iota Horologii is unlikely to be an evaporated Hyades star

TL;DR

High-precision chemical analysis shows iota Horologii's elemental abundances and orbital history are inconsistent with it being an evaporated Hyades star, challenging previous assumptions about its origin.

Contribution

The study provides detailed chemical and orbital evidence that iota Horologii likely did not originate in the Hyades cluster, contradicting earlier hypotheses.

Findings

Elemental abundances match Hyades for Z<=30 elements.

Heavy elements show slight enhancement compared to Hyades.

Star's orbital history places it far from Hyades at formation.

Abstract

We present a high-precision chemical analysis of iota Horologii, a planet-host field star thought to have formed in the Hyades. Elements with atomic number 6<=Z<=30 have abundances that are in excellent agreement with those of the cluster within the +/-0.01 dex (or ~2%) precision errors. Heavier elements show a range of abundances such that about half of the Z>30 species analyzed are consistent with those of the Hyades, while the other half are marginally enhanced by 0.03+/-0.01 dex (~7+/-2%). The lithium abundance, A(Li), is very low compared to the well-defined A(Li)-Teff relation of the cluster. For its Teff, iota Horologii's lithium content is about half the Hyades'. Attributing the enhanced lithium depletion to the planet would require a peculiar rotation rate, which we are unable to confirm. Our analysis of the star's chromospheric activity suggests Prot=5d, which is significantly shorter than previously reported. Models of Galactic orbits place iota Horologii hundreds of parsecs away from the Hyades cluster at formation. Thus, we find the claim of a shared birthplace very difficult to justify.