ar X iv : a st ro - p h / 01 06 20 3 v 1 1 2 Ju n 20 01 CHANDRA observation of the narrow - line Seyfert 1 galaxy IRAS 13224 - 3809

The narrow-line Seyfert 1 galaxy (NLS1) IRAS 13224–3809 has been observed with the CHANDRA High Resolution Camera (HRC-I) for 12 ksec on February, 2, 2000. The source was proposed for CHAN-DRA observations to precisely determine the X-ray centroid position and to investigate the timing properties of the most X-ray variable Seyfert galaxy. The position derived from CHANDRA confirms that the X-ray emission is associated with IRAS 13224–3809. The CHANDRA HRC-I light curve shows indications for a possible presence of a quasi-periodic oscillation. The strongest signal is found at 2500 sec. Accretion disk instabilities may provide a plausible explanation for the quasi-periodic oscillations. 1. Introduction The narrow-line Seyfert 1 galaxy (NLS1) IRAS 13224– 3809 was the first galaxy proposed for monitoring observations with the ROSAT High Resolution Imager (HRI) (Boller et al., 1997). The most important observational fact is the detection of multiple strong flaring events during the 30 day observations. The authors found five giant-amplitude variations with the most extreme variability of a factor of 57 in 2 days. In addition, other ROSAT observations were performed, mostly with the HRI detector during 1992 and 1998. To measure the precise X-ray position, IRAS 13224–3809 has been proposed for an observation with the CHANDRA satellite.