Spotting Stellar Activity Cycles in Gaia Astrometry

TL;DR

Gaia astrometry can detect starspot-induced centroid jitter in nearby active stars but is unlikely to detect activity cycles solely through astrometry in the TGAS sample.

Contribution

This study assesses Gaia's capability to detect stellar activity cycles and starspot-induced jitter using astrometry, highlighting its limitations and potential for nearby active stars.

Findings

Gaia can detect centroid jitter in highly active nearby stars.

Astrometry alone is insufficient to detect activity cycles in the TGAS sample.

Active low-mass stars show significant spot-induced jitter detectable by Gaia.

Abstract

Astrometry from Gaia will measure the positions of stellar photometric centroids to unprecedented precision. We show that the precision of Gaia astrometry is sufficient to detect starspot-induced centroid jitter for nearby stars in the Tycho-Gaia Astrometric Solution (TGAS) sample with magnetic activity similar to the young G-star KIC 7174505 or the active M4 dwarf GJ 1243, but is insufficient to measure centroid jitter for stars with Sun-like spot distributions. We simulate Gaia observations of stars with 10 year activity cycles to search for evidence of activity cycles, and find that Gaia astrometry alone likely can not detect activity cycles for stars in the TGAS sample, even if they have spot distributions like KIC 7174505. We review the activity of the nearby low-mass stars in the TGAS sample for which we anticipate significant detections of spot-induced jitter.