The same physics underlying SGRs, AXPs, and radio pulsars
  Unexpected sign, significant magnitude and time-variation of frequency second derivative exist not only in singular radio pulsars but also in Soft Gamma repeaters (SGRs) and Anomalous X-ray pulsars (AXPs). This paper shows that the these phenomena are related, and can be interpreted by a simple unified model, long-term orbital effect. Thus many of previous ``isolated'' pulsars may be binary pulsars, i.e., orbital period   $P_b\approx(47, 72)$min for AXP 1E 2259+586, and $P_b\approx (20, 34)$min for PSR J1614-5047, $P_b\approx (3.6, 6.4)$min for SGR 1900+14, and $P_b\approx (1.5, 5.8)$min for SGR 1806-20. In addition to X-ray pulsar, 1E 1207.4-5209, these two SGRs may be the new ultra-compact binary pulsars with orbital period of a few minutes. There might be more binary pulsars that suitable for gravitational wave detection than we had thought. 
Biping Gong