Climbing the cosmic ladder with stellar twins

TL;DR

This paper introduces a novel spectroscopic twin star method for estimating stellar distances, achieving high accuracy and complementing Gaia, especially for distant stars where traditional methods struggle.

Contribution

The authors develop a new approach using spectroscopically-identified twin stars to measure stellar distances with improved accuracy over existing indirect methods.

Findings

Achieved 7.5% agreement with Hipparcos parallaxes.

Method's accuracy remains stable with increasing stellar distance.

Identified 175 twin pairs from ESO HARPS archives.

Abstract

Distances to stars are key to revealing a three-dimensional view of the Milky Way, yet their determination is a major challenge in astronomy. Whilst the brightest nearby stars benefit from direct parallax measurements, fainter stars are subject of indirect determinations with uncertainties exceeding 30%. We present an alternative approach to measuring distances using spectroscopically-identified twin stars. Given a star with known parallax, the distance to its twin is assumed to be directly related to the difference in their apparent magnitudes. We found 175 twin pairs from the ESO public HARPS archives and report excellent agreement with Hipparcos parallaxes within 7.5%. Most importantly, the accuracy of our results does not degrade with increasing stellar distance. With the ongoing collection of high-resolution stellar spectra, our method is well-suited to complement Gaia.