arXiv subjects

David Vartanyan

Publications and source records attributed to David Vartanyan.

At least 19 recordsLinked to original sources

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

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

Deep-Ocean Application-Specific Neutrino Experiment

This report introduces the concept, prototype design, projected costs, and scientific goals of a mobile experiment for detecting geoneutrinos originating from uranium and thorium decay chains in the Earth's mantle. This will constrain the planet's radiogenic heat production and unearth its geochemical makeup. This design of a deep-ocean mobile neutrino experiment, which is not mirrored by any active or planned experiments, supports physics and geoscience's goal of multi-modal data on the Earth's internal composition and structure. Based on geoscientific studies, this design is expected to achieve a 50--100-fold reduction in crustal background compared to similarly sized continental detectors, thereby enabling direct measurements of mantle geoneutrinos. The multiple stereoscopic projections enabled by the detector's unique mobility can map spatial variations in heat-producing elements within the mantle. Beyond discussing the design, we report on our collaboration's most recent hardware developments in the active prototyping of this detector. We briefly highlight the potential multiuse and interdisciplinary nature of this detector.

physics.ins-det↗

arXiv2026

Towards imaging Earth's large-scale structures by directional geoneutrino detection with Ocean Bottom Detector

Geoneutrinos, electron antineutrinos produced by radioactive decays of heat-producing elements (HPEs) within the Earth, provide unique insights into Earth's interior and heat budget since their first detection in 2005 by KamLAND. Conventional geoneutrino detectors currently provide integrated global information and lack the capability to spatially resolve structures deep within the Earth. Here, we evaluate the ability of angular-sensitive geoneutrino detectors to distinguish between homogeneous and heterogeneous mantle models, focusing on Large Low Shear Velocity Provinces (LLSVPs). Our results show that LLSVPs enriched in Th and U yield a distinct flux of geoneutrinos with distinctive angular patterns. An oceanic site above the Pacific LLSVP is considered a particularly favorable detector location. The Ocean Bottom Detector (OBD) project aims to leverage this spatial resolving advantage by deploying a kiloton-scale liquid scintillator detector directly on the ocean floor, enabling unprecedented sensitivity for mantle geoneutrino detection. These findings demonstrate the critical role of combining geophysical and geochemical data to guide detector site selection, ultimately improving constraints on Earth's internal heat and the HPE distribution.

physics.geo-ph↗

arXiv2026

An Exploration of the Equation of State Dependence of Core-Collapse Supernova Explosion Outcomes and Signatures

We explore, using a state-of-the-art simulation code in 3D and to late enough times to witness final observables, the dependence of core-collapse supernova explosions on the nuclear equation of state. Going beyond questions of explodability, we compare final explosion energies, nucleosynthetic yields, recoil kicks, and gravitational-wave and neutrino signatures using the SFHo and DD2 nuclear equations of state (EOS) for a 9-$M_{\odot}$/solar-metallicity progenitor star. The DD2 EOS is stiffer and has a lower effective nucleon mass. The result is a more extended protoneutron star (PNS) and lower central densities. As a consequence, the mean neutrino energies, final explosion energy, and recoil kick speed are lower. Moreover, the evolution of PNS convection differs between the two EOS models in significant ways. This translates in part into interestingly altered neutrino ``light" curves and noticeably altered gravitational-wave signal strengths and frequency characteristics that may be diagnostic. The faster exploding model (SFHo) yields slightly more neutron-rich ejecta and more species with atomic weights between 60 and 90 and a weak r-process. However, this is merely a preliminary study. The next step is a more comprehensive and multi-progenitor set of 3D supernova simulations for various EOSes to late times when the observables have asymptoted. Such a future investigation will have a direct bearing on the neutron star and black hole birth mass functions and the quest towards a fully quantitative theory of supernova observables.

astro-ph.HE↗

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

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

Neutrino Heating in 1D, 2D, and 3D core-collapse supernovae: characterizing the explosion of high-compactness stars

