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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 ...
EXOSAT X-ray spectra of quasars
(IOP Publishing, 1992)
Measurements of the X-ray spectra in the 0.1-10-keV energy range for 17 AGN (mostly PG quasars) using the Exosat Low and Medium Energy arrays are presented. For each object, the best-fit spectral parameters in the medium-energy ...
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 ...
Multiwavelength Observations of Short-Timescale Variability in NGC 4151. I. Ultraviolet Observations
(IOP Publishing, 1996)
We present the results of an intensive ultraviolet monitoring campaign on the Seyfert I galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC ...
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 ...
Optical Detection of the Hidden Nuclear Engine in NGC 4258
(IOP Publishing, 1995)
The subparsec masing disk recently found to be orbiting a central mass of ~3.6 × 107 M☉ in the Seyfert/LINER galaxy NGC 4258 (Miyoshi and coworkers) provides the most compelling evidence to date for the existence of a ...
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 ...