THE LINE OF DEATH, THE LINE OF BIRTH

We discuss classical arguments leading to the theoretical death-line of radio pulsars. We show that the consideration of an additional constraint on the one-photon e+/- pair creation in the presence of a strong magnetic field, namely that the electron energy sufficient to trigger this process does not exceed the maximal energy set by the balance between the electron acceleration and cooling rates, yields an additional death-line. This extra line is significantly flatter in the P-P plane than the usually invoked death-line and becomes relevant for short-period pulsars (P less than or similar 0.1 s). We discuss briefly the likely enhancement of the one-photon e+/- pair production rate due to the presence of rotation-induced electric fields and its influence on the slopes of both death-lines. When shifted to fit observations of millisecond pulsars, this additional death-line nearly coincides with the Hubble limit. Millisecond pulsars are thought to be recycled pulsars, spun up in binary systems, and thus cannot be subject to restrictions imposed by the finite age of the Universe. We therefore attribute their absence below the line of the Hubble limit to the presence of this additional death-line.