Search results for "SUPERNOVA"
showing 10 items of 330 documents
The origin of the X-ray-emitting plasma in the eastern edge of the Cygnus Loop
2010
The Cygnus Loop is interacting with a protrusion of the cavity wall in its eastern edge (the XA region), where the X-ray emission is very bright. The complexity of the environment and the non-linear physical processes of the shock-cloud interaction make the origin of the X-ray emission still not well understood. Our purpose is to understand the physical origin of the X-ray emission in the XA region, addressing, in particular, the role of thermal conduction in the interaction process. We analyzed two XMM-Newton data sets, performing image analysis and spatially resolved spectral analysis on a set of homogeneous regions. We applied a recently developed diagnostic tool to compare spectral anal…
Unveiling the spatial structure of the overionized plasma in the supernova remnant W49B
2011
W49B is a mixed-morphology supernova remnant with thermal X-ray emission dominated by the ejecta. In this remnant, the presence of overionized plasma has been directly established, with information about its spatial structure. However, the physical origin of the overionized plasma in W49B has not yet been understood. We investigate this intriguing issue through a 2D hydrodynamic model that takes into account, for the first time, the mixing of ejecta with the inhomogeneous circumstellar and interstellar medium, the thermal conduction, the radiative losses from optically thin plasma, and the deviations from equilibrium of ionization induced by plasma dynamics. The model was set up on the basi…
Nucleosynthesis in magneto-rotational supernovae
2020
Abstract We present the nucleosynthesis of magneto-rotational supernovae (MR-SNe) including neutrino-driven and magneto-rotational-driven ejecta based, for the first time, on two-dimensional simulations with accurate neutrino transport. The models analysed here have different rotation and magnetic fields, allowing us to explore the impact of these two key ingredients. The accurate neutrino transport of the simulations is critical to analyse the slightly neutron rich and proton rich ejecta that are similar to the, also neutrino-driven, ejecta in standard supernovae. In the model with strong magnetic field, the r-process produces heavy elements up to the third r-process peak (A ∼ 195), in agr…
The chemical signature of jet-driven hypernovae
2020
Hypernovae powered by magnetic jets launched from the surface of rapidly rotating millisecond magnetars are one of the leading models to explain broad-lined Type Ic supernovae (SNe Ic-BL), and have been implicated as an important source of metal enrichment in the early Universe. We investigate the nucleosynthesis in such jet-driven hypernovae using a parameterised, but physically motivated, approach that analytically relates an artificially injected jet energy flux to the power available from the energy in differential rotation in the proto-neutron star. We find ejected $^{56}\mathrm{Ni}$ masses of $0.05\,\mathrm{M}_\odot - 0.45\,\mathrm{M}_\odot$ in our most energetic models with explosion…
Core-collapse supernova simulations in one and two dimensions: comparison of codes and approximations
2018
We present spherically symmetric (1D) and axisymmetric (2D) supernova simulations for a convection-dominated 9 Msun and a 20 Msun progenitor that develops violent activity by the standing-accretion-shock instability (SASI). We compare in detail the Aenus-Alcar code, which uses fully multidimensional two-moment neutrino transport with an M1 closure, with a ray-by-ray-plus (RbR+) version of this code and with the Prometheus-Vertex code that employs RbR+ two-moment transport with a Boltzmann closure. Besides testing consequences of ignored non-radial neutrino-flux components in the RbR+ approximation, we also discuss the influence of various transport ingredients applied or not applied in rece…
Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum
2020
Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD cameras, which creates a degeneracy between the best-fit values of abundances and emission measure. The combined contribution of shocked ambient medium and ejecta to the X-ray emission complicates the determination of the ejecta mass and chemical composition, leading to big uncertainties in mass estimates and it can introduce a bias in the comparison between the observed ejecta composition and the yields predicted by explosive nucleosynthesis. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature which …
Magnetorotational core collapse of possible GRB progenitors – II. Formation of protomagnetars and collapsars
2020
We assess the variance of the post-collapse evolution remnants of compact, massive, low-metallicity stars, under small changes in the degrees of rotation and magnetic field of selected pre-supernova cores. These stellar models are commonly considered progenitors of long gamma-ray bursts. The fate of the proto-neutron star (PNS) formed after collapse, whose mass may continuously grow due to accretion, critically depends on the poloidal magnetic field strength at bounce. Should the poloidal magnetic field be sufficiently weak, the PNS collapses to a black hole (BH) within a few seconds. Models on this evolutionary track contain promising collapsar engines. Poloidal magnetic fields smooth over…
Dark gamma-ray bursts
2016
Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is …
Spatial distribution of X-ray emitting ejecta in Tychos SNR: indications of shocked Titanium
2015
Young supernova remnants show a characteristic ejecta-dominated X-ray emission that allows us to probe the products of the explosive nucleosynthesis processes and to ascertain important information about the physics of the supernova explosions. Hard X-ray observations have recently revealed the radioactive decay lines of 44Ti at ~67.9 keV and ~78.4 keV in the Tycho's SNR. We here analyze the set of XMM-Newton archive observations of the Tycho's SNR. We produce equivalent width maps of the Fe K and Ca XIX emission lines and find indications for a stratification of the abundances of these elements and significant anisotropies. We then perform a spatially resolved spectral analysis by identify…
1.6 GHz VLBI observations of SN 1979C: almost-free expansion
2009
We report on 1.6 GHz Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN 1979C made on 18 November 2002. We derive a model-dependent supernova size. We also present a reanalysis of VLBI observations made by us on June 1999 and by other authors on February 2005. We conclude that, contrary to our earlier claim of strong deceleration in the expansion, SN 1979C has been undergoing almost-free expansion ($m = 0.91\pm0.09$; $R \propto t^m$) for over 25 years.