Narrow Results

In the following we present the status of SNOLAB, a new international facility for Underground Physics currently nearing completion in Sudbury, Canada. We describe the infrastructure available, as well as the scientific programme envisioned.

We review the observational status of the Supernova/Gamma-Ray Burst connection. Multiwavelengths observations of long duration Gamma-ray bursts obtained in the last decade suggest that a significant fraction of them (but not all) are associated with bright SNe of type Ib/c. Current estimates of the SN and GRB rates indicate that the ratio GRB/SNe-Ibc is in the range ~ 0.4% – 3%. An analysis of the association GRB 060218/SN 2006aj finds that the SN and the GRB are coeval events within ~ 0.1 days and the size of the progenitor is consistent with the dimensions of a Wolf-Rayet star. Recent observations of GRB 060614 point out the existence of a new class of long-duration Gamma-ray Burst not accompanied by a bright supernova.

Core-collapse supernovae are a diverse population with energetic broad-line events, that include their off-spring in ultra-relativistic gamma-ray bursts and a recently discovered highly superluminous event ASASSN-15L (SN2015L). They may be associated with the formation of black holes, rather than magnetars, by their ample baryon-poor energy reservoir in angular momentum desribed by the Kerr metric. Black holes formed herein evolve through various phases that may include direct accretion, Bardeen accretion and spin down to slow rotation, down to a dimensionless spin parameter 0.36 defined by a fixed point in equations of suspended accretion. Evidence may come from gravitational wave emission from associated non-axisymmetric accretion flows, especially from high density matter at the Inner Most Stable Circular Orbit (ISCO) during the latter phase of spin down. We here present a chirp-based spectrogram based on a recently developed “butterfly” filter to probe nearby events by LIGO-Virgo and KAGRA for ascending and descending chirps, making use of embarrassingly parallel computing. Included is a demonstration on the nearby SN2010br Type Ibc (D ≃ 12 Mpc) event covered by LIGO S6. Comments on the recently discovered GWB150914 are included.

After the big bang, production of heavy elements in the early universe takes place starting from the formation of the first (Pop III) stars, their evolution, and explosion. The Pop III supernova (SN) explosions have strong dynamical, thermal, and chemical feedback on the formation of subsequent stars and evolution of galaxies. However, the nature of Pop III stars/supernovae (SNe) have not been well-understood. The signature of nucleosynthesis yields of the first SN can be seen in the elemental abundance patterns observed in extremely metal-poor (EMP) stars. We show that the abundance patterns of EMP stars, e.g. the excess of C, Co, Zn relative to Fe, are in better agreement with the yields of hyper-energetic explosions (Hypernovae, (HNe)) rather than normal supernovae. We note the large variation of the abundance patterns of EMP stars propose that such a variation is related to the diversity of the GRB-SNe and posssibly superluminous supernovae (SLSNe). For example, the carbon-enhanced metal-poor (CEMP) stars may be related to the faint SNe (or dark HNe), which could be the explosions induced by relativistic jets. Finally, we examine the various mechanisms of SLSNe.

Our concept of induced gravitational collapse (IGC paradigm) starting from a supernova occurring with a companion neutron star, has unlocked the understanding of seven different families of gamma ray bursts (GRBs), indicating a path for the formation of black holes in the universe. An authentic laboratory of relativistic astrophysics has been unveiled in which new paradigms have been introduced in order to advance knowledge of the most energetic, distant and complex systems in our universe. A novel cosmic matrix paradigm has been introduced at a relativistic cosmic level, which parallels the concept of an S-matrix introduced by Feynmann, Wheeler and Heisenberg in the quantum world of microphysics. Here the “in” states are represented by a neutron star and a supernova, while the “out” states, generated within less than a second, are a new neutron star and a black hole. This novel field of research needs very powerful technological observations in all wavelengths ranging from radio through optical, X-ray and gamma ray radiation all the way up to ultra-high-energy cosmic rays.

