arXiv subjects

Adam Burrows

Publications and source records attributed to Adam Burrows.

At least 19 recordsLinked to original sources

arXiv2026

The Mass Function of Neutron Stars from Core-Collapse Supernova Simulations

Using the mapping between progenitor core structure and the gravitational mass of neutron stars derived from sophisticated 3D supernova simulations, we determine the theoretical mass distribution of neutron stars at birth and compare it with neutron star mass function measurements. In the process, we explore the effects of islands of black hole formation and subsequent mass accretion. We show that supernova theory can explain the observed neutron star mass function from its lower-mass peak near $\sim$1.35 $M_{\odot}$ to its higher-mass tail. Moreover, the lower predicted kick speeds expected during the birth of lower-mass neutron stars and the higher expected kick speeds expected on average for higher mass neutron stars both sculpt the observed mass function in desired directions. The upshot of all these influences is to imprint upon the measured neutron star mass function features that reflect the varied physics of both neutron star origins and the neutron-star/black-hole dichotomy. Very approximately, we derive a black hole birth fraction of $\sim$21\%. In summary, we suggest that supernova theory can now be used to explain, however provisionally, various measured attributes of the population of compact objects and that an era of productive engagement between supernova theory and observation is at hand.

astro-ph.HE↗

arXiv2026

Effects of Rotation on 3D Core-Collapse Supernova Models for Low-Mass Progenitors

We explore the dependence upon rotation rate alone of various supernova observables simulated to their saturation for the explosion of a 9-$M_{\odot}$ progenitor. We find that the explosion energy is non-monotonic with, and weakly dependent upon, spin across a broad range of initial spins. The asymmetries of the blast depend weakly on spin, with faster spins leading to only slightly greater asymmetries. There is little significant pole-equator neutrino heating asymmetry during explosion, even for rapid rotation, and only for the fastest rotator does the neutrino heating rate diminish noticeably. Hence, the effects of rotation alone on all salient aspects of supernova dynamics are not large. We find that the recoil kick and spin are clearly aligned only for the most rapidly rotating model. Interestingly, for the fastest rotator, we witness a $T/|W|$ corotation instabilities near a value of 0.05 and spiral arm modes emerge. We find that the nucleosynthetic yields depend little upon the rotation rate and determine that the ratio of initial to final core spin period is near $\sim$4000, implying, given the modest inferred radio pulsar periods at birth, that the initial spin periods of most supernova cores are likely quite long. However, we focus on only one progenitor and do not include magnetic fields. Nevertheless, at least for low-mass progenitors which explode early, we find muted consequences of rotation in most major particulars across a wide range of initial spins.

astro-ph.HE↗

arXiv2026

Next-Generation Atmosphere Models for Giant Planets with Application to Coupled Interior Composition and Spectral Evolution I: Cloudless Models with Equilibrium Chemistry

We present updated atmosphere models designed for calculating the post-formation evolution and cooling of giant planets with masses between $0.3$ and $10$ $M_J$. Our tables provide the entropy in the convective region at the base of the atmosphere, temperature ($T$)pressure ($P$) profiles, and emergent spectra for atmospheres calculated using the radiative transfer code \texttt{CoolTLusty} for $T_{\mathrm{eff}}$s over the range 100 to 1400 Kelvin and log$_{10}$($g$) from 2.8 to 4.4 ($cgs$) with the latest opacities and equations of state. Each spectrum and thermal profile is calculated using line-by-line opacity sampling. We construct tables at 3 different metallicities ($Z = 1, 3.16, 10 Z_\odot$) and 2 different helium fractions ($Y=0.15, 0.275$), with the improvement that we adopt a metal-inclusive EOS that treats heavy elements consistently with the opacity metallicity (rather than folding it into an effective $Y$). The result is tables that accommodate both changes in $Y$ due to helium rain and potential variations in $Z$ during envelope evolution. We present a comparison between TP profiles, modeled spectra, and evolutionary tracks, and find that on-the-fly interpolation of boundary conditions in atmospheric composition has a notable impact on the late stages of giant planet evolution, altering the timing of helium rain and therefore the subsequent cooling history and atmospheric helium depletion. We also provide an available toolkit that generates spectra and boundary conditions via efficient interpolation across the 4D parameter space $(T_{\rm eff}, \log_{10} g, Y, Z)$, which is useful for post processing evolutionary tracks to produce fully time-resolved spectral evolutions.