Massive stars can end their lives with a successful supernova explosion (leaving behind a neutron star or, more rarely, a black hole), or a failed explosion that leaves behind a black hole. The density structure of the pre-collapse progenitor star already encodes much of the information regarding the outcome and properties of the explosion. However, the complexity of the collapse and subsequent shock expansion phases prevents drawing a straightforward connection between the pre-collapse and post-explosion properties. In order to derive such a connection several explodability studies have been performed in recent years. However, different studies can predict different explosion outcomes. In this article, we show how compactness, which is related to the average density of the star's core, has an important role in determining the efficiency of neutrino heating, and therefore the outcome of the explosion. Commonly, high-compactness progenitors are assumed to yield failed explosions, due to their large mass accretion rates, preventing the shock from expanding. We show by analyzing $\sim$ 150 2D FLASH and Fornax simulations and 20 3D Fornax simulations that this is not the case. Instead, due to the rapid increase of neutrino heating with compactness, high-compactness progenitors lead to successful shock revival. We also show that 1D+ simulations that include $ν$-driven convection using a mixing-length theory approach correctly reproduce this trend. Finally, we compare 1D+ models, which we show can reproduce some aspects of multi-D simulations with reasonable accuracy, with other widely used 1D models in the literature.

astro-ph.HE↗

arXiv2025

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↗

arXiv2025

Gravitational-Wave and Gravitational-Wave Memory Signatures of Core-Collapse Supernovae

In this paper, we calculate the energy, signal-to-noise ratio, detection range, and angular anisotropy of the matter, matter memory, and neutrino memory gravitational wave (GW) signatures of 21 three-dimensional initially non-rotating core-collapse supernova (CCSN) models carried to late times. We find that inferred energy, signal-to-noise ratio, and detection range are angle-dependent quantities, and that the spread of possible energy, signal-to-noise, and detection ranges across all viewing angles generally increases with progenitor mass. When examining the low-frequency matter memory and neutrino memory components of the signal, we find that the neutrino memory is the most detectable component of a CCSN GW signal, and that DECIGO is best-equipped to detect both matter memory and neutrino memory. Moreover, we find that the polarization angle between the $h_+$ and $h_{\times}$ strains serves as a unique identifier of matter and neutrino memory. Finally, we develop a galactic density- and stellar mass-weighted formalism to calculate the rate at which we can expect to detect CCSN GW signals with Advanced LIGO. When considering only the matter component of the signal, the aLIGO detection rate is around 24$\%$ of the total galactic supernova rate, but increases to 92$\%$ when incorporating the neutrino memory component. We find that all future detectors (ET, CE, DECIGO) will be able to detect CCSN GW signals from the entire galaxy, and for the higher-mass progenitors even into the local group of galaxies.

astro-ph.HE↗

arXiv2025

A 3D Simulation of a Type II-P Supernova: from Core Bounce to Beyond Shock Breakout

In order to better connect core-collapse supernovae (CCSN) theory with its observational signatures, we have developed a simulation pipeline from the onset of core collapse to beyond shock breakout. Using this framework, we present a three-dimensional simulation study following the evolution from five seconds to over five days of a 17-M$_{\odot}$ progenitor that explodes with $\sim$10$^{51}$ erg of energy and $\sim$0.1 M$_{\odot}$ of $^{56}$Ni ejecta. The early explosion is highly asymmetric, expanding most prominently along the southern hemisphere. This early asymmetry is preserved to shock breakout, $\sim$1 day later. Breakout itself evinces strong angle-dependence, with as much a day delay in shock breakout by direction. The nickel ejecta closely tails the forward shock, with velocities at breakout as high as $\sim$7000 km s$^{-1}$. A delayed reverse shock forming at the H/He interface on hour timescales leads to the formation of Rayleigh-Taylor instabilities, fast-moving nickel bullets, and almost complete mixing of the metal core into the hydrogen envelope. For the first time, we illustrate the angle-dependent emergent broadband and bolometric light curves from simulations evolved in three-dimensions in entirety, continuing through hydrodynamic shock breakout a CCSN model of a massive stellar progenitor evolved with detailed, late-time neutrino microphysics and transport. Our case study of a single progenitor suggests that 3D simulations initiated with detailed neutrino heating can begin to generically produce the cornucopia of suggested asymmetries and features in CCSNe observations, while establishing the methodology to study this problem in breadth.

