Supernova Circumstellar Interaction
Publications
The Evolution of Supernovae in Circumstellar Wind Bubbles II:
Case of a Wolf-Rayet star
Vikram V Dwarkadas, 2007, ApJ, accepted
Abstract:Mass-loss from massive stars leads to the
formation of circumstellar wind-blown bubbles surrounding the star,
bordered by a dense shell. When the star ends its life in a supernova
(SN) explosion, the resulting shock wave will interact with this
modified medium. In a previous paper \citep{d05} we discussed the
basic parameters of this interaction with idealized models. In this
paper we go a step further and study the evolution of SNe in the wind
blown bubble formed by a 35 $\msun$ star that starts off as an O star,
goes through a red supergiant phase, and ends its life as a Wolf-Rayet
star. We model the evolution of the circumstellar medium throughout
its lifetime, and then the expansion of the SN shock wave within this
medium. Our simulations clearly reveal fluctuations in density and
pressure within the surrounding medium, due to the changing mass-loss
parameters over the star's evolution. The SN shock interacting with
these fluctuations, and then with the dense shell surrounding the
wind-blown cavity, gives rise to a variety of transmitted and
reflected shocks in the wind bubble. The interactions between these
various shocks and discontinuities is examined, and its effects on the
emission from the remnant, especially in the X-ray regime, is
noted. In this particular case the shock wave is trapped in the dense
shell for a large number of doubling times, and the remnant size is
restricted by the size of the surrounding circumstellar bubble. Our
multi-dimensional simulations reveal the presence of several
hydrodynamic instabilities. They show that the turbulent interior,
coupled with the large fluctuations in density and pressure, gives
rise to an extremely corrugated SN shock wave. The shock shows
considerable wrinkles as it impacts the dense shell, and the impact
occurs in a piecemeal fashion, with some parts of the shock wave
interacting with the shell before the others. As each interaction is
accompanied by an increase in the X-ray and optical emission,
different parts of the shell will `light-up' at different times. The
reflected shock that is formed upon shell impact will comprise of
several smaller shocks with different velocities, and which are not
necessarily moving radially inwards. The non-spherical nature of the
interaction means that it will occur over a prolonged period of time,
and the spherical symmetry of the initial shock wave is completely
destroyed by the end of the simulation.
Hydrodynamics of Supernova Evolution in the
Winds of Massive Stars
Vikram V Dwarkadas, 2007, Astrophysics and Space Science
Abstract:
Core-Collapse supernovae arise from stars greater than 8
$\msun$. These stars lose a considerable amount of mass during their
lifetime, which accumulates around the star forming wind-blown
bubbles. Upon the death of the star in a spectacular explosion, the
resulting SN shock wave will interact with this modified medium. We
study the evolution of the shock wave, and investigate the properties
of this interaction. We concentrate on the evolution of the SN shock
wave in the medium around a 35 solar mass star. We discuss the
hydrodynamics of the resulting interaction, the formation and growth
of instabilities, and deviations from sphericity.
The Evolution of Supernovae in Circumstellar Wind-Blown Bubbles. I. Introduction and One-Dimensional Calculations Vikram V Dwarkadas, 2005, ApJ
Abstract:
Mass loss from massive stars (>~8 Msolar) can result in the formation
of circumstellar wind-blown cavities surrounding the star, bordered by
a thin, dense, cold shell. When the star explodes as a core-collapse
supernova (SN), the resulting shock wave will interact with this
modified medium around the star, rather than the interstellar
medium. In this work we first explore the nature of the circumstellar
medium around massive stars in various evolutionary stages. This is
followed by a study of the evolution of SNe within these wind-blown
bubbles. The evolution depends primarily on a single parameter ?, the
ratio of the mass of the dense shell to that of the ejected
material. We investigate the evolution for different values of this
parameter. We also plot approximate X-ray surface brightness plots
from the simulations. For very small values ?<<1 the effect of the
shell is negligible, as one would expect. Values of ?<~1 affect the SN
evolution, but the SN ``forgets'' about the existence of the shell in
about 10 doubling times or so. The remnant density profile changes,
and consequently the X-ray emission from the remnant will also
change. The initial X-ray luminosity of the remnant is quite low, but
interaction of the shock wave with the dense circumstellar shell can
increase the luminosity by 2-3 orders of magnitude. As the reflected
shock begins to move inward, X-ray images will show the presence of a
double-shelled structure. Larger values result in more SN energy being
expended to the shell. The resulting reflected shock moves quickly
back to the origin, and the ejecta are thermalized rapidly. The
evolution of the remnant is speeded up, and the entire remnant may
appear bright in X-rays. If ?>>1, then a substantial amount of energy
may be expended in the shell. In the extreme case the SN may go
directly from the free expansion to the adiabatic stage, bypassing the
Sedov stage. Our results show that in many cases the SNR spends a
significant amount of time within the bubble. The low density within
the bubble can delay the onset of the Sedov stage and may end up
reducing the amount of time spent in the Sedov stage. The complicated
density profile within the bubble makes it difficult to infer the
mass-loss properties of the pre-SN star by studying the evolution of
the resulting SNR.
