Hypernova Explosions Research Articles

Disruption of a massive molecular cloud by a supernova in the Galactic Centre

The Milky Way’s Central Molecular Zone (CMZ) differs dramatically from our local solar neighbourhood, both in the extreme interstellar medium conditions it exhibits (e.g. high gas, stellar, and feedback density) and in the strong dynamics at play (e.g. due to shear and gas influx along the bar). Consequently, it is likely that there are large-scale physical structures within the CMZ that cannot form elsewhere in the Milky Way. In this paper, we present new results from the Atacama Large Millimeter/submillimeter Array (ALMA) large programme ACES (ALMA CMZ Exploration Survey) and conduct a multi-wavelength and kinematic analysis to determine the origin of the M0.8–0.2 ring, a molecular cloud with a distinct ring-like morphology. We estimate the projected inner and outer radii of the M0.8–0.2 ring to be 79″ and 154″, respectively (3.1 pc and 6.1 pc at an assumed Galactic Centre distance of 8.2 kpc) and calculate a mean gas density >104 cm−3, a mass of ~106 M⊙, and an expansion speed of ~20 km s−1, resulting in a high estimated kinetic energy (>1051 erg) and momentum (>107 M⊙ km s−1). We discuss several possible causes for the existence and expansion of the structure, including stellar feedback and large-scale dynamics. We propose that the most likely cause of the M0.8–0.2 ring is a single high-energy hypernova explosion. To viably explain the observed morphology and kinematics, such an explosion would need to have taken place inside a dense, very massive molecular cloud, the remnants of which we now see as the M0.8–0.2 ring. In this case, the structure provides an extreme example of how supernovae can affect molecular clouds.

SPICE: the connection between cosmic reionization and stellar feedback in the first galaxies

ABSTRACT We present SPICE, a new suite of radiation-hydrodynamic, cosmological simulations targeting the epoch of reionization. The goal of these simulations is to systematically probe a variety of stellar feedback models, including ‘bursty’ and ‘smooth’ forms of supernova energy injection, as well as poorly explored physical scenarios such as hypernova explosions and radiation pressure on dust. We show that even subtle differences in the behaviour of supernova feedback drive profound differences in reionization histories, with burstier forms of feedback causing earlier reionization. However, we also find that some global galaxy properties, such as the dust-attenuated luminosity functions and star formation main sequence, remain degenerate between models. In particular, we show that stellar feedback and its strength determine the morphological mix of galaxies emerging by $z \, = \, 5$ and that the reionization history is inextricably connected to intrinsic properties such as galaxy kinematics and morphology. While star-forming, massive discs are prevalent if supernova feedback is ‘smooth’, ‘bursty’ feedback preferentially generates dispersion-dominated systems. Different modes of feedback produce different strengths of outflows, altering the interstellar/circumgalactic medium in different ways, and in turn strongly affecting the escape of Lyman continuum (LyC) photons. We establish a correlation between galaxy morphology and LyC escape fraction, revealing that dispersion-dominated systems have escape fractions 10–50 times higher than their rotation-dominated counterparts at all redshifts. At the same intrinsic luminosity, dispersion-dominated systems should thus preferentially generate large H ii regions as compared to their rotation-dominated counterparts. Since dispersion-dominated systems are more prevalent if stellar feedback is more explosive, reionization occurs earlier in our simulation with burstier feedback. We argue that statistical samples of post-reionization galaxy morphologies (using both stellar and gaseous components) probed with telescopes such as JWST, ALMA, and MUSE can constrain stellar feedback at z > 5 and models of cosmic reionization.

