Uncovering the Primary X-Ray Emission and Possible Starburst Component in the Polarized NLS1 Mrk 1239

X-ray observations of the unique NLS1 galaxy Mrk 1239 spanning 18 yr are presented. Data from XMM-Newton, Suzaku, Swift, and NuSTAR are combined to obtain a broadband, multi-epoch view of the source. There is spectral variability in the 3–10 keV band over the 18 yr. An analysis of the NuSTAR and Suzaku lightcurves also suggests rapid variability in the 3–10  keV band, which is consistent with the NLS1 definition of the source. However, no variability is seen below 3 keV on any timescale. Two distinct physical models are adopted to describe the data above and below $\sim 3keV$. The low energies are dominated by a hot, diffuse gas likely associated with a starburst component at large physical scales. The higher-energy spectrum is dominated by emission from the central region. Ionized partial covering and relativistic blurred reflection are considered for the central region emission. In both cases, the underlying power law has a photon index of Γ ∼ 2.3–2.4. A distant reflector, a neutral partial covering component with a covering fraction near ∼1, and contributions from starburst emission are always required. The blurred reflection model requires a reflection-dominated spectrum, which may be at odds with the low emissivity index and radio properties of the source. By contrast, the two absorption components required in the ionized partial covering model may correspond to the two distinct regions of polarization observed in the optical. Regardless of the physical model, spectral changes between epochs are driven by the absorption components—and on short timescales, by intrinsic active galactic nucleus variability.