Timing properties of the narrow-line Seyfert 1 galaxy IRAS 13224-3809 
observed by CHANDRA

Pfefferkorn F. and Boller Th.$^1$

$^1$Max-Planck-Institut f\"ur extraterrestrische Physik,
Giessenbachstra{\ss}e, Postfach 1312, 85741 Garching, Germany


The narrow-line Seyfert 1 galaxy (NLS1) IRAS~13224-3809 was observed
with the CHANDRA High Resolution Camera (HRC-I) for 12 ksec on the 2nd
of February 2000. The source was proposed for CHANDRA observations to
precisely determine the X-ray centroid position and to investigate the
timing properties. The position derived from the CHANDRA observation
confirms the strongly variable X-ray emission (Boller et al., 1997)
associated with IRAS~13224-3809. Most interestingly, the CHANDRA HRC-I
light curve shows quasi-periodic oscillations. The strongest signal is
found at 2500 seconds. Obscurations by Compton-thick matter might
provide a plausible explanation for the quasi-periodic oscillations.