We report evidence for a candidate pulsational signal at $\sim0.22$~Hz from NGC7456 ULX-1, a previously identified ultraluminous X-ray source (ULX). The signal is identified in the 2023 XMM-Newton observation using independent timing techniques including accelerated searches, $Z^2_n$ statistics, and an orbital-demodulation analysis designed to restore phase coherence in the presence of binary motion. The candidate pulsation frequency drift within the observation suggests rapid spin evolution driven by accretion torque. We further estimate the surface dipole magnetic field strength to be $B\sim 10^{12}-10^{14}$ G. These results provide evidence that NGC7456 ULX-1 may host an accreting neutron star, although confirmation with independent datasets or additional observations is required.

Analysis of observational data and theoretical modeling favors a bimodal distribution of the natal velocity kick of neutron stars. For $\sim200$ normal isolated radio pulsars with well-determined spin and kinematic parameters, we determine if they belong to the low- or high-velocity mode of the distribution. Our results demonstrate that about $30\%$ belong to the low-velocity mode. We then analyze the differences in the properties of the two sets of pulsars. For some parameters (characteristic ages, distances, and radio luminosities), we see a clear difference between the two modes. However, for these quantities, it can be easily attributed to selection bias. For those parameters that are not a subject of strong selection, such as pulse width, we do not observe any difference. Interestingly, we detect a significant difference in the magnetic field distribution between the two modes. Lower field pulsars ($B\lesssim 10^{12}$~G) are overabundant among objects from the low-velocity mode in comparison to the high-velocity one. Among pulsars with low field ($\lesssim 10^{11}$~G), we do not identify any objects from the high-velocity mode of the kick distribution. The origin of this discrepancy is not clear, and we discuss several possibilities.

Context: Superbursts are very energetic explosions in the crust of neutron stars in Low-Mass X-ray Binaries (LMXBs). These are triggered by unstable carbon burning at $T\leq 10^{9}$ K. In recent years, there has been a re-examination of the carbon fusion rate, finding that at these temperatures it might be either smaller or higher with respect to the classic rate from Caughler \& Fowler (1988) by a factor $10^{3}$. Aims: We explore the consequences changing the carbon fusion rate has over the physics of superbursts. Methods: For simulating superbursts, we employ the public code MESA v.24.08.1, as well as four versions of the carbon fusion reaction rate. Results: An enhancement of the reaction rate by a factor $10^{3}$ at $T\leq 10^9$~K reduces the recurrence and decay times of the superburst, as well as the column depth at ignition. The opposite behavior is observed when the carbon fusion rate is reduced by the same factor. The maximum temperature reached during the explosion is also sensitive to these changes, leading to either an enhancement or a reduction in the synthesis of $α$-nuclides. These changes are comparable to the effect of reducing the amount of base heating at the bottom of the envelope.

Accreting millisecond pulsars (AMSPs) and transitional millisecond pulsars (tMSPs) are neutron star low-mass X-ray binaries which can evolve into "recycled" radio millisecond pulsars. In both types of systems, X-ray pulsations have been detected during phases of X-ray activity when matter accretion through a disc is turned on. On the other hand, when accretion stops, and these systems enter the quiescent, low-luminosity X-ray state, only tMSPs become visible as radio pulsars. Despite several attempts, radio pulsations have never been detected in quiescent AMSPs, except for IGR J18245$-$2452. In this manuscript, we present the results of two observational campaigns performed on the AMSPs IGR J00291+5934 and MAXI J1957+032 with the Five-hundred-meter Aperture Spherical Telescope ($\it{FAST}$) in L-band (1-1.5 GHz). Both sources have most likely been observed in quiescence, as suggested by the upper limits on their X-ray and optical flux obtained with Swift and the Las Cumbres Observatory, respectively. We have performed a deep search for coherent periodicities in radio but found no significant candidate signal, either at the known spin frequency of those sources or at other frequencies. Assuming a pulse duty cycle of 10%, we derive upper limits on the pulsed radio flux density of 3.3 $μ$Jy and 5.6 $μ$Jy for IGR J00291+5934 and MAXI J1957+032, respectively, which are the most stringent limits so far for any known persistent AMSP.