The Evolution of Supernovae in the Winds
of Massive Stars Vikram V. Dwarkadas, 2003, in procedings of
3-D Signatures in Stellar Explosions, A Workshop Honoring J. Craig
Wheeler's 60th Birthday, Edited by Pawan Kumar, Craig Wheeler and
Peter Hoeflich, Cambridge University Press
Abstract:
We study the evolution of supernova remnants in the circumstellar
medium formed by mass loss from the progenitor star. The properties of
this interaction are investigated, and the specific case of a 35
$\msun$ star is studied in detail. The evolution of the SN shock wave
in this case may have a bearing on other SNRs evolving in wind-blown
bubbles, especially SN 1987A.
The Interaction of Supernova Shock Waves
with Circumstellar Wind-Blown Bubbles Vikram V. Dwarkadas,
2002, in Interacting Winds from Massive Stars. ASP Conference
Proceedings, Vol. 260. Edited by Anthony F. J. Moffat and Nicole
St-Louis, p.141
Abstract:
During their lifetime, massive stars lose considerable mass in the
form of stellar winds. These winds may evacuate a cavity in the
surrounding medium, bordered by a dense shell. If the star ends its
life in a supernova explosion, the resulting shock wave will interact
with this shell. The subsequent evolution of the supernova remnant
depends in particular on the ratio of the mass of the shell to the
ejecta mass. Using numerical techniques this evolution is studied for
a range of parameter values.
Interaction
of Supernova Remnants With the Ambient medium - Vikram
V. Dwarkadas, 2001, JKAS, 34, 243
Abstract:
We summarize various aspects of the interaction of supernova remnants
(SNRs) with the ambient medium. We discuss the evolution of SNRs in
environments sculpted by the progenitor star, and summarize the
factors on which this evolution depends. As a specific example, we
consider the evolution of the medium around a 35Msun star, and the
interaction of the shock wave with this medium when the star explodes
as a SN. We also discuss the interaction of Type Ia SNe with the
ambient medium, especially the formation and growth of hydrodynamic
instabilities.
SUPERNOVA REMNANTS, PULSARS AND THE INTERSTELLAR MEDIUM - SUMMARY OF A WORKSHOP HELD AT U SYDNEY, MARCH 1999 -Vikram Dwarkadas , Lewis Ball , James Caswell , Anne Green , Simon Johnston , Brian Schmidt , Mark
Wardle, PASA, Vol 17, #1
Abstract: We summarise the proceedings of the SRCfTA workshop on ``Supernova Remnants, Pulsars and the
Interstellar Medium'' that was held at the University of Sydney on Mar 18 and 19, 1999.
Interaction
of Supernova Remnants with a Circumstellar Shell
V. V. Dwarkadas, 1995, AAS 187th Meeting
Abstract: We are studying the interaction of supernova
remnants (SNRs) with circumstellar shells, with an emphasis on Type II
supernovae (SNe). These supernovae arise from massive progenitor stars
(> 8 M_{sun}), which lose mass during their lifetime, primarily in the
form of a stellar wind. Often the stellar wind creates a circumstellar
bubble surrounded by a dense shell. When the star explodes as a
supernova, the resulting shock wave eventually collides with this
dense shell. In a recent paper on SN 1987A (Chevalier & Dwarkadas,
ApJL, 452, L45) we have shown that from the radio and X-ray emission,
one can infer the presence of a high density region interior to the
dense circumstellar shell. This can be explained as an HII region
photoionized by the flux from the pre-supernova star. Using the Zeus
code and assuming spherical symmetry, we have studied the dynamics of
the shock wave interacting first with the HII region and then the
circumstellar shell in SN 1987A. Collision with the HII region results
in a significant deceleration of the shock wave, forming a
high-density shocked region that grows with time, and is primarily
responsible for the X-ray emission. X-ray emission from the reflected
shock may begin to dominate when the forward shock hits the dense
circumstellar shell and is considerably slowed down. Simulations are
in progress with parameters suited to other remnants such as Cas A and
W44. Radio and X-ray images of Cas A show a shell structure, which may
result from interaction with a stellar bubble. W44 also shows a
double-shell structure that may have been produced by a SN explosion
inside a pre-existing wind bubble. The interaction is subject to
instabilities that may give rise to filamentary structure.
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Vikram
Dwarkadas - vikram_at_oddjob.uchicago.edu