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ABSTRACT We present the first end-to-end calculation connecting the accretion-induced collapse (AIC) of a magnetized, rapidly rotating white dwarf to observable kilonova signatures, combining two-dimensional (2D) general-relativistic neutrino-magnetohydrodynamic simulations, followed by radiation hydrodynamics with in-situ nuclear network and 2D Monte Carlo radiative transfer with spatially resolved heating rates. Unlike all previous unmagnetized AIC models – which predicted proton-rich, $$^{56}$$Ni-dominated ejecta – strong magnetic fields eject $${\approx }\, 0.2\, \mathrm{ M}_\odot$$ of neutron-rich material ($$\langle Y_e \rangle \sim 0.24$$) on dynamical time-scales, before neutrino irradiation can raise the electron fraction, enabling strong r-process nucleosynthesis up to and beyond the third peak. The resulting kilonova is lanthanide-rich ($$X_{\rm lan} \approx 8~{{\ \rm per\ cent}}$$) and dominated by near-infrared emission. We compute synthetic light curves in the Large Synoptic Survey Telescope and James Webb Space Telescope bands and find striking agreement, without parameter tuning, between the observations of AT 2023vfi/GRB 230307A and our broadband light curves for polar viewing angles. These results establish magnetized AIC as a viable channel for heavy r-process element production and a compelling progenitor candidate for long-duration gamma-ray bursts with kilonova signatures. 

Abstract Gravitational waves (GWs) from compact binary coalescences arestandard sirensthat provide a direct measure of the source’s luminosity distance, enabling an independent measurement of the Hubble constant (H₀). While abright siren—a GW event with an identified electromagnetic (EM) counterpart—provided the first such constraint, most detections, currently dominated by black hole mergers, lack EM signatures. A measurement ofH₀is still possible with thesedark sirensby statistically associating GW events with galaxies in existing catalogs based on the sky localization. In this work, we explore the potential of two subsets of dark sirens categorized by their localization precision: ’golden’ dark sirens, defined by a sky area localization ≤0.1deg², and ’silver’ dark sirens, which are more common but less precisely localized (≤1deg²). Using thefifth internal data releaseof the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX), we assess the suitability of the Visible Integral-field Replicable Unit Spectrograph (VIRUS) for spectroscopic follow-up of dark sirens. VIRUS exposures of the standard HETDEX depth provide precise redshifts and exquisite completeness withinz= 0.2. After a single year of observations with the upgraded LIGO-A^#network, the combined sample of golden and silver dark sirens withz≤ 0.2 atH₀ = 70 km s⁻¹Mpc⁻¹and follow-up VIRUS observations can potentially yield a few-percent constraint onH₀. Our predictions suggest that spectroscopic redshift surveys such as HETDEX can play a key role in realizing high-precision cosmology with dark sirens in the near future. 

Abstract The upcoming Deep Synoptic Array 2000 (DSA-2000) will map the radio sky at 0.7–2 GHz (2.9 – 8.3 μeV) with unprecedented sensitivity. This will enable searches for dark matter and other physics beyond the Standard Model, of which we study four cases: axions, dark photons, dark matter subhalos and neutrino masses.We forecast DSA-2000's potential to detect axions through two mechanisms in neutron star magnetospheres: photon conversion of axion dark matter and radio emission from axion clouds, developing the first analytical treatment of the latter.We also forecast DSA-2000's sensitivity to discover kinetically mixed dark photons from black hole superradiance, constrain dark matter substructure and fifth forces through pulsar timing, and improve cosmological neutrino mass inference through fast radio burst dispersion measurements. Our analysis indicates that in its planned five year run the DSA-2000 could reach sensitivity to QCD axion parameters, improve current limits on compact dark matter by an order of magnitude, and enhance cosmological weak lensing neutrino mass constraints by a factor of three. 

Abstract The origin of a number of proton-rich isotopes in the solar system has been a long-standing puzzle. A promising explanation is theνp-process, which is posited to operate in the neutrino-driven outflows that form inside core-collapse supernovae after shock revival. While recent studies have analyzed several relevant physical effects that influence the efficiency of this process, the impact of General Relativity (GR) on it remains unexplored. We perform a comparative analysis of the time-integratedνp-process yields in Newtonian and fully GR calculations, using detailed models of time-evolving outflow profiles. The GR effects are seen to suppress the production of seed nuclei, significantly boosting the resulting p-nuclide abundances. Our reference GR model, with an 18 M_⊙progenitor, reproduces both the relative and absolute solar system abundances of the entire set of thepnuclides in the mass range 74 ≤A≤ 102. The yields are suboptimal in our 12.75 M_⊙GR model, where the outflow transitions to the supersonic regime several seconds into the explosion, suppressing furtherp-nuclide production. In both models, most of the production of the crucial^92,94Mo and^96,98Rupisotopes occurs relatively early, 1–3 seconds after shock revival. In contrast, a large fraction of the shielded isotope⁹²Nb is produced in the subsequent ejecta. The impact of GR on this isotope is especially large, with its final abundance boosted by a factor of 25 compared to a Newtonian calculation. In summary, with the GR effects taken into account, theνp-process in a sufficiently massive progenitor can provide a unifying explanation for the origin of allpnuclei in the solar system up to¹⁰²Pd. 