Millisecond pulsars (MSPs) are abundant in globular clusters (GCs) and probably also in galactic nuclei. They offer the potential to form a miniature pulsar timing array (mini-PTA) to detect nanohertz gravitational-wave (GW) sources located inside the array. Since the size of such an array is comparable to the wavelength of GW, the conventional plane-wave approximation becomes invalid, and near-field effects, including wavefront curvature, non-radiative self-field of the GW source, and direct perturbation of pulsar by GW, become significant. In this work, we incorporate these effects in a comprehensive model to calculate the timing residual induced by a GW source inside a mini-PTA. We also consider realistic GW source configurations in GCs (M15 and $ω$ Centauri) and in galactic nuclei (Sgr A* and M31), and find that for MSPs located sufficiently close to the GW source (within a few wavelengths), the residual can reach $1~μ\mathrm{s}$ in GCs and up to milliseconds in galactic centers, within the potential detection reach of current radio telescopes. Crucially, when the pulsar lies within a few GW wavelengths of the source, the non-radiative field dominates and causes the residual to rise much more steeply (between $1/r_e^2$ and $1/r_e^4$, where $r_e$ is the distance to the source) than the conventional far-field scaling ($1/r_e$). These results demonstrate that mini-PTAs in GCs or galactic nuclei can serve as powerful probes of otherwise invisible GW sources, including intermediate-mass and supermassive black hole binaries.

The Imaging X-ray Polarimetry Explorer (IXPE) has opened a new observational window on the physics of supernova remnants (SNRs) by providing the first spatially resolved X-ray polarimetry measurements. These data directly probe the geometry and turbulence of magnetic fields in regions of efficient particle acceleration, thereby constraining models of diffusive shock acceleration and magnetic-field amplification. IXPE has so far observed six young SNRs (Cas A, Tycho, SN 1006, RX J1713.7-3946, Vela Jr., and RCW 86) with published results on the first five. The observations reveal significant polarization in all cases, with degrees of polarization ranging from 5% to over 30%, reflecting different turbulence levels and environmental conditions. Three remnants (Cas A, Tycho, and SN 1006) show predominantly radial magnetic fields, while RX J1713.7-3946 and Vela Jr. display tangential morphologies. This dual behavior, not simply correlated with evolutionary stage, challenges the long-standing dichotomy inferred from radio observations and suggests that both shock velocity and circumstellar medium density play key roles in shaping magnetic-field topology. IXPE's results mark a major step toward disentangling the processes governing cosmic-ray acceleration in young SNR shocks, with ongoing and future observations expected to further constrain the interplay between turbulence, shock dynamics, and particle acceleration.

Accreting stellar-mass black holes exhibit dramatic variability across the electromagnetic spectrum, including spectral state transitions, outbursts, and jet production, making them unique laboratories for understanding accretion processes in strong gravitational fields. This review synthesizes recent progress in understanding these systems, focusing on their continuum emission, timing properties, emission lines, and X-ray polarization. A complex interplay between the accretion disk, the so-called corona, and jet underlies the observed spectral and timing behavior, with quasi-periodic oscillations and broadband noise providing windows into the dynamics of the innermost accretion flow. Emission lines across all wavelengths serve as critical diagnostics of disk structure, outflows, and reprocessing, while iron K lines in the X-ray band probe the properties of the inner disk through relativistic reflection. Polarization studies suggest that the corona is likely extended perpendicular to the jet axis in the hard state, while the soft state remains poorly understood, with observations that do not yet conform to simple theoretical expectations; a puzzle that continues to challenge our interpretation of accretion geometry. Despite significant advances, fundamental questions remain about the physical origins of state transitions, the role of magnetic fields in driving outflows and shaping the accretion flow, and the connection between disk instabilities and jet launching. This review underscores the need for future multi-wavelength, timing, and polarimetric studies to deepen our understanding of accretion physics in strong-gravity environments.

The pulsar PSR B0450-69 has both a braking index measurement and spin-down state change. After its spin-down state change, it shows an increasing braking index with time. Previously, it is pointed out that the spin-down state change may be caused by an enhanced particle wind. The prediction is that its braking index in the high spin-down state will be smaller. The current measured braking index is approaching the previous prediction. The transient variation of braking index may be due to a small varying part of the particle number density. The final braking index evolution is found to be in an exponential form. The braking index of PSR B0540-69 is expected to approach some steady value. Future braking index measurement may make clear the physics for the braking index evolution. It may also help to make test different particle acceleration potential in the pulsar magnetosphere. Finally, a phenomenological treatment of wind braking model of pulsars is presented. It can simplify the applications to pulsar braking index, intermittent pulsars and PSR B0540-69.

