We report optical and near-infrared follow-up observations of GRB 011121. We discover a break in the afterglow light curve after 1.3 days, which implies an initial jet opening angle of ˜9°. The jet origin of this break is supported by the achromatic spectral energy distribution. During later phases, GRB 011121 shows significant excess emission

We show that photoabsorption by fullerenes and buckyonions (multishell fullerenes) explain the shape, width, and peak energy of the most prominent feature of interstellar absorption, the UV bump at 2175 Å. The predicted optical and near-infrared transitions for these molecules also offer a potential explanation for the long-standing problem of the

Proof corrections were not carried faithfully to the printed version of this paper, resulting in an error in the text below equation (12). The equation en=∇A/∇A=-ez should read en=∇A/∇A; i.e., the final equivalence should be omitted. The Press sincerely regrets this error.

As a result of an error at the Press, the second panel of Figure 9 was repeated twice in the top row of the printed, black-and-white version of this figure, and the first panel was omitted. This error appears in the print edition and the PDF and postscript (PS) versions available with the electronic edition of the journal, although the panels of

A comparison is made of the light curves and and dust production of the initial target for the ROSETTA mission, 46P/Wirtanen and the new target 67P/Churyumov-Gerasimenko during their recent 2002/2003 apparition. The study is based on amateur CCD monitoring using a standardised method to produce consistent photometry in Johnson-Kron-Cousins system

La tesis está dividido en dos partes, si bien muy relacionadas. En la primera parte se desarrolla y aplica un método para detectar sistemas de galaxias en el óptico 0.2