astro-ph.EP↗

arXiv2026

ORCHARD: A General Planetary Evolution Code

We present \texttt{ORCHARD}, a publicly available planetary evolution code based on the gas giant evolution code, \texttt{APPLE}, capable of modeling the evolution and structures of terrestrial, super-Earth, sub-Neptune, Neptune, and gas giant planets and exoplanets from 0.5 M$_\oplus$ to 10 M$_J$. It supports not only the inhomogeneous and non-adiabatic evolution of gas giants and sub-Neptunes, but also the solidification of the mantles and cores of terrestrial planets, sub-Neptunes, and super-Earths. \texttt{ORCHARD} incorporates a state-of-the-art hydrogen-helium equation of state, ``metal" equations of state (water, ice mixtures, enstatite/perovskite, olivine/forsterite, iron), and atmospheric boundary conditions ranging from detailed non-gray radiative transfer models for Solar System giants to irradiated sub-Neptune atmospheres and bare rocky surfaces. \txt{ORCHARD} also supports static calculations with state-of-the-art equations of state. The purpose of \texttt{ORCHARD} is to provide the scientific community with a flexible, unified tool for modeling planetary structures and evolution across the entire mass continuum of general astrophysical and planetary interest.

astro-ph.EP↗

arXiv2026

Saturn's Evolutionary History and Seismology: Survival of Deep Stably Stratified Regions in Evolutionary Models of Saturn Consistent with Ring Seismology

With recent advances in the modeling of the solar system giant planets, rapid progress has been made in understanding the remaining questions pertaining to their formation and evolution. However, this progress has largely neglected the significant constraints on the interior of Saturn's structure imposed by the observed oscillation frequencies in its rings. Here, we study initial conditions for Saturn's evolution that, after $4.56\;\mathrm{Gyr}$ of evolution, give rise to planetary structures admitting oscillation frequencies consistent with those observed via Saturn's ring seismology. Restricting our attention to models without compact rocky cores, we achieve simultaneous good agreement with most observed properties of Saturn at the level of current evolutionary models and with key frequencies in the observed oscillation spectrum. Our preliminary work suggests that Saturn's interior stably stratified region may be moderately less extended ($\sim 0.4$--$0.5R_{\rm Sat}$) than previously thought, which is important for reconciling the seismic constraints with evolutionary models. We also tentatively find that the deep helium gradients inferred by previous, static structural modelling of Saturn's ring seismology may not be required to reproduce the observed seismology data.

astro-ph.EP↗

arXiv2025

Sub-Neptune Memories I: Implications of Inefficient Mantle Cooling and Silicate Rain

We explore the evolution of sub-Neptune (radii between $\sim$1.5 and 4 R$_\oplus$) exoplanet interior structures using our upgraded evolution code, \texttt{APPLE}, which self-consistently couples the thermal and compositional evolution of the whole structure. We incorporate stably stratified regions with convective mixing and, for the first time, ab initio results on the phase separation of silicate-hydrogen mixtures to model silicate rain in sub-Neptune envelopes. We demonstrate that inefficient mantle cooling can retain sufficient heat to Gyr ages: inefficient heat transport from mantle to envelope alone keeps radii $\sim$10\% larger than predicted by adiabatic models at late times. Silicate rain can contribute an additional $\sim$5\% to the radius, depending on envelope mass and initial metal abundance. The silicate-hydrogen immiscibility region may lie in the middle or even upper envelope, far above the envelope-mantle boundary layer, and bifurcates the envelope into two an upper, hydrogen-rich region and a lower, metal-rich region above the mantle. If silicate rain occurs, atmospheres should appear depleted of silicates while radii remain inflated at late ages. To demonstrate the effects of inefficient mantle cooling, we present interior evolution models for GJ 1214 b, K2-18 b, TOI-270 d, and TOI-1801 b, showing that hot, liquid silicate mantles with thin envelopes reproduce their radii and mean densities, providing an alternative to water-world interpretations. These results imply that bulk compositions inferred from mean density must account for the mantle thermal state and the envelope mixing/phase-separation history; such thermal ``memories'' may constrain formation entropies and temperatures when metallicities are more precisely measured.

