can be decomposed into at least two distinct components. The low-velocity components have semi-amplitudes of approximately 170 km s$^{-1}$ (H$\beta$) and 147 km s$^{-1}$ (\ion{He}{ii}), while the high-velocity components reach about 317 km s$^{-1}$ and 460 km s$^{-1}$, respectively. The low-velocity component is likely associated with the irradiated side of the secondary star facing the white dwarf and/or the vicinity of the L$_1$ point, whereas the high-velocity component is related to the accretion-stream structure. A redshifted absorption component in the emission-line wings is detected at orbital phases near $\phi \approx 0.0$, reaching velocities up to $\sim1400$ km s$^{-1}$ and likely produced by accretion-stream material crossing the line of sight.

Comets can supply volatile and prebiotic material to rocky planets, but survival of fragile molecules depends on atmospheric entry and impact. Compact planet chains can transfer comets inward at low velocity. We test whether modest planetary eccentricity preserves this route. We follow 64,000 comets from the region between the two outermost planets of an eight-planet chain to an Earth-mass planet on a temperate orbit around a $0.1 M_\odot$ star. A second suite of simulations isolates the last transfer to the innermost planet across initial planet eccentricities $e_{p,0}=0$–$0.05$ and separations of 10 and 30 mutual Hill radii; a $\Delta=12$ comparison tests the influence of the near-3:2 period ratio at $\Delta=10$. At $e_{p,0}=0.05$, the fraction of comets intercepted by the outermost planet falls by 11 per cent and 6 per cent more reach the inner region. The innermost planet's impact probability changes by less than 3 per cent, while the fraction of impacts below 15 km s$^{-1}$ falls from 25 to 18 per cent. The fraction of all injected comets producing impacts below 15 km s$^{-1}$ consequently decreases by 30 per cent. Measurements of the comet-planet speed before the final close encounter show that eccentricity preferentially removes the slowest approaches. Applying an impact-chemistry model gives a 31 per cent lower HCN survival-equivalent yield. Modest planetary eccentricity can therefore increase inward transport while reducing the prebiotic material delivered under chemically favourable impact conditions.

The composition of gamma-ray burst (GRB) jets remains uncertain. We analyze eight Fermi Gamma-ray Burst Monitor (GBM) GRBs with reported redshift information, selected from 126 events by prespecified fluence and spectral criteria. After excluding compound-model DIC evaluations classified as unstable by the posterior-stability tests, a stable added-blackbody (BB) comparison gives $\Delta\mathrm{DIC}>10$ in 203 of 215 accepted bins (60–100\% per burst); independently, a multicolor-blackbody plus power-law (mBB+PL) decomposition gives $F_{\rm mBB}/F_{\rm tot}>0.5$ in 214 of 215 bins. The cutoff-power-law (CPL)–mBB correlations ($r=0.83$ and 0.78) exceed the Band–mBB correlations ($r=0.41$ and 0.48), demonstrating model dependence. Time-integrated BB fractions span 0.005–0.311, with six of eight below 0.12. We then apply the non-dissipative photosphere prescriptions of \citet{2013A&A...551A.124H} (H2013) and \citet{2015ApJ...801..103G} (G2015). After excluding boundary or physically inadmissible inversions, the H2013 numbers with $\epsilon_{\rm Th}>0.5$ are 1/2, 1/4, and 2/8 among valid solutions at $R_0=21$, 100, and 1000 km, respectively; the corresponding G2015 numbers with $\sigma_0<1$ are 0/1, 1/4, and 1/8. The large number of invalid solutions at small $R_0$ (six and seven at 21 km for H2013 and G2015) is itself evidence that those assumed radii are incompatible with the adopted inversion for most events. Among bursts having valid solutions at more than one radius, increasing $R_0$ generally lowers $\epsilon_{\rm Th}$ and raises $\sigma_0$. Thus launch radius, efficiency, and spectral decomposition dominate the conditional jet constraints; no universal jet class or unique non-thermal mechanism is inferred.

The 35-day superorbital modulation of the X-ray binary Her X-1 was systematically investigated using a 35-year multi-instrument X-ray observational baseline. We developed a Rank-Searching method using the peak intensity of the main high state to identify anomalous low states (ALSs) with an objective and reproducible criterion. The method recovers the known ALSs, identifies two previously unrecognized candidate episodes, ALS 1991 and ALS 2015, and independently recovers the recently reported ALS 2025. We then characterized the long-term superorbital phase evolution, identifying seven epochs that alternate between smooth and variable behavior. The smooth component is empirically described by a cubic trend, while the recurrent variable epochs have a characteristic timescale of approximately 3400 days. Within a first-order tilted-disk framework, the secular phase evolution corresponds to an inferred cumulative disk-mass increase of $\sim1.8\%$ and an outer-disk-radius expansion of $\sim0.9\%$, while the short-term phase excursions can be reproduced by disk-mass variations of $\lesssim2.4\%$. A viscous diffusion timescale of approximately 168 days provides a characteristic timescale for the short-term disk response. Finally, the stable phase relation and high profile similarity between the main and short high states indicate that the warped disk maintains a remarkably stable global geometry over the observational baseline.

We present an analysis of a high-resolution optical spectrum of V1180 Cas obtained with HIRES at the W. M. Keck Observatory during a bright photometric state of the source. The spectrum is dominated by strong emission lines, including H$\alpha$, the Ca II infrared triplet, He I, and O I, along with numerous Fe I and Fe II transitions and several forbidden lines such as [O I] and [S II], indicating ongoing accretion and mass-loss activity. A weak Li I $\lambda$6708 absorption feature confirms the youth of the source. Using the Li I absorption and selected Fe I emission lines, we report for the first time a radial velocity of $-16 \pm 3$ km s$^{-1}$ for V1180 Cas. The H$\alpha$ and H$\beta$ profiles exhibit asymmetric structures with blueshifted absorption components, suggesting outflowing material along the line of sight. The He I $\lambda$5876 line displays a narrow component likely associated with post-shock accretion regions and a broad, slightly blueshifted component probably arising from magnetospheric flows and/or inner disk winds. The [O I] $\lambda$6300 profile is decomposed into low- and high-velocity components, tracing a slow disk wind and a fast jet. Using the forbidden [O I] line, we estimate for the first time a disk inclination angle of $\approx50^\circ$. The derived mass accretion and jet mass-loss rates imply $\dot{M}_{jet}/\dot{M}_{acc} \sim 0.01$–$0.03$, at the lower end of, but consistent with, the range observed for Class II YSOs. Forbidden-line diagnostics indicate densities $\sim10^{3}$ and $10^{6}$ cm$^{-3}$ with temperatures of $\sim10^{4}$ K, supporting a multi-component outflow scenario. Overall, the results support a picture in which V1180 Cas is an actively accreting, moderately inclined system hosting a multi-component outflow.

Convective-reactive events are phases of stellar evolution where turbulent mixing and nuclear burning directly compete, since their timescales become similar within convection zones. During these events the convection zone structure is shaped by a complex and dynamic interaction of convective transport and nuclear burning of individual chemical elements, with plasma streams connecting the entrainment regions with the burning layers. Here we analyse a 3D hydrodynamic simulation of an oxygen–neon shell merger in a massive pre-supernova star. We study the emergent structure using the Reynolds-Averaged Navier-Stokes (RANS) mean-field composition transport equation. We find that the merged convective zone develops a complex, turbulence-driven mixing structure of multiple nested convective-reactive shells, all contained within the single convection zone. Key controlling factors include not only the mean stratification and mixing, but also emergent collective behaviour of involved nuclear reactions for every chemical isotope. Almost all layers show a quasi-steady balance between burning and mixing. We categorise the various layers, and discuss/contrast with 1D stellar evolution code treatments, highlighting some implications.

