Observations of the yellow hypergiant \rho Cas obtained in 2007–2011 in a wide wavelength region with spectral resolution R \geq 60 000 have enabled studies of features of its optical spectrum in detail and brought to light previously unknown characteristics of the extended atmosphere of the star .
The radial velocity measured from symmetric absorptions of metals varies with an amplitude of about \pm 7 km/s around the systemic velocity Vsys = -47 km/s , due to low-amplitude pulsations of the atmospheric layers near the photosphere .
At some times , a velocity gradient was found in deep atmospheric layers of the star .
A slight velocity stratification in the stellar atmosphere was detected for the first time , manifested as a difference of 3–4 km/s in the velocities measured from absorption lines of neutral metals and of ions .
The long-wavelength components of split absorptions of BaII , SrII , TiII , and other strong lines with low excitation potentials for their lower levels are distorted by nearby emission lines .
It is suggested that the short-wavelength components , whose locations correspond to the narrow velocity range Vr ( blue ) from approximately -60 to -70 km/s , are formed in a circumstellar envelope ; one component of the D NaI doublet and the emission components of the FeII 6369.46 and 6432.68 Å ions are also formed there . Keywords : massive stars , evolution , hypergiants , envelopes , spectra .