| Abstract: In this talk I will describe two new ideas to discover (or constrain) new hypothetical particles, such as axions and axion-like particles. In the first part of the talk, in particular, I will show how we can use luminosity curves and spectra of low-energy supernovae to detect exotic energy injection due to particles produced in the newborn proto neutron star. Then, in the second part of the talk, I will advance the clock in the life of the neutron star and propose a new analytical criterion to study the impact on new particles on the cooling of old neutron stars. |