Extremely Energetic Supernova Explosions Embedded in a Massive Circumstellar Medium: The Case of SN 2016aps

Abstract We perform one-dimensional radiation-hydrodynamic simulations of energetic supernova (SN) ejecta colliding with a massive circumstellar medium (CSM) aimed at explaining SN 2016aps, likely the brightest SN observed to date. SN 2016aps was a superluminous Type IIn SN, which released as much as erg of thermal radiation. Our results suggest that the multiband light curve of SN 2016aps is well explained by the collision of a SN ejecta with the explosion energy of 1052 erg and a wind-like CSM with the outer radius of 1016 cm, that is, a hypernova explosion embedded in a massive CSM. This finding indicates that very massive stars with initial masses larger than , which supposedly produce highly energetic SNe, occasionally eject their hydrogen-rich envelopes shortly before the core collapse. We suggest that the pulsational pair-instability SNe may provide a natural explanation for the massive CSM and the energetic explosion. We also provide the relations among the peak luminosity, the radiated energy and the rise time for interacting SNe with the kinetic energy of 1052 erg, which can be used for interpreting SN 2016aps–like objects in future surveys.

Evidence for an Aspherical Population III Supernova Explosion Inferred from the Hyper-metal-poor Star HE 1327–2326∗

Abstract We present observational evidence that an aspherical supernova explosion could have occurred in the first stars in the early universe. Our results are based on the first determination of a Zn abundance in a Hubble Space Telescope/Cosmic Origins Spectrograph high-resolution UV spectrum of a hyper-metal-poor (HMP) star, HE 1327−2326, with . We determine [Zn/Fe] = 0.80 ± 0.25 from a UV Zn i line at 2138 Å, detected at 3.4σ. Yields of a 25 M ⊙ aspherical supernova model with artificially modified densities exploding with E = 5 × 1051 erg best match the entire abundance pattern of HE 1327−2326. Such high-entropy hypernova explosions are expected to produce bipolar outflows, which could facilitate the external enrichment of small neighboring galaxies. This has already been predicted by theoretical studies of the earliest star-forming minihalos. Such a scenario would have significant implications for the chemical enrichment across the early universe, as HMP carbon-enhanced metal-poor (CEMP) stars such as HE 1327−2326 might have formed in such externally enriched environments.

On the Most Powerful Chiral Influence on Biomolecules in Space

Powerful astrophysical sources of chiral influence on biomolecules in the Galaxy and outside it in the cosmic scenario of the origin of life are studied. The effect of such sources and their precursors on sugars is based on right circularly polarized ultraviolet from bremsstrahlung of positrons produced by the radioactive decay of cobalt 56 Co. The maximum mass of radioactive cobalt 56Co is reached during Hypernova explosions; it can exceed ten solar masses. It was shown that the power of chiral ultraviolet from the Hypernova exceeds that from the type 1a Supernova and relativistic fireball approximately by factors of 4.5 and 9, respectively.

Globular Cluster formation in a collapsing supershell

Primordial clouds are supposed to host the so-called population III stars. These stars are very massive and completely metal-free. The final stage of the life of population III stars with masses between 130 and 260 solar masses is a very energetic hypernova explosion. A hypernova drives a shock, behind which a spherically symmetric very dense supershell forms, which might become gravitationally unstable, fragment, and form stars. In this paper we study under what conditions can an expanding supershell become gravitationally unstable and how the feedback of these supershell stars (SSSs) affects its surroundings. We simulate, by means of a 1-D Eulerian hydrocode, the early evolution of the primordial cloud after the hypernova explosion, the formation of SSSs, and the following evolution, once the SSSs start to release energy and heavy elements into the interstellar medium. Our results indicate that a shell, enriched with nucleosynthetic products from SSSs, propagates inwards, towards the center of the primordial cloud. In a time span of a few Myr, this inward-propagating shell reaches a distance of only a few parsec away from the center of the primordial cloud. Its density is extremely high and its temperature very low, thus the conditions for a new episode of star formation are achieved. We study what fraction of these two distinct populations of stars can remain bound and survive until the present day. We study also under what conditions can this process repeat and form multiple stellar populations. We extensively discuss whether the proposed scenario can help to explain some open questions of the formation mechanism of globular clusters.

