We present the results of a study of spectral features and the velocity field in the atmosphere and the circumstellar envelope of the hypergiant V1302 Aql , the optical counterpart of the IR source IRC+10420 , based on high-resolution spectroscopic observations obtained in 2001–2014 .
We measured radial velocities of the following types of lines : forbidden and permitted pure emissions , absorption and emission components of lines of ions , pure absorptions ( e.g. , He i , Si ii ) , and interstellar components of the Na i D–lines , K i , and DIBs .
The heliocentric radial velocity measured for pure absorptions as well as for the forbidden and permitted pure emissions is close to the systemic radial velocity and equal to V _ { r } = 63.7 \pm 0.3 , 65.2 \pm 0.3 , and 62.0 \pm 0.4 km s ^ { -1 } , respectively .
Positions of the absorption components of the lines with inverse P Cyg profiles are stable and indicate the presence of clumps moving toward the star with a velocity of \sim 20 km s ^ { -1 } .
The average radial velocity of the DIBs is V _ { r } ( DIB ) = 4.6 \pm 0.2 km s ^ { -1 } .
Comparison of the absorption lines observed in 2001–2014 and those in earlier data shows no noticeable variations .
We conclude that the hypergiant reached a phase of slowing down ( or termination ) of the effective temperature growth and is currently located near the high-temperature boundary of the Yellow Void in the Hertszprung-Russell diagramme .