We show that elementary aligned electromagnetic excitations of black holes, as coming from exact Kerr-Schild solutions, represent light-like beams pulses which have a very strong back reaction on the metric and change the topology of the horizon. Based on York's proposal, that elementary deformations of the BH horizon are related with elementary

Angular momentum exchange between a bar and a massive halo is thought to be responsible for producing strong bars in disk galaxies (Athanassoula, 2003), while gas transport to the center is believed to weaken or even dissolve bars (Bournaud and Combes 2002). We are carrying out a systematic survey of early-type disk galaxies with the main emphasis

We present an analysis of the second solar spectrum, as plotted in graphical form in the three volumes of the atlas “The Second Solar Spectrum”, in the wavelength range between 3160 Å and 6995 Å. All the strongest positive linear polarization signals produced by atomic spectral lines are identified, and their amplitudes are listed, along with the

We report new spectroscopic and photometric observations of the parent stars of the recently discovered transiting planets TrES-3 and TrES-4. A detailed abundance analysis based on high-resolution spectra yields [Fe/H] = -0.19 ± 0.08, T eff = 5650 ± 75 K, and log g = 4.4 ± 0.1 for TrES-3, and [Fe/H] = +0.14 ± 0.09, T eff = 6200 ± 75 K, and log g =

Using the Wide Field Imager (WFI) at the ESO 2.2 m telescope at La Silla and the CPAPIR camera at the CTIO 1.5 m telescope at Cerro Tololo, we have performed an extensive, multiband photometric survey of the open cluster IC 2391 (D~146 pc, age~50 Myr, solar metallicity). Here we present the results from our photometric survey and from a

We have analyzed the X-ray lightcurve of the star CI Cam, the optical counterpart of the X-ray transient XTE J0421+56 using data from XMM-Newton. Our motivation is based on evidence from ground based optical interferometry from the Keck and IOTA observatories which suggests that the dust surrounding CI CAM has a taurus morphology rather than a