Natures of progenitors of type Ia Supernovae (SNe Ia) have not yet been clarified. There has been long and intensive discussion on whether the so-called single degenerate (SD) scenario or the double degenerate (DD) scenario, or anything else, could explain a major population of SNe Ia, but the conclusion has not yet been reached. With rapidly increasing observational data and new theoretical ideas, the field of studying the SN Ia progenitors has been quickly developing, and various new insights have been obtained in recent years. This paper aims at providing a summary of the current situation regarding the SN Ia progenitors, both in theory and observations. It seems difficult to explain the emerging diversity seen in observations of SNe Ia by a single population, and we emphasize that it is important to clarify links between different progenitor scenarios and different sub-classes of SNe Ia.

The evolution of close-orbit progenitor binaries of double neutron star (DNS) systems leads to supernova (SN) explosions of ultra-stripped stars. The amount of SN ejecta mass is very limited from such, more or less, naked metal cores with envelope masses of only 0.01 - 0.2 M_⊙. The combination of little SN ejecta mass and the associated possibility of small NS kicks is quite important for the characteristics of the resulting DNS systems left behind. Here, we discuss theoretical predictions for DNS systems, based on Case BB Roche-lobe overflow prior to ultra-stripped SNe, and briefly compare with observations.

Despite their importance, we still do not know exactly which stellar systems produce Type Ia supernovae. However, we do know the physical mechanism that powers the explosion. Type Ia supernovae originate from the explosion of carbon-oxygen white dwarfs. Whether this is due to accretion from a non-degenerate companion, to the merger of two white dwarfs or the core of a red giant and a white dwarf shortly after the common envelope phase or, finally, as a consequence of the collision of two white dwarfs in the dense cores of globular clusters or nuclei of galaxies, still remains to be elucidated. In this work we review the recent advances on the later scenario, the so-called white dwarf collision channel.

Understanding the circumstellar (CS) environment around type Ia supernovae (SNe Ia) is important in two respects. (1) It should reflect the mass loss history of an yet-unresolved progenitor star, and (2) it may be related to the non-standard extinction property toward SNe Ia. Especially, it has been suggested that multiple scatterings of SN photons by CS dust (created by the progenitor mass loss) may explain the non-standard extinction law. In this paper, we suggest that it is possible to obtain strong constraints on the CS environment through multi-epoch monitoring observations of SNe Ia in the infrared (IR) wavelengths, and demonstrate a power of such diagnostics using available observational data. The idea relies on the effect of re-emission of photons by CS dust in the IR wavelength regime, i.e., the so-called echo emission. For most intensively observed SNe Ia, we place an upper limit of $\dot{M}{\underset{˜}{\text{<}}10}^{\text{-8}}-{\text{10}}^{\text{-7}}{M}_{\odot }{\text{yr}}^{\text{-1}}$ (for the wind velocity of ∼ 10 km s⁻¹) for a mass loss rate from a progenitor up to ∼ 0.01 pc, and $\dot{M}{\underset{˜}{\text{<}}10}^{\text{-7}}-{\text{10}}^{\text{-6}}{M}_{\odot }{\text{yr}}^{\text{-1}}$ up to ∼ 0.1 pc. Our results show that the CS dust scattering model is encountered by a difficulty to be a general explanation of the non-standard extinction law toward SNe Ia, while it may still apply to a sub-sample of highly reddened SNe Ia.

We have analyzed XMM-Newton, Chandra, and Suzaku observations of three young Type Ia supernova remnants (SNRs), i.e., Kepler’s SNR, Tycho’s SNR, and SNR 0509-67.5 in the LMC, to investigate the properties of both the SN ejecta and the circumstellar medium (CSM). By simply comparing the X-ray spectra, we find that line intensity ratios of iron-group elements (IGE) to intermediate-mass elements (IME) for Kepler’s SNR and SNR 0509-67.5 are much higher than those for Tycho’s SNR. We therefore argue that Kepler is the product of an overluminous Type Ia SN. This inference is supported by our spectral modeling, which reveals the IGE and IME masses respectively to be 0.95 (0.58–1.29) M_⊙ and 0.12 (0.07–0.31) M_⊙ (Kepler’s SNR), 0.75 (0.6–1.26) M_⊙ and 0.34 (0.09–0.42) M_⊙ (SNR 0509–67.5), and 0.35 (0.2–0.9) M_⊙ and 0.70 (0.42–0.82) M_⊙ (Tycho’s SNR). On the other hand, there are a number of dense, N-rich CSM knots in Kepler’s SNR, which were found by optical observations and are now confirmed by our X-ray observations. Their optical proper motions as well as X-ray measured ionization states indicate that they were located a few pc away from the progenitor system at the SN explosion. Therefore, we argue that Kepler’s SN was an overluminous event that started to interact with massive CSM a few hundred years after the explosion, which supports the possible link between overluminous SNe and the so-called “Ia-CSM” SNe.

