On the spherical-axial transition in supernova remnants

A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR, SN1987a, are modeled. In the case of SN1987a the three observed rings are simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics & Space Science in the year 201

Time-Dependent Models for a decade of SN 1993J

A classical and a relativistic law of motion for a supernova remnant (SNR) are deduced assuming an inverse power law behavior for the density of the interstellar medium and applying the thin layer approximation. A third equation of motion is found in the framework of relativistic hydrodynamics with pressure, applying momentum conservation. These new formulas are calibrated against a decade of observations of \snr. The existing knowledge of the diffusive processes of ultrarelativistic electrons is reviewed in order to explain the behavior of the `U' shaped profile of intensity versus distance from the center of SN 1993J.Comment: 20 pages 19 figures, Accepted for pubblication in Astrophysics and Space Science 201

Dust in Supernovae and Supernova Remnants I : Formation Scenarios

Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.Peer reviewe

Dust in Supernovae and Supernova Remnants II: Processing and survival

Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations

Sugarcane growth and yield responses to a 3-month summer flood

Sugarcane (Saccharum spp.) in south Florida is often subjected to flooding due to interacting effects of soil subsidence, pumping restrictions, and tropical storms. While there has been considerable research on the response of sugarcane cultivars to high water tables and periodic flooding, there is a lack of information on commercial cultivar yield response to long-term flooding. An experiment was established in Belle Glade, FL to examine the effect of a 3-month summer flood (JulySeptember) on the growth and yield of cultivars CP 80-1743 and CP 72-2086 during the plant cane (2003) and second ratoon (2005) crop. Harvest samples were taken early-, mid-, and late-season. Flooding sugarcane in the summer caused sequentially greater yield reductions throughout the harvest season in plant cane. Sucrose yields for flooded cane, compared with the non-flooded control, were 9.6 t sucrose ha?1 versus 11.7 t sucrose ha?1 early, 9.2 t sucrose ha?1 versus 12.8 t sucrose ha?1 mid-season and 7.8 t sucrose ha?1 versus 12.3 t sucrose ha?1 at late harvest. In the second ratoon crop, flooding reduced sugarcane tonnage and sucrose yield by 5464% across sampling dates, and preliminary results indicated that flooding reduced leaf nutrient content by 1078%. Yield reductions due to flooding in both crops were attributed more to reduced tonnage rather than sucrose content. CP 72-2086 yielded 1828% greater sucrose than CP 80-1743 when harvested late. However the flood × cultivar interaction was not significant as both cultivars recorded similar yield reductions under flooded conditions. Our results identified severe yield losses caused by a 3-month summer flood in these cultivars, particularly in ratoon crops. Strategies to increase summer on-farm water storage in Florida should focus on short-duration periodic flooding rather than long-term flooding.

Some Questions of International Law Arising from the Russo-Japanese War, Pt. III

Most massive stars end their lives in core-collapse supernova explosions and enrich the interstellar medium with explosively nucleosynthesized elements. Following core collapse, the explosion is subject to instabilities as the shock propagates outwards through the progenitor star. Observations of the composition and structure of the innermost regions of a core-collapse supernova provide a direct probe of the instabilities and nucleosynthetic products. SN 1987A in the Large Magellanic Cloud (LMC) is one of very few supernovae for which the inner ejecta can be spatially resolved but are not yet strongly affected by interaction with the surroundings. Our observations of SN 1987A with the Atacama Large Millimeter/Submillimeter Array (ALMA) are of the highest resolution to date and reveal the detailed morphology of cold molecular gas in the innermost regions of the remnant. The 3D distributions of carbon and silicon monoxide (CO and SiO) emission differ, but both have a central deficit, or torus-like distribution, possibly a result of radioactive heating during the first weeks (“nickel heating”). The size scales of the clumpy distribution are compared quantitatively to models, demonstrating how progenitor and explosion physics can be constrained