  Recently, Weinberg proposed a scenario where Goldstone bosons may be
masquerading as fractional cosmic neutrinos. We calculate the energy loss rates
through the emission of these Goldstone bosons in a post-collapse supernova
core. Invoking the well established emissivity bound from the Supernova 1987A
observations and simulations, we find that nuclear bremsstrahlung processes can
notably impose a bound on the Goldstone boson coupling to the Standard Model
Higgs, $g$, dependent on the mass of the associated radial field, $m_r$. For
$m_r$ large enough compared with the temperature in the post-collapse supernova
core, our bound is $|g| \lesssim 0.011\, (m_r / 500~{\rm MeV})^2$, very
competitive to that derived from collider experiments.
