STELLAR (innovative STructures for improvEd Light colLection in ARgon-based TPCs) goal is to boost the advancement of noble gas and liquid optical Time Projection Chamber (TPC) detectors for rare-event searches, with Dark Matter (DM) being one of the most compelling puzzles of todays fundamental physics. STELLAR plans to contribute to the development of novel amplification structures based on Micropattern Gas Detectors (MPGDs) technology incorporating wavelength-shifting materials, capable of providing improved light collection and greater operating stability at higher gains. STELLAR programme can further contribute to the understanding of underlying mechanisms of signal formation in TPCs, opening the possibility of studying the electron extraction efficiency and electroluminescence in electronegative gas mixtures. This is a specially relevant topic considering the recent technological developments observed in DM searches with the use of Negative Ion TPCs, eventually optically readout. It is anticipated that the floating wavelength-shifting Field-Assisted Gas Electron Multipliers (FAT-GEM) mechanical characteristics and performance, can be a valuable alternative to current amplification structures used in noble-element TPCs for DM searches, for instance DarkSide-LowMass, or currently planned for long baseline neutrino experiment DUNE.

Neutron stars are one of the most exciting nuclear physics laboratories in the Universe. With interior densities well above nuclear saturation density they allow us to probe conditions impossible to replicate on Earth. In addition the thermal energy of the star is negligible compared to the Fermi energy, and neutrons in the interior will be superfluid. Superfluidity affects the dynamics of the star, as now neutrons can flow relative to the ‘normal’ components of the star with little viscosity. A direct probe of such an effect is thought to come from pulsar ‘glitches’, sudden jumps in frequency observed in otherwise spinning down radio pulsars. Most theories of glitches are based on the idea that a large scale superfluid component of the star is decoupled from the spin-down of the ‘normal’ component, and its sudden re-coupling leads to a glitch. On theoretical grounds we expect this effect as a superfluid rotates by forming an array of quantised vortices, and these vortices are strongly attracted, or ‘pinned’, by ions in the neutron star crust (or superconducting flux tubes in the core). If the superfluid cannot expel ‘pinned’ vortices it cannot spin-down and builds up a lag with respect to the normal component, until hydrodynamical lift forces become strong enough to break the pinning. Despite the success of this picture in interpreting glitches, only recently has progress been made in quantitatively describing glitches with large scale hydrodynamical simulations, and statistics throughout the pulsar population with small scale quantum-mechanical simulations of vortex motion. This proposal aims to bridge the gap between these two scales by using inputs from quantum mechanical simulations to describe vortex unpinning in hydrodynamical simulations, which will include state of the art crustal physics and thermal conduction. We will thus quantitatively describe the response of the star to different kinds of glitches and obtain, for the first time, robust statistics.

Understanding the behaviour of matter in the close environments of astrophysical black holes (BH) is one of the biggest challenges of modern astrophysics. This project aims to address the fundamental problem of determining the geometry of the inflowing matter around accreting BHs. The geometrical distribution of the accreted gas is a hotly disputed and still unsolved issue. Its relevance is tightly linked to the possibility of testing the effects of General Relativity in the vicinity of BHs. Moreover, it is strictly related to other fundamental problems, in particular regarding the nature and location of the X-ray source, the mechanism responsible for the launch of the jet and the determination of the BH spin. We propose to use a novel approach known as “X-ray reverberation”. This is based on the use of innovative cross-spectral-timing techniques to study the temporal response of the accreting gas to flux variations of the central X-ray source, thus allowing distances among the different emitting regions to be constrained. This project will use the best quality data, including those provided by the ASTROSAT satellite and the NICER payload. We aim to: map the evolving geometry of the accretion flow as a function of accretion state in Galactic BH X-ray binaries; study the coupling between the accretion flow and the jet; develop theoretical spectral-timing models to explain the data; investigate how these behaviours extend to the supermassive BHs in active galactic nuclei. The candidate is an experienced researcher (ER) in the field of observational X-ray astronomy, and has pioneered the application of the X-ray reverberation method to several accreting BH systems. By exploiting the long-term and renowned expertise in theoretical modelling of accretion processes around BHs of the High Energy Astrophysics group at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Science, this research will allow the ER to emerge with new and competitive skills.