RX J2217.9-5941: A highly X-ray variable Narrow-Line Seyfert1 galaxy

We report the discovery of a highly X-ray variable AGN, RX J2217.9-5941. Th is object uas bright during the ROSAT All-Sky Survey (RASS), during which a decrease in the count 1 ai;e by a factor of 12 was observed. It was found to be much fainter in follow-up HRI observations and is therefore an X-ray transient AGN candidate. On long time scales of years. its count rate decea sed by a factor of about 30 between the RASS and the ROSAT HRI and ASCA obs ervations in 1998. Analysis of the ASCA data, complicated by source confusi on and poor statistics, tentatively indicates: a steep spectrum in the fain t state, There is no evidence for variability among 5 optical observations of the object obtained between 1992 and 1998, We discuss the variability of RX J2217.9-5941 and its possible X-ray transient nature.