Narrow Results

Neutrinos in astrophysical environments, such as Supernovae (SNe), may interact through pair interactions. These interactions are density and temperature-dependent. Under certain conditions, a neutrino-condensate may form. In this work, we have adapted the separable nonlocal pairing interactions to the SN conditions and studied the temperature and density dependence of the pairing gap as well as the collective response with respect to these variables. We have applied the Bogoliubov transformations and solved the Bardeen, Cooper and Schrieffer (BCS) equations to construct the free quasi-particle sector of the Hamiltonian. The residual two-quasi-particle terms have been treated by applying the Tamm–Dancoff approximation (TDA) and random-phase approximation (RPA), suited to the extended neutrino media. With this, we have constructed neutrino energy distributions both in the superfluid and normal regimes and extracted critical values of the density and temperature.

Neutrinos play an important role in core-collapse supernova events since they are a key piece to understanding the explosion mechanisms. The analysis of the neutrino fluxes can bring answers to neutrino’s related problems e.g., mass hierarchy, spectral splitting, sterile neutrinos, etc. In this work, we study the impact of neutrino oscillations and the possible existence of eV sterile neutrinos upon the supernova neutrino flux ($F_{\nu }(E)$). We have calculated the energy distribution of the neutrino flux from a supernova and the total number of events that would be detected in a liquid scintillator. We also present an analysis for the conversion probabilities as a function of the active-sterile neutrino mixing parameters. Finally, we have carried out a statistical analysis to extract values for the mixing parameters of the model.

The neutrino dynamics in hot and dense magnetized matter corresponding to a supernova explosion is considered. It is shown that accounting for fluctuations during interaction of neutrinos with matter leads to the Fokker–Planck equation for the dynamics of the phase space distribution function. The addition to the energy transfer component of the kinetic equation is determined by straggling in neutrino collisions with a magnetized nucleon gas caused by the neutral current Gamow–Teller interaction. When accounting for the effect of fluctuations, the switching of acceleration and stopping regimes in neutrino evolution is evident for average energy. The effect of fluctuations leads to an additional increase in the hardness of the neutrino spectra. It is shown that the high-energy component of the electron antineutrino flux is enhanced in addition due to the effect of neutrino oscillations. Such a strengthening of the spectrum hardness is especially noticeable in the case of the inverted mass ordering and makes the signal more registrable by ground-based detectors. The possibilities of detecting supernova neutrinos by KM3NeT and Baikal-GVD observatories are discussed. The sensitivity of counting rate to the mass ordering is demonstrated to increase at growing difference in the hardness of energy spectra for various flavors.

We report on an equation of state (EOS) of hot asymmetric nuclear matter constructed using the variational method and its application to hydrodynamic simulations of core-collapse supernovae. This nuclear EOS is based on the AV18 two-body potential and UIX three-body potential, and the energy per nucleon at zero temperature is constructed with the cluster variational method. At finite temperatures, the free energies per nucleon are calculated with an extension of the variational method devised by Schmidt and Pandharipande. This EOS is in good agreement with that by the Fermi hypernetted chain variational calculations at zero and finite temperatures, and the structure of neutron stars calculated with this EOS is consistent with recent observational data. Using this nuclear EOS, we perform a spherically symmetric general-relativistic adiabatic simulation of the SN explosion. The explosion energy calculated with our EOS in the present simulation is larger than that obtained with the Shen EOS, implying that the variational EOS is softer than the Shen EOS.

In this work I present numerical magnetohydrodynamic (MHD) simulations of the early dynamics around newly born neutrons stars using the AMR Flash method. When the core-collapse supernovae occurs a reverse shock is formed allowing strong accretion onto the neutron star surface (hypercritical phase). In such regime large amounts of matter are deposited on the neutron star surface, submerging the magnetic field in the new crust. When the hypercritical regime is over, the magnetic field can suffer a reemergence episode due to magnetic diffusion processes, allowing the delayed switch-on of pulsars.

The 4m International Liquid Mirror Telescope (ILMT) is a zenith-pointing optical observing facility at ARIES Devasthal observatory (Uttarakhand, India). The first light preparatory activities of the ILMT were accomplished in April 2022 followed by on-sky tests that were carried out at the beginning of May 2022. This telescope will perform a multi-band optical (SDSS $g^{\prime }$, $r^{\prime }$ and $i^{\prime }$) imaging of a narrow strip ($\sim 22^{\prime }$) of sky utilizing the time-delayed integration technique. Single-scan ILMT images have an integration time of 102s and consecutive-night images can be co-added to further improve the signal-to-noise ratio. An image subtraction technique will also be applied to the nightly recorded observations in order to detect transients, objects exhibiting variations in flux or position. Presently, the facility is in the commissioning phase and regular operation will commence in March 2023. This paper presents a discussion of the main preparation activities before first light, along with preliminary results obtained.