astro-ph.EP↗

arXiv2025

The Effect of the Fast-Flavor Instability on Core-Collapse Supernova Models: II. Quasi-Equipartition and the Impact of Various Angular Reconstruction Methods

In this work, we explore in a consistent fashion the effects of fast flavor conversion (FFC) in 1D and 2D core-collapse supernova (CCSN) simulations. In addition, we investigate the impact of various angular reconstruction methods and compare the ``3-species'' and ``4-species'' neutrino transport schemes. We find that the FFC effects are insensitive to the different methods tested and that the FFC alters supernova hydrodynamics is only minor ways. We also present a ``quasi-equipartition'' approximation which can be used to estimate the FFC-altered neutrino properties by post-processing the neutrino signals extracted from no-oscillation CCSN simulations. The relative errors in neutrino number and energy luminosities of this phenomenological method are less than 2\% for 1D models, and less than 10\% for 2D models. This method provides a simple way to include the effects of FFC on neutrino signals without implementing a complex and expensive FFC scheme or redoing simulations.

astro-ph.HE↗

arXiv2025

The Fate of Hydrogen and Helium: From Planetary Embryos to Earth- and Neptune-like Worlds

Hydrogen, helium, silicates, and iron are key building blocks of rocky and gas-rich planets, yet their chemical interactions remain poorly constrained. Using first-principles molecular dynamics and thermodynamic integration, we quantify hydrogen and helium partitioning between molten silicate mantles and metallic cores for Earth-to-Neptune-mass planets. Hydrogen becomes strongly siderophilic above $\sim$25 GPa but weakens beyond $\sim$200 GPa, whereas helium remains lithophilic yet increasingly soluble in metal with pressure. Incorporating these trends into coupled structure-chemistry models suggests that majority of hydrogen and helium reside in planetary interiors, not atmospheres, with abundances strongly depending on planet mass. Such volatile exchange may influence the redox states of secondary atmospheres, longevity of primordial envelopes, predicted CHNOPS abundances, and emergence of helium-enriched atmospheres, while He 1083 nm and H Lyman-$\alpha$ lines provide potential probes of atmosphere-interior exchange. These findings link atomic-scale interactions to planetary-scale observables, providing new constraints on the origins of Earth-to-Neptune-sized worlds.

astro-ph.EP↗

arXiv2025

Next-Generation Improvements in Giant Exoplanet Evolutionary and Structural Models

Many evolutionary models of giant exoplanets still rely on simplifying assumptions that are no longer adequate given detailed constraints from Jupiter, Saturn, and modern exoplanet observations. Here, we identify the key physical improvements required for next-generation planetary evolution models using our code, \texttt{APPLE}, which enables systematic emulation and extension of legacy studies. We quantify the effects of updated equations of state, helium rain, fuzzy cores, non-adiabatic and compositionally inhomogeneous envelopes, and improved atmospheric boundary conditions by first isolating the impact of each physical ingredient and then constructing combined baseline models for planets with masses between 0.3 and 4~$M_{\rm Jup}$ to assess their collective influence on planetary structure and observable properties. We find that the adoption of modern equations of state and realistic heavy-element distributions leads to systematic, but sometimes subtle, differences ($\sim 5$ to 10\%) in radius evolution, while helium rain and the treatment of convection can significantly alter thermal histories and atmospheric compositions (by $\sim$ 5 to 20\%). These updated physical processes must be incorporated into the next-generation exoplanet evolutionary models to achieve physically consistent interpretations of planetary observations.

