24 research outputs found
Long term variability of the Broad Emission Line profiles in AGN
Results of a long-term monitoring ( years) of the broad line and
continuum fluxes of three Active Galactic Nuclei (AGN), 3C 390.3, NGC 4151, and
NGC 5548, are presented. We analyze the H and H profile
variations during the monitoring period and study different details (as bumps,
absorption bands) which can indicate structural changes in the Broad Line
Region (BLR). The BLR dimensions are estimated using the time lags between the
continuum and the broad lines flux variations. We find that in the case of 3C
390.3 and NGC 5548 a disk geometry can explain both the broad line profiles and
their flux variations, while the BLR of NGC 4151 seems more complex and is
probably composed of two or three kinematically different regions.Comment: 10 pages, 9 figures, New Astronomy Reviews (Proceeding of 7th
SCSLSA), in pres
Electroweak Phase Transitions in left-right symmetric models
We study the finite-temperature effective potential of minimal left-right
symmetric models containing a bidoublet and two triplets in the scalar sector.
We perform a numerical analysis of the parameter space compatible with the
requirement that baryon asymmetry is not washed out by sphaleron processes
after the electroweak phase transition. We find that the spectrum of scalar
particles for these acceptable cases is consistent with present experimental
bounds.Comment: 20 pages, 5 figures (included), some comments added, typos corrected
and new references included. Final version to appear in PR
Wind-Blown Bubbles around Evolved Stars
Most stars will experience episodes of substantial mass loss at some point in
their lives. For very massive stars, mass loss dominates their evolution,
although the mass loss rates are not known exactly, particularly once the star
has left the main sequence. Direct observations of the stellar winds of massive
stars can give information on the current mass-loss rates, while studies of the
ring nebulae and HI shells that surround many Wolf-Rayet (WR) and luminous blue
variable (LBV) stars provide information on the previous mass-loss history. The
evolution of the most massive stars, (M > 25 solar masses), essentially follows
the sequence O star to LBV or red supergiant (RSG) to WR star to supernova. For
stars of mass less than 25 solar masses there is no final WR stage. During the
main sequence and WR stages, the mass loss takes the form of highly supersonic
stellar winds, which blow bubbles in the interstellar and circumstellar medium.
In this way, the mechanical luminosity of the stellar wind is converted into
kinetic energy of the swept-up ambient material, which is important for the
dynamics of the interstellar medium. In this review article, analytic and
numerical models are used to describe the hydrodynamics and energetics of
wind-blown bubbles. A brief review of observations of bubbles is given, and the
degree to which theory is supported by observations is discussed.Comment: To be published as a chapter in 'Diffuse Matter from Star Forming
Regions to Active Galaxies' - A volume Honouring John Dyson. Eds. T. W.
Harquist, J. M. Pittard and S. A. E. G. Falle. 22 pages, 12 figure
Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XIV. Intensive Optical Spectrophotometric Observations of NGC 7469
We present results of an intensive 2 month campaign of ground-based spectrophotometric monitoring of the Seyfert 1 galaxy NGC 7469, with a temporal resolution [approximately less than]1 day. The broad Hα and Hβ emission lines respond to ~35% ultraviolet continuum variations with an amplitude of ~10% and time delays of 5.6±1.3 days and 5.4±0.8 days, respectively. We interpret this as evidence of variable Balmer line gas ~5-6 light days from the central source in this object, widely believed to be a supermassive black hole. The virial mass of the central source implied by line widths and time delays is ~106-107 M◉ Concomitantly, we find evidence for wavelength-dependent continuum time delays : optical continuum variations lag those at 1315 Å by 1.0±0.3 days at 4865 Å to 1.5±0.7 days at 6962 Å. . This suggests a stratified continuum reprocessing region extending several light days from the central source, possibly an accretion disk
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. VII. Variability of the optical spectrum of NGC 5548 over 4 years
We report on the results of a continuation of a large monitoring program of optical spectroscopy of the Seyfert 1 galaxy NGC 5548. The new observations presented here were obtained between 1990 December and 1992 October, and extend the existing database to nearly 1400 days, dating back to 1988 December. The continuum variations are generally smooth and well-resolved, except during the third year of this 4 year project, when the variations were apparently more rapid and of lower amplitude than observed at other times. The broad Hβ emission line is found to vary in response to the continuum variations with a lag of about 18 days, but with some changes from year to year. The Hβ transfer functions for each of the 4 yr and for the entire 4 yr database are derived by using a maximum entropy method