astro-ph.HE↗

arXiv2024

The Lunar Gravitational-wave Antenna: Mission Studies and Science Case

The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response of the Moon to gravitational waves (GWs). Given the size of the Moon and the expected noise produced by the lunar seismic background, the LGWA would be able to observe GWs from about 1 mHz to 1 Hz. This would make the LGWA the missing link between space-borne detectors like LISA with peak sensitivities around a few millihertz and proposed future terrestrial detectors like Einstein Telescope or Cosmic Explorer. In this article, we provide a first comprehensive analysis of the LGWA science case including its multi-messenger aspects and lunar science with LGWA data. We also describe the scientific analyses of the Moon required to plan the LGWA mission.

gr-qc↗

arXiv2024

Physical Correlations and Predictions Emerging from Modern Core-Collapse Supernova Theory

In this paper, we derive correlations between core-collapse supernova observables and progenitor core structures that emerge from our suite of twenty state-of-the-art 3D core-collapse supernova simulations carried to late times. This is the largest such collection of 3D supernova models ever generated and allows one to witness and derive testable patterns that might otherwise be obscured when studying one or a few models in isolation. From this panoramic perspective, we have discovered correlations between explosion energy, neutron star gravitational birth masses, $^{56}$Ni and $α$-rich freeze-out yields, and pulsar kicks and theoretically important correlations with the compactness parameter of progenitor structure. We find a correlation between explosion energy and progenitor mantle binding energy, suggesting that such explosions are self-regulating. We also find a testable correlation between explosion energy and measures of explosion asymmetry, such as the ejecta energy and mass dipoles. While the correlations between two observables are roughly independent of the progenitor ZAMS mass, the many correlations we derive with compactness can not unambiguously be tied to a particular progenitor ZAMS mass. This relationship depends upon the compactness/ZAMS mass mapping associated with the massive star progenitor models employed. Therefore, our derived correlations between compactness and observables may be more robust than with ZAMS mass, but can nevertheless be used in the future once massive star modeling has converged.

astro-ph.HE↗

arXiv2024

A Theory for Neutron Star and Black Hole Kicks and Induced Spins

Using twenty long-term 3D core-collapse supernova simulations, we find that lower compactness progenitors that explode quasi-spherically due to the short delay to explosion experience smaller neutron star recoil kicks in the $\sim$100$-$200 km s$^{-1}$ range, while higher compactness progenitors that explode later and more aspherically leave neutron stars with kicks in the $\sim$300$-$1000 km s$^{-1}$ range. In addition, we find that these two classes are correlated with the gravitational mass of the neutron star. This correlation suggests that the survival of binary neutron star systems may in part be due to their lower kick speeds. We also find a correlation of the kick with both the mass dipole of the ejecta and the explosion energy. Furthermore, one channel of black hole birth leaves masses of $\sim$10 $M_{\odot}$, is not accompanied by a neutrino-driven explosion, and experiences small kicks. A second is through a vigorous explosion that leaves behind a black hole with a mass of $\sim$3.0 $M_{\odot}$ kicked to high speeds. We find that the induced spins of nascent neutron stars range from seconds to $\sim$10 milliseconds, {but do not yet see a significant spin/kick correlation for pulsars.} We suggest that if an initial spin biases the explosion direction, a spin/kick correlation {would be} a common byproduct of the neutrino mechanism of core-collapse supernovae. Finally, the induced spin in explosive black hole formation is likely large and in the collapsar range. This new 3D model suite provides a greatly expanded perspective and appears to explain some observed pulsar properties by default.

astro-ph.HE↗

arXiv2023

Characterizing the Directionality of Gravitational Wave Emission from Matter Motions within Core-collapse Supernovae

We analyze the directional dependence of the gravitational wave (GW) emission from 15 3D neutrino radiation hydrodynamic simulations of core-collapse supernovae. Using spin weighted spherical harmonics, we develop a new analytic technique to quantify the evolution of the distribution of GW emission over all angles. We construct a physics-informed toy model that can be used to approximate GW distributions for general ellipsoid-like systems, and use it to provide closed form expressions for the distribution of GWs for different CCSN phases. Using these toy models, we approximate the PNS dynamics during multiple CCSN stages and obtain similar GW distributions to simulation outputs. When considering all viewing angles, we apply this new technique to quantify the evolution of preferred directions of GW emission. For nonrotating cases, this dominant viewing angle drifts isotropically throughout the supernova, set by the dynamical timescale of the protoneutron star. For rotating cases, during core bounce and the following tens of ms, the strongest GW signal is observed along the equator. During the accretion phase, comparable -- if not stronger -- GW amplitudes are generated along the axis of rotation, which can be enhanced by the low T/|W| instability. We show two dominant factors influencing the directionality of GW emission are the degree of initial rotation and explosion morphology. Lastly, looking forward, we note the sensitive interplay between GW detector site and supernova orientation, along with its effect on detecting individual polarization modes.