astro-ph.EP↗

arXiv2025

Simulated 3D $^{56}$Ni Distributions of Type IIp Supernovae

We present the first three-dimensional study of the asymptotic ejecta distributions for a suite of theoretical Type IIp supernovae originating from red supergiant progenitors. We simulate using the radiation-hydrodynamic code F{\sc{ornax}} from core bounce through the first seconds of the neutrino-driven explosion and then follow using a hydrodynamic variant of the code FLASH until shock breakout of the star and through to homologous expansion of the ejecta into the circumstellar environment. Our studied progenitor models range from 9 to 25 M$_{\odot}$, with explosion energies spanning $\sim$0.1$-$1 Bethe. The shock breakout times span the range $\sim$1$-$4 days, with a breakout time spread by direction ranging from hours to over a day. We find that the dipole orientation of the $^{56}$Ni ejecta is well-preserved from the first seconds out to shock breakout. The $^{56}$Ni ejecta penetrates through the initially outer oxygen shell, and its global structure is imprinted with small-scale clumping as the ejecta evolve through the stellar envelope. For the majority of our models, the neutron star kick is anti-aligned with the $^{56}$Ni ejecta. Models with strongly dipolar ejecta morphology and a massive hydrogen/helium envelope with an inner boundary located deep see as much as $\sim$70\% of the $^{56}$Ni ejecta mixed into that outer envelope, reaching asymptotic velocities ranging from $\sim$350 to 3200 km s$^{-1}$. Supernovae arising from red supergiant progenitors and exhibiting prominent nickel features generally display significant $^{56}$Ni mixing into the stellar envelope.

astro-ph.HE↗

arXiv2025

The Effect of the Collisional Flavor Instability on Core-Collapse Supernova Models

We explore the effects of the neutrino collisional flavor instability (CFI) based on 1D and 2D core-collapse supernova (CCSN) simulations done using the sophisticated radiation-hydrodynamic code Fornax. We compare the growth rates of homogeneous CFI (hCFI) modes calculated by numerically solving the multi-group dispersion relation to those calculated using the monochromatic approximation. We find that the widely-used monochromatic approximation leads to incorrect growth rates} when applied in multi-group scenarios. As opposed to the $\sim10^5$ s$^{-1}$ values given by the monochromatic approximation, the actual growth rates of non-resonance multi-group hCFI are at most $\sim$200 s$^{-1}$ in all our models and they are too slow to affect CCSN outcomes. We adopt a BGK flavor conversion scheme in the simulations to include the effects of resonance-like hCFI. We find that the CCSN dynamics and neutrino emission properties are only weakly influenced, and the intrinsic stochasticity due to convection and neutrino-driven turbulence can naturally lead to comparable effects. Hence, our analysis of the non-resonance and resonance-like hCFI into CCSN simulations suggests that the effects of neutrino flavor conversion triggered by hCFI modes are in general small.

astro-ph.HE↗

arXiv2025

The Evolution of Jupiter and Saturn as a function of the Parameter R$_{\rho}$

Computed using the APPLE planetary evolution code, we present updated evolutionary models for Jupiter and Saturn that incorporate helium rain, non-adiabatic thermal structures, and "fuzzy" extended heavy-element cores. Building on our previous Ledoux-stable models, we implement improved atmospheric boundary conditions that account for composition-dependent effective temperatures and systematically explore the impact of varying the parameter $R_{\rho}$, which allows one to explore in an approximate way the efficiency of semiconvection. For both Jupiter and Saturn, we construct models spanning from $R_{\rho}=1$ (Ledoux) to $R_{\rho}=0$ (Schwarzschild), and identify best-fit solutions that match each planet's effective temperature, equatorial radius, lower-order gravitational moments, and atmospheric composition at 4.56 Gyr. We find that lower $R_{\rho}$ values lead to stronger convective mixing, resulting in higher surface metallicities and lower deep interior temperatures, while requiring reduced heavy-element masses and lower initial entropies to stabilize the dilute inner cores. Our Saturn models also broadly agree with the observed brunt frequency profile inferred from Cassini ring seismology, with stable layers arising from both the helium rain region and the dilute core. These findings support the presence of complex, compositionally stratified interiors in both gas giants.

