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Mixing of materials in magnetized core-collapse supernova remnants
Meyer D. M.-A., Pohl M., Petrov M., Egberts K.
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Mixing of materials in core-collapse supernova remnants |
Core-collapse supernova remnants are structures of the interstellar medium (ISM) left behind the explosive death of most massive stars (smaller than 40Mo). Since they result in the expansion of the supernova shock wave into the gaseous environment shaped by the star's wind history, their morphology constitutes an insight into the past evolution of their progenitor star. Particularly, fast-moving massive stars can produce asymmetric core-collapse supernova remnants. We investigate the mixing of materials in core-collapse supernova remnants generated by a moving massive 35 Mo star, in a magnetized ISM. Stellar rotation and the wind magnetic field are time-dependently included into the models which follow the entire evolution of the stellar surroundings from the zero-age main-sequence to 80 kyr after the supernova explosion. It is found that very little main-sequence material is present in remnants from moving stars, that the Wolf-Rayet wind mixes very efficiently within the 10 kyr after the explosion, while the red supergiant material is still unmixed by 30 per cent within 50kyr after the supernova. Our results indicate that the faster the stellar motion, the more complex the internal organization of the supernova remnant and the more effective the mixing of ejecta therein. In contrast, the mixing of stellar wind material is only weakly affected by progenitor motion, if at all.
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The sculpting of rectangular and jet-like morphologies in supernova remnants by anisotropic equatorially-confined progenitor stellar winds
Velazquez P. F., Meyer D. M.-A., Chiotellis A., Cruz-Alvarez A. E., Schneiter E. M., Toledo-Roy J. C., Reynoso E. M., Esquivel A.
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Synchrotron maps of rectangular and jet-like core-collapse supernova remnants |
Thermonuclear and core-collapse supernova remnants (SNRs) are the nebular leftovers of defunct stars. Their morphology and
emission properties provide insights into the evolutionary history of the progenitor star. But while some SNRs are spherical,
as expected from a point-like explosion expanding into a roughly uniform medium, many others exhibit complex non-spherical
morphologies which are often not easily explained. In this work, we use three-dimensional magnetohydrodynamic simulations to
show that rectangular and jet-like morphologies can be explained by supernovae (SNe), either type Ia or type II, expanding within
anisotropic, bipolar stellar wind bubbles driven by the progenitor star. The stellar wind has an anisotropic density distribution,
which channels the SN ejecta differently depending on the anisotropy characteristics. We compute synthetic thermal (X-ray) and
non-thermal (synchrotron) emission maps from our numerical simulations to compare with observations. We find rectangular
morphologies are generated when the stellar wind has a high mass loss rate and forms a dense, narrow disk at the equatorial
region. Instead, a jet-like or ear-like morphology is obtained when the stellar wind develops a wide, dense disk. Stellar winds
with low mass-loss rates do not strongly influence the SNR morphology. Finally, our synthetic synchrotron and X-ray maps for
the high mass-loss rate case qualitatively agree with the observations of the SNRs G332.5-5.6 and G290.1-0.8.
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Rectangular core-collapse supernova remnants: application to Puppis A
Meyer D. M.-A., Velazquez P. F., Petruk O., Chiotellis A., Pohl M., Camps-Farina F., Petrov M., Reynoso E. M., Toledo-Roy J. C., Schneiter E. M., Castellanos-Ramirez A., Esquivel A.
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Synchrotron and inverse Compton emission maps of a rectangular core-collapse supernova remnant |
Core-collapse supernova remnants are the gaseous nebulae of galactic interstellar media (ISM) formed after the explosive death
of massive stars. Their morphology and emission properties depend both on the surrounding circumstellar structure shaped by
the stellar wind-ISM interaction of the progenitor star and on the local conditions of the ambient medium. In the warm phase
of the Galactic plane (n = 1 cm-3, T = 8000 K), an organised magnetic field of strength 7 microG has profound consequences
on the morphology of the wind bubble of massive stars at rest. In this paper we show through 2.5D magneto-hydrodynamical
simulations, in the context of a Wolf-Rayet-evolving 35 Mo star, that it affects the development of its supernova remnant. When
the supernova remnant reaches its middle age (15-20 kyr), it adopts a tubular shape that results from the interaction between
the isotropic supernova ejecta and the anisotropic, magnetised, shocked stellar progenitor bubble into which the supernova blast
wave expands. Our calculations for non-thermal emission, i.e. radio synchrotron and inverse Compton radiation, reveal that such
supernova remnants can, due to projection effects, appear as rectangular objects in certain cases. This mechanism for shaping a
supernova remnant is similar to the bipolar and elliptical planetary nebula production by wind-wind interaction in the low-mass
regime of stellar evolution. If such a rectangular core-collapse supernova remnant is created, the progenitor star must not have
been a runaway star. We propose that such a mechanism is at work in the shaping of the asymmetric core-collapse supernova
remnant Puppis A.