The Sun's atmosphere is significantly influenced by events that often measure only tens of kilometres in the horizontal direction. They happen in both quiet and active regions and are determined by magneto-hydro-dynamic processes. Their origins often lie in the lowest layers of the solar atmosphere. To improve the understanding of chromospheric and coronal heating, the solar dynamo and its activity cycle, or to improve the prediction of space weather events we must therefore enhance our understanding of such small-scale events. In this work I first describe the process of calibrating spectropolarimetric observations with very high spatial resolution and put together the building blocks for the mathematical proof the MOMFBD image reconstruction algorithm. In the second part I describe the FISS-SP prototype which is designed to fully exploit the resolution power of a 1.6m telescope. This instrument is built to provide suitable data for image reconstruction of spectropolarimetric data. The resulting data can resolve small-scale features down to the diffraction limit. The simultaneous interpretation of a few lines is still the norm for spatially highly resolved solar spectra. Theoretical works have shown that the simultaneous interpretation of multiple solar lines can greatly improve the robustness against noise. Using observations from FISS-SP I advance the theoretical idea into a practical technique. With this I can retrieve a coherent model of the local solar atmosphere, resolving structures down to a horizontal size of about 49 km. Finally, I use those new techniques to interpret an observation of a solar pore. In this last part I describe and analyse small-scale structures, which could not be spectropolarimetrically resolved before. Typical pore-boundary features - namely, dark striations with bright grains moving into the pore - are identified as convective features.

We present a phenomenological study of a hypothetical compact object with a traversable 2 Kerr-type wormhole geometry connecting two asymptotically distinct regions. One mouth of the wormhole is assumed to reside in an active galactic nucleus (AGN) environment with ongoing accretion, while the second mouth is located in a comparatively quiescent galactic nucleus without accretion activity. In such a configuration, matter accreted near the AGN-side mouth may traverse the wormhole throat and emerge from the opposite mouth. Because the inflowing matter possesses angular momentum, the resulting outflow is expected to be predominantly equatorial, producing a disk-like structure fundamentally different from a conventional accretion disk around a black hole. Several dynamical regimes are considered depending on the outflow velocity relative to the local escape and orbital velocities. Possible observational manifestations, thermal properties, recombination signatures, and magnetic field effects are discussed. Special attention is given to the possibility of jet formation in the absence of a conventional accretion disk. We explicitly distinguish the weak-field, large-radius Newtonian classification used for the outer flow from the strong-field region near the throat, where the dynamics should be treated in a general-relativistic and magnetohydrodynamic framework. We further discuss the specific energy and angular momentum inherited from the inner edge of the accretion flow, the possible modification of these quantities by magnetic stresses and energy-extraction processes, and the effects of an intrinsic dipolar magnetic field of the wormhole.

Magnetic oscillations permeating the solar atmosphere can be altered by flares. This could be due to changes in the atmospheric magnetic waveguide, the thermodynamic stratification, or both. To investigate this, we examine oscillations in a magnetic pore crossed in part by the ribbon of a C8.2 flare, using observations from the Sunrise Ultraviolet Spectropolarimeter and Imager (SUSI) aboard Sunrise III. We track the core intensities of eight spectral lines between 327-329 nm and show that oscillatory power in the 4.2-7.0 mHz range, measured around 30 minutes after the flare peak, exceeds the pre-event value in all eight lines by factors of 1.60-8.71. Conversely, in the 7.0-11.5 mHz band, the post-event intensity power is lower - approximately 0.13-0.41 of the original power in seven of the observed lines. Line-center velocity measurements support the lower-frequency enhancement. This delayed, line-dependent shift toward the lower-frequency band is consistent with flare-induced changes in wave transmission, reflection, or resonant response, although thermodynamic and magnetic effects cannot yet be separated.

Massive pulsators in eclipsing binaries provide precise, model-independent stellar parameters that, combined with asteroseismic constraints, provide powerful probes of interior properties and angular-momentum transport in massive stars. This study investigates the pulsational characteristics and their impact on the structure and evolution of $\beta$ Cep pulsators in eclipsing binaries. We analyse an ensemble of 65 $\beta$ Cep stars in eclipsing binaries, identify rotationally split modes where possible, and statistically investigate the dependence of pulsational properties on binary orbital parameters. We derive their interior properties using MESA model grids and associated StORM pulsation frequencies, together with an asteroseismic routine that tracks stellar age and rotation across the $\beta$ Cep instability region. Interior rotation rates are derived for 14 systems that exhibit rotational mode splitting. While differential rotation is tentatively inferred for HD 112485, the other systems, except CZ Vel, are consistent with quasi-rigid rotation. The seismic and evolutionary properties of HD 112485 and EK Cru are derived through detailed forward asteroseismic modelling. HD 112485 is one of the least evolved $\beta$ Cep stars asteroseismically modelled to date, with a core hydrogen mass fraction $X_{c}= 0.501_{-0.013}^{+0.009}$. The two reproduced zonal modes in HD 112485 are the first radial-order dipole pressure mode and the second radial-order quadrupole gravity mode, while the zonal modes in EK Cru are the second-order quadrupole mixed mode and the third order dipole pressure mode. A multivariate regression shows a negative correlation of the pulsation amplitude with pulsation frequency, and no statistically significant relationship with the orbital period. In addition, no significant relationship is observed between the pulsation frequency and the orbital period in this sample.

The galaxy bispectrum directly probes the non-linear gravitational evolution of large-scale structure (LSS) and can break parameter degeneracies that remain in power-spectrum analyses. We present a joint full-shape cosmological analysis of three luminous red galaxy (LRG) redshift bins and the quasar (QSO) sample from the first Data Release (DR1) of the Dark Energy Spectroscopic Instrument (DESI). We model the redshift-space power spectrum at one loop and the tree-level bispectrum within the Effective Field Theory of LSS. The bispectrum is decomposed in the Tripolar Spherical Harmonics basis, for which the convolution with the survey window function can be formulated as a direct linear transformation of the theoretical multipoles. Our power-spectrum constraints are in good agreement with the official DESI DR1 full-modelling results. We investigate the impact of including the bispectrum in the inference, finding that the monopole substantially improves the constraints on the cold dark matter density and amplitude of matter fluctuations by 9-18% and 8-20%, respectively, in the individual-tracer analyses. The corresponding reductions are 15% and 10% for the combined LRG sample, and 6% and 4% when all tracers are combined. In a restricted test using the first LRG bin, the bispectrum quadrupole changes the marginalised uncertainties by only a few percent. Extending the analysis to $w_0w_a$CDM substantially broadens the cosmological posteriors, while the bispectrum produces only a mild change in the allowed dark-energy parameter region, which remains sensitive to the adopted prior ranges. Our results demonstrate the potential of higher-order clustering statistics to improve cosmological constraints, while providing a framework for incorporating the bispectrum into full-shape analyses of current and future spectroscopic galaxy surveys.

A growing number of gamma-ray bursts (GRBs) have been observed at large projected offsets from the centres of their putative host galaxies, sometimes extending to several tens of kiloparsecs. When the GRB is associated with a kilonova, a compact binary with at least one neutron star is expected to be involved, and the cause of the offset can be attributed to the neutron star natal kick. In this work, we explore an alternative mechanism: the gravitational scattering of compact binaries populating the nuclear region of the host galaxy, by an intermediate-mass black hole or secondary supermassive black hole. We specifically consider populations of neutron star-neutron star (NS-NS), neutron star-black hole (NS-BH), and neutron star-white dwarf (NS-WD) binaries, and analyse the ejection of bound systems from the nuclear region through a gravitational-slingshot effect. We proceed analytically to derive the conditions for binary survival and to parametrise the post-encounter velocity. To quantify the associated merger offsets, we numerically integrate the post-slingshot trajectory of the binary centre-of-mass in host-galaxy potentials that include the primary SMBH, the stellar component, and the dark-matter halo, considering both elliptical-like and spiral-like galaxy profiles. Our parameter sampling shows that NS-NS and NS-WD binaries typically merge farther from the galactic centre than NS-BH systems, with approximately 30-45% of successful ejections merging at three-dimensional distances exceeding 100 kpc; these extreme-offset mergers occur within $\sim$0.1-10 Gyr after ejection. These results motivate the analysed mechanism as a candidate channel for observed extreme-offset transients.

