Related papers: Pair-Instability Explosions: observational evidenc…
With central densities as high as 5-10 times the nuclear saturation density, neutron stars exhibit extreme conditions that cannot be observed elsewhere. They are ideal astrophysical laboratories for probing the composition and properties of…
SN2018ibb is a recently observed hydrogen poor super-luminous supernova which appears to be powered by the decay of $30\;\rm{M_\odot}$ of radioactive nickel. This supernova has been suggested to show hybrid signatures of a pair instability…
Recent developments in multi-dimensional simulations of core-collapse supernovae have considerably improved our understanding of this complex phenomenon. In addition to that, one-dimensional (1D) studies have been employed to study the…
Recent observational studies of core-collapse supernovae suggest only stars with zero-age main sequence masses smaller than $16$-$18\ M_\odot$ explode when they are red supergiants, producing type IIP supernovae. This may imply that more…
Physical collisions and close approaches between stars play an important role in the formation of exotic stellar systems. Standard theories suggest that collisions are rare, occurring only via random encounters between stars in dense…
Supermassive black holes are now realized to exist in the centers of most galaxies. The recent discoveries of luminous quasars at redshifts higher than 6 require that these black holes were assembled already when the Universe was less than…
Pair Instability Supernovae have been suggested as candidates for some Super Luminous Supernovae, such as SN 2007bi, and as one of the dominant types of explosion occurring in the early Universe from massive, zero-metallicity Population III…
The intense emission of 511 keV photons from the Galactic center and within terrestrial thunderstorms is attributed to the formation of parapositronia' clouds. Unbound electron-positron pairs and positronia can be created by strong…
Single-year spikes in radiocarbon production are caused by intense bursts of radiation from space. Supernovae emit both high-energy particle and electromagnetic radiation, but it is the latter that is most likely to strike the atmosphere…
Supernovae are nature's grandest explosions and an astrophysical laboratory in which unique conditions exist that are not achievable on Earth. They are also the furnaces in which most of the elements heavier than carbon have been forged.…
Neutral stellar core at or over nuclear densities is described by a positive charged baryon core and negative charged electron fluid since they possess different masses and interactions. Based on a simplified model of a gravitationally…
Though it is agreed that the post-bounce, pre-explosion cores of massive stars are unstable to transonic, Rayleigh-Taylor-like instabilities, the role convective motions may play in igniting the supernova explosion itself is not yet clear.…
Pair-instability and pulsational pair-instability supernovae (PPISN) have not been unambiguously observed so far. They are, however, promising candidates for the progenitors of the heaviest binary black hole (BBH) mergers detected. If these…
Core-collapse supernovae are one of the most energetic events in the universe ($10^{46} J$). When a massive star (M $>$ 8 M$_{\odot}$) ignites its last fusion stage where silicon fusion makes iron, its end is then very close. Basically, the…
An inhomogeneous compactification of a higher dimensional spacetime can result in the formation of type I dimension bubbles, i.e., nontopological solitons which tend to absorb and entrap massive particle modes. We consider possible…
Under the hypothesis that some fraction of massive stellar core collapses give rise to unusually energetic events, termed hypernovae, I examine the required rates assuming some fraction of such events yield gamma ray bursts. I then discuss…
The formation of massive stars in close binary systems is complicated due to their high radiation pressure, the crowded environment and the expected minimum separation for fragmentation being many times greater than the orbital separation.…
In a recent paper (Ushov, PRL, 80, 230, 1998), it has been claimed that the bare surface of a strange star can emit electron-positron pairs of luminosity \~10^{51} ergs/s for about 10s. If true, obviously, this mechanism may explain the…
Planetary nebulae (PNe) are circumstellar gas ejected during an intense mass-losing phase in the the lives of asymptotic giant branch stars. PNe have a stunning variety of shapes, most of which are not spherically symmetric. The debate over…
Thorne-\.Zytkow Objects (T\.ZOs) are hypothetical hybrid stars with a neutron star at the core of a large, diffuse envelope. (T\.ZOs) may be formed when a newly formed neutron star that is kicked by its supernova collides with its…