Birth accelerations of neutron stars

Abstract

We suggest that neutron stars experienced at birth three related physical changes, which may originate in magneto-rotational instabilities: (i) an increase in period from the initial value P_0 to the current value P_s, implying a change of rotational energy \Delta E_rot; (ii) an exponential decay of its magnetic field from the initial value B_0 to the current surface value B_s, implying a change of radiative energy \Delta E_rad; and (iii) an increase of space velocity from the initial value v_0 to the current value v, implying a change of kinetic energy \Delta E_kin. These changes are assumed to be connected by \Delta E_rad + \Delta E_kin =\Delta E_rot. This means that the radiation loss and increase of kinetic energy are both at the expense of a rotational energy loss. It is shown that this energy conversion occurs during times of order of 10^(-4) s if the neutron stars are born with magnetic fields in the range of 10^(15)-10^(16) G and initial periods in range 1-20 ms. It is shown that the birth accelerations of neutron stars are of the order of 10^(8) g.