A Spectral-line Analysis of the G8 III Standard epsilon VIR

作者：Gray David F^*

来源：Astrophysical Journal, 2017, 845(1): 62.

DOI：10.3847/1538-4357/aa7f77

• convection
• line: profiles
• stars: atmospheres
• stars: late-type
• Sun: granulation
• techniques: spectroscopic

Eleven seasons of spectroscopic data comprised of 107 exposures for the stable G8. III standard star, epsilon 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 zeta(RT) = 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 similar to 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 lambda 6253 line bisector on to the third-signature plot indicates a normal-for-giants flux deficit area of 12.8%, indicating similar to 134 K temperature difference between granules and lanes. Deficit velocities of GK giants are seen to shift to higher values with higher luminosity, similar to 0.75 km s(-1) over Delta M-V similar to 1.5, indicating larger velocity differences between granules and lanes for giants higher in the HR diagram.

• 出版日期2017-8-10