Searches for radiative decays of keV-mass dark matter have been limited by energy resolution. We propose a strategy for the XRISM/Resolve low count rate observations, and search the 3.48-3.56 keV band for a decay line from the Milky Way halo. Despite a lower exposure, our bounds are stronger than those from XRISM observations of galaxy clusters. We also identify a residual at E = 3.5311 keV with  3sigma local significance, coincident with the previously reported unidentified feature, and having no plausible atomic or instrumental counterpart. These bounds will continue to tighten as additional pointings become available.

Accurate stellar parameters underpin much of astrophysics, from exoplanetary systems to Galactic archaeology. For isolated field stars, masses and especially ages are usually inferred from stellar evolution models, yet these inferences depend on the chosen model grid, and the systematic differences between grids can rival the statistical uncertainties of any single pipeline. We present LACHESIS, a Python package that determines stellar masses, radii, and ages from photometry and spectroscopy while explicitly accounting for the systematic uncertainty from the choice of model grid. We interpolate five independent isochrone grids in [Fe/H], log age, and equivalent evolutionary phase conditioned on the data, sample each with nested sampling, and combine the per-grid posteriors by Bayesian model averaging, weighting each grid by its Bayesian evidence. We validate LACHESIS against a benchmark of Kepler asteroseismic dwarfs and subgiants. Masses are recovered with a robust scatter of  4% and radii to  2%, with negligible radius bias (<1%) and a small  3% mass systematic. Age is recovered with a robust scatter of 30% that depends strongly on evolutionary state; the grid-to-grid systematic contributes a  9% floor, a subdominant but real term that a single-grid fit omits. Model averaging is better calibrated than selecting a single grid: its credible intervals approach nominal coverage once the reference uncertainty is included, and cover near the nominal rate in injection tests even when the generating model lies outside the ensemble. By marginalizing over an ensemble of stellar model grids, LACHESIS folds the choice-of-grid systematic directly into the posterior, so the reported uncertainties no longer reflect only within-grid data noise. This delivers homogeneous, well-characterized masses, radii, and ages for exoplanet hosts and stellar population studies.

Mass-loss in red supergiants (RSGs) is poorly understood and stellar evolution models rely on empirical prescriptions. In recent years, new superwind mass-loss ideas, including an $L/M$ dependence have been proposed, unlike traditional RSG wind recipes which are formulated on a $L$ dependence alone. We investigate how contrasting RSG mass-loss prescriptions affect the late-time evolution of massive stars from their RSG phase onwards. We used MESA to create a series of stellar evolution models with masses ranging from $10\,{\rm M}_\odot - 40\,{\rm M}_\odot$, using the RSG \cite{VS23} $L/M$ recipe and traditional mass-loss prescriptions. Independent of the treatment of the stellar envelope, we find for a 25$\,{\rm M}_\odot$ star that the $L/M$ recipe reaches an order of magnitude higher mass-loss rate than traditional recipes due to its inverse mass dependence. As the RSG luminosity is set by the core mass and becomes largely insensitive to the current stellar mass, this creates a positive feedback loop driving runaway envelope stripping. Consequently, stars with an initial mass $M_{\rm init} \sim \,20\,{\rm M}_\odot$ are able to strip their hydrogen envelope and form classical Wolf-Rayet (WR) stars. We draw this conclusion not solely on the basis of their HRD location, but also on their predicted emission-line spectrum that we compute with the PoWR stellar atmosphere code. Stars with $M_{\rm init}<20\,{\rm M}_\odot$ do not fully strip, meaning they expand after core helium burning. In Appendix A we present a generic analytical model showing that the tendency for runaway stripping increases rapidly with the strength of the inverse mass-loss scaling with mass. Our models demonstrate a viable single-star pathway into the yellow supergiant and WR regimes. The amounts of full and partial stripping have a direct effect on supernova (SN) progenitors, including partially stripped type IIb SNe.

Layered viscoelastic interiors control the frequency dependence of planetary tidal dissipation, but repeated layered Love-number calculations are expensive in long-term orbital and spin integrations. Equivalent homogeneous rheologies provide a cheaper representation of the same response, but their effective parameters do not by themselves identify the interior layers they represent. We develop a local interpretation of such parameters by differentiating the layered-to-homogeneous construction about a fixed-geometry baseline, perturbing only selected layer rigidities and viscosities. We use the pole-residue representation of the degree-two Love number to construct a physical-to-effective transfer matrix. We then use its singular values, resolution matrix, and mode-dominance matrix to determine which physical perturbations are visible in the Love-number response and how they appear in effective-rheology coordinates. Applied to a five-layer lunar model, the full degree-two response is sensitive to seven of eight solid-layer rheological parameters. The single near-null direction is the inner-core rigidity, consistent with shielding by the fluid outer core and with the weak dependence of Love numbers on core elastic structure. Over the LLR frequency interval, fewer physical directions are visible. To first order, the elastic spring, isolated dashpot, and two Voigt elements reproduce the nine-pole response over this interval. Finite perturbations confirm the tangent prediction to within a few percent, with the validity radius limited by a nearly degenerate pair of long-timescale modes.

We present a framework for propagating systematic data mismatches into parameter biases and posterior deformations beyond the Gaussian Fisher approximation. Using the Derivative Approximation for Likelihoods (DALI), we derive analytic expressions for the maximum a posteriori (MAP) point and posterior mean, including a semi-analytic response expansion in systematic amplitude. We validate the framework against direct numerical calculations and Markov Chain Monte Carlo (MCMC) sampling in a controlled nonlinear two-parameter benchmark up to a covariance-weighted data-space mismatch of $d_{data}=5$. At $d_{data}=5$, Fisher predicts the wrong direction of the shift in one parameter and differs from the numerical result by a Fisher-metric distance of 23.1, whereas the analytic DALI MAP prediction remains within 0.091, with componentwise errors of 0.04% and 0.46%. The response expansion reproduces the posterior mean with errors of 0.02% and 0.18%, while the DALI posterior closely reproduces the displacement and deformation of the fully sampled nonlinear posterior. Mismatches of equal significance but different directions produce markedly different parameter shifts and posterior deformations, while multiple additive mismatches can produce nonadditive parameter responses through nonlinear inference. By reconstructing the posterior under systematic mismatch, the framework captures the nonlinear response and non-Gaussian geometry of parameter bias: how mismatches move and reshape the posterior, why their direction matters, and how their combined effects can be dissected to understand the interplay between multiple systematics.

