1,721,037 research outputs found
Weak reprocessed features in the broad-line radio galaxy 3C 382
No full textWe present a detailed X-ray study of the broad-line radio galaxy 3C 382, observed with the BeppoSAX satellite in a very bright state. The continuum emission is well modeled with a power law that steepens at high energies, with an e-folding energy of similar to 120 keV. At soft energies a clear excess of emission is detected, which cannot be explained solely by the extended thermal halo seen in a ROSAT / HRI image. A second, more intense soft X-ray component, possibly related to an accretion disk, is required by the data. Both a reflection component (Omega /2 pi = 0.3) and an iron line (EW similar to 50) are detected at levels much weaker than in Seyfert galaxies, suggesting a common origin. Combining our measurements with results from the literature we find that the iron line has remained approximately constant over 9 yr while the continuum varied by a factor of 5. Thus, the fluorescent gas does not respond promptly to the variations of the X-ray continuum, suggesting that the reprocessing site is located away from the X-ray continuum, likely at parsec distances. While the continuum shape indicates that X-rays derive from a thermal Comptonization process, the weakness of other spectral features implies that either the upper layers of the optically thick accretion disk are completely ionized or the corona above the disk is outflowing with mildly relativistic velocity
The Hubble Space Telescope survey of BL lacertae objects. I. Surface brightness profiles, magnitudes, and radii of host galaxies
No full text
Reprocessing and variable cold absorption in the broad-line radio galaxy 3C 390.3
No full textA BeppoSAX observation of the Broad Line Radio-Galaxy 3C 390.3 is reported. For the first time, both the K-alpha iron line and a strong reflection hump, produced by the illumination of the primary X-ray emission on cold matter, are detected in this source. The 0.1-100 keV continuum is modeled by an absorbed hard power law (Gamma similar to 1.8) reflected at high energies by material with a fairly large covering factor (Omega/2 pi similar or equal to 1). The iron line is centered at similar or equal to 6.4 keV (rest frame), is intrinsically narrow (sigma = 73+/-(207)(73) eV), and has an equivalent width of similar or equal to 140 eV. We discuss the results in the context of current models for AGNs and suggest that the primary X-ray power law continuum is probably produced by a hot inner flow, while the reprocessed radiation comes from an outer cold thin disk, and/or from a thick torus at even larger radii. Further observations with BeppoSAX could distinguish between the latter two cases. Beamed radiation associated to the radio jet is unlikely to contribute significantly to the X-ray emission. Finally an historical study of the column density NH, also reported here, shows that the absorption along the Line of sight changes in time. The N-H time variability, which is not correlated with that of the primary continuum, seems to imply variations of the geometry of the absorber rather than Variations in the ionization state of the gas
ROSAT, ASCA, and OSSE observations of the broad-line radio galaxy 3C 120
No full textWe present simultaneous observations of the superluminal radio galaxy 3C 120 performed with the ASCA and GRO (OSSE) satellites in 1994 February-March, as well as an analysis of all the ROSAT archival data. The ASCA spectrum of this object can be described by an absorbed (N-H = 1.6 x 10(21) cm(-2)) power law with a photon index of T-ASCA = 2 and a very broad (sigma > 0.8 keV) intense iron line (EW > 400 eV) at similar to 6 keV. The combined ASCA-OSSE data do not exclude the presence of a narrower (sigma = 0.4 keV) and less intense (EW < 300 eV) iron line plus a hard component, corresponding either to reflection from an accretion disk or to a flatter power law from a jet. However, a single power law plus broad Fe line is preferred from a statistical point of view by the ASCA data. The ROSAT data yield a column density in excess of the Galactic value. The spectral slopes, ranging from Gamma(ROSAT) = 2.5 to 3.3, are steeper than that measured by ASCA, suggesting the presence of a soft excess. The 0.1-2 keV power-law slope is variable and softer at higher intensity. These results show that the combined soft and hard X-ray spectrum of 3C 120 is rather complex. The intrinsic absorption, the soft excess, and the iron line indicate that the X-ray emission from this blazar-like radio galaxy is dominated by a Seyfert-like component, at least in the 0.1-10 keV energy band. The jet contribution, if present, becomes important only at higher energies
The Hubble Space Telescope survey of BL Lacertae objects: Gravitational lens candidates and other unusual sources
No full textBright radio galaxies with BeppoSAX
No full textAlthough a strong similarity between radio galaxies and Seyferts has been pointed out with ASCA, some radio galaxies do not seem to fit very well the cold thin accretion disk model proposed for radio quiet AGN. The BeppoSAX observations of 3C390.3 and Centaurus A show that cold material responsible for the photon reprocessing is present in these sources but not necessarily near to the primary X-ray source. The featureless spectrum of the broad line radio galaxy 3C111 indicates the absence of cold material near the X-ray source or, alternatively, the presence of a strong jet X-ray component
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