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Pulsar wind nebulae of runaway massive stars
Meyer D. M.-A., Meliani Z.
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Synchrotron image of a pulsar wind nebulae from a runaway progenitor |
A significant fraction of massive stars move at speed through the interstellar medium of galaxies. After their death as
core collapse supernovae, a possible final evolutionary state is that of a fast rotating magnetised neutron star,
shaping its circumstellar medium into a pulsar wind nebula. Understanding the properties of pulsar wind nebulae
requires knowledge of the evolutionary history of their massive progenitors. Using 2.5D magnetohydrodynamical
simulations, we demonstrate that, in the context of a runaway high mass red supergiant supernova progenitor, the
morphology of its subsequent pulsar wind nebula is strongly affected by the wind of the defunct progenitor star
preshaping the stellar surroundings throughout its entire past life. In particular, pulsar wind nebulae of obscured
runaway massive stars harbour asymmetries function of the morphology of the progenitors wind blown cavity,
inducing projected asymmetric up down synchrotron emission.
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Spectral softening in core-collapse supernova remnant expanding inside wind-blown bubble
Das S., Brose R., Meyer D. M.-A., Pohl M., Sushch I., Plotko P.
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Evolution of non-thermal emission of a supernova in a stellar wind bubble. |
Context. Galactic cosmic rays are widely assumed to arise from diffusive shock acceleration, specifically at shocks
in supernova remnants (SNRs). These shocks expand in a complex environment, particularly in the core-collapse
scenario as these SNRs evolve inside the wind-blown bubbles created by their progenitor stars. The cosmic rays
(CRs) at core-collapse SNRs may carry spectral signatures of that complexity. Aims. We study particle acceleration
in the core-collapse SNR of a progenitor with initial mass 60 M⊙ and realistic stellar evolution. The SNR shock
interacts with discontinuities inside the wind-blown bubble and generates several transmitted and reflected shocks.
We analyse their impact on particle spectra and the resulting emission from the remnant. Methods. The hydrodynamic
equations for the evolution of SNR inside the pre-supernova circumstellar medium have been solved simultaneously
with the transport equation for cosmic rays in test-particle approximation and with the induction equation for the
magnetohydrodynamics (MHD) in 1-D spherical symmetry. Results. The evolution of core-collapse SNRs inside complex
wind-blown bubbles modifies the spectra of both the particles and their emission. We have found softer particle
spectra with spectral indices close to 2.5 during shock propagation inside the shocked wind, and this softness
persists at later evolutionary stages. Further, our calculated total production spectrum released into the
interstellar medium demonstrates spectral consistency at high energy with the galactic CRs injection spectrum,
required in propagation models. The magnetic field structure effectively influences the emission morphology of
SNR as it governs the transportation of particles and the synchrotron emissivity.
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Non-thermal radio supernova remnants of exiled Wolf-Rayet stars
Meyer D. M.-A, Pohl M., Petrov M., Oskinova L.
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Magnetic field in a Wolf-Rayet remnant |
A signification fraction of Galactic massive stars (>8 Mo) are ejected from their parentcluster
and supersonically sail away through the interstellar medium (ISM). The winds ofthese fast-moving stars blow
asymmetric bubbles thus creating a circumstellar environment in which stars eventually die with a supernova
explosion. The morphology of the resultingremnant is largely governed by the circumstellar medium of the defunct
progenitor star. Inthis paper, we present 2D magneto-hydrodynamical simulations investigating the effect of the
ISM magnetic field on the shape of the supernova remnants of a 35 M* evolving through a Wolf-Rayet phase and
running with velocity 20 and 40 km/s, respectively. A 7 microG ambientmagnetic field is sufficient to modify
the properties of the expanding supernova shock frontand in particular to prevent the formation of filamentary
structures. Prior to the supernova ex-plosion, the compressed magnetic field in the circumstellar medium
stabilises the wind/ISMcontact discontinuity in the tail of the wind bubble. A consequence is a reduced mixing
effi-ciency of ejecta and wind materials in the inner region of the remnant, where the supernova shock wave
propagates. Radiative transfer calculations for synchrotron emission reveal thatthe non-thermal radio emission
has characteristic features reflecting the asymmetry of exiledcore-collapse supernova remnants from Wolf-Rayet
progenitors. Our models are qualitatively consistent with the radio appearance of several remnants of high-mass
progenitors, namelythe bilateral G296.5+10.0 and the shell-type remnants CTB109 and Kes 17, respectively.
