A spectral-line analysis of the G8 III standard ε VIR.
Abstract (from CDS):
Eleven seasons of spectroscopic data comprised of 107 exposures for the stable G8 III standard star, ε Vir are analyzed for projected rotation rate and granulation parameters. A Fourier analysis of the line shapes yield v sin i = 3.06 ± 0.20 km s–1 and a radial-tangential macroturbulence dispersion ζRT = 5.16 ± 0.08 km s–1. The radial velocity over nine seasons is constant to 18 m s–1. The absolute radial velocity with granulation blueshifts (but not gravitational redshift) removed is -14120 ± 75 m s–1. Line-depth ratios show the temperature to be constant to 0.7 K over 11 years, although a small secular rise or cyclic variation ∼1 K cannot be ruled out. The third-signature plot shows that the star has granulation velocities 10% larger than the Sun's. Mapping the Fe I λ6253 line bisector on to the third-signature plot indicates a normal-for-giants flux deficit area of 12.8%, indicating ∼134 K temperature difference between granules and lanes. Deficit velocities of GK giants are seen to shift to higher values with higher luminosity, ∼0.75 km s–1 over ΔMV ∼ 1.5, indicating larger velocity differences between granules and lanes for giants higher in the HR diagram.