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The extreme high frequency peaked BL Lac 1517+656
Volker Beckmann, Norbert Bade, Olaf Wucknitz
We present optical spectroscopy data that allowed a measurement of the redshift for the X-ray selected BL Lacertae object 1517+656. With a redshift of z = 0.702 this object has an…
Optical observations of the black hole candidate XTE J1550-564 during the Sep/Oct 1998 outburst
C. Sanchez-Fernandez, A. J. Castro-Tirado, H. W. Duerbeck +11
We report here optical observations during the September/October 1998 outburst of the black hole candidate XTE J1550-564. CCD photometry was obtained for the optical counterpart wi…
X-ray luminous radio-quiet high redshift QSOs in the ROSAT All-Sky Survey
Xue-Bing Wu, Norbert Bade, Volker Beckmann
X-ray luminous radio-quiet high redshift QSOs are rare and can be used for the investigation of several important astronomical questions. We have conducted a large area survey for…