  thermal radiation emitted by a %hot cobalt wire in the temperature range from
\(T\approx 400\,\)K up to melting. The radiation is linearly polarized
perpendicular to the wire.
  \(P\) decreases from \(30\,\%\) just above room temperature down to
\(6.5\,\%\) near melting and does not show any particular behavior neither at
the martensitic {\em hcp}$-${\em fcc} transition at \(\approx 700\,\)K nor at
the Curie point at \( \approx 1400\,\)K. However, \(P\) shows a rapid decrease
for \(T\gtrsim 1000\,\)K and, contrary to previous measurements with tungsten
wires, it hysteretically behaves if the temperature change is reversed. This
behavior is rationalized by %taking into account accounting for the
irreversible thermal demagnetization of the wire with magnetic domain size
change.
