We present the method devised for inferring the Gaia stellar activity index from the analysis of the Ca II infrared triplet (IRT) at 850.03, 854.44, and 866.45 nm in the Gaia Radial Velocity Spectrometer (RVS) spectrum, an overview of the content of the chromospheric activity catalogue published in DR3, and its scientific validation. A sample of well studied PMS stars is considered to identify the regime in which the Gaia stellar activity index may be affected by mass accretion. The correlation with the amplitude of the photometric rotational modulation is also discussed. Three regimes of the chromospheric stellar activity are identified, confirming suggestions made by previous authors on much smaller chromospheric activity indices datasets. The highest stellar activity regime is associated with PMS stars and RS CVn systems, in which activity is enhanced by tidal interaction. Some evidence of a bimodal distribution in MS stars with Teff > 5000 K is also found, which defines the two other regimes, without a clear gap in between. Stars with 3500 K < Teff < 5000 K are found to be either very active PMS stars or active MS stars with a unimodal distribution in chromospheric activity. A dramatic change in the activity distribution is found for Teff < 3500 K, with a dominance of low activity stars close to the transition between partially- and fully-convective stars and a rise in activity down into the fully-convective regime. Overall, the 2M catalogue of chromospheric activity in Gaia DR3 represents a gold mine for studies related to stellar magnetic activity and mass accretion in the solar vicinity.

The ASTRI Mini-Array is an International collaboration, led by the Italian National Institute for Astrophysics (INAF), that is constructing and operating an array of nine Imaging Atmospheric Cherenkov Telescopes to study gamma-ray sources at very high energy (TeV) and perform optical stellar intensity interferometry observations.
Angular resolutions below 100 microarcsec are achievable with stellar intensity interferometry (SII), using telescopes separated by hundreds to thousands of meters baselines. At this level of resolution it turns out to be possible to reveal details on the surface and of the environment surrounding bright stars on the sky. The ASTRI Mini-Array will provide a suitable infrastructure for performing these measurements thanks to the capabilities offered by its 9 telescopes, which provide 36 simultaneous baselines over distances between 100 m and 700 m.
After providing an overview of the scientific context and motivations for performing SII science with the ASTRI Mini-Array telescopes, we present the baseline design for the ASTRI Stellar Intensity Interferometry Instrument (SI3), a fast single photon counting instrument that will be mounted on the ASTRI telescopes and dedicated to performing SII observations of bright stars.

In occasione della Notte Europea dei Ricercatori 2022, l’INAF-Osservatorio Astrofisico di Catania ha organizzato varie attività per il pubblico che si svolgeranno tra il 28 e il 30 settembre.

In occasione della Notte Europea dei Ricercatori 2022, l’INAF-Osservatorio Astrofisico di Catania ha organizzato varie attività per il pubblico che si svolgeranno tra il 29 settembre e l’1 ottobre.

The Oppenheimer-Snyder-Datt model for homogeneous dust collapse describes how a black hole forms. Considering semi-classical corrections at large curvature obtained from general relativity coupled to non-linear electrodynamics may lead to the resolution of the central singularity and the formation of a regular black hole.

Il 25 ottobre sarà possibile assistere da Catania a un'eclissi parziale di Sole, con inizio alle ore 11:36, massimo di visibilità alle 12:31 e fine alle 13:27.