Young Stars in the Time Domain: A Cool Stars 16 Splinter Summary

TL;DR

This paper reviews recent advances in understanding the time-variable phenomena in young stars and their disks, highlighting multi-epoch observations revealing diverse variability mechanisms across wavelengths and timescales.

Contribution

It summarizes recent observational results from multi-epoch campaigns, emphasizing new insights into variability processes in young stellar objects and circumstellar disks.

Findings

Many young stars show significant mid-IR variability.

Variations can be due to stellar photosphere or disk structures.

Evidence of high-frequency pulsations and correlated optical/X-ray variability.

Abstract

Variability is a defining characteristic of young stellar systems, and optical variability has been heavily studied to select and characterize the photospheric properties of young stars. In recent years, multi-epoch observations sampling a wider range of wavelengths and time-scales have revealed a wealth of time-variable phenomena at work during the star formation process. This splinter session was convened to summarize recent progress in providing improved coverage and understanding of time-variable processes in young stars and circumstellar disks. We begin by summarizing results from several multi-epoch Spitzer campaigns, which have demonstrated that many young stellar objects evidence significant mid-IR variability. While some of these variations can be attributed to processes in the stellar photosphere, others appear to trace short time-scale changes in the circumstellar disk which can be successfully modeled with axisymmetric or non-axisymmetric structures. We also review recent studies probing variability at shorter wavelengths that provide evidence for high frequency pulsations associated with accretion outbursts, correlated optical/X-ray variability in Classical T Tauri stars, and magnetic reversals in young solar analogs.