It is known that very distant galaxies, much like our own, show remarkably high receding velocities, the magnitude of which increases with distance. Therefore, in this study, a gravitational analog of the photoelectric effect was investigated by replacing the classical (wave) theory of gravity with a gravity quanta hypothesis. The significance of this concept regarding the motion of distant galaxies is evaluated by comparing the results obtained for a photon traveling through a Planck lattice model of spacetime to the observational data for both the cosmological redshift and time dilation effects of light from distant Type Ia supernovae. The photogravity effect does not necessarily invalidate the standard big bang cosmology and may in fact add a layer of fidelity to its conclusions concerning the evolution and age of the universe.

In 1986 Alex Dalgarno published a paper entitled Is Interstellar Chemistry Useful?¹ By the middle 1970s, and perhaps even earlier, Alex had hoped that astronomical molecules would prove to: possess significant diagnostic utility; control many of the environments in which they exist; stimulate a wide variety of physicists and chemists who are at least as fascinated by the mechanisms forming and removing the molecules as by astronomy. His own research efforts have contributed greatly to the realization of that hope. This paper contains a few examples of: how molecules are used to diagnose large-scale dynamics in astronomical sources including star forming regions and supernovae; the ways in which molecular processes control the evolution of astronomical objects such as dense cores destined to become stars and very evolved giant stars; theoretical and laboratory investigations that elucidate the processes producing and removing astronomical molecules and allow their detection.

We discuss numerical method based on Implicit completely conservative Lagrangian operator-difference scheme on triangular grid of variable structure. The method was successfully applied for the simulations of magnetorotational supernova explosion.

There has recently been an increasing interest in a possible population of type Ia supernovae (SNe Ia) triggered by helium detonation on the surface of a massive white dwarf. In this paper, we first summarize possible observational signatures of the He detonationtriggered SNe Ia, emphasizing the new diagnostics of the He detonation mode potentially seen in the SN light within the first few days since the explosion. We then argue that observational properties of a peculiar SN Ia, MUSSES1604D as discovered by the Hyper Suprime-Cam (HSC) attached with the Subaru telescope, are best explained by the He-detonation scenario. We then discuss possible origins, including the He detonation scenario, of the diversity seen in the photometric properties of SNe Ia in the first few days. While the He detonation could reproduce observational properties of a fraction of SNe Ia showing the excessive emission in the first few days, it is likely that a bulk of them are linked to a different explosion mechanism where the early excess would arise due to an extensive mixing of ⁵⁶Ni during the explosion. A combined analysis of the very early phase observations and the maximum-phase observations will be key in mapping the diverse SN Ia zoo into different populations reflecting different progenitors and/or different explosion modes.

We present results from general-relativistic (GR) three-dimensional (3D) core-collapse simulations with approximate neutrino transport for three non-rotating progenitors (11.2, 15, and 40 M_⊙) using different nuclear equations of state (EOSs). We find that the combination of progenitor’s higher compactness at bounce, that is a consequence of the use of softer EOS, leads to stronger activity of the standing accretion shock instability (SASI). We confirm previous predication that the SASI produces characteristic time modulations both in neutrino and gravitational-wave (GW) signals. Our results indicate that the correlation of the neutrino and GW signals, if detected, would provide a new signature of the vigorous SASI activity in the supernova core.

It is generally believed that General Relativity (GR) is of secondary importance in the explosion of core-collapse supernovae (CCSN). However, as 3D simulations are becoming more and more detailed, GR effects can be strong enough to change the hydrodynamics of the supernova and affect the explosion. Since a 3D simulation in full GR is computationally extremely challenging, it is valuable to modify simulations in a spherically symmetric spacetime to incorporate 3D effects. This permits exploration of the parameter dependence of CCSN with a minimum of computational resources. In this proceedings contribution we report on the formulation and implementation of general relativistic neutrino-driven turbulent convection in the spherically symmetric code GR1D. This is based upon STIR, a recently proposed Newtonian model based on mixing length theory. When the parameters of this model are calibrated to 3D simulations, we find that our GR formulation significantly alters the correspondence between progenitor mass and explosion vs. black-hole formation. We therefore believe that, going forward, simulating CCSNe in full GR is of primary importance.

