Complete RR Lyrae Las Campanas spectra

This directory contains spectra that have been used in multiple papers on

RR Lyrae stars by George Preston and collaborators (e.g, ``The Axial Rotation 

and Variable Macroturbulence of RR Lyrae Stars'', 2019, AJ, 157, 153;

G. W. Preston, C. Sneden, M. Chadid, I. B. Thompson, and S. A. Shectman),

and in related investigations (e.g., ``On the Use of Field RR Lyrae as 

Galactic Probes. II. A new Delta-S calibration to estimate their metallicity'',

2021, ApJ, 908, 20; J. Crestani et al.).

These spectra of RR Lyrae variables were obtained with the Las Campanas

Observatory Du Pont Telescope and its echelle spectrograph.  This instrument 

has a spectral resolving power R ~= 27,000.  Integration times were almost 

always < 900 sec in order to avoid velocity phase smearing of the absorption 

features.  Therefore the typical S/N values are < 30 in the individual 

spectra.  Essentially all Du Pont spectra for this work collected in the

years 2006-2014 on the RR Lyrae work led by George Preston are gathered here.

The doubly-dimensioned echelle spectra are fully reduced and are on a 

laboratory wavelength scale.  They are organized in subdirectories labeled by 

year and month of the observation.  For example, subdirectory "files1005" 

contains the spectra obtained in May 2010.  In a separate subdirectory 

"velocities" we have placed MS-EXCEL files that give the velocities of the 

target stars, along with the velocity uncertainties.  Tabulated values of 

VREL, VOBS, and VHELIO are those defined in the VELOCITY COMPUTATION 

ALGORITHM section of the IRAF help page for fxcor.