2016MNRAS.459.4183K

We present the results of a study of spectral features and the velocity field in the atmosphere and circumstellar envelope of the yellow hypergiant V1302 Aql, the optical counterpart of the IR source IRC+10420, based on high-resolution optical spectroscopic observations in 2001-2014. We measured heliocentric radial velocities of the following types of lines: forbidden and permitted pure emission, absorption and emission components of lines of ions, pure absorption (e.g. He i, Si ii) and interstellar components of the Na i D lines, K i and diffuse interstellar bands (DIBs). Pure absorption and forbidden and permitted pure emission, which have heliocentric radial velocities V_r=63.7±0.3, 65.2±0.3 and 62.0±0.4 km/s, respectively, are slightly redshifted relative to the systemic radial velocity (V_sys ∼ 60 km/s). The positions of the absorption components of the lines with inverse P Cyg profiles are redshifted by ∼20 km/s, suggesting that clumps falling on to the star have been stable over all observing dates. The average heliocentric radial velocity of the DIBs is V_r(DIB)=4.6±0.2 km/s. A Hα line profile with the red peak slightly stronger than the blue one was observed only once, on 2007 November 24. Comparison of pure absorption lines observed in 2001-2014 with those in earlier data does not show noticeable variations. The kinematic picture in the atmosphere was stable for observations during 2001-2014. Our results as a whole let us conclude that the hypergiant has reached a phase of slowing down (or termination) of effective temperature growth and is currently located near the high-temperature boundary of the Yellow Void in the Hertszprung-Russell diagram.