641 research outputs found
On the Baldwin Effect in Active Galactic Nuclei: I. The Continuum-Spectrum - Mass Relationship
We suggest that the Baldwin Effect is a result of the spectral dependence of
the line-driving ionizing continuum on the black hole mass. We derive a
relationship between the mass of the central black hole and the broad emission
line luminosity in active galactic nuclei (AGN). Assuming the UV spectrum of
AGN is emitted from an optically thick medium we find an expression for the
characteristic energy of the ``UV bump'' in terms of the observable luminosity
and emission-line width. We show empirically and analytically that the bump
energy is anti-correlated with the black-hole mass and with the continuum
luminosity. Our model reproduces the observed inverse correlation between
equivalent width and continuum luminosity, yielding an explanation of the
Baldwin effect from first principles. The model gives a good fit to the Baldwin
Effect of the CIV line for a mean quasar EUV spectrum (Zheng et al. 1997) and
for several model spectra. The model also predicts a correlation between the
strength of the Baldwin Effect (the slope of the equivalent width as a function
of luminosity) and the ionization potential, consistent with recent data.Comment: 19 pages Latex, 2 figures. Accepted for publication in the
Astrophysical Journa
Far-Ultraviolet Observations of NGC 3516 using the Hopkins Ultraviolet Telescope
We observed the Seyfert 1 galaxy NGC 3516 twice during the flight of Astro-2
using the Hopkins Ultraviolet Telescope in March 1995. Simultaneous X-ray
observations were performed with ASCA. Our far-ultraviolet spectra cover the
spectral range 820-1840 A with a resolution of 2-4 A. No significant variations
were found between the two observations. The total spectrum shows a red
continuum, , with an observed flux of at 1450 A, slightly above the historical
mean. Intrinsic absorption in Lyman is visible as well as absorption
from O~vi 1032,1038, N~v 1239,1243, Si~iv 1394,1403, and C~iv 1548,1551. The UV
absorption lines are far weaker than is usual for NGC~3516, and also lie closer
to the emission line redshift rather than showing the blueshift typical of
these lines when they are strong. The neutral hydrogen absorption, however, is
blueshifted by relative to the systemic velocity, and it is
opaque at the Lyman limit. The sharpness of the cutoff indicates a low
effective Doppler parameter, . For
the derived intrinsic column is . As in
NGC~4151, a single warm absorber cannot produce the strong absorption visible
over the wide range of observed ionization states. Matching both the UV and
X-ray absorption simultaneously requires absorbers spanning a range of
in both ionization parameter and column density.Comment: 18 pages, 4 PostScript figures, uses aaspp4.sty To appear in the
August 20, 1996, issue of The Astrophysical Journa
The rise of an ionized wind in the Narrow Line Seyfert 1 Galaxy Mrk 335 observed by XMM-Newton and HST
We present the discovery of an outflowing ionized wind in the Seyfert 1
Galaxy Mrk 335. Despite having been extensively observed by most of the largest
X-ray observatories in the last decade, this bright source was not known to
host warm absorber gas until recent XMM-Newton observations in combination with
a long-term Swift monitoring program have shown extreme flux and spectral
variability. High resolution spectra obtained by the XMM-Newton RGS detector
reveal that the wind consists of three distinct ionization components, all
outflowing at a velocity of 5000 km/s. This wind is clearly revealed when the
source is observed at an intermediate flux state (2-5e-12 ergs cm^-2 s^-1). The
analysis of multi-epoch RGS spectra allowed us to compare the absorber
properties at three very different flux states of the source. No correlation
between the warm absorber variability and the X-ray flux has been determined.
The two higher ionization components of the gas may be consistent with
photoionization equilibrium, but we can exclude this for the only ionization
component that is consistently present in all flux states (log(xi)~1.8). We
have included archival, non-simultaneous UV data from HST (FOS, STIS, COS) with
the aim of searching for any signature of absorption in this source that so far
was known for being absorption-free in the UV band. In the COS spectra obtained
a few months after the X-ray observations we found broad absorption in CIV
lines intrinsic to the AGN and blueshifted by a velocity roughly comparable to
the X-ray outflow. The global behavior of the gas in both bands can be
explained by variation of the covering factor and/or column density, possibly
due to transverse motion of absorbing clouds moving out of the line of sight at
Broad Line Region scale.Comment: 24 pages, 12 figures, ApJ accepte
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