2016ApJ...826...92G

The red giant α Ser was observed over 10 seasons, 2001-2010, at the Elginfield Observatory with the high-resolution coude spectrograph. Season-mean radial velocities appear to show a small secular rise ∼11±3 m/s/yr. The absolute spectroscopic radial velocity with convective blueshifts taken into account is 2730 m/s. Ten line-depth ratios were investigated and show that the star's temperature is constant with any secular variation below 1.3±1.0 K over the 11 years of observation. Fourier analysis of the line broadening yields v sin i=2.0±0.3 km/s and a radial-tangential macroturbulence dispersion ζ_RT=4.50±0.10 km/s. The third-granulation-signature plot shows that the granulation velocities of α Ser are only 0.55±0.10 as large as the Sun's. The line bisector of Fe i λ6253 has the usual "C" shape and when mapped onto the third-signature plot results in a flux deficit that is slightly broader than seen in other measured K giants. The deficit fractional area of 12.3±1.5% suggests a temperature difference between granules and lanes of 105 K as seen averaged over the stellar disk.