We derive the canonically normalized modes of a two-field inflationary system with arbitrary constant quadratic mixing and unequal sound speeds $c_\varphi$ and $c_\sigma$ for the curvature and isocurvature perturbations, respectively. A Laplace representation reduces the coupled dynamics to a second-order Heun equation and gives the exact late-time curvature power spectrum for arbitrary values of the mixing parameter and entropy mass. The sound-speed ratio $r_c=c_\sigma/c_\varphi$ controls the separation between the two sound horizons. At fixed nonzero mixing and $r_c\ll1$, the power exhibits power-law enhancement, growth as $\ln^2(1/r_c)$, or bounded oscillations in $\ln r_c$, depending on the mass and mixing. For $r_c\gg1$, the correction to the unmixed spectrum vanishes as $\ln r_c/r_c^2$ at fixed mass and mixing. Using the same normalized modes, we compute the tree-level bispectrum for three representative cubic interactions, with the mixing parameter treated exactly. For heavy entropy fields, unequal speeds modify the collider amplitude and phase while preserving the strict squeezed frequency set by the final entropy mass. The power-normalized amplitude can vary nonmonotonically with $r_c$, and a sound-speed hierarchy can delay the approach to this asymptotic regime.

Physical processes in solar flares span many orders of magnitude in spatiotemporal scales, so a single unified model accounting for all relevant processes remains computationally intractable. Instead, specialized codes have been developed, targeting specific domains that tackle specific aspects of the solar flare problem. Here, we present a comprehensive framework that links three models to capture flare initiation and energy release, the subsequent particle acceleration, the propagation and thermalization of those particles, and ultimately the heating of the lower solar atmosphere. We use the 2.5D ARMS magnetohydrodynamics (MHD) code to model stressing of the magnetic field in a simulated active region, the formation of a current sheet, magnetic reconnection, and the evolution of newly formed flare loops. We use the conditions in the ARMS' current sheet to initialize the kglobal model, which predicts time-dependent nonthermal electron and proton distributions. Finally, we use RADYN+FP to inject these distributions into a newly reconnected ARMS loop and compute subsequent particle transport, atmospheric heating, and radiative emissions. This is the first detailed presentation of a RADYN+FP simulation tracking nonthermal electrons and protons in the same loop. As well as discussing the interesting physics that takes place, we note how this results in white-light flare emission height consistent with observations. This work is a first step toward building a fully 3D flare modeling framework.

Starobinsky's original model of inflation, driven by the trace anomaly of conformal fields, and its $R+R^2$ (scalaron) formulation are often treated separately. The original anomaly-driven evolution connects an early de Sitter phase supported by the Euler anomaly to a scalaron regime, where the observable modes leave the horizon. Building on this known background connection, we compute the scalar and tensor spectra on the exact background and find that the anomaly corrections are controlled by $aN_*/(18b)$, where $a$ and $b$ are the Euler-anomaly and $R^2$ coefficients and $N_*$ the number of e-folds after the pivot exits the horizon; scalaron inflation is recovered as this parameter vanishes. The observed tilt at $N_*=60$ then requires only $b/a\simeq35$, rather than the $b/a\gtrsim10^9$ of early realizations. At this benchmark the scalar spectrum is redder than in scalaron inflation at fixed $N_*$, and the tensor-to-scalar ratio is about 17% lower at fixed tilt, a quantitative signature of the anomaly. For minimal gravitational reheating, $N_*\simeq53$, the tilt remains within $1\sigma$ of the Planck value for $b/a\gtrsim35$. In the de Sitter analysis, a finite range of the Weyl coupling excludes an extra real spin-two pole and keeps the causal response decaying. A companion paper gives the full analysis.

We demonstrate that an axion field can develop perturbations peaked at an intermediate wavenumber through its inflationary dynamics. We compute the resultant spectrum of gravitational waves (GWs) and primordial black holes (PBHs) generated through the curvaton mechanism. The GW spectrum exhibits a triangular shape, with UV and IR slopes determined by the axion's inflationary evolution and treatable as free parameters. In computing the PBH abundance, we properly account for the nonlinear relation between curvature and density perturbations and the primordial non-Gaussianity generated by the curvaton. The PBHs can account for all of dark matter, accompanied by blue-tilted isocurvature perturbations at small scales. The IR slope of the GW spectrum is anti-correlated with the magnitude of the dark matter isocurvature perturbations, offering a multi-messenger test of the model.

We study the production of QCD axion dark matter (DM) via vacuum and kinetic misalignment mechanisms during an extended reheating period after the end of slow-roll inflation. With pre-inflationary Peccei-Quinn breaking and considering a monomial inflaton potential during reheating, we classify our study into three different perturbative reheating scenarios in which the inflaton decays into (i) a pair of Standard Model (SM)-like bosons, (ii) a pair of SM-like fermions, or (iii) exclusively into a pair of heavy right-handed neutrinos, which eventually decays into the SM final states after dominating the energy density of the Universe for an intermediate epoch. For each of these reheating scenarios, we study the details of QCD axion relic separately via vacuum and kinetic misalignment mechanisms. For different combinations of reheating, monomial inflaton potential and misalignment mechanisms, we identify the parameter space consistent with the observed DM relic density while satisfying other cosmological and laboratory constraints. We also check the scope of probing the currently allowed parameter space at axion-detection and gravitational wave (GW) experiments.

If strange quark matter (SQM) is absolutely stable, hadronic neutron stars (NSs) and strange quark stars (QSs) may coexist in the so-called two-families scenario. A key issue is explaining how hadronic NSs can survive as long-lived metastable objects, rather than promptly converting into stable QSs. Since all NSs are born as hot proto-neutron stars (PNSs), a necessary condition for their existence is that the conditions for conversion, triggered by the nucleation of the first critical SQM droplet, are not reached in every PNS. We investigate the thermal nucleation of critical SQM droplets under representative PNS conditions, accounting for flavor-composition fluctuations and finite-size effects on color superconductivity by suppressing pairing in droplets smaller than the diquark coherence length. We define the nucleation conditions as the thermodynamic state at which a critical SQM droplet is expected to nucleate statistically within the characteristic dynamical timescale of the system. Under these conditions, the reduced nucleation barrier is nearly universal, with $W_*/T\simeq167$ to within a few units. Exploring the SQM parameter space, we show that requiring a canonical $1.4~\rm{M}_{\odot}$ NS to survive the PNS stage sets a lower bound on the hadron-quark surface tension $\sigma\gtrsim 67$ MeVfm$^{-2}$.

The Starobinsky model provides a successful realization of inflation and serves as a benchmark for alternative inflationary models. Motivated by its observational success, we investigate the dynamical evolution of the early Universe within this framework. Incorporating radiation production from scalaron decay, we formulate a coupled system of dynamical equations describing scalaron depletion and radiation buildup while ensuring exact energy conservation in the expanding background. In the Friedmann equation, both scalaron and radiation components gravitate, thereby accounting for the backreaction of the generated radiation. Starting with a radiation-free Universe and initial conditions from the standard slow-roll approximations, exact numerical evolution shows that inflationary dynamics is predominantly governed by the scalaron. Despite continuous radiation production, the radiation component remains subdominant, and the slow-roll conditions persist throughout inflation, yielding approximately 60 e-folds. Following inflation, the scalaron enters a damped oscillatory phase accompanied by rapid radiation growth. This transition provides a graceful exit from inflation and a smooth entry into reheating. During reheating, radiation grows continuously as the scalaron energy is depleted, with the radiation energy density ultimately becoming substantially larger than the residual scalaron energy density. This indicates the onset of a hot, radiation-dominated phase, satisfying the Kofman-Yi criterion for successful reheating. Our results demonstrate that the coupled scalaron-radiation dynamics provides a self-consistent realization of graceful exit and the transition to radiation domination in the Starobinsky model.

