Strangelet Searches from Neutron Stars, Binary Mergers, and Gamma-Ray Bursts with Current and Future Observatories

Abstract

Strange quark matter (SQM) is considered a possible true ground state of QCD at high densities. This idea motivates research on exotic compact objects and certain cosmic-ray phenomena. For instance, the remnant HESS J1731-347 contains a low-mass neutron star, about $0.77^{+0.20}_{-0.17}$ $M_\odot$ and $10.4^{+0.86}_{-0.78}$ km in radius, making it a strong candidate for a strange quark star. Other events, such as GW170817 and GRB 250702B, provide conditions that may favor the formation of strangelets. Strangelets are stable clusters of SQM, potentially created during the phase transition between the 2SC and CFL color-superconducting states. These clusters could generate monochromatic $\gamma$-ray lines in very-high-energy spectra through self-annihilation. This work analyzes the stability of strangelets, production cross-sections, and mass-to-charge ratios using QCD-based models. Data from H.E.S.S., Fermi-LAT, MAGIC-II, and CTA were used to set limits on spectral features and possible fluxes. Detecting narrow $\gamma$-ray lines will require improved instrument sensitivity. By integrating evidence from multimessenger astrophysics and dense QCD simulations, this study investigates the equations of state for compact stars and explores the potential cosmological influence of SQM.