The nature of the envelope of the hydrogen deficient variable MV Sagittarii.

Summary. MV Sgr, generally considered as a very hot R CrB star, is surrounded by an envelope giving rise to line emission and probably also containing dust. Most of the Fe ii emission lines are optically thick and scanty information on the emitting envelope can be derived from their intensity. The emission in Ca n comes from a region with the same surface area perpendicular to the line of sight, as that of a disk with a radius of less than 500 stellar radii. This envelope may be not spherically symmetrical, with different amounts of absorption in different directions. Key words: circumstellar dust - emission lines - helium stars - R CrB stars