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Astron. Astrophys. 331, 925-933 (1998)

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RX J0947.0+4721 - an extremely soft Narrow Line QSO *

K. Molthagen **, N. Bade and H.J. Wendker

Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany

Received 17 February 1997 / Accepted 22 December 1997


RX J0947.0+4721 is a newly discovered example of a narrow-line Seyfert 1 type object with a quasar level luminosity ([FORMULA]). It was detected in the ROSAT All-Sky Survey (RASS) and later in 17 pointed observations of the ROSAT Position sensitive Proportional Counter (PSPC). The optical spectrum contains strong FeII emission. We apply several spectral models to the X-ray data. A single power law fit yields a photon index [FORMULA]. Single component thermal models underestimate the flux above 1 keV. A good fit is obtained with a blackbody plus power law model ([FORMULA] fixed) modified by Galactic absorption. The best fit temperature is [FORMULA], and the flux ratio in the ROSAT band is [FORMULA]. Large count rate variations are visible with a maximum amplitude of a factor [FORMULA]. The fastest change is a drop of a factor 2.7 in 25 hours. No spectral variations were observed. The maximum and minimum luminosities in the two component model are [FORMULA] and [FORMULA], respectively. We discuss possible explanations for the extreme softness and the observed variability.

Key words: quasars: general – quasars: individual: RX J0947.0+4721, RX J0947.1+4721 – X-rays: galaxies

* Based partly on observations from the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie, Heidelberg, jointly with the Spanish National Commission for Astronomy
** present address: MPI für extraterresrtr. Physik, D-85740 Garching, Germany

Send offprint requests to: K. Molthagen, kmolt@mpe.mpg.de

© European Southern Observatory (ESO) 1998

Online publication: March 3, 1998