2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/970We present a study of the X-ray properties of several NLS1 galaxies, focusing on their warm absorbers. In the first part, we discuss properties of dusty and dust-free warm absorbers in NLS1s, and study their potential contribution to high-ionization optical iron lines. In the second part, we summarize our work on the exceptional spectral variability of the NLS1 galaxy RX J0134.3-4258 (from Gamma about -4.4 in the ROSAT all-sky survey observation, to about -2.2 in our subsequent pointed observation).Contributed talk presented at the Joint MPE,AIP,ESO workshop on NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at http://wave.xray.mpe.mpg.de/conferences/nls1-workshopAstrophysicstext