Wrinkles in Time -- I: Rapid Rotators Found in High Eccentricity Orbits

TL;DR

This paper develops pipelines to measure stellar rotation periods using TESS data, identifying rapidly rotating stars in eccentric orbits that suggest recent dynamical interactions in the Milky Way.

Contribution

It introduces new rotation measurement pipelines tested on benchmark samples and applies them to identify young, fast rotators in eccentric orbits, revealing recent dynamical events.

Findings

89% recovery rate of rotation periods across benchmark samples

Identified 141 rapidly rotating stars in eccentric orbits

Some stars appear as young as 120 million years

Abstract

Recent space-based missions have ushered in a new era of observational astronomy, where high-cadence photometric light curves for thousands to millions of stars in the solar neighborhood can be used to test and apply stellar age-dating methods, including gyrochronology. Combined with precise kinematics, these data allow for powerful new insights into our understanding of the Milky Way's dynamical history. Using TESS data, we build a series of rotation period measurement and confirmation pipelines and test them on 1,560 stars across five benchmark samples: the Pleiades, Pisces--Eridanus, Praesepe, the Hyades, and field stars from the MEarth Project. Our pipelines' recovery rates across these groups are on average 89\%. We then apply these pipelines to 4,085 likely single stars with TESS light curves in two interesting regions of Galactic action space. We identify 141 unique, rapidly rotating stars in highly eccentric orbits in the disk, some of which appear as rotationally young as the 120-Myr-old Pleiades. Pending spectroscopic analysis to confirm their youth, this indicates these stars were subject to fast-acting dynamical phenomena, the origin of which will be investigated in later papers in this series.