Probing light scalars with dense stars

In this talk, I’ll discuss new ways of probing BSM physics using environmental effects - in particular the dense environments of stellar remnants . I‘ll present new bounds on lighter QCD axion models from white dwarves, and discuss how sourcing a light scalar may effect the properties of neutron stars. Next, I’ll summarize our analysis of the in-medium properties of the QCD axion. Finally, I‘ll show how the existence of neutron stars places constraints on relaxion models.