2019PASP..131b4201W

To track the formation and evolution links of the millisecond pulsars (MSPs) powered by accretion and rotation in the Galactic field, we investigate the spin period (P) and spin-down power ({dot}E) distributions of the MSPs observed at the wavebands of radio, X-ray, and γ-ray. We find that all but one (119/120) of the γ-ray MSPs have been detected with the radio signals (radio+γ MSPs); on the contrary, nearly half of the radio MSPs (118/237) have not been detected with γ-rays (radio-only MSPs). In addition, the radio+γ MSPs are shown to be the relative faster and more energetic objects (<P>∼3.28ms and <{dot}E>∼4.5×10³⁴ergs^–1) compared with the radio-only MSPs (<P>∼4.70ms and <{dot}E>∼1.0×10³⁴ergs^–1), while the spin periods of these two MSP populations are compatible with the log-normal distributions by the statistical tests. Most rotation-powered MSPs (RMSPs) with the radio eclipsing (31/34) exhibit the radio+γ signals, which share the faster spin (<P>∼2.78ms) and larger spin-down power (<{dot}E>∼4.1×10³⁴ergs^–1) distributions than the non-eclipsing ones (<P>∼4.19ms, <{dot}E>∼2.4×10³⁴ergs^–1), implying the radio+γ MSPs to be younger than the radio-only MSPs. It is noticed that the spin distribution of the accretion-powered X-ray MSPs shows a clustering phenomenon around ∼1.6-2.0 ms, which is not observed in RMSPs, hinting that the RMSPs may experience the multiple possible origins. Particularly, all the three super-fast spinning RMSPs with P ∼ 1.4-1.6 ms exhibit the non-eclipsing, and we argue that they may be the distinctive sources formed by the accretion induced collapse (AIC) of white dwarfs.