High-resolution optical spectroscopy of the yellow hypergiant V1302 Aql (=IRC+10420) in 2001–2014

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−1, respectively, are slightly redshifted relative to the systemic radial velocity (V sys ∼ 60 km s−1). The positions of the absorption components of the lines with inverse P Cyg profiles are redshifted by ∼20 km s−1, 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−1. 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.