Rotation and Macroturbulence in Metal-poor Field Red Giant and Red Horizontal Branch Stars

Abstract

We report the results for rotational velocities, Vrot sin i, and macroturbulence dispersion, zeta(RT), for 12 metal-poor field red giant branch stars and 7 metal-poor field red horizontal branch stars. The results are based on Fourier transform analyses of absorption line profiles from high-resolution (R ~ 120,000), high-S/N (~ 215 per pixel) spectra obtained with the Gecko spectrograph at CFHT. We find that the zeta(RT) values for the metal-poor RGB stars are very similar to those for metal-rich disk giants studied earlier by Gray and his collaborators. Six of the RGB stars have small rotational values, less than 2.0 km/sec, while five show significant rotation, over 3 km/sec. The fraction of rapidly rotating RHB stars is somewhat lower than found among BHB stars. We devise two empirical methods to translate the line-broadening results obtained by Carney et al. (2003, 2008) into Vrot sin i for all the RGB and RHB stars they studied. Binning the RGB stars by luminosity, we find that most metal-poor field RGB stars show no detectable sign, on average, of rotation. However, the most luminous stars, with M(V) <= -1.5, do show net rotation, with mean values of 2 to 4 km/sec, depending on the algorithm employed, and these stars also show signs of radial velocity jitter and mass loss.

accepted for publication in the Astronomical Journal

References in corpus (3)

• A Keck/HIRES Doppler Search for Planets Orbiting Metal-Poor Dwarfs. I. Testing Giant Planet Formation and Migration Scenarios
• Line Broadening in Field Metal-poor Red Giant and Red Horizontal Branch Stars
• HST Observations of Chromospheres in Metal Deficient Field Giants

Cited by in corpus (15)

• The Magnetic Fields at the Surface of Active Single G-K Giants
• Rapid Rotation of Low-Mass Red Giants Using APOKASC: A Measure of Interaction Rates on the Post-main-sequence
• A Giant Planet Around a Metal-poor Star of Extragalactic Origin
• The Penn State - Torun Centre for Astronomy Planet Search stars. II. Lithium abundance analysis of the Red Giant Clump sample
• Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields
• 3D hydrodynamical CO5BOLD model atmospheres of red giant stars: I. Atmospheric structure of a giant located near the RGB tip
• A likely exoplanet orbiting the oscillating K-giant α Arietis
• Rotational velocities of the giants in symbiotic stars: III. Evidence of fast rotation in S-type symbiotics
• An Overview of the Rotational Behavior of Metal--Poor Stars
• Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants
• Tidal Effects on the Radial Velocities of V723 Mon: Additional Evidence for a Dark $3M_{\odot }$ Companion
• A new class of dark matter-free dwarf galaxies? I. Clues from FCC 224, NGC 1052-DF2 and NGC 1052-DF4
• Characterization of Kepler targets based on medium-resolution LAMOST spectra analyzed with ROTFIT
• The Axial Rotation and Variable Macroturbulence of RR Lyrae and Red Horizontal Branch Stars
• The complex stellar system M 22: constraining the chemical enrichment from AGB stars using magnesium isotope ratios