New solar twins and the metallicity and temperature scales of the Geneva Copenhagen Survey

TL;DR

This paper identifies new solar twin stars using high-resolution spectroscopy and evaluates the metallicity and temperature calibration scales of the Geneva-Copenhagen Survey, revealing potential offsets from solar values.

Contribution

The study introduces a method to find solar twins spectroscopically and assesses the GCS temperature and metallicity scales, suggesting possible systematic offsets.

Findings

Six new solar twins identified.

GCS temperature scale may be offset by 100K.

GCS metallicity scale may be offset by 0.1 dex.

Abstract

We search for "solar twins" in the Geneva-Copenhagen Survey (GCS) using high resolution optical spectroscopy. We initially select Sun-like stars from the GCS by absolute magnitude, b-y colour and metallicity close to the solar values. Our aim is to find the stars which are spectroscopically very close to the Sun using line depth ratios and the median equivalent widths and depths of selected lines with a range of excitation potentials. We present the ten best stars fulfilling combined photometric and spectroscopic criteria, of which six are new twins. We use our full sample of Sun-like stars to examine the calibration of the metallicity and temperature scale in the GCS. Our results give rise to the conclusion that the GCS may be offset from the solar temperature and metallicity for sun-like stars by 100K and 0.1dex, respectively.