A total of 85 UBVRI observations of BL Lac objects is presented. For most of them, an average continuum can be traced by means of well-defined color indices...

UBVRI observations of 37 QSOs are reported. The sample is considered as a good representation of the bright (V not greater than 17) quasars in the compilation...

Although ultra diffuse galaxies (UDGs) are found in large numbers in clusters of galaxies, the role of the cluster environment in shaping their low surface...

Ultra high energy photons and neutrinos are carriers of very important astrophysical information. They may be produced at the sites of cosmic ray acceleration...

We report the very bright detection of cold molecular gas with the IRAM NOEMA interferometer of the strongly lensed source WISE J132934.18+224327.3 at z = 2.04...

Aims: We try to identify ultra-cool dwarfs from the seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7) with SDSS i-z and r-z colors. We also obtain...

A number of scenarios have been proposed to explain the low velocity dispersion (and hence possible absence of dark matter) of the low surface brightness...

Using Gemini North telescope ultra-deep and high-resolution (sub-kiloparsec) K-band adaptive optics imaging of a sample of four nearby (z ~ 0.15) massive (~1011...

There is an ongoing debate as to whether ultra-diffuse galaxies are regular dwarf galaxies with low star formation or massive `failed' objects that quenched...