We investigate how dark matter (DM) admixture modifies the conformal properties and phase structure of dense neutron-star matter within a self-consistent single-fluid framework, with the global DM fraction $F_\chi=N_\chi/N_B$ fixing the local relation $n_\chi=F_\chi n_B$. We derive an exact decomposition of the total trace anomaly, $\Delta_{\rm tot}$, into microscopic contributions. For collider-motivated Higgs-portal benchmarks, explicit Higgs, vector-mediator, and contact-interaction contributions are negligible, while heavy nonrelativistic DM has an intrinsic trace anomaly close to the nonrelativistic limit, $\Delta_\chi\simeq1/3$. Consequently, the DM rest-mass energy fraction dominates the DM-induced modification of $\Delta_{\rm tot}$, producing a smooth upward shift of up to $\sim0.1$ for $F_\chi\sim0.2\%$. In the pressureless, comoving heavy-WIMP regime, we further identify a universal dark-sector scaling governed by the mass-loading parameter $\lambda=F_\chi m_\chi/m_N$: numerical calculations with different $(F_\chi,m_\chi)$ pairs at fixed $\lambda$ exhibit overlapping trace-anomaly, sound-speed, and mass–radius responses for a given baryonic equation of state. In hybrid stars, DM leaves the coexistence pressure and chemical potential essentially unchanged, whereas first-order hadron–quark deconfinement produces sharp discontinuities in the squared sound speed $c_s^2$, $\Delta_{\rm tot}$, and $\Delta_{\rm tot}-\Delta_B$. The combined softening substantially reduces the maximum stellar mass, placing $F_\chi\sim0.2\%$ in tension with the observed $2\,M_\odot$ neutron stars. These results show that the trace anomaly and its density evolution provide a sensitive diagnostic for distinguishing smooth DM-induced modifications of dense matter from genuine first-order deconfinement.

Galaxy model fitting is widely employed to estimate properties such as galaxy shape, size, and color. Understanding how the outputs of galaxy model fitting respond to weak-lensing shear distortions is crucial for accurate shear estimation and mitigating shear-related systematics in weak lensing image analyses. In this paper, we investigate how the fitted parameters - specifically flux, size, and shape - respond to weak-lensing shear distortions within the AnaCal framework. To achieve this, we introduce quintuple numbers, a novel algebraic system inspired by dual numbers from automatic differentiation. Quintuple numbers enable the propagation of shear response information throughout the entire model-fitting process by linking analytical pixel shear responses to those of the fitted parameters. We integrate quintuple numbers into the AnaCal framework to derive the shear responses of shapes estimated with model fitting and validate the pipeline using image simulations that include realistic blending. Our results demonstrate that the multiplicative bias remains below 0.003 for ground-based, oversampled images.

We investigate the clustering of Primordial Black Holes (PBHs) within the framework of Excursion Set Theory (EST). The EST formalism is extended to compute the joint probability of forming PBH pairs within a clustering distance, based on two stochastic trajectories with a shared history. Our results show that an enhanced power spectrum not only increases the formation of PBHs in specific mass ranges but also enhances their clustering probability. We find a one-to-one correspondence between the blue-tilted spectral index and the mass ranges in which PBHs form and cluster. Additionally, we demonstrate that the clustering probability decreases asymptotically with increasing clustering distance, while a higher critical density threshold (barrier) leads to a suppression of clustering abundance.

Extracting cosmological information from nonlinear and non-Gaussian large-scale structure remains a major challenge. We introduce the Zel'dovich-inspired (ZI) transform, a simple one-parameter local nonlinear transform in which $\eta$ controls the weighting of higher-order information in the transformed density field. For $\eta\geq3$, the transform can substantially suppress gravitational non-Gaussianity. Using real-space matter density fields from the \textsc{Quijote} suite and Fisher analysis, we find that the joint data vector of three transformed-field power spectra with $\{\eta=\infty, 6, 3\}$, denoted $P_\mathrm{ZI}$, reduces marginalized errors for all parameters considered. The improvements range from several-fold for some $\Lambda$CDM parameters to factors of 290 for local primordial non-Gaussianity and 107 for the summed neutrino mass. Tests on independent fiducial simulations yield nearly unbiased parameter estimates. Compared with other state-of-the-art summary statistics, $P_\mathrm{ZI}$ provides tighter cosmological constraints.

Microquasars are radio-emitting X-ray binaries with relativistic jets and are established sources of $\sim 100$ TeV gamma rays, making them promising candidates for cosmic-ray acceleration. Motivated by recent detections of $\sim 100~$TeV photons from Cygnus X-1 and multi-PeV photons from Cygnus X-3, we employ the Astrophysical Multimessenger Emission Simulator (AMES) to model their multimessenger emission from radio to ultrahigh-energy gamma rays. Our modeling suggests that particle acceleration is extremely efficient in the jet region. The observed $\gtrsim 0.1$ PeV gamma rays can originate from either $p\gamma$ or $pp$ interactions, depending on the location and physical conditions of the emission region, while also reproducing the lower-energy spectra. These configurations yield observationally testable predictions. In the poorly constrained $0.1$-$10$ TeV band, the models predict either a deep valley, a mild suppression, or a power-law spectrum. Additionally, models involving compact emission regions comparable to the orbital separation predict strong variability, while those invoking more extended and static external zones show more stable behavior. We also provide a possible qualitative explanation for the energy-dependent modulation patterns, relying primarily on changes in the Doppler factor and external $\gamma\gamma$ absorption. In particular, explaining the PeV emission from Cygnus X-3 favors a compact emission region, for which a magnetic field strength of order $10^2~\mathrm{G}$ is required. Finally, after accounting for pion and muon cooling, the predicted neutrino flux is suppressed, implying that detection is more challenging than previously thought.

TESS is enabling the discovery of transiting planets around young stars. These observations suggest that most close-in planets were born in chains of mean-motion resonances that break on a characteristic timescale of order 100 Myr. This observation is surprising because the same dissipative forces that capture planets into resonance render their orbits long-term stable. We explore a two-stage disruption scenario for resonant chains of super-Earths. First, the chains have their (free) eccentricities excited by some mechanism. We show that any such mechanism that seeds eccentricities of a few percent sets in motion a second stage of dynamical instability on a $\sim$100 Myr timescale. A possible stage-one mechanism is the accretion of a handful of Mercury-sized bodies totaling a few percent of the planetary system mass, which excites the requisite eccentricities and triggers a stage two that reproduces the observed decline in the incidence of resonance. Impacts from such bodies can also explain why some young systems have period ratios narrow of commensurability. We sketch how these impactors may have grown out of debris left over from an earlier epoch of planet formation. We also identify two new trends in the observational data: a decline in multiplicity on the same timescale as the decline in the incidence of resonance, and an increase in the occupation of resonances with multiplicity.

The origin of intergalactic magnetic fields (IGMFs) remains one of the key open questions in cosmology. Gamma-ray pair halos produced by electromagnetic cascades from TeV-emitting blazars provide a powerful indirect probe of these fields. In this work, we present a novel search for pair halos that explicitly exploits their expected anisotropic morphology, aligning with the projected orientation of blazar jets on the sky. Using a Monte Carlo framework to model the spatial distribution of cascade emission, we identify an optimal sample of 21 high-synchrotron-peaked BL Lac objects with well-constrained jet position angles from radio interferometry. By rotating and stacking \textit{Fermi}-LAT observations of these sources along their jet directions, we enhance sensitivity to anisotropic extended emission that would be diluted in traditional orientation-agnostic analyses. Applying a likelihood analysis to the combined dataset, we find evidence for a non-zero IGMF, excluding the null hypothesis at $3.8\sigma$ level and obtaining a best-fit field strength of $B_0 = 2.8 \times 10^{-16}\,\mathrm{G}$, with a $99\%$ confidence interval of $0.9 \times 10^{-16}\,\mathrm{G} < B_0 < 8.9 \times 10^{-16}\,\mathrm{G}$. Our result is consistent with previous constraints from spectral, spatial, and temporal studies, while demonstrating that incorporating anisotropic information provides a significant gain in sensitivity. This approach opens a new avenue for probing intergalactic magnetism and highlights the potential of future high-angular-resolution gamma-ray observations to directly image pair halos and map magnetic fields in cosmic voids.