astro-ph.HE↗

arXiv2023

Black-Hole Formation Accompanied by the Supernova Explosion of a 40-M$_{\odot}$ Progenitor Star

We have simulated the collapse and evolution of the core of a solar-metallicity 40-M$_{\odot}$ star and find that it explodes vigorously by the neutrino mechanism. This despite its very high "compactness". Within $\sim$1.5 seconds of explosion, a black hole forms. The explosion is very asymmetrical and has a total explosion energy of $\sim$1.6$\times$10$^{51}$ ergs. At black hole formation, its baryon mass is $\sim$2.434 M$_{\odot}$ and gravitational mass is 2.286 M$_{\odot}$. Seven seconds after black hole formation an additional $\sim$0.2 M$_{\odot}$ is accreted, leaving a black hole baryon mass of $\sim$2.63 M$_{\odot}$. A disk forms around the proto-neutron star, from which a pair of neutrino-driven jets emanates. These jets accelerate some of the matter up to speeds of $\sim$45,000 km s$^{-1}$ and contain matter with entropies of $\sim$50. The large spatial asymmetry in the explosion results in a residual black hole recoil speed of $\sim$1000 km s$^{-1}$. This novel black-hole formation channel now joins the other black-hole formation channel between $\sim$12 and $\sim$15 M$_{\odot}$ discovered previously and implies that the black-hole/neutron-star birth ratio for solar-metallicity stars could be $\sim$20\%. However, one channel leaves black holes in perhaps the $\sim$5-15 M$_{\odot}$ range with low kick speeds, while the other leaves black holes in perhaps the $\sim$2.5-3.0 M$_{\odot}$ mass range with high kick speeds. However, even $\sim$8.8 seconds after core bounce the newly-formed black hole is still accreting at a rate of $\sim$2$\times$10$^{-2}$ M$_{\odot}$ s$^{-1}$ and whether the black hole eventually achieves a significantly larger mass over time is yet to be determined.

astro-ph.SR↗

arXiv2023

Correlation analysis of gravitational waves and neutrino signals to constrain neutrino flavor conversion in core-collapse supernova

Recent multi-dimensional (multi-D) core-collapse supernova (CCSN) simulations characterize gravitational waves (GWs) and neutrino signals, offering insight into universal properties of CCSN independent of progenitor. Neutrino analysis in real observations, however, will be complicated due to the ambiguity of self-induced neutrino flavor conversion (NFC), which poses an obstacle to extracting detailed physical information. In this paper, we propose a novel approach to place a constraint on NFC from observed quantities of GWs and neutrinos based on correlation analysis from recent, detailed multi-D CCSN simulations. The proposed method can be used even in cases with low significance - or no detection of GWs. We also discuss how we can utilize electro-magnetic observations to complement the proposed method. Although our proposed method has uncertainties associated with CCSN modeling, the present result will serve as a base for more detailed studies. Reducing the systematic errors involved in CCSN models is a key to success in this multi-messenger analysis that needs to be done in collaboration with different theoretical groups.

astro-ph.HE↗

arXiv2023

Neutrino Signatures of One Hundred 2D Axisymmetric Core-Collapse Supernova Simulations

We present in this paper a public data release of an unprecedentedly-large set of core-collapse supernova (CCSN) neutrino emission models, comprising one hundred detailed 2D-axisymmetric radiation-hydrodynamic simulations evolved out to as late as ~5 seconds post-bounce and spanning a extensive range of massive-star progenitors. The motivation for this paper is to provide a physically and numerically uniform benchmark dataset to the broader neutrino detection community to help it characterize and optimize subsurface facilities for what is likely to be a once-in-a-lifetime galactic supernova burst event. With this release we hope to 1) help the international experiment and modeling communities more efficiently optimize the retrieval of physical information about the next galactic core-collapse supernova, 2) facilitate the better understanding of core-collapse theory and modeling among interested experimentalists, and 3) help further integrate the broader supernova neutrino community.

astro-ph.HE↗