Eddington Values
A certain fundamental limit exists for how luminous an accreting object can be, called the Eddington luminosity.
Having a particle nature, photons can transfer momentum to other particles during scattering. Thus, any source of light exhibits an outward pressure, called simply the radiation pressure. This radiation force has already been applied in terrestrial laboratories to manipulate atoms using lasers, and may provide efficient propulsion systems on futuristic spacecraft based on solar sails.
On the grander scale of accreting neutron stars, the outward radiation force due to X-rays may become large enough to start pushing the accreted gases away. When the luminosity is so strong that it equals the inward gravity, further accretion of gases may cease. This limit is the Eddington luminosity. Since accretion fuels the production of persistent X-rays from neutron stars, the Eddington luminosity implies a maximum accretion rate, above which the resulting radiation pressure would stop further accretion. This maximum accretion rate is the Eddington accretion rate.
Numerically, in terms of the sun's mass Msun and luminosity Lsun , the Eddington luminosity is:
where M is the mass of the compact object.