Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...289...76w&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 289, no. 1, p. 76-82
Astronomy and Astrophysics
Astrophysics
22
Balmer Series, H Lines, Seyfert Galaxies, Transfer Functions, Variability, Cross Correlation, Kinematics, Light Curve, Maximum Entropy Method, Spectrum Analysis, Time Dependence, Velocity
Scientific paper
We use a maximum-entropy method to show that the transfer function (TF) of the broad-line region (BLR) in the Seyfert-1 galaxy NGC 3516 is time-varying. The TF decreased by nearly a factor of two over a time scale less than half a year during a monitoring campaign in 1990. We conclude that the observed time dependency is likely to be either due to variations of the spectral index of the ionizing continuum spectrum; due to a change in the number or covering fraction of broad-line clouds; due to nonlinear line response; or due to nonstationary anisotropy of the continuum source on time scales of several weeks to months. An extended continuum source could also explain the observed time-dependency. The symmetry of the time lag for variations in the red and blue wings of H-alpha indicates that the BLR kinematics is not dominated by organized radial inflow or outflow. If we assume circular orbits, the observed time lag 14 days at velocity v = 4000 km/s suggests a mass of the central object of approximately 2 x 107 solar mass. The H-alpha TF peaks away from zero delay, indicating that the H-alpa BLR is either non-spherical or inwardly emitting.
Horne Keith
Wanders Ignaz
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