Using the Illustris cosmological simulation, we investigate the origin of fossil groups in the {M}200={10}13{--}{10}13.5 {M}⊙ {h}-1 mass regime. We examine the...
Are high polarization quasars and BL Lacertae objects really different? A study of the optical spectral properties.
The continuum and emission lines properties of a sample of 73 blazars is studied, investigating differences and similarities among normal low-polarization...
Are isolated planetary-mass objects really isolated?. A brown dwarf-exoplanet system candidate in the σ Orionis cluster
Context: .Free-floating planetary-mass objects have masses below the deuterium burning mass limit at about 13 Jupiter masses, and have mostly been found in very...
Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?
We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2 Jy radio galaxies at intermediate redshifts (0.05...
Are Q-stars a serious threat for stellar-mass black hole candidates?
We examine the status of the threat posed to stellar-mass black hole candidates by the possible existence of Q-stars (compact objects with an exotic equation of...
Are small-scale magnetic concentrations spatially coincident with bright facular points?
The usually assumed identification of small-scale magnetic concentrations with bright facular or network points on the photosphere is observationally checked by...
We have studied the statistical properties of the energy of individual acoustic modes, extracted from 310 days of GOLF data near the solar minimum. The...
Are solar chromospheric fibrils tracing the magnetic field?
Fibrils are thin elongated features visible in the solar chromosphere in and around magnetized regions. Because of their visual appearance, they have been...
Are the small active regions related to the decay of the larger ones?
To investigate the location of the actual limit for the different behavior, the active regions with fluxes greater than 10 to the 20 Mx are investigated. After...