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

¹ MPI für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
² MPI für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
³ Columbia Astrophysics Laboratory, 538 West 120th St., New York, NY 10027, USA
⁴ Dept. of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019, USA

Corresponding author: D. Grupe, dgrupe@xray.mpe.mpg.de

Received: 26 October 2000
Accepted: 12 January 2001

Abstract

We report the discovery of a highly X-ray variable AGN, RX J2217.9-5941. This object was bright during the ROSAT All-Sky Survey (RASS), during which a decrease in the count rate 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 decreased by a factor of about 30 between the RASS and the ROSAT HRI and ASCA observations in 1998. Analysis of the ASCA data, complicated by source confusion and poor statistics, tentatively indicates a steep spectrum in the faint 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.