EU Del: exploring the onset of pulsation-driven winds in giant stars

الأصل · EN

We explore the wind-driving mechanism of giant stars through the nearby (117 pc), intermediate-luminosity (L ≈ 1600 L) star EU Del (HIP 101810, HD 196610). APEX observations of the CO (3--2) and (2--1) transitions are used to derive a wind velocity of 9.51 ± 0.02 km s⁻¹, a ¹²C/¹³C ratio of 14 ⁺⁹₋₄, and a mass-loss rate of a few × 10⁻⁸ M yr⁻¹. From published spectra, we estimate that the star has a metallicity of [Fe/H] = --0.27 ± 0.30 dex. The star's dusty envelope lacks a clear 10-μm silicate feature, despite the star's oxygen-rich nature. Radiative transfer modelling cannot fit a wind acceleration model which relies solely on radiation pressure on condensing dust. We compare our results to VY Leo (HIP 53449), a star with similar temperature and luminosity, but different pulsation properties. We suggest the much stronger mass loss from EU Del may be driven by long-period stellar pulsations, due to its potentially lower mass. We explore the implications for the mass-loss rate and wind velocities of other stars.