Abstract
We present new analysis of the birth rate of AXPs and SGRS and their associated SNRs. Using Kolmogorov-Smirnov statistics together with parametric fits based on a robust estimator, we find a birth rate of ∼1/(1000 years) for AXPs/SGRs and their associated SNRs. These high rates suggest that all massive stars (greater than ∼(23–32)M⊙) give rise to remnants with magnetar-like fields. Observations indicate a limited fraction of high magnetic fields in these progenitors; thus our study is suggestive of magnetic field amplification. Dynamo mechanisms during the birth of the neutron stars require spin rates much faster than either observations or theory indicate. We propose that massive stars produce neutron stars with normal (∼1012 G) magnetic fields, which are then amplified to1014-1015 G after a delay of hundreds of years. The amplification is speculated to be a consequence of color ferromagnetism and to occur with a delay after the neutron star core reaches quark deconfinement density (i.e., the quark-nova scenario). The delayed amplification allows one to interpret simultaneously the high birth rate and high magnetic fields of AXPs/SGRs and their link to massive stars.
Highlights
Studies of association of Anomalous X-ray Pulsars (AXPs) with supernova remnants (SNRs) suggested that 5% of core-collapse SN results in AXPs [1]
Our reasoning is as follows: (i) high birth rates of magnetars imply that all massive stars with M > Mlow produce magnetars; (ii) observations of massive stars imply need of magnetic field amplification mechanism; (iii) observations of associated SNRs imply that the dynamo mechanism is unlikely to cause the amplification; (iv) we propose delayed magnetic field amplification associated with delayed quark star formation after neutron star birth
Our study of the birth rate of AXPs and SGRS and their associated SNRs suggests that about 1/5 to 1/10 of all corecollapse SN leads to AXPs/soft gamma-ray repeaters (SGRs)
Summary
Studies of association of Anomalous X-ray Pulsars (AXPs) with supernova remnants (SNRs) suggested that 5% of core-collapse SN results in AXPs [1]. This was based on 3 SNR associations out of a total of 6 AXPs. Since evidence has mounted that AXPs and soft gamma-ray repeaters (SGRs) are the same type of objects [2] and more AXPs, SGRs and associated SNRs have been identified. (An independent study by Gill and Heyl [3], based on a population synthesis of AXPs detected in the ROSAT AllSky Survey, yields a birth rate of ∼0.22 per century.) This high frequency of occurrence of AXPs/SGRs brings into focus issues related to the origin of the strong magnetic fields which we address here.
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