Measurements of cosmic-ray proton and helium spectra below the knee show deviations from simple power laws, including multi-TeV structures. A possible explanation is that one or a few nearby sources contribute an additional component to the local spectrum. However, previous study shows that a dominant local contribution is statistically unlikely under a homogeneous diffusion model. In this work, we investigate how this probability changes if cosmic rays experience inefficient transport near their sources, motivated by observations of extended gamma-ray emission around Galactic accelerators. We derive a series Green's function that enables fast calculation of the particle distribution in this scenario, making Monte Carlo calculations for Galactic source populations feasible. The inner slow-diffusion region delays escape and redistributes the arriving particles in time and energy. In Monte Carlo realizations, the probability that the strongest local source becomes comparable to the background at $10\,\rm{TeV}$ increases from about $0.4\%$ in homogeneous diffusion to $1.7$--$2.2\%$ in the two-zone models. Thus inhibited near-source transport weakens, but does not remove, the statistical difficulty. We then examine cataloged nearby candidate supernova remnants and show that a $10\,\rm{TeV}$ feature can be reproduced only with additional assumptions, especially a harder local injection spectrum and a favorable diffusion coefficient. The predicted contribution of a given source changes strongly among different particle transport model. Therefore, the local source interpretations are plausible but highly model dependent, and require independent constraints on source injection history, particle transport mechanisms, and local interstellar turbulence.

Hierarchical triples are promising environments for producing exotica such as black hole mergers and hot Jupiters, because of the von Zeipel-Lidov-Kozai (ZLK) effect, whereby a distant tertiary can torque an inner binary to high eccentricity over secular timescales. In the double-averaged (DA) approximation to ZLK, this eccentricity excitation is suppressed by apsidal precession due to `short-range forces' (SRFs) like relativity and tidal/rotational bulges. Here we show that, when the DA approximation is relaxed, SRFs often catalyze, rather than suppress, extreme eccentricity behavior. This occurs because SRFs can drive large, discrete jumps in the binary's effective `adiabatic invariants' during high-eccentricity episodes. These nonadiabatic jumps can dramatically alter the maximum/minimum eccentricity and secular period of astrophysically relevant triples, including some for which SRFs were previously thought irrelevant. Even the angular momentum component $j_z$ evolves secularly -- to our knowledge, this is the first time such evolution has been demonstrated from a quadrupole-order, three-body mechanism. In short, binaries may explore much more of phase space than is implied by any (semi-)analytic ZLK theory of which we are aware. We demonstrate this at the test-particle quadrupole level; in a companion paper we show how even more-extreme behavior occurs when the jumps are combined with octupolar ZLK evolution.

We investigate the propagation of low-frequency fast-magnetosonic (FMS) waves in highly magnetized environments. Such conditions are relevant to the escape of GHz fast radio bursts potentially produced in the inner magnetospheres of magnetars. It remains an open question whether such waves can escape without substantial reprocessing. Using relativistic force-free electrodynamics simulations, we confirm the key theoretical predictions of Golbraikh & Lyubarsky (2023) and demonstrate that FMS waves undergo efficient nonlinear conversion into secondary FMS and Alfvén waves via the parametric decay instability. This process continues to drain energy from the primary FMS waves even after approximate energy equipartition between the FMS and Alfvén components is established. The resulting spectrum of excited waves is broad, extending across much of the inertial range in $k$-space within the simulation domain. Our results indicate that FMS waves likely do not escape magnetar magnetospheres without substantial dissipation and spectral broadening.

We investigate the propagation of fast radio bursts (FRBs) through magnetar magnetospheres. Previous work showed that, in the inner magnetosphere, GHz radio waves propagate as fast magnetosonic waves and undergo resonant three-wave interactions that transfer their energy into trapped Alfvén waves. Using three-dimensional force-free electrodynamics simulations, we demonstrate that FRBs would excite Alfvénic fluctuations, leading to strong nonlinear attenuation of the radio signal. In quiescent dipolar magnetospheres, the nonlinear decay stays efficient within $\sim10$--$100$ magnetar radii; charge starvation of the excited Alfvén waves stops the decay at larger radii. For FRBs propagating within relativistic magnetic outflows launched during magnetospheric eruptions, three-wave interactions remain efficient and constrain the escape radius to $\gtrsim10^2$--$10^3$ magnetar radii for luminous bursts. Our results confirm that nonlinear plasma processes strongly limit the escape of FRBs from the inner magnetospheres of magnetars.

