Low-mass X-ray binaries are interacting stellar systems in which a compact object accretes matter from a low-mass companion star, releasing most of its energy in the X-ray band. These systems play a central role in modern high-energy astrophysics, as they allow us to study accretion processes under physical conditions that cannot be reproduced elsewhere. In this talk, I will provide an overview of low-mass X-ray binaries, focusing in particular on systems hosting neutron stars, and explain why they are key targets for understanding the interplay between gravity, rotation, magnetic fields, and radiation.
Here, I will introduce accreting millisecond X-ray pulsars, a small but particularly informative subclass of neutron-star binaries, and discuss their main observational properties. I will show how their rapid variability and coherent X-ray pulsations provide a direct probe of the interaction between accretion flows and rapidly rotating, magnetised neutron stars, offering unique insight into the physics of accretion close to the neutron-star surface. These systems also represent a key evolutionary link between low-mass X-ray binaries and recycled radio millisecond pulsars, making them essential for understanding the long-term spin evolution of neutron stars and the role of accretion in shaping their observational phenomenology.
In the second part of the talk, I will present the HERMES mission concept, a distributed observatory designed to monitor the hard X-ray and soft gamma-ray sky continuously. Based on a constellation of CubeSats, HERMES can provide wide-sky coverage and localise high-energy transients in a scalable, cost-effective way. I will discuss the current status of the HERMES Pathfinders and the SpIRIT mission, and illustrate how all-sky monitoring at high energies complements targeted observations, supporting time-domain and multi-messenger studies across a broad range of astrophysical phenomena.
Aru Beri