In this article, I review the current understanding of the mechanism of core-collapse supernovae, one of the most energetic events in the present universe. I will not only summarize the neutrino-heating mechanism, the standard paradigm at present, but also pay special attention to the recent topics such as the standing accretion shock instability and the acoustic revival scenario proposed by Burrows very recently.

The energy density of the universe seems to be dominated by a mysterious "dark-energy" which drives the acceleration of the expansion. This phenomenon was discovered by mapping out the history of cosmic expansion using Type Ia supernovae (SNe Ia) as distance indicators. SNe Ia currently provide one of the best way to characterize the nature of dark energy, by placing tight limits on its equation of state w = p/ρ. Current high-redshift supernova surveys, such as the 5-year Supernova Legacy Survey will deliver ~ 1000 SN Ia detections with well-sampled griz light curves. Using this unprecedented dataset, a statistical precision of about 5% will be obtained on Ω_Λ and w. In this contribution, I review the ongoing Type Ia surveys and present the recent constraints obtained on the dark energy equation of state.

Nuclear astrophysics is a active, rapidly developing field that addresses fundamental scientific questions. Advances in astronomy have to be matched with advances in nuclear physics to address these questions in the future. I discuss some of the major open questions and future directions, using as examples supernovae, the rapid neutron capture process, and processes on the surface of accreting neutron stars. In all cases nuclear physics is needed to interpret observations and to guide and constrain theoretical models. While a wide range of experimental facilities is required, one of the major challenges for the future is the study of unstable nuclei that play a central role in many of the major open questions. Therefore, an advanced radioactive beam facility such as the proposed Rare Isotope Accelerator (RIA) is of particular importance for the future of this field.

I discuss the state of the art in the search for stellar collapse neutrinos and the perspectives of this field. The implications for neutrino physics of a high statistics supernova neutrino burst detection by the network of operating experiments are also reviewed.

Vastly different time and length scales are a common problem in numerical simulations of astrophysical phenomena. Here, we present an approach to numerical modeling of such objects on the example of Type Ia supernova simulations. The evolution towards the explosion proceeds on much longer time scales than the explosion process itself. The physical length scales relevant in the explosion process cover 11 orders of magnitude and turbulent effects dominate the physical mechanism. Despite these challenges, three-dimensional simulations of Type Ia supernova explosions have recently become possible and pave the way to a better understanding of these important astrophysical objects.

We construct the equation of state (EOS) for infinite nuclear matter at zero and finite temperatures with the variational method starting from the realistic nuclear Hamiltonian composed of the Argonne V18 two-body potential and the UIX three-body interaction (TNI). At zero temperature, we evaluate the expectation value of the two-body nuclear Hamiltonian using the Jastrow-type wave function in the two-body cluster approximation with two conditions: The extended Mayer's condition and the healing-distance condition. Then we take into account the TNI contribution which includes adjustable parameters whose values are determined so as to reproduces the empirical saturation data. The maximum mass of the neutron star with the present nuclear EOS is 2.2 M_⊙. At finite temperatures, we employ a method by Schmidt and Pandharipande, to obtain the free energy for nuclear matter. The critical temperature is about 18 MeV. We also calculate the free energy for asymmetric nuclear matter.

Due to the difficulty of hydrodynamic simulations to reproduce type II supernovae explosions, we investigate possible missing microscopic physics, such as neutrino trapping near the critical temperature of the nuclear liquid-gas phase transition, temperature dependant neutrino mean free paths or electron capture rates on nuclei to evaluate the impact on the improvement of the supernova outgoing shock propagation.

One could call 2006 as the year of cosmology since in the year two US scientists were awarded by the Nobel prize for their studies of Cosmic Microwave Back-ground (CMB) spectrum and anisotropy. Studies of CMB anisotropy done with the Soviet spacecraft Prognoz-9 by the Relikt-1 team are reminded. Problems of modern cosmology are outlined. We discuss conformal cosmology parameters from supernovae data in brief. Two approaches to solve the basic problems of cosmology, such as dark matter and dark energy, are discussed, the first (standard) possibility is to introduce new particles, fields etc, the second possibility is to try to change a gravity law to fit observational data. We discuss advantages and disadvantages of the second choice.