Stars are born in darkness, deep within cold, dense molecular clouds where gravity drives the collapse of gas and dust, giving rise to protostars, the earliest stages of stellar evolution. Once considered purely thermal sources, these young systems are now emerging as sites of energetic non-thermal activity. While radio synchrotron jets hinted at the presence of relativistic electrons, direct confirmation of proton acceleration remained elusive. Here we report a statistically significant detection of gamma rays from a population of young stellar objects, revealing a Galactic class of Gamma-Loud Protostars. Observations point towards particle acceleration within protostellar jets, where gamma-ray emission arises from protons interacting with surrounding molecular clouds via pion decay. We find a correlation between cosmic-ray output and bolometric luminosity, suggesting that particle acceleration scales with the system's mechanical power. These findings open a new observational window into the role of non-thermal processes in protostellar evolution and suggest that gamma-ray studies of protostars can provide critical insights into accretion, ejection, and feedback in star formation. This previously overlooked emission traces the energetic feedback that young stars inject into their surroundings, shaping the conditions for subsequent star and planet formation.

We present a scintillation study of the first-known pulsar planetary system, PSR~B1257+12, using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). A total of 31 observations with durations greater than or equal to 30 minutes were analyzed. For 14 longer observations (greater than or equal to 120 minutes), one-dimensional autocorrelation function analyses yielded the scintillation timescale, scintillation bandwidth, and frequency-drift rate for 12 epochs. Two observations show strong periodic modulation in the frequency-domain auto-correlation function, likely caused by astronomical-unit-scale structures along the propagation path, preventing reliable measurements of the scintillation timescale and bandwidth. In three observations, secondary spectra reveal simultaneous detections of inner, middle, and outer arcs. Analysis of the annual modulation of the inner-arc curvature indicates isotropic scattering, with a screen distance of $233\pm28$~pc and transverse velocity $V_{\rm scr,α}=-7.16\pm2.16$ km~s$^{-1}$, $V_{\rm scr,δ}=-41.07\pm5.69$ km~s$^{-1}$. Delay-profile analysis for both the inner and outer arcs suggest spectral exponents consistent with, or smaller than, the Kolmogorov value. Under isotropic scattering, the screen--pulsar distances are $354\pm22$~pc and $166\pm12$~pc for the middle and outer arcs. Combining the results from long-term timing analyses with our scintillation measurements, we find that the dispersion measure (DM) variations are primarily dominated by plasma located further away from the pulsar. The low DM-change rate of the outer arc and the absence of nearby scattering screens suggest that the immediate environment of the pulsar may be relatively clean. Alternatively, scattering screens closer to the pulsar may exist but remain undetected, requiring higher-sensitivity or longer-duration observations.

The SS433, a well-known binary system with an internal black hole, have shown since half a century, an inner (a few year light distances) twin precessing jets spirals. These beams are made by tidal forces while stripping mass from large stellar companion feeding an inner BH accretion disk and an orthogonal accelerating twin jet. From it, the radio, X gamma jet emission. A couple of years ago H.E.S.S telescope as well as HAWC and LHAASO array detectors, discovered also the surprising signature of an unexpected far twin separated gamma beam at tens TeV energy. At a hundred light years distances from its central source. We suggest that it is the legacy of a past rare eruption, a century ago, of tens PeV (10^16 eV) relativistic twin neutron beams. Their beta decay in flight at far distances, into proton, neutrino and in particular into tens TeV electrons, could feed the observed TeV gamma traces. They are originated by the same secondary tens TeV electrons emitting hard gamma, by Inverse Compton Scattering onto interstellar infrared photons.

We investigate neutrino effects of new long-range forces arising from gauging $B-L$, $L_e-L_{μ/τ}$ or $L_μ-L_τ$ symmetries of the Standard Model. The leptonic potential generated by astronomical bodies, such as the Earth, the Sun or a neutron star, results in the Schwinger pair production of neutrinos charged under the new gauge symmetry. The oppositely charged particles accumulate in the potential well forming a degenerate Fermi gas, while equally charged particles fly away forming a steady flux of neutrinos. We find that, for the $B-L$ and $L_e-L_{μ/τ}$ forces, these effects are too weak to be observable. For the $L_μ-L_τ$ force these effects are significant in neutron stars if the gauge coupling is $g\gtrsim 10^{-18}$. The muonic force changes the element abundances of a neutron star in equilibrium and suppresses its $L_μ-L_τ$ charge. This invalidates the constraint on $g$ from neutron star mergers, at $g\gtrsim 10^{-17}$. Furthermore, for such values of $g$, the neutrino flux produced by the Schwinger effect could potentially be detected from a single young neutron star at a distance of $\simeq 100$ pc, with the typical neutrino energy $E_ν\sim 100$ MeV. A dedicated search for such a signal will reassert the bound $g\lesssim 10^{-18}$.

