La presencia de estructura espiral en galaxias (incluso antes de saber que las nebulosas eran objetos realmente extragalácticos) es uno de los temas que más interés ha despertado en la Astronomía. La teoría más famosa enunciada en los años 60 para explicar la presencia de esta estructura, la teoría de las ondas de densidad, no ha sido aún

We have computed the photometric magnitudes of rotating atmospheres-based on the simple model of Collins-for a grid suitable for main-sequence and slightly evolved stars of spectral type A0 to F5. A gravity-darkening law valid for radiative and convective envelopes has been considered. The general results are given as magnitude differences between

We present the results of a study of the star formation rates (SFRs) of a sample of disk galaxies in nearby compact groups compared with the SFRs of a sample of field galaxies. For this purpose, Hα luminosities and equivalent widths were derived for the galaxies of our sample. A direct comparison of the equivalent widths and Hα luminosities

Ambiguity is shown in the context of the differential calculus of several variables and with the help of the language of category theory, a way to solve it in its most general form is offered. It is also shown that this new definition is related to other well-known definitions in the literature.

We have obtained for the first time K-band infrared spectra of the soft X-ray transient V616 Mon (=A0620-00). We determine the 2-sigma upper limit to the fraction of light arising from the accretion disc to be 27 percent. The effect this has on the binary inclination, determined from modelling the infrared ellipsoidal variations is to increase it

Using CGS4 on UKIRT, we have obtained 2.00-2.45 mu m infrared spectra of a number of low-mass X-ray binaries including Sco X-1, Sco X-2 and GX1 3+1. Sco X-1 shows emission lines only, supporting our previous conclusion that the spectral type of the evolved secondary must be earlier than G5. Emission lines are also seen in the spectrum of Sco X-2