Reassessing the Relationship Between Stellar X-ray Luminosity and Age with eROSITA Data Release 1

TL;DR

This study reevaluates the correlation between stellar X-ray luminosity and age using eROSITA data, confirming a relationship but highlighting variability and limitations for age estimation accuracy.

Contribution

It provides new X-ray luminosity data for four stars and reassesses the age relationship for 24 older stars, revealing a shallower slope and variability issues.

Findings

Confirmed correlation between X-ray luminosity and age beyond 1 Gyr.

Found a shallower slope in the luminosity-age relationship for older stars.

Identified significant variability in stellar X-ray luminosity affecting age estimates.

Abstract

Accurate stellar dating provides crucial information about the formation and development of planetary systems. Existing age-dating techniques are limited in terms of both the spectral type and age range they can accurately probe, and many are unreliable for stars older than 1 Gyr. Recent studies have suggested that a star's X-ray luminosity correlates strongly with stellar age and shows a steep fall-off at ages older than 1 Gyr. In this work, we present X-ray luminosity relationship values from eROSITA for four previously unassessed stars. Additionally, we reassess the X-ray luminosity/age relationship present in 24 main-sequence stars older than a gigayear. We confirm that a correlation does appear to exist between stellar age and X-ray luminosity at ages older than 1 Gyr. However, we measure a shallower slope with age than previous research for older stars, similar to what was found for younger stars. We also find evidence for significant astrophysical variability in a star's X-ray luminosity, which will likely limit the precision with which X-ray measurements can yield age estimates. We also find weak evidence for mass dependence in the X-ray luminosity/age relationship. These results suggest that although X-ray luminosity correlates with stellar age, it may not serve as a reliable standalone age indicator and is better used as part of a broader suite of age-dating methods.