Cosmological Impact of the Population III Hypernovae

We investigate the stellar feedback of Pop III hypernovae by using cosmology simulations with GADGET. Recent studies of the Pop III star formation suggested that these stars might be very massive and many of them might have died as hypernovae, which are about ten times more energetic than conventional core-collapse supernovae. Such exotic supernovae might posit a strong impact on the early universe by injecting a large amount of energy and heavy elements. For investigating the cosmological impact of the first hypernovae, we use the realistic Pop III stellar evolution models including the relevant physics to simulate the formation, evolution, and hypernova explosion of a 60 M⊙ Pop III star. Our results show that the gas inside the host minihalo is effectively blown out by the ramp pressure of radiation and hypernova shock. It delays the star formation inside the halo for at least 50 million years. More importantly, the pristine gas of the intergalactic medium around the halo is chemically enriched to an average metallicity of 10-4 — 10-3 Z⊙, out to ∼ 2kpc within five hundred million years after the star dies. Such metal enrichment is able to transform the later star formation mode from Pop III to Pop II.

OPTICAL SYNCHROTRON PRECURSORS OF RADIO HYPERNOVAE

We examine the bright radio synchrotron counterparts of low-luminosity gamma-ray bursts (llGRBs) and relativistic supernovae (SNe) and find that they can be powered by spherical hypernova (HN) explosions. Our results imply that radio-bright HNe are driven by relativistic jets that are choked deep inside the progenitor stars or quasi-spherical magnetized winds from fast-rotating magnetars. We also consider the optical synchrotron counterparts of radio-bright HNe and show that they can be observed as precursors several days before the SN peak with an r-band absolute magnitude of M_r ~ -14 mag. While previous studies suggested that additional trans-relativistic components are required to power the bright radio emission, we find that they overestimated the energy budget of the trans-relativistic component by overlooking some factors related to the minimum energy of non-thermal electrons. If an additional trans-relativistic component exists, then a much brighter optical precursor with M_r ~ -20 mag can be expected. Thus, the scenarios of radio-bright HNe can be distinguished by using optical precursors, which can be detectable from < 100 Mpc by current SN surveys like the Kiso SN Survey, Palomar Transient Factory, and Panoramic Survey Telescope & Rapid Response System.

A study of the evolution of the close binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 using the “scenario machine”

Evolutionary tracks for the X-ray binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 are computed using the Scenario Machine code. The compact objects in IC 10 X-1, NGC 300 X-1, and M33 X-7 are the most massive stellar mass black hole candidates. Cyg X-3, IC 10 X-1, and NGC 300 X-1 are the only currently known Wolf-Rayet stars with degenerate companions. SS 433 is the only known superaccretor in the Milky Way. Therefore, the stars studied provide excellent laboratories for testing scenarios for the evolution of binaries under extreme conditions. The classical evolutionary scenario is consistent with modern observational data. During the evolution of these binaries, hypernova explosions accompanied by the collapse of stellar cores with large angular momenta can occur, leading to long gamma-ray bursts. At the end of their evolution, Cyg X-3, IC 10 X-1, NGC 300 X-1, and SS 433 may form binary relativistic objects, which will subsequently merge due to the radiation of gravitational waves. The gravitational waves emitted during mergers of relativistic stars should be detectable by existing and future gravitational-wave antennas. In the course of its future evolution, M33 X-7 will pass through a Thorne-Zytkow stage. The formation of a Thorne-Zytkow object can also be accompanied by gravitational-wave radiation. Figure 2 contains two merging black holes with masses almost identical to the second LIGO event GW151226.

