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We present a study of the radial distribution of RR Lyrae variables, which present a range of photometric and pulsational properties, in the dwarf spheroidal galaxy Tucana. We find that the fainter RR Lyrae stars, having a shorter period, are more centrally concentrated than the more luminous, longer period RR Lyrae variables. Through comparison

Coordinates, redshifts, SDSS (ugriz) and 2MASS (JHK) photometry, IRAC and MIPS fluxes for the 278 SWIRE/SDSS quasars in the SWIRE EN1, EN2 and Lockman fields, ordered by RA. (2 data files).

Coordinates, redshifts, SDSS (ugriz) and 2MASS (JHK) photometry, IRAC and MIPS fluxes for the 278 SWIRE/SDSS quasars in the SWIRE EN1, EN2 and Lockman fields, ordered by RA. (2 data files).

We present results from Hubble Space Telescope ultraviolet spectroscopy of the massive X-ray and black hole binary system, HD 226868 = Cyg X-1. The spectra were obtained at both orbital conjunction phases in 2002 and 2003, when the system was in the X-ray high/soft state. The UV stellar wind lines suffer large reductions in absorption strength when

Context: A good correlation has been found in star-forming galaxies, between the soft X-ray and the far infrared or radio luminosities. The soft X-ray emission in star-forming regions is driven by the heating of the diffuse interstellar medium, and by the mechanical energy released by stellar winds and supernova explosions, both directly linked to