LSP-MIST: Long Secondary Periods as Tracers of Companions Around Red Giants.

Long Secondary Periods (LSPs) in pulsating red giants remain one of the major unsolved puzzles in stellar variability. The ERC project LSP-MIST investigates whether the LSP variability may be caused by low-mass, possibly substellar companions embedded in dusty clouds, orbiting around evolved giant stars. If confirmed, this scenario would open a new way to study remnants of planetary systems in evolved stellar environments, including regions of the Milky Way and nearby galaxies that are inaccessible to classical exoplanet detection methods. The project combines large-scale photometric surveys, spectroscopic follow-up, astrometric constraints, and hydrodynamical modelling to test the binary hypothesis and understand the physical origin of the LSP variability.