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The rate of supernovae in our local Galactic neighbourhood within a distance of about 100 parsecs from Earth is estimated to be one every 2-4 million years, based on the [...]

A new class of ultra-long-duration (more than 10,000 seconds) γ-ray bursts has recently been suggested (1-3). They may originate in the explosion of stars with much larger radii than those producing normal long-duration γ-ray bursts (3,4) or in the tidal disruption of a star (3). No clear supernova has yet been associated with an ultra-long-duration γ-ray burst. Here we report that a supernova (SN 2011kl) was associated with the ultra-long-duration γ-ray burst GRB 111209A, at a redshift z of 0.677. This supernova is more than three times more luminous than type Ic supernovae associated with long-duration γ-ray bursts (5-7), and its spectrum is distinctly different. The slope of the continuum resembles those of super-luminous supernovae (8,9), but extends further down into the rest-frame ultraviolet implying a low metal content. The light curve evolves much more rapidly than those of super-luminous supernovae. This combination of high luminosity and low metalline opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae (10)., GRB 111209A was detected by the Swift satellite at 07:12 UT on 9 December 2011. The X-ray and optical counterparts were discovered within minutes (11). The extraordinarily long duration of [...]

The origin of lithium (Li) and its production process have long been uncertain. Li could be produced by Big Bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low-mass stars, novae, and supernova explosions. Chemical evolution models and observed stellar Li abundances suggest that at least half the Li may have been produced in red giants, asymptotic giant branch (AGB) stars, and novae (1-3). No direct evidence, however, for the supply of Li from evolved stellar objects to the Galactic medium has hitherto been found. Here we report the detection of highly blue-shifted resonance lines of the singly ionized radioactive isotope of beryllium, [sup.7]Be, in the near-ultraviolet spectra of the classical nova V339 Del (Nova Delphini 2013) 38 to 48 days after the explosion. [sup.7]Be decays to form [sup.7]Li within a short time (half-life of 53.22 days (4)). The [sup.7]Be was created during the nova explosion via the alpha-capture reaction ³He(α,γ)[sup.7]Be (ref. 5). This result supports the theoretical prediction that a significant amount of [sup.7]Li is produced in classical nova explosions., V339 Del (Nova Delphini 2013) is a classical nova that was discovered as a bright 6.8-magnitude (unfiltered) source on 2013 August 14.584 Universal Time (UT) (6). 40 h after the [...]

A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive [sup.56]Ni (refs 1-3). After the explosion, the decay chain from [sup.56]Ni to [sup.56]Co to [sup.56]Fe generates y-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of [sup.56]Co lines at energies of 847 and 1,238 kiloelectronvolts and a γ-ray continuum in the 200-400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 ± 0.1 solar masses of radioactive [sup.56]Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometres per second. The observed γ-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of [sup.56]Ni., The detailed physics of the explosion of type Ia supernovae (for example deflagration or detonation) and the evolution (4,5) of a compact object towards explosion remain a matter of debate [...]

Betelgeuse, a nearby red supergiant, is a fast-moving star with a powerful stellar wind that drives a bow shock into its surroundings (1-4). This picture has been challenged by the discovery of a dense and almost static shell (5) that is three times closer to the star than the bow shock and has been decelerated by some external force. The two physically distinct structures cannot both be formed by the hydrodynamic interaction of the wind with the interstellar medium. Here we report that a model in which Betelgeuse's wind is photoionized by radiation from external sources can explain the static shell without requiring a new understanding of the bow shock. Pressure from the photoionized wind generates a standing shock in the neutral part of the wind (6) and forms an almost static, photoionization-confined shell. Other red supergiants should have much more massive shells than Betelgeuse, because the photoionization-confined shell traps up to 35 per cent of all mass lost during the red supergiant phase, confining this gas close to the star until it explodes. After the supernova explosion, massive shells dramatically affect the supernova light curve, providing a natural explanation for the many supernovae that have signatures of circumstellar interaction., Red supergiants are massive stars near the end of their lives, and are direct progenitors of core-collapse supernovae (7,8). They evolve from O- and B-type stars (hot, luminous sources of [...]

