Warm absorbers in narrow-line Seyfert 1 galaxies

We present a study of the X-ray properties of several NLS1 galaxies, focusi ng on their warm absorbers. In the first part, we discuss properties of dus ty and dust-free warm absorbers in NLS1s, and study their potential contrib ution to high-ionization optical iron lines. In the second part, we summari ze our work on the exceptional spectral variability of the NLS1 galaxy RXJ0 134.3-4258 (from Gamma similar or equal to -4.4 in the ROSAT all-sky survey observation, to similar or equal to -2.2 in our subsequent pointed observa tion). (C) 2000 Elsevier Science B.V. All rights reserved.