Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray Observations of Bow Shocks around Runaway O Stars. The case of
  $\zeta$ Oph and BD+43$^{\circ}$3654   Non-thermal radiation has been predicted within bow shocks around runaway
stars by recent theoretical works. We present X-ray observations towards the
runaway stars $\zeta$ Oph (Chandra and Suzaku) and BD+43$^{\circ}$3654
(XMM-Newton) to search for the presence of non-thermal X-ray emission. We found
no evidence of non-thermal emission spatially coincident with the bow shocks,
nonetheless, diffuse emission is detected in the vicinity of $\zeta$ Oph. After
a careful analysis of its spectral characteristics we conclude that this
emission has a thermal nature with a plasma temperature of $T \approx 2
\times10^{6}$ K. The cometary shape of this emission seems to be in line with
recent predictions of radiation-hydrodynamic models of runaway stars. The case
of BD+43$^{\circ}$3654 is puzzling as non-thermal emission has been reported in
a previous work for this source.

20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph