An Improved Determination of the Lithium Depletion Boundary Age of Blanco 1 and a First Look on the Effects of Magnetic Activity

TL;DR

This study refines the age of the Blanco 1 cluster using the Lithium Depletion Boundary method and highlights the significant impact of magnetic activity on age estimates, suggesting previous ages may need revision.

Contribution

The paper provides a new LDB age for Blanco 1 and demonstrates the importance of including magnetic activity effects in stellar age determinations.

Findings

LDB age of Blanco 1 is 126 Myr before activity correction.

Magnetic activity correction reduces the age to 114 Myr.

Blanco 1's age is coeval with the Pleiades cluster.

Abstract

The Lithium Depletion Boundary (LDB) is a robust method for accurately determining the ages of young clusters, but most pre-main-sequence models used to derive LDB ages do not include the effects of magnetic activity on stellar properties. In light of this, we present results from our spectroscopic study of the very low-mass members of the southern open cluster Blanco 1 using the Gemini-North telescope, program IDs: GN-2009B-Q-53 and GN-2010B-Q-96. We obtained GMOS spectra at intermediate resolution for cluster candidate members with $I$$\approx$13--20 mag. From our sample of 43 spectra, we find 14 probable cluster members by considering proximity to the cluster sequence in an $I/I-K\rm_s$ color-magnitude diagram, agreement with the cluster's systemic radial velocity, and magnetic activity as a youth indicator. We systematically analyze the H$\alpha$ and Li features and update the LDB age of Blanco 1 to be $126^{+13}_{-14}$ Myr. Our new LDB age for Blanco 1 shows remarkable coevality with the benchmark Pleiades open cluster. Using available empirical activity corrections, we investigate the effects of magnetic activity on the LDB age of Blanco 1. Accounting for activity, we infer a corrected LDB age of $114^{+9}_{-10}$ Myr. This work demonstrates the importance of accounting for magnetic activity on LDB inferred stellar ages, suggesting the need to re-investigate previous LDB age determinations.