Birth rates of SGRs and AXPs: delayed amplification of magnetic field

We present new determination of the birth rate of AXPs and SGRS and their associated SNRs. We find a high birth rate of 1/(500 yr) for AXPs/SGRs and 1/(1700 yr) for associated SNRs. These high rates suggest that all massive stars (greater than ~ 25 M_sun) give rise to remnants with magnetar-like fields. Recent observations indicate that fossil fields cannot explain such high fields in the progenitor stars. Dynamo mechanisms during the birth of the neutron stars require spin rates much faster than either observations or theory indicate. Here, we propose the neutron stars form with normal (~ 10^{12} G) magnetic fields, which are then amplified to 10^{14}-10^{15} G after a delay of a few hundred years. The amplification is speculated to be a consequence of color ferromagnetism and occurs after the neutron star core reaches quark-deconfinement density. This delayed amplification alleviates many difficulties in interpreting simultaneously the high birth rate and high magnetic fields of AXPs/SGRs and their link to massive stars.