Monday

Double neutron stars (DNS) prior to merger due to gravitational wave decay will be sufficiently close so that their magnetospheres interact and possibly release short duration transient emission. We present solutions of axisymmetric pulsar magnetospheres located within a uniform magnetic field. We find that the structure of the magnetosphere is drastically modified because of the external magnetic field leading to an increase of the fraction of open magnetic field lines and a current sheet of finite size depending on the ratio of the magnetic field strength and the rotational frequency. If the external magnetic field is sufficiently strong and antiparallel to the dipole, it leads to solutions where the pulsar magnetic field is fully enclosed within an ellipsoidal surface. Such configuration may appear in a double neutron star (DNS) where one of the components is a slowly rotating, strongly magnetized pulsar and the other one a weakly magnetized millisecond pulsar. The twisted field lines from the millisecond pulsar could form an asymmetric wind. More dramatic consequences could appear closer to merger: there, the neutron star with the weaker magnetic field may undergo a stage where it alternates between an open and a fully enclosed magnetosphere releasing up 10^37 erg. Under favourable combinations of magnetic fields DNSs can spend up to a thousand years in the coupled phase. Potential observational signatures of this interaction are discussed including the possibility of powering recurring fast radio bursts.