EU Del: exploring the onset of pulsation-driven winds in giant stars. Issue 4 (23rd January 2016)

• Record Type: Journal Article
• Authors: McDonald, I.; Zijlstra, A. A.; Sloan, G. C.; Lagadec, E.; Johnson, C. I.; Uttenthaler, S.; Jones, O. C.; Smith, C. L.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 456:Issue 4(2016)
• Page Start: 4542
• Page End: 4550
• Publication Date: 2016-01-23
• Subjects: stars: AGB and post-AGB -- circumstellar matter -- stars: individual: EU Del -- stars: mass-loss -- stars: winds, outflows; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stv2942
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: 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). Atacama Pathfinder Experiment 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 12 C/ 13 C ratio of 14$^{+9}_{-4}$ and a mass-loss rate of a few × 10 −8 M⊙ yr −1 . Analysis of published spectra show 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.