Core and Conal Component Analysis of Pulsar B1237+25
  The paper provides a new analysis of this famous five-component ({\bf M}) pulsar. In addition to the star's core-active ``abnormal'' mode, we find two distinct behaviors within its ``normal'' mode, a ``quiet-normal'' mode with regular 2.8-period subpulse modulation and little or no core activity, and a ``flare-normal'' mode, where the core is regularly bright and a nearly 4-period modulation is maintained. The ``flare-normal'' mode appears to be an intermediate state between the ``quiet normal'' and ``abnormal'' behaviors. Short 5--15-pulse ``flare-normal''-mode ``bursts'' and ``quiet normal'' intervals alternate with each other quasi-periodically, making a cycle some 60--80 pulses in duration. ``Abnormal''-mode intervals are interspersed within this overall cycle, usually persisting for only a few pulses, but occasionally lasting for scores or even many hundreds of pulses. Within subsequences where the core is exceptionally quiet, the pulsar provides a nearly ``textbook'' example of a central PA sightline traverse--with a PA rate measured to be at least some 180$\deg/\deg$. On this basis it is shown that the sightline impact angle $\beta$ must be about 0.25\degr or some 5% of the outer conal beam radius. The star's core component is found to be incomplete, despite the fact that the core's full antisymmetric circularly polarized signature is present. We find that the star's PA traverse is disrupted through the action of orthogonally polarized linear power in the longitude range of the core component. This behavior is modeled to show its effect. Finally, the star provides two well defined fiducial points from which emission-height estimates can be computed, the respective centers of both the linear PA traverse and the zero-crossing point of the circular polarization signature. 
Zuzana Srostlik and Joanna M. Rankin