In modern cosmology, the rapid growth of high-precision observational data, along with significant theoretical advances, has intensified the challenge of identifying a robust, model-independent framework to probe the expansion history of the Universe. In this work, we propose a novel artificial neural network (ANN)-based framework for the non-parametric reconstruction of the late-time cosmic expansion. The framework is trained and validated through a three-stage screening pipeline prior to its application to real observational data. As a demonstration of its effectiveness, we reconstruct the Hubble parameter $H(z)$ using the latest cosmic chronometer measurements. Our results show that the reconstructed expansion history aligns with the predictions of the $\Lambda$CDM model within observational uncertainties, thereby supporting the robustness and reliability of the proposed approach.

Magnetic fields with field strengths between $10^{-17}\,$G and a few Nanogauss are expected to exist today in the intergalactic medium (IGM). Their origin is unknown, but may be of primordial nature, in which case they would have influenced the thermal and ionization history of the IGM as well as the growth of small-scale matter perturbations. In this work, we revisit constraints on Primordial Magnetic fields (PMFs) by consistently accounting for their energy losses through ambipolar diffusion and decaying turbulences from recombination through the epoch of reionization, which progressively reduces the magnetic field strength over time. We implement these effects in ${\tt HyRec}$ and ${\tt exo21cmFAST}$ to model the interplay between PMFs and astrophysical processes up to reionization. Using a neural-network emulator (${\tt NNERO}$), we perform a MCMC analysis that combines late-time probes of the reionization history and galaxy UV luminosity functions. We find that including PMF energy losses significantly relaxes previous bounds, as the reduced field strength suppresses their imprint on observables. Employing a Fisher matrix analysis, we estimate the sensitivity of the 21$\,$cm signal experiment HERA to the PMFs' imprint on intergalactic medium perturbations and show that 21$\,$cm cosmology could significantly improve on current bounds, depending on assumptions on the astrophysics. Our results highlight the importance of modeling PMF evolution self-consistently with the IGM evolution to extract current bounds and future sensitivities.

Baryonic physics is anticipated to be a major source of systematic uncertainty in current and future large-scale cosmological surveys. We investigate how baryonic effects on halo density profiles vary with secondary halo properties at fixed halo mass, using the large-volume MillenniumTNG hydrodynamical simulation and its dark matter-only counterpart. We focus on the impact of halo concentration and large-scale environment on the ratio of density profiles of matched halos in the hydrodynamical and dark matter-only simulations. At redshift $z = 0.0$, we find a strong dependence on halo concentration, especially at lower halo mass ($12.5 < \log(M_h/h^{-1}M_{\odot}) < 13.0$), where more concentrated halos exhibit weaker inner enhancement and stronger intermediate-radius suppression at fixed halo mass, with variations reaching $\sim 15\%$ at small scales and decreasing toward larger scales. This trend weakens and reverses at higher halo mass. In contrast, the secondary dependence on large-scale environment is weaker ($\sim 2\%$) and largely scale-independent, with halos in denser regions exhibiting slightly weaker intermediate suppression. By separating internal profile redistribution from total mass suppression, we show that concentration impacts both components, whereas the environmental dependence is primarily associated with an overall mass shift. These secondary dependencies persist at $ z = 0.5$ and correlate with variations in internal baryonic properties. We examine additional halo properties, including halo spin and velocity dispersion, and find significant secondary dependence. Overall, our results highlight the important role of secondary halo properties in modulating baryonic effects on halo density profiles, with potential implications for future modeling efforts.

A rapid estimate of gravitational-wave (GW) detectability associated with astronomical transients is crucial for optimizing multi-messenger follow-up strategies and for constraining the physical origin of the transient itself. We introduce here the Targeted Detectability Range (TDR), designed to evaluate, with minimal computational effort, the detectability of compact binary coalescences under the hypothesis of association with an external messenger, such as an electromagnetic or neutrino signal. Unlike the standard GW range, which is based on averaged source parameters, the TDR incorporates prior information from observations of the external messenger, including sky localization, inclination constraints, and physically motivated bounds on component masses. We report the TDR of all short- and long-duration gamma-ray bursts, observed during the first three observing runs of Advanced LIGO and Advanced Virgo. The method is validated by performing a systematic comparison with the 90$\%$ exclusion distances provided by modeled targeted GW searches. In the absence of a coincident detection by all-sky, all-time GW searches, the TDR provides a rapid and quantitative constraint on a possible merger origin of the astrophysical source. Its low-latency implementation and public availability would enable timely prioritization of follow-up observations and optimized allocation of observational resources, with direct impact on the physical interpretation of astronomical transients.

Event Horizon Telescope (EHT) images of black holes appear as rings with a brightness asymmetry. Here, we expand on our previous study of the asymmetry magnitude $a_1$ to study the position angle of the peak brightness asymmetry $\mathrm{PA}_1$ in general relativistic magnetohydrodynamic (GRMHD) models. For larger spin magnitudes ($a_{*}>0$ and $a_{*}\lesssim-0.5$), the mean $\mathrm{PA}_1$ falls within $1\sigma$ of the approaching limb of the black hole, regardless of viewing inclination, disk magnetization, or source. By comparing the $(a_1, \mathrm{PA}_1)$ distribution in M87* observations with models, we demonstrate that we can mildly disfavor low-magnitude spins and strongly disfavor all spin vectors that point toward Earth. The alignment of $\mathrm{PA}_1$ relative to the large-scale jet axis may suggest that M87*'s disk does not have a large tilt. By combining $\mathrm{PA}_1$ with the pattern speed measured in optimistic 2026 M87* video conditions, the EHT can constrain whether M87* is prograde or retrograde with $\sim 84\%$ accuracy. In Sgr A*, we show that a detection of $(a_1, \mathrm{PA}_1)$ could constrain the magnitude and direction of the galactic center spin vector. Finally, if future EHT expansions increase the sample of horizon-scale sources, a simple set of observables (ring diameter, asymmetry magnitude, and asymmetry angle) could enable robust constraints on black hole mass, spin, and inclination.

The cosmological distribution of neutral hydrogen (HI) during the post-reionization era is highly non-Gaussian due to the underlying non-linear structure formation, complex galaxy biasing, and potential primordial non-Gaussianity. One needs higher-order (beyond two-point) statistics to maximally extract the non-Gaussian information out of the 21-cm intensity maps. This chapter summarizes the potential of several higher-order statistics, including voxel intensity distribution, emission line stacking, probability density functions, $\ell_1$-norm, bispectrum, and various marked statistics. Additionally, image-based morphological descriptors, such as the Largest Cluster Statistic, local dimensions, and Minkowski functionals, etc., can potentially characterize the morphology and geometry of the cosmic web encoded in the 21-cm intensity maps. This chapter presents forecasts of the detectability of these higher-order statistics in the context of the future SKAO observations. These forecasts incorporate instrumental noise, observational effects, and, in some cases, foreground removal in their analyses. With its unprecedented sensitivity, the future SKAO 21-cm observations will enable us to measure these higher-order statistics more precisely, possibly helping to break degeneracies between astrophysical and cosmological parameters, and maximizing the science outcome from these surveys.