HIGH VELOCITY COMPACT CLOUDS IN THE SAGITTARIUS C REGION

We report the detection of extremely broad emission toward two molecular clumps in the Galactic central molecular zone. We have mapped the Sagittarius C complex ($-0^\circ.61 < l < -0^\circ.27$, $-0^\circ.29 < b < 0^\circ.04$) in the HCN $J$ = 4--3, $\mathrm{^{13}CO}$ $J$ = 3--2, and $\mathrm{H^{13}CN}$ $J$ = 1--0 lines with the ASTE 10 m and NRO 45 m telescopes, detecting bright emission with $80\mbox{--}120$\ $\mathrm{km\,s^{-1}}$ velocity width (in full-width at zero intensity) toward CO$-0.30$$-0.07$ and CO$-0.40$$-0.22$, which are high velocity compact clouds (HVCCs) identified with our previous CO $J$ = 3--2 survey. Our data reveal an interesting internal structure of CO$-0.30$$-0.07$ comprising a pair of high velocity lobes. The spatial-velocity structure of CO$-0.40$$-0.22$ can be also understood as multiple velocity component, or a velocity gradient across the cloud. They are both located on the rims of two molecular shells of about 10 pc in radius. Kinetic energies of CO$-0.30$$-0.07$ and CO$-0.40$$-0.22$ are $\left(0.8\mbox{--}2\right)\times10^{49}$ erg and $\left(1\mbox{--}4\right)\times10^{49}$ erg, respectively. We propose several interpretations of their broad emission: collision between clouds associated with the shells, bipolar outflow, expansion driven by supernovae (SNe), and rotation around a dark massive object. There scenarios cannot be discriminated because of the insufficient angular resolution of our data, though the absence of visible energy sources associated with the HVCCs seems to favor the cloud--cloud collision scenario. Kinetic energies of the two molecular shells are $1\times10^{51}$ erg and $0.7\times10^{51}$ erg, which can be furnished by multiple SN or hypernova explosions in $2\times10^5$ yr. These shells are candidates of molecular superbubbles created after past active star formation.

Cosmic ray acceleration in hypernova remnants expanding in wind bubbles of Wolf-Rayet progenitor stars

The determination of the origin of cosmic rays with observed energies in excess of 1017 eV that exceed the expected energies of cosmic rays accelerated by supernova remnants in the galaxy is a pressing problem in modern astrophysics. Hypernova remnants are one of the possible galactic sources of cosmic rays with energies of up to 1019 eV. Hypernovae constitute a class of extremely powerful supernova explosions, whose supposed progenitors are massive Wolf-Rayet stars. We analyze the special aspects of acceleration of cosmic rays in hypernova remnants that expand in wind bubbles of Wolf-Rayet progenitor stars. We show that these cosmic rays may attain maximum energies of 1018 eV even with a relatively conservative choice of acceleration parameters and account for tens of percent of the total cosmic ray flux observed in the vicinity of the earth in the energy range of 1016–1018 eV if the galactic hypernova explosion rate in the modern epoch reaches ṄS ∼ 10−4 year−1.

COSMIC CONNECTIONS: FROM COSMIC RAYS TO GAMMA RAYS, COSMIC BACKGROUNDS AND MAGNETIC FIELDS

Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances, including a theory explaining the hard spectra of distant blazars and the measurements of intergalactic magnetic fields based on the spectra of distant sources. Furthermore, we discuss the possible contribution of transient galactic sources, such as past gamma-ray bursts and hypernova explosions in the Milky Way, to the observed flux of ultrahigh-energy cosmic-rays nuclei. The need for a holistic treatment of gamma rays, cosmic rays, and magnetic fields serves as a unifying theme for these seemingly unrelated phenomena.

