CMB distortions from superconducting cosmic strings

We reconsider the effect of electromagnetic radiation from superconducting strings on cosmic microwave background mu and y distortions and derive present (COBE-FIRAS) and future (PIXIE) constraints on the string tension, mu(s), and electric current, I. We show that absence of distortions of the cosmic microwave background in PIXIE will impose strong constraints on mu(s) and I, leaving the possibility of light strings (G mu(s) less than or similar to 10(-18)) or relatively weak currents (I less than or similar to 10 TeV).