Type Iax supernovae are stellar explosions that are spectroscopically similar to some type Ia supernovae at the time of maximum light emission, except with lower ejecta velocities (1,2). They are also distinguished by lower luminosities. At late times, their spectroscopic properties diverge from those of other supernovae (3-6), but their composition (dominated by iron-group and intermediate-mass elements (1,7)) suggests a physical connection to normal type Ia supernovae. Supernovae of type Iax are not rare; they occur at a rate between 5 and 30 per cent of the normal type Ia rate (1). The leading models for type Iax supernovae are thermonuclear explosions of accreting carbon-oxygen white dwarfs that do not completely unbind the star (8-10),implying that they are 'less successful' versions of normal type Ia supernovae, where complete stellar disruption is observed. Here we report the detection of the luminous, blue progenitor system of the type Iax SN 2012Z in deep pre-explosion imaging. The progenitor system's luminosity, colours, environment and similarity to the progenitor of the Galactic helium nova V445 Puppis (11-13) suggest that SN 2012Z was the explosion of a white dwarf accreting material from a helium-star companion. Observations over the next few years, after SN 2012Z has faded, will either confirm this hypothesis or perhaps show that this supernova was actually the explosive death of a massive star (14,15)., SN 2012Z was discovered (16) in the Lick Observatory Supernova Search on 2012 January 29.15 UT. It had an optical spectrum similar to the type Iax (previously called SN 2002cx-like) [...]

A rare class of 'superluminous' supernovae that are about ten or more times more luminous at their peaks than other types of luminous supernova has recently been found at low [...]

Type Ia supernovae have been used empirically as 'standard candles' to demonstrate the acceleration of the expansion of the Universe (1-3) even though fundamental details, such as the nature of their progenitor systems and how the stars explode, remain a mystery (4-6). There is consensus that a white dwarf star explodes after accreting matter in a binary system, but the secondary body could be anything from a main-sequence star to a red giant, or even another white dwarf. This uncertainty stems from the fact that no recent type Ia supernova has been discovered close enough to Earth to detect the stars before explosion. Here we report early observations of supernova SN 2011fe in the galaxy M101 at a distance (7) from Earth of 6.4 megaparsecs. We find that the exploding star was probably a carbon-oxygen white dwarf, and from the lack of an early shock we conclude that the companion was probably a main-sequence star. Early spectroscopy shows high-velocity oxygen that slows rapidly, on a timescale of hours, and extensive mixing of newly synthesized intermediate-mass elements in the outermost layers of the supernova. A companion paper (8) uses pre-explosion images to rule out luminous red giants and most helium stars as companions to the progenitor., Supernova 2011fe was detected in the Pinwheel galaxy (M101; Fig. 1) on 2011 August 24.167 (03:59 UT) with a g-band magnitude of 17.35 mag by the Palomar Transient Factory (PTF). [...]

Observations with the Hubble Space Telescope (HST), conducted since 1990, now offer an unprecedented glimpse into fast astrophysical shocks in the young remnant of supernova 1987A. Comparing observations taken in 2010 with the use of the refurbished instruments on HST with data taken in 2004, just before the Space Telescope Imaging Spectrograph failed, we find that the Ly[alpha] and H[alpha] lines from shock emission continue to brighten, whereas their maximum velocities continue to decrease. We observe broad, blueshifted Ly[alpha], which we attribute to resonant scattering of photons emitted from hot spots on the equatorial ring. We also detect N v [lambda][lambda]1239, 1243 angstrom line emission, but only to the red of Ly[alpha]. The profiles of the N v lines differ markedly from that of Ha, suggesting that the N4+ ions are scattered and accelerated by turbulent electromagnetic fields that isotropize the ions in the collisionless shock. 10.1126/science.1192134

Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae (1,2). Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The 'old' environment near the supernova location, and the very low derived ejected mass (~0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous (3,4) or a regular (1) type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive [sup.44]Ti., We discovered a supernova explosion (SN 2005E; Fig. 1) on 2005 January 13 (UT dates are used throughout this paper) shortly after it occurred (it was not detected on 2004 [...]