We study high-frequency electromagnetic propagation in the rotating García--Díaz solution of Einstein gravity coupled to NLED. In this system, light is not governed only by the null cone of the spacetime metric, because the NLED field also behaves as an optical medium whose constitutive response determines the physical optical cones. Starting from the mixed electromagnetic potentials, we project the field $F$ and the excitation $P$ on a principal tetrad and obtain the aligned scalars $E$, $B$, $D$ and $H$. These scalars allow us to reconstruct the regular local constitutive branch connected with Maxwell theory through the map $(D,B)\mapsto(E,H)$. We then insert the resulting response matrix into the Fresnel characteristic problem. At the perturbative order considered here, the Fresnel quartic factorizes into two quadratic branches, each defining an effective optical metric. Both optical metrics admit Carter-type separation of the Hamilton--Jacobi equation and possess their own radial and angular potentials, critical constants and unstable critical families. By projecting these families onto the celestial sphere of a finite-distance observer, we obtain two critical contours, $Γ_+$ and $Γ_-$, which coincide in the Maxwell limit and split when the nonlinear constitutive response is active. We quantify this birefringent splitting through the maximum angular separation, the relative diameter shift and the normalized birefringent width. Numerical scans over the nonlinear coupling, spin and observer inclination show that the splitting is generated by the constitutive response, redistributed by rotation and stable under local projection changes within the perturbative domain. This provides a direct geometrical link between the local NLED response and a polarization-dependent critical structure on the observer screen.

The Wilson-Daubechies-Meyer (WDM) time-frequency transform has been widely used in gravitational-wave astronomy, yet a self-contained, mathematically explicit reference for practitioners remains lacking. This is especially true for those wishing to adopt the transform in modern Python and JAX inference workflows. We present wdm_transform, an open-source Python package implementing the WDM wavelet-packet time-frequency transform, and document its mathematical foundations, statistical properties, and practical implementation for gravitational-wave data analysis. The package supplies NumPy and JAX backends, both transforms (forward and inverse) validated to floating-point precision, with the JAX backend enabling GPU-accelerated transforms of million-point data streams in tens of milliseconds. As a worked example, we verify that the WDM-domain likelihood reproduces frequency-domain posteriors for a resolved LISA galactic binary under a shared stationary noise model, confirming numerical equivalence of the two representations in that controlled setting. This work paves the way for systematic optimisation of WDM tilings, a particularly promising direction for the non-stationary noise, stochastic backgrounds, and data gaps anticipated in future detectors, and for direct comparisons with alternative time-frequency representations needed to meet the challenges of future gravitational-wave data analysis.

We present a comprehensive study of hybrid stars composed of hadrons, leptons, and quarks within a relativistic mean-field framework. Using coupling constants derived from QCD sum rules (QCDSR), we first determine the bulk properties of nuclear matter and evaluate the single-particle potentials of nucleons and hyperons to constrain the hadronic sector. The equation of state (EOS) under beta equilibrium is then constructed employing the $σ-ω-ρ$ model for the hadronic phase, while the quark phase is described using both the MIT bag model and the Nambu-Jona-Lasinio (NJL) model. The hadron-quark phase transition is analyzed through both Gibbs and Maxwell constructions. Based on resulting EOSs, we obtain the mass-radius relations of hybrid stars, investigate particle fractions and their radial distributions, and calculate the tidal Love number ($\mathcal{K}_{2}$) and the dimensionless tidal deformability ($\varLambda$). Our results provide quantitative predictions relevant for comparison with current multimessenger astrophysical observations.