We present a field-level inference framework for testing gravity with large-scale structure, exploiting the full information of the galaxy distribution. Traditional analyses based on the power spectrum discard non-Gaussian and Fourier phase information, resulting in strong degeneracies between modified gravity (MG) and galaxy bias. Our approach overcomes this limitation by performing a Bayesian analysis directly on the three-dimensional galaxy number counts, jointly constraining MG and bias parameters using both amplitudes and phases. As an illustrative application, we analyse mock data in real space in the context of $f(R)$ gravity and a non-linear galaxy bias model designed to mimic the real-data 2M++ BORG analysis of Jasche&Lavaux (2019). Non-linear structure formation is modelled using COmoving Lagrangian Acceleration (COLA) under different gravity strengths, parameterised by $f_{R0}$. The resulting dark-matter fields are then mapped to mock galaxy catalogues via a non-linear bias prescription. We demonstrate that, with the initial phases assumed known, including non-Gaussian and phase information yields tighter constraints on both $f_{R0}$ and the primary bias parameter $\beta$ (corresponding to the linear galaxy bias on large scales), relative to power-spectrum-only analyses. Notably, the field-level approach breaks the degeneracies between MG and galaxy bias inherent to two-point statistics. Through a cosmic-web classification into voids, walls, filaments and clusters, we find that under-dense regions are the primary drivers in distinguishing gravity at the field level. Finally, we establish the robustness of our pipeline against variations in initial conditions, Poisson noise, and galaxy-field thresholding, providing a powerful path forward for field-level tests of gravity.

Gamma-ray bursts (GRBs) are promising cosmological probes, but their use as standard candles is limited by the circularity problem, necessitating model-independent calibration of GRB luminosity correlations. We revisit the two-dimensional (2D) and three-dimensional (3D) Dainotti correlations using Bayesian Neural Networks (BNNs) trained on the updated Observational Hubble Data (OHD) and Pantheon+ Type Ia Supernova sample. The reconstructed luminosity distances are used to calibrate the Platinum and Narendra et al. GRB samples. We constrain the parameters of the 2D Dainotti relation and the 3D fundamental plane, and examine the impact of calibration datasets and GRB sample selection. Calibration achieved using Pantheon+ yields tighter constraints than OHD, while the 3D correlation exhibits lower intrinsic scatter than the 2D relation. Our results demonstrate that BNNs provide a robust framework for model independent calibration of GRB luminosity correlations with reliable uncertainty propagation. Further, the underlying distance probe is a key factor in model-independent calibration, determining both the size of the GRB samples and the precision of the resulting constraints.

We perform joint Baryon Acoustic Oscillation (BAO) + Big Bang Nucleosynthesis (BBN) and BAO+BBN+Cosmic Microwave Background (CMB) analyses with Planck CMB and DESI DR2 BAO data, explicitly marginalizing over BBN nuisance parameters for the first time with these data combinations and paying particular attention to the impact of BBN on these results. We find in our fiducial analyses $h=0.6833^{+0.0048}_{-0.0053}$ ($\Lambda$CDM, BAO+BBN), $h=0.6823^{+0.0027}_{-0.0026}$ ($\Lambda$CDM, BAO+BBN+CMB), as well as $h=0.6791^{+0.0069}_{-0.0075},N_{\rm{eff}}=2.974^{+0.098}_{-0.099}$ ($\Lambda$CDM+$N_{\rm{eff}}$, BAO+BBN), and $h=0.6838^{+0.0052}_{-0.0054},N_{\rm{eff}}=3.065^{+0.078}_{-0.076}$ ($\Lambda$CDM+$N_{\rm{eff}}$, BAO+BBN+CMB). We demonstrate how investigator choices can impact results of joint analyses involving BBN. We provide recommendations for the treatment of BBN in light of recent work, and demonstrate a pipeline that accurately accounts for prediction uncertainties in BBN.

The LUX-ZEPLIN (LZ) collaboration recently reported a singular anomalous nuclear recoil event at $248 \pm 23 \, \rm keV$, accompanied by a strict null result for unexplained excesses in their primary $5.4-50 \, \rm keV$ search window. The macroscopic momentum transfer required to generate this event is kinematically inaccessible to standard halo cold dark matter (CDM), naturally motivating models featuring light, relativistic relics. In this work, we investigate whether a contemporary flux of Hawking-boosted dark matter (DM) emitted by evaporating Primordial Black Holes (PBHs) in the $10^{11}-10^{13} \, \rm g $ mass range can source the anomaly. By parameterizing the nuclear scattering with heavy non-relativistic effective field theory (NREFT) operators and endothermic inelastic mass transitions, we formulate a strict kinematic exclusion. We demonstrate that the inherent thermal nature of the Hawking emission, coupled with the relativistic kinematics of the incident flux, inevitably overproduces low-energy recoils, aggressively violating the LZ background bounds. Utilizing this failure, we map the LZ low-energy null results into novel, highly stringent upper limits on the PBH abundance fraction, excluding $f_{\rm PBH} \gtrsim 10^{-6}$ for $M_{\rm PBH} \sim 2 \times 10^{11} \, \rm g $ at $ 90 \% $ confidence level.

How and when dust settles in young protostellar disks is a key open question for the dust concentration needed to form planetesimals and, ultimately, planets. However, directly measuring the vertical dust distribution in embedded (Class 0/I) systems remains challenging. We show that brightness asymmetry along the minor axis of highly inclined disks provides a simple, powerful geometric diagnostic of vertical dust structure. Using radiative transfer modeling with RADMC-3D, we generate synthetic continuum images showing that the observed asymmetry arises naturally from disk inclination, optical depth, and dust scale height. We apply this framework to nine Class 0 and I disks from the ALMA Large Program, Early Planet Formation in Embedded Disks (eDisk), using Markov Chain Monte Carlo (MCMC) fitting. Outflow observations independently validate the inferred near- and far-side geometries: all eight sources with useful outflow constraints agree with the orientations predicted by the dust continuum modeling. Our results indicate that most embedded disks show no strong evidence of significant dust settling, with dust scale heights comparable to the gas scale height. Given that the literature indicates Class II disks tend to be well settled, our results reinforce the notion that significant dust settling occurs during the Class I phase, when deeply embedded Class 0 disks transition to their more revealed Class II counterparts. Intriguingly, the timing of dust settling appears to broadly coincide with the development of widespread dust substructures, suggesting that gravitationally driven vertical dust concentration may have triggered substructure formation.

By combining the ($u$,$d$) I-spin doublets or ($d$,$s$) U-spin doublets, the SU(3) flavor symmetry of light quarks can be decomposed into SU(2)$_I\times$U(1)$_Y$ or SU(2)$_U\times$U(1)$_Q$ subgroups, which have been widely adopted to categorize hadrons and their decay properties. The standard I-spin counterpart for the interactions among nucleons, namely the nuclear symmetry energy $E_\mathrm{sym}(n_\mathrm{b})$, characterizes the variation of binding energy as the neutron to proton ratio in a nuclear system. We propose the U-spin symmetry energy $E_\mathrm{U}(n_\mathrm{b})$ for hyperonic matter to characterize the variation of binding energy with the inclusion of hyperons. In particular, we include $\Lambda$ hyperons in dense matter and neglect contributions from other hyperons, then constrain $E_\mathrm{U}(n_\mathrm{b})$ using nuclear physics and astrophysical observations through a Bayesian inference approach. Our results show that $E_\mathrm{U}(n_\mathrm{b})$ is much smaller than 9$E_\mathrm{sym}(n_\mathrm{b})$, indicating a substantially weaker dependence of the adopted binding energy functional on the U-spin asymmetry than on the corresponding I-spin asymmetry. Consequently, the $\Lambda$ hyperon potential increases significantly with density and becomes repulsive at higher densities, leading to more than 50\% probability for the emergence of $\Lambda$ hyperons in the posterior, which are likely to vanish again at densities $n_\mathrm{b} \gtrsim 5\,n_0$. In scenarios where $\Lambda$ hyperons do emerge, the onset density $n_{\mathrm{b}}^\Lambda$ typically falls in the range $2\,n_0$–$5\,n_0$, corresponding to central densities of neutron stars more massive than $1.0\,\rm{M_\odot}$.