Massive stars end their short lives in spectacular explosions--supernovae--that synthesize new elements and drive galaxy evolution. Historically, supernovae were discovered mainly through their 'delayed' optical light (some days after the [...]

This paper presents the hardware architecture and the main features of the ICARUS trigger system. The ICARUS detector is a very massive liquid Argon Time Projection Chamber aimed at the study of some of the fundamental issues of astroparticle physics such as solar and atmospheric neutrino interactions, neutrinos following a Supernova explosion, neutrino oscillations with beams from particle accelerators and nucleon decay as predicted by Grand Unification Theories. The main feature of the proposed trigger design is its 'segmentation,' i.e., the capability to trigger different sectors of the detector on different events allowing for the efficient detection of rare events. Index Terms--Field programmable gate arrays, projection chamber, segmented trigger, supernova, trigger architecture, wire planes.

When massive stars exhaust their fuel, they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration [gamma]-ray burst. One would then expect that these long [gamma]-ray bursts and core-collapse supernovae should be found in similar galactic environments. Here we show that this expectation is wrong. We find that the [gamma]-ray bursts are far more concentrated in the very brightest regions of their host galaxies than are the core-collapse supernovae. Furthermore, the host galaxies of the long [gamma]-ray bursts are significantly fainter and more irregular than the hosts of the core-collapse supernovae. Together these results suggest that long-duration [gamma]-ray bursts are associated with the most extremely massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that long [gamma]-ray bursts are relatively rare in galaxies such as our own Milky Way. Not in our back yard In their death throes massive stars often produce supernovae, and occasionally a long-duration [gamma]-ray burst (GRB). That suggests that GRBs and supernovae should be found in similar environments, but work based on more than a thousand hours of Hubble Space Telescope observation time shows that expectation to be wrong. Most long GRBs are found in small, faint, irregular galaxies. Supernovae appear equally divided between spiral and irregular galaxies. GRBs are concentrated in the brightest regions of their host galaxies whereas supernovae occur throughout their host galaxies. A happy conclusion of this finding is that GRBs, which would cause havoc here on Earth if exploding nearby, should be relatively rare in the Milky Way. [gamma]-ray bursts are more concentrated in the very brightest regions of their host galaxies than are supernovae -- in addition, the host galaxies of the [gamma]-ray bursts are significantly fainter and more irregular than the hosts of the supernovae., Author(s): A. S. Fruchter [sup.1] , A. J. Levan [sup.1] [sup.2] [sup.3] , L. Strolger [sup.1] [sup.4] [sup.23] , P. M. Vreeswijk [sup.5] , S. E. Thorsett [sup.6] , D. [...]

Cosmological implications from observations of type IA supernovae (SNe Ia) are discussed. New values for cosmological parameters seem to have given a solution to the long-standing proglem of the dynamical age of the universe. However, the size of the acceleration, seen as a cosmological constant, clearly contradicts particle theory predictions. Matter density and the cosmological constant are equal contributors to cosmic expansion at this time, a very privileged period.

Gamma-ray bursts (GRBs) are only just beginning to be understood, and at least one GRB is known to be of extragalactic origin. Supernovae are similar explosive events, but are more numerous. Radio observation of the supernova SN1998bw, which exploded at around the same time and direction as the gamma-ray burst GRB980425, suggest a link between some GRBs and supernovae. It may mean that GRB980425 is a new type of GRB with different optical and radio properties.

Research done in the 1990s on Type Ia supernova (SNe Ia) shows that they are well suited for measuring the Hubble constant (H0). The minority of observed events that are intrinsically subluminous or significantly obscured by dust can be eliminated through use of a straightforward maximum-light color criterion. There is then a majority subsample with observational absolute-magnitude dispersions less than sigma obs (MsubB) about equal to sigma obs(M subV) about equal to 0.3 mag. Absolute magnitudes can be standardized to a greater extent through use of correlations between absolute magnitude and a minimum of one distance-independent SN Ia or parent-galaxy observables.

Large numbers of distant supernovae can now be found, and their redshifts and apparent brightnesses can be measured. The most distant spectroscopically confirmed supernova is reported, which is similar to nearby, recent type Ia supernovae. The new measurements indicate a low-mass-density universe.