The Spectral Energy Distributions of Narrow-line Seyfert 1 Galaxies

Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLS1s reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of behavior observed, illustrating with a comparison of the XMM-Newton and HST data from the NLS1s 1H0707-495 and TonS180, and discuss how the spectral energy distribution may causally link the UV and X-ray properties.