The short-duration gravitational-wave (GW) event GW231123 has component masses inferred to lie in the pair-instability mass gap and exhibits a burst-like morphology without a clear inspiral phase, making it an interesting target for testing alternatives to the standard binary black hole (BBH) interpretation. Motivated by its phenomenological similarity to GW190521, we test a wormhole-echo interpretation by modeling a leading echo pulse with a phenomenological \texttt{sine-Gaussian} wavepacket. Bayesian model comparison against a BBH interpretation described by the \texttt{IMRPhenomXPHM-SpinTaylor} waveform yields $\ln \mathcal{B}^{\rm Echo}_{\rm BBH}=1.87$. This preference is sensitive to the BBH waveform family and Echo-prior choices, and the observed statistic is not unusual within the targeted BBH-null ensembles. The positive Bayes factor therefore does not provide robust evidence for a wormhole-echo interpretation, with the analyses considered here supporting the standard BBH interpretation of GW231123.

The composition of the neutron star is one of the most fundamental and long-standing problems in nuclear- and astro-physics. The known properties of nuclear matter, together with the astronomical observations, impose the stringent and interconnected constraints on the theoretical descriptions. In this work, by using the most general quantum hadrodynamics model including $\sigma, \omega, \rho$ and $a_0$ in addition to nucleons, and performing a Bayesian joint analysis of experimental nuclear matter data, the heavy-ion flow pressure, and astrophysical observations including the mass-radius inferences of PSR J0740+6620, PSR J0437$-$4715, PSR J0614$-$3329 and HESS J1731$-$347 and the tidal posterior of GW170817, we point out that the nuclear matter made of only hadrons can provide a unified description of nuclear matter properties and astrophysical this http URL addition, we find that the speed of sound in the GQHD develops a non-monotonic, peak-like structure which is absent in the Walecka-type models TM1, NL3 and FSU-$\delta6.7$. This soft-to-stiff transition, accompanied by a pronounced softening of the symmetry energy, results in small size intermediate mass neutron stars, $R_{1.4}\simeq (11.1-11.4)$ km, together with the maximum mass $(2.2-2.3)M_\odot$, and, to our knowledge, has not been found before in the Walecka-type relativistic mean-field models. What we find here indicate that the sequential measurement of neutron star mass and radius by the next generation facilities, especially that of the intermediate mass neutron stars, is crucial for distinguishing the pure nucleonic stars from the hybrid ones.

We compute the gravitational wave spectrum from a phase transition associated with the spontaneous breaking of a $\mathcal{Z}_2^{\rm DW}$ symmetry. If the transition is second-order, the only source of gravitational waves is the annihilation of domain walls (biased by quantum gravity) formed after this breaking. However, if the transition is first-order, this yields a twin-peaked signal from both the transition itself and the biased domain wall annihilation. Both scenarios originate when a scalar singlet odd under the $\mathcal{Z}_2^{\rm DW}$ obtains a non-zero vacuum expectation value. An additional $\mathcal{Z}_2^{\rm DM}$ odd scalar doublet strengthens the transition by keeping the singlet scalar in thermal equilibrium with the Standard Model plasma at early times. Additionally, the same scalar doublet produces fermionic dark matter via freeze-in, matching observed dark matter relic density.

The Diffuse Supernova Neutrino Background (DSNB), an isotropic flux arising from the cumulative neutrino emission of all stellar core-collapse events throughout cosmic history, is expected to be detected by next-generation neutrino observatories. As DSNB neutrinos propagate over cosmological distances through the cosmic neutrino background (C$\nu$B), they may undergo non-standard neutrino self-interactions ($\nu$SI), leaving distinct spectral imprints on the observed flux. In this work, we investigate the impact of scalar ($\phi$)-mediated $\nu$SI on the DSNB within a full three-flavor framework that retains the complete PMNS structure. We consider four representative flavor-diagonal coupling structures–universal, $e$-, $\mu$-, and $\tau$-specific. The resonant scattering $\nu_i\nu_k\to\phi\to\nu_j\nu_l$ off the lightest, relativistic C$\nu$B state produces broad spectral depletion whose pattern depends on the coupling structure and the neutrino mass ordering, generating distinctive signatures across the six flavor fluxes. We compute the resulting event spectra at JUNO, Hyper-Kamiokande with gadolinium loading, and DUNE, and derive projected $3\sigma$ sensitivities in the $(m_{\phi},~g)$ parameter plane. We find that these experiments can probe couplings as low as $g\sim10^{-8}$ for $m_\phi\sim100$–$300$ eV, surpassing existing bounds by up to a few orders of magnitude in the sub-100 eV mass range. Moreover, unlike the flavor-blind cosmological and supernova bounds, the DSNB sensitivity is flavor-discriminating, offering a unique opportunity to identify the underlying flavor structure of $\nu$SI in the event of a detection.

We extend our study of a cosmological scenario in which dark matter is non-minimally coupled to gravity at the fluid level. In previous work, we showed that this interaction can drive an early phase of accelerated expansion, addressing the horizon and flatness problems, and can also lead to a cosmological bounce in the presence of negative spatial curvature. Here we analyse the evolution of linear perturbations in this framework. We derive the equations governing scalar, vector and tensor perturbations, and obtain analytic solutions in the relevant cosmological regimes. We find that perturbations generated during the accelerated expansion phase produce a strongly blue scalar power spectrum and are therefore incompatible with observations. By contrast, if primordial fluctuations are generated during the contracting phase of a bouncing solution, the model yields an approximately scale-invariant scalar power spectrum while keeping the tensor-to-scalar ratio compatible with current bounds. Although our treatment relies on simplifying approximations that should be refined in future work, these results indicate that an observationally viable primordial spectrum can be obtained only with a bouncing solution, and hence with a non-singular early-time evolution.

We analytically determine the leading backreaction of a spherically symmetric massive complex scalar quasi-bound state (with mass $\mu$) on a Schwarzschild black hole with (initial) gravitational radius $r_0$. Working in the small-coupling regime, $r_0 \mu \ll 1$, we evaluate the stress-energy tensor of the fundamental scalar $s$-wave and solve the Einstein equations through quadratic order in its amplitude in ingoing Eddington-Finkelstein coordinates. We also determine the small-mass quasi-resonant frequency of the fundamental $s$-wave analytically by matched asymptotic expansions and validate it numerically using Leaver's method. Unlike steady-state treatments, the calculation retains the exponential decay of the quasi-bound state. We obtain explicit expressions for the metric perturbations and Misner-Sharp mass and derive the evolution of the future outer trapping horizon. The black-hole mass grows monotonically with the decaying horizon flux and saturates when the finite scalar cloud has been absorbed, with the decrease of the cloud mass exactly balancing the horizon growth at the perturbative order considered. We also determine the domain in which the scalar small-coupling approximation and the gravitational perturbative expansion are simultaneously valid.

It has been proposed that primordial quark pellets or PQPs –ultra-dense quark-matter mini- stars– formed at $T\sim 1$ GeV may be a good candidate accounting for the dark matter of the universe. If correct, dark matter would consist of very compact objects with a maximum mass of $10^{-2} \ M_\odot$ and radii of approximately 100 m, although smaller objects would be much more abundant and encompass the bulk of the dark matter content. Here we describe a viable formation mechanism based on the enhancement of the local baryon density when supra-horizon Peccei-Quinn domain walls formed at an earlier epoch sweep and accumulate quarks and gluons before entering the horizon. Assuming an efficient baryon concentration by contracting Peccei-Quinn domain walls, we derive the resulting primordial quark pellet mass spectrum, minimum mass and cosmological abundance.