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Discovery of Associated Absorption Lines in an X-Ray Warm Absorber:[ITAL]Hubble Space Telescope[/ITAL] Observations of PG 1114+445
(IOP Publishing, 1998)
The unified picture of X-ray/UV absorbers offers a unique opportunity to probe the nuclear environment of active galactic nuclei. To test the unified absorber scenario and to understand the physical properties of the ...
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. II - an intensive study of NGC 5548 at optical wavelengths
(IOP Publishing, 1991)
A large, international program of ground-based optical spectroscopy and photometry of the variable Seyfert 1 galaxy NGC 5548 undertaken in support of an IUE monitoring campaign is described. This contribution presents the ...
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. III - Further observations of NGC 5548 at optical wavelengths
(IOP Publishing, 1992)
The results of the second year of an intensive ground-based spectroscopic and photometric study of variability in the bright Seyfert 1 galaxy NGC 5548 are reported in order to study the relationship between continuum and ...
The Cambridge-Cambridge ROSAT Serendipity Survey -- V. Catalogue and optical identifications
(Oxford University Press (OUP), 1997)
We report the results of a medium-depth X-ray survey of 20 ROSAT Position Sensitive Proportional Counter (PSPC) fields. 123 X-ray sources were detected down to a flux limit of S(0.5–2 keV) > 2 × 10−14 erg s−1 cm−2 lying ...
X-ray absorption toward the red quasar 3C 212
(IOP Publishing, 1994)
A Roentgen Satellite (ROSAT) X-ray spectrum of the z = 1.049 'red quasar' 3C 212 has a strong low-energy cutoff. The spectrum can be fitted with a power law (of energy index 1.4(+0.8, -0.6) with low-energy photoelectric ...
X-ray and optical continua of active galactic nuclei with extreme Fe II emission
(Oxford University Press (OUP), 1997)
We present the results of ROSAT PSPC observations of three active galactic nuclei (AGN) with extremely strong Fe ii emission (PHL 1092, IRAS 07598 + 6508 and I Zw 1) and two AGN with very weak Fe ii emission (Mrk 10 and ...
The Complex Optical to Soft X-Ray Spectrum of Low-Redshift Radio-quiet Quasars. II. Comparison with Free-Free and Accretion Disk Models
(IOP Publishing, 1995)
We compare the optical to soft X-ray spectral energy distributions (SEDs) of a sample of bright low-redshift (0.048 < z < 0.155), radio-quiet quasars, with a range of thermal models which have been proposed to explain the ...
The Cambridge-Cambridge ROSAT Serendipity Survey -- IV. The X-ray properties
(Oxford University Press (OUP), 1997)
We present a detailed X-ray spectral analysis in the 0.1–2.4 keV ROSAT band of a complete sample of X-ray-selected AGN using the 80 AGNs in the Cambridge-Cambridge ROSAT Serendipity Survey (68 QSOs and 12 narrow-emission-line ...
Testing Models for the Quasar Big Blue Bump via Color-Color Diagrams
(IOP Publishing, 1995)
We discuss several models of quasar big blue bump emission in color-color and color-luminosity diagrams. We define several broad passbands: IR (0.8-1.6 μm), VIS (4000-8000 Å), UV (1000-2000 Å), UV1 (1400-2000 Å) and UV2 ...
Absorption in X-ray spectra of high-redshift quasars
(IOP Publishing, 1994)
We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are ...