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We present near-IR and far-UV observations of the pre-transitional (gapped)disk in HD 169142 using NASA's Infrared Telescope Facility and Hubble SpaceTelescope. The combination of our data along with existing data sets into thebroadband spectral energy distribution reveals variability of up to 45% between~1.5-10 {\mu}m over a maximum timescale of 10 years. All observations known tous separate into two distinct states corresponding to a high near-IR state inthe pre-2000 epoch and a low state in the post-2000 epoch, indicating activitywithin the <1 AU region of the disk. Through analysis of the Pa {\beta} and Br{\gamma} lines in our data we derive a mass accretion rate in May 2013 of (1.5- 2.7) x 10^-9 Msun/yr. We present a theoretical modeling analysis of the diskin HD 169142 using Monte-Carlo radiative transfer simulation software toexplore the conditions and perhaps signs of planetary formation in ourcollection of 24 years of observations. We find that shifting the outer edge (r= 0.3 AU) of the inner disk by 0.05 AU toward the star (in simulation ofaccretion and/or sculpting by forming planets) successfully reproduces theshift in NIR flux. We establish that the ~40-70 AU dark ring imaged in the NIRby Quanz et al. (2013) and Momose et al. (2013) and at 7 mm by Osorio et al.(2014) may be reproduced with a 30% scaled density profile throughout theregion, strengthening the link to this structure being dynamically cleared byone or more planetary mass bodies.

Variability of Disk Emission in Pre-Main Sequence and Related Stars. III. Exploring Structural Changes in the Pre-transitional Disk in HD 169142