Abstract We present the second release of theGR-Athena++waveform catalog, comprising four new quasi-circular, non-precessing, spinning binary black hole simulations. These simulations are performed at high resolutions and represent a step toward generating high-fidelity gravitational waveforms that can eventually meet the accuracy requirements of upcoming next-generation detectors, including LISA, cosmic explorer, and Einstein Telescope. Gravitational waves are extracted at future null infinity ( $I^{+}$ ) using both Cauchy characteristic extraction and finite-radius extraction. For each simulation, we provide strain data across multiple resolutions and analyze waveform accuracy via convergence studies and self-mismatch analyses. The absolute phase and relative amplitude differences reach their largest values near the merger, while the smallest errors are of order $O\left({10}^{-2}\right)$ and $O\left({10}^{-3}\right)$ , respectively. A self-mismatch analysis of the dominant (2, 2) mode yields mismatches between $O\left({10}^{-5}\right)$ and $O\left({10}^{-7}\right)$ for a total binary mass of ${10}^6{M}_{\odot }$ over the frequency range $f\in [0.002,0.1]\mathrm{Hz}$ using LISA’s noise curve. All waveforms are publicly available viaScholarSphere. 

Abstract Multimessenger observations of binary neutron star mergers can provide valuable information on the nuclear equation of state (EOS). Here, we investigate the extent to which electromagnetic observations of the associated kilonovae allow us to place constraints on the EOS. For this, we use state-of-the-art three-dimensional general-relativistic magnetohydrodynamics simulations and detailed nucleosynthesis modeling to connect properties of observed light curves to properties of the accretion disk, and hence, the EOS. Using our general approach, we use multimessenger observations of GW170817/AT2017gfo to study the impact of various sources of uncertainty on inferences of the EOS. We constrain the radius of a 1.4M_⊙neutron star to lie within 10.30 ≤R_1.4≤ 13.0 km and the maximum mass to beM_TOV≤ 3.06M_⊙. 

Abstract We consider the question of whether core-collapse supernovae (CCSNe) can produce rapid neutron capture process (r-process) elements and how future MeV gamma-ray observations could address this. Rare types of CCSNe characterized by substantial magnetic fields and rotation, known as magnetorotational supernovae (MR-SNe), are theoretically predicted to produce these elements, although direct observational evidence is lacking. We suggest that this critical question be addressed through the study of some of the 11 CCSN remnants located within 10 kpc, as well as through the detection of gamma-ray emission from a future Galactic supernova. We use a two-dimensional MR-SN model to estimate the expected gamma flux stemming from nuclear decays in the range of a few tens of keV to a few MeV. Our results indicate that an observation of¹²⁶Sn (¹²⁶Sb) in a remnant stands out as a signature of anr-process-producing supernova. Since the neutron-rich conditions that lead to the production of ther-process could also enhance the production of⁶⁰Fe, the detection of substantial⁶⁰Fe (⁶⁰Co) would be indicative of favorable conditions for ther-process. In the case of a future supernova explosion, when the evolution of the spectrum is studied over 10 days to a few years, a rich picture emerges. At various epochs, the second peakr-process isotopes such as¹²⁵Sn,¹³¹I,¹³²Te,¹³²I, and¹⁴⁰La produce signals that are not obscured by the gamma emission from explosive burning products and electron–positron annihilation. The weakr-process isotopes⁹⁵Nb,¹⁰³Ru, and¹⁰⁶Rh also have periods of prominence. 

Abstract The first direct detection of gravitational waves by the LIGO collaboration, GW150914, marked the start of a new exciting era in astronomy, enabling the study of the Universe through a new messenger. Since then, the field has grown rapidly, with the development of increasingly more sophisticated techniques to detect, analyze and interpret the signals. In this paper we revisit GW150914, presenting updated estimates of its source parameters using a waveform model developed within the EOB formalism, able to describe gravitational-wave emission from generic non-circular, non-planar binaries. We provide a comprehensive analysis of the signal and its properties, considering and contrasting various scenarios for the source: from the simplest, aligned-spin quasi-circular (QC) binary black hole (BBH) merger, to more complex scenarios, including precession, eccentricity or both. Unsurprisingly, we find that the signal is consistent with a QC (e < 0.08 at 15 Hz), slowly spinning $({\chi }_{\text{eff}}=-{0.03}_{-0.13}^{+0.12})$ BBH merger, a-posteriori validating a considerable body of works. This is the first analysis performed with an inspiral-merger-ringdown model containing both eccentricity and precession. 

A<sc>bstract</sc> We investigate two-neutrino double beta decay (2νββ) in chiral effective field theory. We find contributions from weak magnetism and double-weak pion-exchange at next-to-leading-order in the chiral power counting. We discuss the impact of the chiral corrections on the electron spectra and find that they should be included in analyses of 2νββdecay that aim to uncover new physics signatures in the electron spectrum. We illustrate this point by revisiting the effect of sterile neutrinos and non-standard charged interactions. We also find that the pion-exchange contributions involve nuclear matrix elements that are related to those appearing in neutrinoless double beta decay (0νββ). We investigate whether the 0νββnuclear matrix elements can be obtained from detailed measurements of the energy spectrum of the outgoing electrons in 2νββtransitions. 

Abstract The remnant black hole–accretion disk system resulting from binary neutron star mergers has proven to be a promising site for synthesizing the heaviest elements via rapid neutron capture (r-process). A critical factor in determining the fullr-process pattern in these environments is the neutron richness of the ejecta, which is strongly influenced by neutrino interactions. One key ingredient shaping these interactions is fast neutrino flavor conversions (FFCs), which arise due to angular crossings in neutrino distributions and occur on nanosecond timescales. We present the first three-dimensional in situ angle-dependent modeling of FFCs in postmerger disks, implemented within general relativistic magnetohydrodynamics with Monte Carlo neutrino transport. Our results reveal that, by suppressing electron neutrinos, FFCs more efficiently cool the disk and weaken the early thermally driven wind. Less releptonization due to electron neutrino absorption makes this cooler wind more neutron rich, producing a more robustr-process at higher latitudes of the outflow. This study underscores the necessity of incorporating FFCs in realistic simulations.