Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray spectral diagnostics of activity in massive stars   X-rays give direct evidence of instabilities, time-variable structure, and
shock heating in the winds of O stars. The observed broad X-ray emission lines
provide information about the kinematics of shock-heated wind plasma, enabling
us to test wind-shock models. And their shapes provide information about wind
absorption, and thus about the wind mass-loss rates. Mass-loss rates determined
from X-ray line profiles are not sensitive to density-squared clumping effects,
and indicate mass-loss rate reductions of factors of 3 to 6 over traditional
diagnostics that suffer from density-squared effects. Broad-band X-ray spectral
energy distributions also provide mass-loss rate information via soft X-ray
absorption signatures. In some cases, the degree of wind absorption is so high
that the hardening of the X-ray SED can be quite significant. We discuss these
results as applied to the early O stars zeta Pup (O4 If), 9 Sgr (O4 V((f))),
and HD 93129A (O2 If*).

14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph