Variability of Active Galactic Nuclei from the Optical to X-ray Regions

Some progress in understanding AGN variability is reviewed. Reprocessing of X-ray radiation to produce significant amounts of longer-wavelength continua seems to be ruled out. In some objects where there has been correlated X-ray and optical variability, the amplitude of the optical variability has exceeded the amplitude of X-ray variability. We suggest that accelerated particles striking material could be linking X-ray and optical variability (as in activity in the solar chromosphere). Beaming effects could be significant in all types of AGN. The diversity in optical/X-ray relationships at different times in the same object, and between different objects, might be explained by changes in geometry and directions of motion relative to our line of sight. Linear shot-noise models of the variability are ruled out; instead there must be large-scale organization of variability. Variability occurs on light-crossing timescales rather than viscous timescales and this probably rules out the standard Shakura-Sunyaev accretion disk. Radio-loud and radio-quiet AGNs have similar continuum shapes and similar variability properties. This suggests similar continuum origins and variability mechanisms. Despite their extreme X-ray variability, narrow-line Seyfert 1s (NLS1s) do not show extreme optical variability.Comment: Invited talk given at Euro Asian Astronomical Society meeting in Moscow, June 2002. 20 pages, 4 figures. References update

The relative wavelength independence of IR lags in active galactic nuclei: implications for the distribution of the hot dust

We show that, contrary to simple predictions, most AGNs show at best only a small increase of lags in the J, H, K, and L bands with increasing wavelength. We suggest that a possible cause of this near simultaneity of the variability from the near-IR to the mid-IR is that the hot dust is in a hollow bi-conical outflow of which we only see the near side. Although most AGNs show near simultaneity of IR variability, there was at least one epoch when NGC 4151 showed the sharply increasing IR lag with the increase of the wavelength. This behaviour might also be present in GQ Comae. We discuss these results briefly. The relative wavelength independence of IR lags simplifies the use of IR lags for estimating cosmological parameters.Comment: 6 pages, 5 figures, for the Odessa Astronomical Publicatio

The Effects of High Liquid Water Content on Thunderstorm Charging

Charge transfer to a riming graupel target during interactions with ice crystals has been investigated in the laboratory. When liquid water contents sufficiently high to cause wet growth are achieved, the charge transfer falls to values which are insignificant to thunderstorm electrification. The implications of this null result to a recent analysis of thunderstorm-charging processes by Wiliams et al. (1991) are discussed

Interpretation of IR variability of AGNs in the hollow bi-conical dust outflow model

We show that, contrary to simple predictions, most AGNs show at best only a small increase of lags with increasing wavelength in the J, H, K, and L bands . We suggest that a possible cause of this near simultaneity of the variability from the near-IR to the mid-IR is that the hot dust is in a hollow bi-conical outflow of which we preferentially see the near side. In the proposed model sublimation or re-creation of dust (with some delay relative luminosity variations) along our line of sight in the hollow cone could be a factor in explaining the changing look phenomenon of AGNs. Variations in the dust obscuration can help explain changes in relationship of H-beta time delay on Luv variability. The relative wavelength independence of IR lags simplifies the use of IR lags for estimating cosmological parameters.Comment: 5 pages, 1 figure, IAU Sym 37

Spectrophotometry of 2 complete samples of flat radio spectrum quasars

Spectrophotometry of two complete samples of flat-spectrum radio quasars show that for these objects there is a strong correlation between the equivalent width of the CIV wavelength 1550 emission line and the luminosity of the underlying continuum. Assuming Friedmann cosmologies, the scatter in this correlation is a minimum for q (sub o) is approximately 1. Alternatively, luminosity evolution can be invoked to give compact distributions for q (sub o) is approximately 0 models. A sample of Seyfert galaxies observed with IUE shows that despite some dispersion the average equivalent width of CIV wavelength 1550 in Seyfert galaxies is independent of the underlying continuum luminosity. New redshifts for 4 quasars are given

First-principles prediction of a decagonal quasicrystal containing boron

We interpret experimentally known B-Mg-Ru crystals as quasicrystal approximants. These approximant structures imply a deterministic decoration of tiles by atoms that can be extended quasiperiodically. Experimentally observed structural disorder corresponds to phason (tile flip) fluctuations. First-principles total energy calculations reveal that many distinct tilings lie close to stability at low temperatures. Transfer matrix calculations based on these energies suggest a phase transition from a crystalline state at low temperatures to a high temperature state characterized by tile fluctuations. We predict B$_{38}$Mg$_{17}$Ru$_{45}$ forms a decagonal quasicrystal that is metastable at low temperatures and may be thermodynamically stable at high temperatures.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Reverberation Mapping Results from MDM Observatory

We present results from a multi-month reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from around the world. We measure broad line region (BLR) radii and black hole masses for six objects. A velocity-resolved analysis of the H_beta response shows the presence of diverse kinematic signatures in the BLR.Comment: To appear in the Proceedings of the IAU Symposium No. 267: Co-Evolution of Central Black Holes and Galaxies, Rio de Janeiro, 200