astro-ph.EP↗

arXiv2025

The Science of the Einstein Telescope

Einstein Telescope (ET) is the European project for a gravitational-wave (GW) observatory of third-generation. In this paper we present a comprehensive discussion of its science objectives, providing state-of-the-art predictions for the capabilities of ET in both geometries currently under consideration, a single-site triangular configuration or two L-shaped detectors. We discuss the impact that ET will have on domains as broad and diverse as fundamental physics, cosmology, early Universe, astrophysics of compact objects, physics of matter in extreme conditions, and dynamics of stellar collapse. We discuss how the study of extreme astrophysical events will be enhanced by multi-messenger observations. We highlight the ET synergies with ground-based and space-borne GW observatories, including multi-band investigations of the same sources, improved parameter estimation, and complementary information on astrophysical or cosmological mechanisms obtained combining observations from different frequency bands. We present advancements in waveform modeling dedicated to third-generation observatories, along with open tools developed within the ET Collaboration for assessing the scientific potentials of different detector configurations. We finally discuss the data analysis challenges posed by third-generation observatories, which will enable access to large populations of sources and provide unprecedented precision.

gr-qc↗

arXiv2025

Predicted Neutrino Signal Features of Core-Collapse Supernovae

In this paper, we examine the neutrino signals from 24 initially non-rotating, three-dimensional core-collapse supernova (CCSN) simulations carried to late times. We find that not only does the neutrino luminosity signal encode information about each stage of the CCSN process, but that the monotonic dependence of the luminosity peak height with compactness enables one to infer the progenitor core structure from the neutrino signal. We highlight a systematic relationship between the luminosity peak height with its timing. Additionally, we emphasize that the total energy radiated in neutrinos is monotonic with progenitor compactness, and that the mean neutrino energy contains a unique spiral SASI signature for nonexploding, BH-forming models. We also find that neutrino emissions are not isotropic and that the anisotropy increases roughly with progenitor compactness. To assess the detectability of these neutrino signal features, we provide examples of the event rates for our models for the JUNO, DUNE, SK, and IceCube detectors using the SNEWPY software, and find that many of the trends in the luminosity signal can be detectable across several detectors and oscillation models. Finally, we discuss correlations between the radiated neutrino energy and the evolution of the gravitational-wave f-mode.

astro-ph.HE↗

arXiv2025

The Effect of the Fast-Flavor Instability on Core-Collapse Supernova Models

Merging our supernova code F{\sc{ornax}} with the Box3D fast-flavor neutrino oscillation formalism, we explore the effects of fast-flavor conversion (FFC) in state-of-the-art 1D and 2D core-collapse supernova simulations. We find that after a few tens of milliseconds after bounce the FFC emerges just interior to and exterior to the stalled shock wave. It does not obtain in the PNS core nor near the average neutrinosphere radii. Interior to the shock, this results in a temporary change in the net neutrino heating rate of $\sim$10\%, due mostly to a hardening of the $\nu_e$ and $\bar{\nu}_e$ neutrino spectra, despite the decrease in their corresponding neutrino number fluxes. In 1D, the hydrodynamic effects are not large, with increases in the stalled shock radius by of order ten to twenty kilometers that abate within a few hundred milliseconds. In 2D, the hydrodynamic effect of the FFC is a bit more noticeable, resulting in slightly earlier explosions for models for lower-mass progenitors, but also potentially inhibiting explosions for some higher-mass progenitors. Fast-flavor conversion continues to operate at larger radii at later times. The net result is a shift upward in the $\nu_{\mu}$ energy and number luminosities and a shift downward in the same quantities for both the $\nu_e$ and $\bar{\nu}_e$ neutrinos. There seems to be a trend at very large radii and later times towards partial species and spectral equipartition. If this is true, it could be an interesting feature of supernova neutrino detection at later times in underground and under-ice facilities.

