We present XMM-Newton observations of Mrk 359 , the first Narrow Line Seyfert 1 galaxy discovered .
Even among NLS1s , Mrk 359 is an extreme case with extraordinarily narrow optical emission lines .
The XMM-Newton data show that Mrk 359 has a significant soft X-ray excess which displays only weak absorption and emission features .
The ( 2–10 ) keV continuum , including reflection , is flatter than the typical NLS1 , with \Gamma \approx 1.84 .
A strong emission line of equivalent width \approx 200 eV is also observed , centred near 6.4 keV .
We fit this emission with two line components of approximately equal strength : a broad iron-line from an accretion disc and a narrow , unresolved core .
The unresolved line core has an equivalent width of \approx 120 eV and is consistent with fluorescence from neutral iron in distant reprocessing gas , possibly in the form of a ‘ molecular torus ’ .
Comparison of the narrow-line strengths in Mrk 359 and other low–moderate luminosity Seyfert 1 galaxies with those in QSOs suggests that the solid angle subtended by the distant reprocessing gas decreases with increasing AGN luminosity .