May 8, 2000
Radiative Fluids
Jon Arons (Univ. California, Berkeley)
I review the basic properties of accretion powered pulsars, with particular
reference
to their being locally extremely super Eddington emitters of X-rays. I outline a
simple
model of an diffusion-advection model of an accretion mound at a magnetic polar
cap, summarize the results of a WKB analysis of the "photon bubble" instability
appropriate to these highly magnetized objects. I show a number of results of 2D
radiation gas dynamic simulations of this instability, which lead to a higly
structured flow
below the accretion shock, in which low density, radiation filled pockets form,
with
elongated structure along B. The effect of these pockets formation and
disappearance,
through radiation being fed into the overlying shock, then to be swept down and
emitted
from the base of the mound, on the time series of the emergent luminosity is
shown, and compared to recent observations of the fluctuations in the light
curve of Cen X-3, with
the conclusion that these fluctuations may be the first clear observation of
photon
bubbles in a super Eddington flow.
astro-ph/9909133
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