On the Prompt Signals of Gamma Ray Bursts

We introduce a new model of gamma ray burst (GRB) that explains its observed prompt signals, namely, its primary quasi-thermal spectrum and high energy tail. This mechanism can be applied to either assumption of GRB progenitor: coalescence of compact objects or hypernova explosion. The key ingredients of our model are: (1) The initial stage of a GRB is in the form of a relativistic quark-gluon plasma "lava"; (2) The expansion and cooling of this lava results in a QCD phase transition that induces a sudden gravitational stoppage of the condensed non-relativistic baryons and form a hadrosphere; (3) Acoustic shocks and Alfven waves (magnetoquakes) that erupt in episodes from the epicenter efficiently transport the thermal energy to the hadrospheric surface and induce a rapid detachment of leptons and photons from the hadrons; (4) The detached $e^+e^-$ and $\gamma$ form an opaque, relativistically hot leptosphere, which expands and cools to $T \sim mc^2$, or 0.5 MeV, where $e^+e^- \to 2\gamma$ and its reverse process becomes unbalanced, and the GRB photons are finally released; (5) The "mode-conversion" of Alfven waves into electromagnetic waves in the leptosphere provides a "snowplow" acceleration and deceleration that gives rise to both the high energy spectrum of GRB and the erosion of its thermal spectrum down to a quasi-thermal distribution. According to this model, the observed GRB photons should have a redshifted peak frequency at $E_p \sim \Gamma(1 + \beta/2)mc^2/(1 + z),$ where $\Gamma\sim {\cal{O}}(1)$ is the Lorentz factor of the bulk flow of the lava, which may be determined from the existing GRB data.

CHEMICAL ABUNDANCES OF THE SECONDARY STAR IN THE BLACK HOLE X-RAY BINARY V404 CYGNI

We present a chemical abundance analysis of the secondary star in the black hole binary V404 Cygni, using Keck I/HIRES spectra. We adopt a $\chi^2$-minimization procedure to derive the stellar parameters, taking into account any possible veiling from the accretion disk. With these parameters we determine the atmospheric abundances of O, Na, Mg, Al, Si, Ca, Ti, Fe, and Ni. The abundances of Al, Si, and Ti appear to be slightly enhanced when comparing with average values in thin-disk solar-type stars. The O abundance, derived from optical lines, is particularly enhanced in the atmosphere of the secondary star in V404 Cygni. This, together with the peculiar velocity of this system as compared with the Galactic velocity dispersion of thin-disk stars, suggests that the black hole formed in a supernova or hypernova explosion. We explore different supernova/hypernova models having various geometries to study possible contamination of nucleosynthetic products in the chemical abundance pattern of the secondary star. We find reasonable agreement between the observed abundances and the model predictions. However, the O abundance seems to be too high regardless of the choice of explosion energy or mass cut, when trying to fit other element abundances. Moreover, Mg appears to be underabundant for all explosion models, which produces Mg abundances roughly 2 times higher than the observed value.

Recycling of neutron stars in common envelopes and hypernova explosions

In this paper we propose a new plausible mechanism of supernova explosions specific to close binary systems. The starting point is the common envelope phase in the evolution of a binary consisting of a red super giant and a neutron star. As the neutron star spirals towards the center of its companion it spins up via disk accretion. Depending on the specific angular momentum of gas captured by the neutron star via the Bondi-Hoyle mechanism, it may reach millisecond periods either when it is still inside the common envelope or after it has merged with the companion core. The high accretion rate may result in strong differential rotation of the neutron star and generation of the magnetar-strength magnetic field. The magnetar wind can blow away the common envelope if its magnetic field is as strong as $10^{15}\,$G, and can destroy the entire companion if it is as strong as $10^{16}\,$G. The total explosion energy can be comparable to the rotational energy of a millisecond pulsar and reach $10^{52}\,$erg. However, only a small amount of $^{56}$Ni is expected to be produced this way. The result is an unusual type-II supernova with very high luminosity during the plateau phase, followed by a sharp drop in brightness and a steep light-curve tail. The remnant is either a solitary magnetar or a close binary involving a Wolf-Rayet star and a magnetar. When this Wolf-Rayet star explodes this will be a third supernovae explosion in the same binary.