The theory of General Relativity deals with very accurate measurements that show significant divergences from Newtonian predictions only with speed near to the velocity of light. The photometry of the radiation from collapsing star’s shells like novae and supernovae is a starting point for relativistic cosmic phenomena. The visual observations described in this paper provided the needed photometrical and timing accuracy to follow these phenomena. More than 1200 observations of variable stars, included the type 1a SN2014J, Nova DEL 2013, Nova CEN 2013 and Nova SGR 2015 no. 2 have been sent to the AAVSO by the author, with SGQ code, during the period 1998-2015, and contributed also to IAU and HST observational campaigns; they have been analyzed to evaluate the photometric accuracy, in the context of the International Year of Light 2015.

The explosion of ultra-stripped stars in close binaries may explain new discoveries of weak and fast optical transients. We have demonstrated that helium star companions to neutron stars (NSs) may evolve into naked metal cores as low as ∼ 1.5 M_⊙, barely above the Chandrasekhar mass limit, by the time they explode. Here we present a new systematic investigation of the progenitor evolution leading to such ultra-stripped supernovae (SNe), in some cases yielding pre-SN envelopes of less than 0.01 M_⊙. We discuss the nature of these SNe (electron-capture vs iron core-collapse) and their observational light-curve properties. Ultra-stripped SNe are highly relevant for binary pulsars, as well as gravitational wave detection of merging NSs by LIGO/VIRGO, since these events are expected to produce mainly low-kick NSs in the mass range 1.10 − 1.80 M_⊙.

The latest results from PAMELA and FERMI experiments confirm the necessity to improve theoretical models of production and propagation of galactic electrons and positrons. There are many possible explanations for the positron excess observed at energies larger than 10 GeV and for some features around 1 TeV in the total flux of electrons and positrons. Supernovae are astrophysical objects with the potential to explain these observations. In this work, we present an updated study of the astrophysical sources of lepton cosmic rays and the possible and the possible explanation of the anomalies in terms of astrophysical sources.

After the first prediction to expect geodetic precession in binary pulsars in 1974, made immediately after the discovery of a pulsar with a companion, the effects of relativistic spin precession have now been detected in all binary systems where the magnitude of the precession rate is expected to be sufficiently high. Moreover, the first quantitative test leads to the only available constraints for spin-orbit coupling of a strongly self-gravitating body for general relativity (GR) and alternative theories of gravity. The current results are consistent with the predictions of GR, proving the effacement principle of spinning bodies. Beyond tests of theories of gravity, relativistic spin precession has also become a useful tool to perform beam tomography of the pulsar emission beam, allowing to infer the unknown beam structure, and to probe the physics of the core collapse of massive stars.

In this paper I shall review the observational status of the supernova (SN) and gamma-ray burst (GRB) connection. With a publishing rate of about 1 referred paper per day in the last decade, the study of gamma-ray bursts is one of the most prolific topics of the modern astrophysics.

This contribution is a review of talks by G.S.Bisnovatyi-Kogan ‘MHD of a large scale magnetic field in the advective accretion disks’, H.C.Spruit ‘Physics of the magnetized accretion disks’ and S.G.Moiseenko ‘Magnetorotational supernovae’ given a the section Black Holes and Magneto-Hydrodynamics (BHT3).

G.S.Bisnovatyi-Kogan’s talk was devoted to the problem of the formation of a largescale magnetic field in the accretion disks around black holes with account of the nonuniform vertical structure of the disk. The high electrical conductivity of the outer layers of the disk prevents the outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole. Global solution of advective accretion disk structure around a black hole is constructed numerically. The presence of the effectively optically thin regions in the innermost part of accretion disks results in a significant increase of the plasma temperature in those regions and this increase can be discriminated in observations in the form of the observed hard radiation tails.

