The UV spectrum of the BL Lac object PKS 0521-36.
Maraschi, L.; Tanzi, E. G.; Treves, A.; Fosbury, R. A. E.; Bergeron, J.; Danziger, I. J.
Germany, France, United Kingdom, Italy
Abstract
Ultraviolet observations (1200-3000 Å) with the IUE satellite of the BL Lac object PKS 0521-36 are presented. The only emission line which appears clearly in the spectrum is Lyα, which is asymmetric with a component displaced ≡3000 km s-1 to the red. The intensity of the line and the upper limits on other lines are compared with the model calculations on QSOs and Seyfert nuclei by Kwan & Krolik. The continuous energy distribution is discussed, combining non-simultaneous observations from the ultraviolet to the infrared. The spectral range of the non-thermal source from far IR to far UV can be described by a single power law of index -1.5.