Any observation of charged lepton flavor violation (CLFV) would be a clear signal of beyond-the-Standard-Model physics. Here, we propose a novel CLFV search using neutrino telescopes with their large cosmic-ray muon samples. Specifically, we use a recent IceCube cosmic-ray muon dataset and propose a new search for muon-to-tau conversion inside the IceCube detector. We illustrate our idea with CLFV interactions described by model-independent Effective Field Theory (EFT) operators and present the IceCube sensitivity on the relevant EFT scale. We also consider a specific realization of the EFT operator in terms of an axial-vector $Z'$ interaction and show sensitivities in the $Z'$ mass-coupling plane. We compare our sensitivities with those from low-energy CLFV searches, as well as from current and future collider experiments. We also show projections from next-generation neutrino telescopes, such as IceCube-Gen2 and HUNT, and demonstrate how neutrino telescopes can provide a powerful complementary probe of CLFV.

We investigate the fully relativistic dynamical tidal response of neutron stars up to second order in the frequency. Combining the worldline effective field theory for extended gravitating bodies with perturbation theory of relativistic stellar models, we derive the tidal deformation induced by an external time-dependent field, including a universal logarithmic running term. In the effective theory, we work in dimensional regularization and, through a consistent matching procedure, obtain for the first time the complete leading-order dynamical tidal corrections to both the conservative dynamics and the gravitational-wave signal of compact binaries, including the scheme-dependent finite terms in addition to the running. We show that, in the relativistic regime, dynamical effects cannot be fully captured by mode excitations alone. The magnitude of the additional contribution depends on the stellar compactness, the equation of state, and the running term. Dynamical Love numbers are significantly enhanced with respect to their static counterparts for relatively small compactness. As a result, although they formally enter the gravitational-wave phase at 8th post-Newtonian order, dynamical tidal effects yield a non-negligible contribution during the late inspiral. Using a Fisher-matrix analysis, we show that third-generation detectors such as the Einstein Telescope could measure dynamical Love numbers for a range of neutron-star masses and equations of state. Conversely, neglecting these effects can lead to significant biases in the inference of static Love numbers, and hence on the nuclear equation of state. Our results highlight the importance of dynamical tidal effects for high-precision gravitational-wave modeling with future detectors.

Abell 2142 (A2142) is a massive, nearby galaxy cluster undergoing a complex merger. It exhibits an elongated X-ray morphology along the northwest-southeast axis and hosts four known cold fronts. Using XMM-Newton observations, we detect a merger shock on the northwest side of the cluster with a Mach number of $M \sim 1.3$. The observed shock front and four cold fronts can be reproduced by numerical simulations of an off-axis merger with a large impact parameter, which imparts significant angular momentum to induce the sloshing of the subcluster core and large-scale ambient gas. In projection, the shock front is spatially coincident with arc-shaped radio filaments observed behind the prominent head-tail radio galaxies T1 and T2. We interpret these radio arcs as partial vortex ring structures (resembling ``smoke rings'') produced by the interaction of the merger shock with the low-density cocoons of radio galaxies. The shock strips and rolls the jet cocoon into a toroidal vortex, as predicted by recent magnetohydrodynamic simulations. We further demonstrate that the merger shock can significantly elongate the radio tails by re-accelerating aged relativistic electrons and stretching the tail plasma via the post-shock wind. This process provides a natural explanation for the $>$500 kpc tail observed in this and other merging clusters. Our findings establish radio arcs and ultra-long radio tails as independent, complementary tracers of merger shocks in galaxy clusters. Our results demonstrate that merger shocks can reshape both the thermal and non-thermal components of galaxy clusters, and that tailed radio galaxies serve as sensitive probes of intracluster medium weather.

Recent developments in widefield radio telescopes have enabled searches of a new region of parameter space in the time domain: timescales of seconds to minutes, that have been overlooked in traditional surveys. These searches have revealed a new population of sources: long period transients, which typically show periodic behaviour of minutes to hours. In addition they have detected phenomena ranging from extreme scintillation to stellar radio bursts. However, almost all searches to date have involved archival data that has been processed in offline, batch mode. In this context, we present VASTER, the first short-timescale imaging and transient detection pipeline running in real time on a widefield radio telescope. VASTER has been running on the Australian SKA Pathfinder (ASKAP) since July 2025, and images most of the ASKAP survey project data on timescales of 15 minutes. In this paper we describe the VASTER system, and present the results from the first two weeks of operation, including the discovery of two long period transients: ASKAP~J165130.3$-$450520 with a period of 6.48 hours and ASKAP~J170036.6$-$445758 with a period of 4.69 hours. The detection of these two sources adds to the small, but growing, population of long period transients, as well as demonstrating the potential of VASTER to explore this region of transient parameter space.

