A Model for (Quasi-)Periodic Multi-wavelength Photometric Variability in Young Stellar Objects

Abstract

We present radiation transfer models of rotating young stellar objects (YSOs) with hotspots in their atmospheres, inner disk warps and other 3-D effects in the nearby circumstellar environment. Our models are based on the geometry expected from the magneto-accretion theory, where material moving inward in the disk flows along magnetic field lines to the star and creates stellar hotspots upon impact. Due to rotation of the star and magnetosphere, the disk is variably illuminated. We compare our model light curves to data from the Spitzer YSOVAR project (Morales-Calderon et al. 2014, Cody et al. 2014) to determine if these processes can explain the variability observed at optical and mid-infrared wavelengths in young stars. We focus on those variables exhibiting "dipper" behavior that may be periodic, quasi-periodic, or aperiodic. We find that the stellar hotspot size and temperature affects the optical and near-infrared light curves, while the shape and vertical extent of the inner disk warp affects the mid-IR light curve variations. Clumpy disk distributions with non-uniform fractal density structure produce more stochastic light curves. We conclude that the magneto-accretion theory is consistent with certain aspects of the multi-wavelength photometric variability exhibited by low-mass YSOs. More detailed modeling of individual sources can be used to better determine the stellar hotspot and inner disk geometries of particular sources.

Accepted to ApJ

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• Multicolor Variability of Young Stars in the Lagoon Nebula: Driving Causes and Intrinsic Timescales
• Synthetic Light Curves of Accretion Variability in T Tauri Stars
• The inner disk of RY Tau: evidence of stellar occultation by the disk atmosphere at the sublimation rim from K-band continuum interferometry
• Examining the Rotation Period Distribution of the 40 Myr Tucana-Horologium Association with TESS
• Modeling of CoRoT and Spitzer lightcurves in NGC 2264 caused by an optically thick warp
• Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei
• Spectroscopic classification of X-ray sources in the Galactic Bulge Survey
• Infrared variability of young solar analogs in the Lagoon Nebula
• The Nature of Class I Sources: Periodic Variables in Orion
• Climate Change in Hell: Long-Term Variation in Transits of the Evaporating Planet K2-22b