The double pulsar J0737--3039 has become an important astrophysical laboratory for testing fundamental physics. Here we demonstrate that the low measured mass of Pulsar B can be used to constrain the equation of state of neutron star matter { \em under the assumption} that it formed in an electron-capture supernova. We show that the observed orbital parameters as well as the likely evolutionary history of the system support such a hypothesis and discuss future refinements that will improve the constraints this test may provide.
Categories: astro-ph