  We present an optical spectrum for Mrk 273x, the X-ray source 1.3' to the
northeast of Mrk 273. The new spectrum indicates that the object is at a much
higher redshift (0.458) than the value (0.0376) previously reported. All the
detected emission lines show properties of Seyfert 2 galaxies. Mrk 273x has one
of the highest X-ray and radio luminosities L_x ~ 1.1 x 10^{44} erg/s, L_{1.37
GHz} ~ 2.0 x 10^{40} erg/s among Seyfert 2 galaxies, yet it has a low neutral
hydrogen column density, N_H ~ 4.4 x 10^{20}/cm^2. These properties seem
difficult to explain in the unified scheme of active galactic nuclei.
  The spectrum previously used to identify the redshift for Mrk 273x turns out
to be for diffuse clumps in the northeast tail/plume about 20'' (~20 kpc in
projected distance) from the nuclear region of Mrk 273. A new spectrum for this
region was obtained; this spectrum is essentially the same as the previous one.
These observations indicate that these clumps have the same redshift as Mrk 273
and are physically associated with the merger. The spectrum is dominated by
strong emission from the [O III] doublet with Seyfert 2-like line ratios, which
indicate that these northeast clumps are probably excited by the shock plus
precursor mechanism during the merging process. This mechanism may be operating
in other ultraluminous IRAS galaxies as well. (abridged)
