SIMBAD references

1998NewA....3..571B - New Astronomy, 3, 571-582 (1998/December-0)

Instability of isothermal stellar wind bowshocks.


Abstract (from CDS):

We present hydrodynamical simulations illustrating the instability of stellar wind bowshocks in the limit of an isothermal equation of state. In this limit, the bowshock is characterized by a thin dense shell bounded on both sides by shocks. In a time-averaged sense the shape of this bowshock shell roughly matches the steady state solution of Wilkin (1996), although the apex of the bowshock can deviate in or out by a factor of two or more. The shape of the bowshock is distorted by large amplitude kinks with a characteristic wavelength of order the standoff distance from the star. The instability is driven by a strong shear flow within the shock-bounded shell, suggesting an origin related to the nonlinear thin-shell instability. This instability occurs when both the forward bowshock and the reverse wind shock are effectively isothermal and the star is moving through the interstellar medium with a Mach number greater than a few. This work therefore suggests that ragged, clumpy bowshocks should be expected to surround stars with a slow, dense wind (which leads to rapid cooling behind the reverse wind shock), whose velocity with respect to the surrounding interstellar medium is of order 60 km s^ - 1 (leading both to rapid cooling behind the forward bowshock and sufficiently high Mach numbers to drive the instability).

Abstract Copyright:

Journal keyword(s): Hydrodynamics - Instabilities - Shock waves - Circumstellar matter

Simbad objects: 2

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