Aims:We investigate the statistical properties of the extreme events of the solar cycle as measured by the sunspot number. Methods: The recent advances in the methodology of the theory of extreme values are applied to the maximal extremes of the time series of sunspots. We focus on the extreme events that exceed a carefully chosen threshold and a

We study the emergence of magnetic flux at very small spatial scales (less than 2") in the quiet-Sun internetwork. To this aim, a time series of spectropolarimetric maps was taken at disk center using the instrument SP/SOT on board Hinode. The LTE inversion of the full Stokes vector measured in the Fe I 6301 and 6302 Å lines allows us to retrieve

Aims:We aim to identify the nature of several objects previously catalogued as ultra-luminous X-ray (ULX) source candidates. Methods: Long-slit spectroscopy of the optical counterparts has been carried out. Results: The eight objects are at higher redshift than their putative parent galaxies. Conclusions: It is found that these eight previously

Transiting extrasolar planets constitute only a small fraction of the range of stellar systems found to display periodic, shallow dimmings in wide-field surveys employing small-aperture camera arrays. Here we present an efficient selection strategy for follow-up observations, derived from analysis of the light curves of a sample of 67 SuperWASP

Aims:Motivated by recent observations of oscillations in coronal arcades, we investigate analytically the influence of longitudinal structuring on the modes of oscillation of a straight coronal loop arcade. As a first step towards more complicated models, we use a simple structure to obtain analytical solutions. Methods: A partial differential

Aims:We searched for infrared flux excesses of planetary-mass candidates in the σ Orionis cluster (~3 Myr, ~350 pc). Methods: Using IJHKs data from the literature and the [3.6], [4.5], [5.8], and [8.0] IRAC images of the σ Orionis cluster from the Spitzer Space Telescope public archives, we constructed colour-colour diagrams and spectral energy