Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aj....140.1329g&link_type=abstract
The Astronomical Journal, Volume 140, Issue 5, pp. 1329-1336 (2010).
Astronomy and Astrophysics
Astronomy
2
Convection, Line: Profiles, Stars: Atmospheres, Techniques: Radial Velocities, Techniques: Spectroscopic
Scientific paper
New high-resolution spectroscopic observations of the supergiant γ Cyg (F8 Iab) taken between 2000 and 2008 consistently show strongly reversed-C-shaped bisectors for all unblended spectral lines. Small-amplitude variations in radial velocity and line shapes occur in an irregular manner with time scales ~100 days and longer. The radial velocities occasionally show changes as large as 2 km s-1, but much smaller changes are going on continuously. Differential line bisectors show shape changes and Doppler displacement characteristic of radial expansion and contraction. These might arise from non-periodic radial pulsation-like motions or from the appearance of giant convection cells that occupy most of the visible hemisphere of the star. Line-depth ratios are correlated with the line shifts on a seasonal basis and indicate temperature changes ranging up to ~15 K, with larger temperature occurring during times of most rapid contraction.
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