n_{ISM}\cdot v^{-3}$ for a given interstellar medium density $n_{ISM}$ (for the number of hydrogen atom in a $\rm cm^{3}$) we will assume that the velocity of our hypothetical objects is close to the velocity, which was really observed for radio pulsars, or, at least is close to spatial velocities observed for the oldest of them (Lyne & Lorimer, 1994). Assuming that in the vicinity of the Sun $n_{ISN}$ is on average $\approx 0.07\, {\rm   H\ cm^{-3}}$, then at $T_{bb}\approx10^{5}\,K$ the corresponding contribution $(G\cdot M\cdot \dot{M}/R)$ to the total bolometric luminosity is only several percent for $ v \ga 200{\rm ~km\cdot s^{-1}}$.

It is evident that because of their assumed low luminosity we can try to look for such objects only in the closest vicinity of the Sun. It refers not only to the optical, but also to the soft X–rays, which are strongly sensitive to inhomogeneities in the interstellar medium distribution (Paresce, 1984). So, keeping in mind the data on interstellar medium close ($ \la 250$ pc) to the Sun and also the absorption not only in the soft X–rays, but also in the far ultra–violet ranges (Welsh et al., 1994), we have to do in the [*optical*]{} only with 