Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Opacity Effects on Pulsations of Main-Sequence A-Type Stars   Opacity enhancements for stellar interior conditions have been explored to
explain observed pulsation frequencies and to extend the pulsation instability
region for B-type main-sequence variable stars. For these stars, the pulsations
are driven in the region of the opacity bump of Fe-group elements at
$\sim$200,000 K in the stellar envelope. Here we explore effects of opacity
enhancements for the somewhat cooler main-sequence A-type stars, in which
$p$-mode pulsations are driven instead in the second helium ionization region
at $\sim$50,000 K. We compare models using the new LANL OPLIB vs. LLNL OPAL
opacities for the AGSS09 solar mixture. For models of 2 solar masses and
effective temperature 7600 K, opacity enhancements have only a mild effect on
pulsations, shifting mode frequencies and/or slightly changing kinetic-energy
growth rates. Increased opacity near the bump at 200,000 K can induce
convection that may alter composition gradients created by diffusive settling
and radiative levitation. Opacity increases around the hydrogen and 1st He
ionization region (13,000 K) can cause additional higher-frequency $p$ modes to
be excited, raising the possibility that improved treatment of these layers may
result in prediction of new modes that could be tested by observations. New or
wider convective zones and higher convective velocities produced by opacity
increases could also affect angular momentum transport during evolution. More
work needs to be done to quantify the effects of opacity on the boundaries of
the pulsation instability regions for A-type stars.

29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