Charged neutron stars and observational tests of a dark force weaker than gravity

Understand

We discuss the possibility of exploring an unbroken U(1) gauge interaction in the dark sector by means of gravitational waves.

• Dark sector states charged under the dark force can give a macroscopic charge to astronomical bodies.
• Yet the requirement of having gravitationally bounded stars limits this charge to negligible values if the force has a sizeable strength.
• Gravitational tests are only possible if the dark force is weaker than gravity.