RR Lyrae Atmospherics: Wrinkles Old and New. A Preview

TL;DR

This paper presents spectroscopic survey results of RR Lyrae stars, exploring atmospheric dynamics, pulsation phenomena, helium emissions, and implications for stellar populations and globular cluster evolution.

Contribution

It provides new spectroscopic insights into RR Lyrae atmospheres, pulsation behaviors, and helium line phenomena, advancing understanding of their physical processes and stellar populations.

Findings

Detection of phase-dependent envelope turbulence.

Observation of helium emission and absorption lines.

Identification of helium emission in Blazhko stars.

Abstract

I report some results of an echelle spectroscopic survey of RR Lyrae stars begun in 2006 that I presented in my Henry Norris Lecture of January 4, 2010. Topics include (1) atmospheric velocity gradients, (2) phase-dependent envelope turbulence as it relates to Peterson's discoveries of axial rotation on the horizontal branch and to Stothers' explanation of the Blazhko effect, (3) the three apparitions of hydrogen emission during a pulsation cycle, (4) the occurrence of He I lines in emission and absorption, (5) detection of He II emission and metallic line-doubling in Blazhko stars, and finally (6) speculation about what helium observations of RR Lyrae stars in omega Centauri might tell us about the putative helium populations and the horizontal branch of that strange globular cluster.