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Production of secondary particles in heavy nuclei interactions in supernova remnants
Bhatt M., Sushch I., Pohl M., Fedynitchf A., Das S., Brose R., Plotko P., Meyer D. M.-A.
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Gamma-ray spectrum of a type II SNR |
Supernova remnants often evolve in material with high abundance of heavy elements such as
carbon or oxygen. Hadronic collisions in these enriched media spawn the production of secondary
particles such as gamma rays, neutrinos, and secondary electrons with spectra that cannot
be scaled from those calculated for pp collisions, potentially leading to erroneous results.
We used Monte-Carlo event generators to calculate the dierential production rate of secondary
particles such as gamma rays, neutrinos, and secondary electrons for H, He, C, and O nuclei as
projectiles and as target material. The cross sections and the multiplicity spectra are separately
computed for each of the 16 combinations of projectile and target. We describe characteristic
eects of heavy nuclei in the shape and normalization of spectra of secondary particles.
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Wind nebulae and supernova remnants of very massive stars
Meyer D. M.-A., Petrov M., Pohl M
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Mixing inside an asymmetric SNR |
A very small fraction of (runaway) massive stars have masses exceeding 60-70 Mo and are
predicted to evolve as Luminous-Blue-Variable andWolf-Rayet stars before ending their lives
as core-collapse supernovae. Our 2D axisymmetric hydrodynamical simulations explore how
a fast wind (2000 km/s) and high mass-loss rate (1.0e-5 Mo/yr) can impact the morphology
of the circumstellar medium. It is shaped as 100 pc-scale wind nebula which can be
pierced by the driving star when it supersonically moves with velocity 20-40 km/s through
the interstellar medium (ISM) in the Galactic plane. The motion of such runaway stars displaces
the position of the supernova explosion out of their bow shock nebula, imposing asymmetries
to the eventual shock wave expansion and engendering Cygnus-loop-like supernova
remnants.We conclude that the size (up to more than 200 pc) of the filamentary wind cavity in
which the chemically enriched supernova ejecta expand, mixing efficiently the wind and ISM
materials by at least 10% in number density, can be used as a tracer of the runaway nature
of the very massive progenitors of such 0:1 Myr old remnants. Our results motivate further
observational campaigns devoted to the bow shock of the very massive stars BD+43 3654 and
to the close surroundings of the synchrotron-emitting Wolf-Rayet shell G2.4+1.4.
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Asymmetric supernova remnants generated by Galactic, massive runaway stars
Meyer D. M.-A., Langer N., Mackey J., Velazquez P. and Gusdorf A.
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Effect of heat conduction on a supernova remnant produced by a runaway star |
After the death of a runaway massive star, its supernova shock wave interacts
with the bow shocks produced by its defunct progenitor, and may lose
energy, momentum, and its spherical symmetry before expanding into the local interstellar medium (ISM). We
investigate whether the initial mass and space velocity of these progenitors can
be associated with asymmetric supernova remnants. We run hydrodynamical models
of supernovae exploding in the pre-shaped medium of moving Galactic
core-collapse progenitors. We find that bow shocks that accumulate more than
about 1.5 Mo generate asymmetric remnants. The shock wave first
collides with these bow shocks 160-750 yr after the supernova, and the
collision lasts until 830 4900 yr. The shock wave is then located
1.35-5 pc from the center of the explosion, and it expands freely into
the ISM, whereas in the opposite direction it is channelled into the region of
undisturbed wind material. This applies to an initially 20 Mo
progenitor moving with velocity 20 km/s and to our initially
40 Mo progenitor. These remnants generate mixing of ISM gas,
stellar wind and supernova ejecta that is particularly important upstream from
the center of the explosion. Their lightcurves are dominated by emission from
optically-thin cooling and by X-ray emission of the shocked ISM gas. We find
that these remnants are likely to be observed in the [OIII]
5007 spectral line emission or in the soft energy-band of X-rays. Finally, we
discuss our results in the context of observed Galactic supernova remnants such
as 3C391 and the Cygnus Loop.
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Credit image : NASA
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