SPECTROSCOPIC STUDIES OF EXTREMELY METAL-POOR STARS WITH THE SUBARU HIGH DISPERSION SPECTROGRAPH. V. THE Zn-ENHANCED METAL-POOR STAR BS 16920-017

We report Zn abundances for 18 very metal-poor stars studied in our previous work, covering the metallicity range −3.2< [Fe/H] <−2.5. The [Zn/Fe] values of most stars show an increasing trend with decreasing [Fe/H] in this metallicity range, confirming the results found by previous studies. However, the extremely metal-poor star BS 16920–017([Fe/H] =−3.2) exhibits a significantly high [Zn/Fe] ratio ([Zn/Fe] = +1.0). Comparison of the chemical abundances of this object with HD 4306, which has similar atmospheric parameters to BS 16920–017, clearly demonstrates a deficiency of α elements and neutron-capture elements in this star, along with enhancements of Mn and Ni, as well as Zn. The association with a hypernova explosion that has been proposed to explain the high Zn abundance ratios found in extremely metal-poor stars is a possible explanation, although further studies are required to fully interpret the abundance pattern of this object.

Rotation speed of the first stars

We estimate the rotation speed of Population III (Pop III) stars within a minihalo at z∼ 20 using a smoothed particle hydrodynamics (SPH) simulation, beginning from cosmological initial conditions. We follow the evolution of the primordial gas up to densities of 1012 cm−3. Representing the growing hydrostatic cores with accreting sink particles, we measure the velocities and angular momenta of all particles that fall on to these protostellar regions. This allows us to record the angular momentum of the sinks and estimate the rotational velocity of the Pop III stars expected to form within them. The rotation rate has important implications for the evolution of the star, the fate encountered at the end of its life, and the potential for triggering a gamma-ray burst (GRB). We find that there is sufficient angular momentum to yield rapidly rotating stars (≳1000 km s−1, or near break-up speeds). This indicates that Pop III stars likely experienced strong rotational mixing, impacting their structure and nucleosynthetic yields. A subset of them was also likely to result in hypernova explosions and possibly GRBs.

Cosmic rays from hypernovae explosions

Cosmic rays from hypernovae explosions

KERR PARAMETERS FOR STELLAR MASS BLACK HOLES AND THEIR CONSEQUENCES FOR GAMMA-RAY BURSTS AND HYPERNOVAE

Recent measurements of the Kerr parameters a⋆ for two black hole binaries in our Galaxy, GRO J1655−40 and 4U 1543−47, of a⋆ = 0.65–0.75 and a⋆ = 0.75–0.85, respectively, fit the predictions of Lee et al. of a⋆ ≅ 0.8. They predicted a⋆>0.5 for 80% of the soft X-ray transient (SXT) sources. The maximum available energy in the Blandford–Znajek formalism for a⋆>0.5 gives E>3 × 1053 erg, orders of magnitude larger than the energy needed for the gamma-ray burst (GRB) and hypernova explosion. We interpret the SXTs to be relics of GRBs and hypernovae. We find that most galactic SXTs were subluminous given that they could use only a small part of the available rotational energy.

Accretion of a massive magnetized torus on a rotating black hole

We present numerical simulations of the axisymmetric accretion of a massive magnetized plasma torus on a rotating black hole. We use a realistic equation of state, which takes into account neutrino cooling and energy loss due to nucleus dissociations. The calculation are performed in the ideal relativistic MHD approximation using an upwind conservative scheme that is based on a linear Riemann solver and the constrained transport method to evolve the magnetic field. The gravitational attraction of the black hole is introduced via the Kerr metric in the Kerr–Schild coordinates. We simulate various magnetic field configurations and torus models, both optically thick and thin for neutrinos. We have found an effect of alternation of the magnetic field orientation in the ultrarelativistic jet formed as a result of the collapse. The calculations show evidence for heating of the wind surrounding the collapsar by the shock waves generated at the jet–wind border. It is shown that the neutrino cooling does not significantly change either the structure of the accretion flow or the total energy release of the system. The angular momentum of the accreting matter defines the time scale of the accretion. Due to the absence of the magnetic dynamo in our calculations, the initial strength and topology of the magnetic field determines the magnetization of the black hole, jet formation properties and the total energy yield. We estimate the total energy of accretion which transformed to jets as 1.3 × 10 52 ergs which was sufficient to explain hypernova explosions like GRB 980425 or GRB 030329.