In the talk of H.C.Spruit the problems of existence of strong, highly ordered and dynamically important magnetic fields in the central regions of accretion disks form observations and circumstantial theoretical arguments were discussed. The magnetic fields power the jets seen from accreting objects ranging from protostars to black holes. The observational evidence and the processes that may be responsible for the origin and maintenance of these fields are reviewed.

S.G.Moiseenko spoke about results of simulations of magnetorotational core collapse supernovae. It was shown in the simulations that amplification of the magnetic field due to the differential rotation leads to the angular momentum transfer and formation of the MHD shock wave. This shock wave produce supernova explosion. The supernova explosion energy in our simulations can be up to 2.6·10⁵¹erg. The shape of the supernova explosion depends on the initial configuration of the magnetic field.

The Chandrasekhar limit is of key importance for the evolution of white dwarfs in binary systems and for the formation of neutron stars and black holes in binaries. Mass transfer can drive a white dwarf in a binary over the Chandrasekhar limit, which may lead to a Type Ia supernova (in case of a CO white dwarf) or an Accretion-Induced Collapse (AIC, in the case of an O-Ne-Mg white dwarf; and possibly also in some CO white dwarfs) which produces a neutron star. The direct formation of neutron stars or black holes out of degenerate stellar cores that exceed the Chandrasekhar limit, occurs in binaries with components that started out with masses ≥ 8 M_⊙.

This paper first discusses possible models for Type Ia supernovae, and then focusses on the formation of neutron stars in binary systems, by direct core collapse and by the AIC of O-Ne-Mg white dwarfs in binaries. Observational evidence is reviewed for the existence of two different direct neutron-star formation mechanisms in binaries: (i) by electron-capture collapse of the degenerate O-Ne-Mg core in stars with initial masses in the range of 8 to about 12 M_⊙, and (ii) by iron-core collapse in stars with inital masses above this range. Observations of neutron stars in binaries are consistent with a picture in which neutron stars produced by e-capture collapse have relatively low masses, ˜1.25M_⊙, and received hardly any velocity kick at birth, whereas neutron stars produced by iron-core collapses are more massive and received large velocity kicks at birth. Many of the globular cluster neutron stars and also some of the neutron stars in low-mass binaries in the Galactic disk are likely to have been produced by AIC of O-Ne-Mg white dwarfs in binaries. AIC is expected to produce normal strongly magnetized neutron stars, which in binaries can evolve into millisecond pulsars through the usual recycling scenario.

Stellar nucleosynthesis is a vastly interdisciplinary field. There is a large number of different problems invoked calling for a variety of different and complementary research fields. Impressive progress has been made in the last decades in the various fields related to nucle-osynthesis, especially experimental and theoretical nuclear physics, as well as in ground-or space-based astronomical observations and astrophysical modelings. In spite of that success, major problems and puzzles remain. The three major nucleosynthesis processes called for to explain the origin of the elements heavier than iron are described and the major pending questions discussed. As far as nuclear physics is concerned, good quality nuclear data is known to be a necessary condition for a reliable model-ling of stellar nu-cleosynthesis. Through some specific examples, the need for further theoretical or experimental developments is also critically discussed in view of their impact on nucleosynthesis predictions.

A unified equation of state (EoS) based on the nuclear energy-density functional theory is presented. This approach is particularly well-suited for describing both the homogeneous and inhomogeneous phases of dense matter at any temperature. We employ generalized Skyrme functionals fitted to essentially all experimental nuclear mass data and constrained to reproduce properties of infinite nuclear matter. Three different EoSs at T = 0 are shown here.

We here discuss how to determine the total neutrino mass and oscillation parameters from supernova nucleosynthesis, the Galactic chemical evolution, and the CMB anisotropies. Neutrinos play the critical roles in nucleosynthesis of light-to-heavy mass nuclei in core-collapse supernovae. We study the nucleosynthesis induced by neutrino interactions and find suitable average neutrino temperatures in order to explain the observed solar system abundances of several isotopes ⁷Li, ¹¹B, ¹³⁸La and ¹⁸⁰Ta. These isotopes are predominantly synthesized by the supernova ν-process. We also study the neutrino oscillation effects on their abundances and propose an astrophysical method to determine the unknown neutrino oscillation parameters θ₁₃ and mass hierarchy.