Characterising the i-band variability of YSOs over six orders of magnitude in timescale

Abstract

We present an $i$-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, which samples timescales from 1 minute to ten years. Using structure functions we show that on all timescales ($\tau$) there is a monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e. the more evolved systems are less variable. The Class Is show an approximately power-law increase (${\tau }^{0.8}$) in variability from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively different behaviour with most showing a power-law increase in variability up to a timescale corresponding to the rotational period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all Class IIs have two primary components to their variability. The first is an underlying roughly power-law variability spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component is approximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longer-timescale variability have a smaller rotational modulation either because they are seen at low inclinations or have more complex magnetic field geometries. We derive a new way of calculating structure functions for large simulated datasets (the "fast structure function"), based on fast Fourier transforms.

23 pages and 22 figures. Accepted for publication in MNRAS. At time of submission the electronic tables are only available from https:// doi.org/10.24378/exe.2124

References in corpus (16)

• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Magnetospheric accretion-ejection processes in the classical T Tauri star AA
• On the formation of H-alpha line emission around classical T Tauri stars
• Results of the ROTOR-program. I. The long-term photometric variability of classical T Tauri stars
• Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry
• Results of the ROTOR-program. II. The long-term photometric variability of weak-line T Tauri stars
• On the variability of quasars: a link between Eddington ratio and optical variability?
• Temperaments of young stars: Rapid mass-accretion rate changes in T Tauri and Herbig Ae stars
• A Correlation Between Pre-Main Sequence Stellar Rotation Rates and IRAC Excesses in Orion
• Photometric variability of the T Tauri star TW Hya on time scales of hours to years
• X-ray emission from dense plasma in CTTSs: Hydrodynamic modeling of the accretion shock
• A continuum of accretion burst behavior in young stars observed by K2
• Mid-Infrared Variability from the Spitzer Deep, Wide-Field Survey
• Determining the recurrence timescale of long-lasting YSO outbursts
• Long-term variability of T Tauri stars using WASP
• Spitzer Observations of Long Term Infrared Variability Among Young Stellar Objects in Chamaeleon I

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