Supernova remnant observations show a high degree of asymmetry, mixing, and inhomogeneity. These asymmetries are seeded during the early seconds of the explosion and are further enhanced and modified as the shock and ejecta move through the stellar progenitor and into the circumstellar medium. We present simulations of a 9.6 solar mass zero-metallicity progenitor initialized after shock revival and evolved for several years when the ejecta is in the circumstellar medium. A suite of 1D and 2D simulations examines the effects of neutron-star wind and radioactive decay heating. In 1D, decay heating forms a low-density bubble that suppresses the reverse shock. While in 2D, the heating is localized to metal-rich pockets, inflating them and compressing the surrounding material into dense shells. In 3D the neutron-star wind and decay heating modify the plume morphology, producing more large-scale structures. The extended plume morphology leads to an asymmetrical shock breakout. After breakout, the leading plumes cannot keep up with the shock front, resulting in deceleration and fragmentation by the reverse shock while retaining the large-scale asymmetry. The projected ejecta morphology and velocities are strongly viewing angle dependent. The relatively uniform metal-rich distribution does not resemble the strongly inhomogeneous ejecta structure of Cas A. The 160-isotope decay network shows that 24.4% of the radioactive heating comes from decay chains other than the canonical Ni-56 chain. The low explosion energy, low Ni-56 yield, and Ni/Fe ratio greater than unity suggest an observational signature similar to an electron capture supernova.

Recent preprints by Key et al. reported the discovery of a short-lived brightening of a star (nicknamed "Phoebe") located in the Large Magellanic Cloud that was interpreted as a short-timescale gravitational microlensing event produced by a lunar-mass primordial black hole (PBH) in the Milky Way dark matter halo. Here, we present an independent re-analysis of the publicly available DECam observations of this object, incorporating additional data from 2020 and 2021. The object underwent at least three distinct, low-amplitude brightenings (one of which was misinterpreted as a short-timescale microlensing event) in addition to long-term variations of its mean magnitude. These characteristics indicate that Phoebe is an ordinary variable star rather than a microlensing event. This finding resolves the apparent tension with the results from earlier microlensing experiments that rule out the hypothesis that a substantial fraction of dark matter is composed of lunar- and planetary-mass PBHs.

The intracluster medium (ICM) is rich in chemical elements, produced by core-collapse (SNcc) and Type Ia supernovae (SNIa) over the last $\sim$12 Gyr. Whereas cluster outskirts are uniformly enriched with Fe at $\sim$0.3 solar - strongly suggesting that the gas had been pre-enriched during or before the assembly of galaxies into clusters, the Fe abundance is known to centrally increase in the core of relaxed clusters. The origin of these central Fe peaks however, as well as the apparent presence of mysterious drops previously reported in the very centre of a number of systems, remain to be clarified. In this paper, we address these two questions by measuring the spatial distribution of Fe and its relative Si/Fe, S/Fe, Ar/Fe, Ca/Fe, Cr/Fe, Mn/Fe, and Ni/Fe ratios in the X-ray bright, nearby Perseus cluster. We take advantage of the unprecedented spectral resolution ($\sim$5 eV) offered by the Resolve microcalorimeter on board XRISM, which observed four distinct pointings of Perseus out to $\sim$250 kpc ($\sim$0.2$r_{500}$) during its Performance Verification phase. Although the presence of an X-ray bright AGN challenges a precise quantification of absolute abundances in the very core, our baseline analysis rules out a strong drop with $>$2$σ$ confidence, at variance with previous CCD measurements. In addition, we find a remarkable spatial uniformity of X/Fe ratios, supporting the idea of negligible late SNIa enrichment from the brightest cluster galaxy NGC 1275. We also compare the overall chemical composition of the Perseus ICM with SNcc and SNIa nucleosynthesis yield models, finding that the co-existence of two separate SNIa enrichment channels is not needed to reproduce the ICM ratios satisfactorily.

