130 research outputs found
Search for surviving companions in type Ia supernova remnants
The nature of the progenitor systems of type~Ia supernovae is still unclear.
One way to distinguish between the single-degenerate scenario and
double-degenerate scenario for their progenitors is to search for the surviving
companions. Using a technique that couples the results from multi-dimensional
hydrodynamics simulations with calculations of the structure and evolution of
main-sequence- and helium-rich surviving companions, the color and magnitude of
main-sequence- and helium-rich surviving companions are predicted as functions
of time. The surviving companion candidates in Galactic type~Ia supernova
remnants and nearby extragalactic type~Ia supernova remnants are discussed. We
find that the maximum detectable distance of main-sequence surviving companions
(helium-rich surviving companions) is ~Mpc (~Mpc), if the
apparent magnitude limit is 27 in the absence of extinction, suggesting that
the Large and Small Magellanic Clouds and the Andromeda Galaxy are excellent
environments in which to search for surviving companions. However, only five
Ia~SNRs have been searched for surviving companions, showing little support for
the standard channels in the singe-degenerate scenario. To better understand
the progenitors of type Ia supernovae, we encourage the search for surviving
companions in other nearby type Ia supernova remnants.Comment: 25 pages, 5 figures, and 2 tables. Accepted for publication in Ap
Masses and envelope binding energies of primary stars at the onset of a common envelope
We present basic properties of primary stars that initiate a common envelope
(CE) in a binary, while on the giant branch. We use the population-synthesis
code described in Politano et al. (2010) and follow the evolution of a
population of binary stars up to the point where the primary fills its Roche
lobe and initiates a CE. We then collect the properties of each system, in
particular the donor mass and the binding energy of the donor's envelope, which
are important for the treatment of a CE. We find that for most CEs, the donor
mass is sufficiently low to define the core-envelope boundary reasonably well.
We compute the envelope-structure parameter {\lambda_\mathrm{env}} from the
binding energy and compare its distribution to typical assumptions that are
made in population-synthesis codes. We conclude that {\lambda_\mathrm{env}}
varies appreciably and that the assumption of a constant value for this
parameter results in typical errors of 20--50%. In addition, such an assumption
may well result in the implicit assumption of unintended and/or unphysical
values for the CE parameter {\alpha_\mathrm{CE}}. Finally, we discuss accurate
existing analytic fits for the envelope binding energy, which make these
oversimplified assumptions for {\lambda_\mathrm{env}}, and the use of
{\lambda_\mathrm{env}} in general, unnecessary.Comment: 6 pages, 3 figures, 1 table; to be published in the proceedings of
the conference "Binary Star Evolution", in Mykonos, Greece, held in June
22-25, 201
Simulations of the symbiotic recurrent nova V407 Cyg. I. Accretion and shock evolutions
The shock interaction and evolution of nova ejecta with a wind from a red
giant star in a symbiotic binary system are investigated via three-dimensional
hydrodynamics simulations. We specifically model the March 2010 outburst of the
symbiotic recurrent nova V407~Cygni from the quiescent phase to its eruption
phase. The circumstellar density enhancement due to wind-white dwarf
interaction is studied in detail. It is found that the density-enhancement
efficiency depends on the ratio of the orbital speed to the red giant wind
speed. Unlike another recurrent nova, RS~Ophiuchi, we do not observe a strong
disk-like density enhancement, but instead observe an aspherical density
distribution with higher density in the equatorial plane than at
the poles. To model the 2010 outburst, we consider several physical parameters,
including the red giant mass loss rate, nova eruption energy, and ejecta mass.
A detailed study of the shock interaction and evolution reveals that the
interaction of shocks with the red giant wind generates strong Rayleigh-Taylor
instabilities. In addition, the presence of the companion and circumstellar
density enhancement greatly alter the shock evolution during the nova phase.
The ejecta speed after sweeping out most of the circumstellar medium decreases
to km-s, depending on model, which is consistent with the
observed extended redward emission in [N~II] lines in April 2011.Comment: ApJ, In Press. Simulation Animation: https://youtu.be/g5Nu7vDfCO
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