Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hypercritical Advection Dominated Accretion Flow   In this note we study the accretion disc that arises in hypercritical
accretion of $\dot M\sim 10^8 M_{\rm Edd}$ onto a neutron star while it is in
common envelope evolution with a massive companion. In order to raise the
temperature high enough that the disc might cool by neutrino emission,
Chevalier found a small value of the $\alpha$-parameter, where the kinematic
coefficient of shear viscosity is $\nu=\alpha c_s H$, with $c_s$ the velocity
of sound and $H$ the disc height; namely, $\alpha\sim 10^{-6}$ was necessary
for gas pressure to dominate. He also considered results with higher values of
$\alpha$, pointing out that radiation pressure would then predominate. With
these larger $\alpha$'s, the temperatures of the accreting material are much
lower, $\lsim 0.35$ MeV. The result is that neutrino cooling during the flow is
negligible, satisfying very well the advection dominating conditions. The low
temperature of the accreting material means that it cannot get rid of its
energy rapidly by neutrino emission, so it piles up, pushing its way through
the accretion disc. An accretion shock is formed, far beyond the neutron star,
at a radius $\gsim 10^8$ cm, much as in the earlier spherically symmetric
calculation, but in rotation. Two-dimensional numerical simulation shows that
an accretion disc is reformed inside of the accretion shock, allowing matter to
accrete onto the neutron star with pressure high enough so that neutrinos can
carry off the energy.

17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
2
The categories of this paper are: math