Relic neutrino nu_r light masses clustering in Galactic and Local Hot Dark Halos act as a beam dump calorimeter. Ultra High Energy nu, above ZeV, born by AGNs, GRBs at cosmic edges, overcoming (GZK) cut-off, may hit near Z resonance and WW-ZZ channels energies: their showering into UHECR fit observed data . Any tiny neutrino mass splitting may reflect into a twin bump at highest GZK energy cut-off. The Z or WW,ZZ showering explain a peculiar clustering in observed UHECR spectra at 10^19, 210^19, 4 10^19 eV found by AGASA. Coincidence of clustered UHECR with highest gamma BLac sources is well tuned to Z-Showering Scenario. Additional prompt TeVs signals occur offering a natural solution of growing Infrared-TeV cut-off paradoxes related to distant TeV BLac sources and a GRB at TeV energy. Electromagnetic Cascades tail explain correlation found between GeV-EGRET Sources and UHECR. Such UHE nu Astrophysics might trace into Horizontal Tau Air-Showers originated by the UHE nu_tau Earth-Skimming in wide Corona Earth Crust around the observer. These Upward and Horizontal tau Air-Showers UPTAUS, HORTAUS, monitor huge volumes from high mountains as well as observing from planes, balloons and satellites. HORTAUS from mountains observe corona masses at UHE neutrino at EeVs energies comparable to few km^3, while from satellites at orbit altitudes, at GZK energies, their corresponding Horizontal Corona Masses may even exceed 150 km^3. The expected event rate may exceed a dozen of event a year in Z-WW Showering model from satellite.

We report the discovery of an exceptionally eccentric binary system, BE Lyncis (BE Lyn), which might host a compact companion with mass $\gtrsim 2.5~M_{\odot}$. By combining TESS photometry with an extensive set of times of maximum light spanning 39 years, we identify BE Lyn as a high-amplitude $δ$ Scuti star in a binary with an orbital period of $\approx15.9$ years and an extraordinary eccentricity of $e=0.9989^{+0.0008}_{-0.0021}$ ($>0.9968$ at 95% confidence) -- the most extreme eccentricity reliably measured for any binary system. Dynamical constraints limit the orbital inclination to $i \lesssim 10^{\circ}.1$, implying a companion mass $M_2 \gtrsim 2.5~M_{\odot}$, which identifies the companion as a compact object. This mass points to it most likely being a black hole; if instead it is a rapidly rotating neutron star, it would be the most massive known. If the black hole interpretation holds, it would be the closest such object to Earth. This system provides a unique laboratory for studying asteroseismology in strong gravitational fields, as well as the formation and evolution of extremely eccentric binaries. Our work demonstrates the use of the light-travel time effect in a pulsating star to reveal a compact companion, offering a novel method for detecting black holes in noninteracting binaries.

We present a summary of gravitational-wave (GW) follow-up using the Las Cumbres Observatory global network of telescopes during the third (O3) and fourth (O4) observing runs of the GW detectors. As in O2, we implemented the Gehrels et al. 2016 galaxy-targeted strategy. Here we test its efficacy in O3 and O4 and analyze the Las Cumbres Observatory response time and depth for nine GW alerts that showed a possibility of having an electromagnetic counterpart (GW190425, GW190426_152155, S190510g, GW190728_064510, GW190814, S190822c, GW191216_213338, S240422ed and S250206dm). We find that Las Cumbres Observatory is able to begin observations in response to GW alerts within minutes of the alert, with the observations being deep enough to detect possible GW170817-like kilonovae out to a median distance of 250 Mpc. In this sense a global rapid-response network of telescopes like Las Cumbres is an excellent GW follow-up facility. However, the galaxy-targeted follow-up strategy was much less efficient in O3 and O4 than originally predicted, given the larger than assumed GW localizations. We conclude that coordination between various facilities to include both wide-field and rapid-response capabilities is required to achieve efficient and comprehensive follow-up of GW events.

We present the results of Green Bank Telescope (GBT) observations of two pulsars discovered with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) during the 19-beam Commensal Radio Astronomy FasT Survey (CRAFTS). We highlight the first timing solutions, pulse profiles, flux densities, and polarization measurements at 820 MHz for PSR J0535-0231, with a spin period of 415 ms, and PSR J1816-0518, with a spin period of 1.93 s, from a year-long follow-up campaign. PSR J0535-0231 appears to be partially recycled, but isolated, and likely belongs to the class of disrupted recycled pulsars (DRPs). We find that the two widely used electron density models, NE2001 and YMW16, both fall short of accurately modeling the line-of-sight to PSR J0535-0231, as the maximum dispersion measure (DM) predicted by both models is lower than the pulsar's DM of 118.1 pc cm$^{-3}$. Finally, we place both pulsar discoveries in the context of other FAST pulsars discovered in the CRAFTS survey and of the currently known pulsar population, in general, and discuss ways in which future FAST discoveries of faint, distant pulsars might facilitate the development of improved versions of the aforementioned electron density models in certain regions of our Galaxy.