  Coalescences of neutron stars and white dwarfs are relatively frequent
phenomena, outnumbering other types of compact object mergers (neutron stars
and black holes without involving white dwarfs) altogether. Such event
potentially can produce not only optical, but also an X-ray burst. Transient
source CDF-S XT2 [1] can be an example of this type of events as suggested by
[2]. In this note we estimate the rate of these transients in the field of view
of X-ray instruments on-board Spectrum-RG satellite. We demonstrate that during
four years of the survey program several thousand of events related to neutron
star - white dwarf mergers might appear in the field of view of eROSITA.
Collimation of X-ray emission can reduce this number. Smaller, but comparable
number of transients is expected in the case of ART-XC telescope. However, due
to relatively short duration - $\lesssim 10^4$ s, - mostly such transients
might be visible just in one scan of telescopes ($\sim 40$ s), and so only a
few photons are expected to be detected which makes definite identification
without additional information very problematic.