astro-ph.HE↗

arXiv2024

Simultaneous Evolutionary Fits for Jupiter and Saturn Incorporating Fuzzy Cores

With the recent realization that there likely are stably-stratified regions in the interiors of both Jupiter and Saturn, we construct new non-adiabatic, inhomogeneous evolutionary models with the same microphysics for each that result at the present time in respectable fits for all major bulk observables for both planets. These include the effective temperature, radius, atmospheric heavy-element and helium abundances (including helium rain), and the lower-order gravity moments J2 and J4. The models preserve from birth most of an extended "fuzzy" heavy-element core. Our predicted atmospheric helium mass fraction for Saturn is ~0.2, close to some measured estimates, but in disagreement with some published predictions. To preserve a fuzzy core from birth, the interiors of both planets must start out at lower entropies than would be used for traditional "hot start" adiabatic models, though the initial exterior mantle entropies can range from hot to warm start values. We do not see a helium ocean in Saturn's interior, and both models have inner envelopes with significant Brunt-Vaisala frequencies; this region for Saturn at the current epoch is more extended and in it, the Brunt is larger. The total heavy-element mass fraction in Jupiter and in Saturn is determined to be ~14% and ~26%, respectively, though there is some play in these determinations.

astro-ph.EP↗

arXiv2024

Channels of Stellar-mass Black Hole Formation

On the basis of a large collection of detailed 3D core-collapse supernova simulations carried to late times, we identify four channels of stellar mass black hole formation. Our examples for Channel 1 involve the formation of lower-gap and above black holes in energetic asymmetric supernova explosions. Our Channel 2 example involves a modest supernova explosion that may leave behind a lower-gap to $\sim$10 $M_{\odot}$ black hole. The latter may not be easily distinguishable from ``standard" supernovae that birth neutron stars. Our Channel 3 example experiences an aborted core-collapse explosion, more often in the context of a low-metallicity progenitor, whose residue is a black hole with a mass perhaps up to $\sim$40 $M_{\odot}$. The latter may be accompanied by a pulsational-pair instability supernova (PPISN). Channel 4 is the only quiescent or ``silent" scenario for which perhaps $\sim$5 to 15 $M_{\odot}$ black holes are left. Where appropriate, we estimate $^{56}$Ni yields, explosion energies, approximate recoil speeds, and residual black hole masses. The progenitor mass density and binding energy profiles at collapse influence the outcome in a systematic way. We speculate that the statistics and prevalence of these various channels depend not only on still evolving supernova theory, but on remaining issues with the theory of massive star evolution, binary interaction, wind mass loss, metallicity, and the nuclear equation of state. Importantly, we suggest, but have not proven, that the silent channel for black hole formation may not be the dominant formation modality.

astro-ph.SR↗

arXiv2024

Leveraging neutrino flavor physics for supernova model differentiation

Neutrino flavor evolution is critical for understanding the physics of dense astrophysical regimes, including core-collapse supernovae (CCSN). Powerful numerical integration codes exist for simulating these environments, yet a complete understanding of the inherent nonlinearity of collective neutrino flavor oscillations and how it fits within the overall framework of these simulations remains an open challenge. For this reason, we continue developing statistical data assimilation (SDA) to infer solutions to the flavor field in a CCSN envelope, given simulated measurements far from the source. SDA is an inference paradigm designed to optimize a model with sparse data. Our model consists of neutrino beams emanating from a CCSN and coherently interacting with each other and with a background of other matter particles in one dimension $r$. One model feature of high interest is the distribution of those matter particles as a function of radius $r$, or the "matter potential" $V(r)$ -- as it significantly dictates flavor evolution. In this paper, we expand the model beyond previous incarnations, by replacing the monotonically-decaying analytic form for $V(r)$ we previously used with a more complex -- and more physically plausible -- set of profiles derived from a one-dimensional (spherically symmetric) hydrodynamics simulation of a CCSN explosion. We ask whether the SDA procedure can use simulated flavor measurements at physically accessible locations (i.e. in vacuum) to determine the extent to which different matter density profiles through which the neutrinos propagate in the matter-dominated regime are compatible with these measurements. Within the scope of our small-scale model, we find that the neutrino flavor measurements in the vacuum regime are able to discriminate between different matter profiles, and we discuss implications regarding a future galactic CCSN detection.

astro-ph.HE↗