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CaII Kgrains, i.e., intermittent, short-lived (about 1 minute), periodic (2-4 minutes), pointlike chromospheric brightenings, are considered to be the manifestations of acoustic waves propagating upward from the solar surface and developing into shocks in the chromosphere. After the simulations of Carlsson and Stein, we know that hot shocked gas moving upward interacting with the downflowing chromospheric gas (falling down after having been displaced upward by a previous shock) nicely reproduces the spectral features of the CaII K profiles observed in such grains, i.e., a narrowband emissionAdvertised on
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Accretion disks around compact objects are expected to enter an unstable phase at high luminosity. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole. Although there are hints of these cycles in a few isolated cases, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle. HereAdvertised on
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Despite the fundamental role that dark matter halos play in our theoretical understanding of galaxy formation and evolution, the interplay between galaxies and their host dark matter halos remains highly debated from an observational perspective. This lack of conclusive observational evidence ultimately arises from the inherent difficulty of reliably measuring dark matter (halo) properties. Based on detailed dynamical modeling of nearby galaxies, in this work we proposed a novel observational approach to quantify the potential effect that dark matter halos may have in modulating galaxyAdvertised on