射电天文研究室知识库

PSR J1023+0038 is a known transitional pulsar, which switches between the accretion-powered X-ray pulsar state and the rotation-powered radio millisecond pulsar (MSP) state. Here, we study the conditions for its state transition by ascribing similar to GHz radio pulse emission to the plasma cutoff oscillation frequency at the magnetosphere, which depends on the plasma density or accretion rate. With the accretion X-ray luminosity declining fromhigh to low state (e.g., similar to 10(35) erg s(-1) to similar to 10(32) erg s(-1)), the magnetosphere boundary expands to the light cylinder, where the plasma density is low enough to permit the emission of radio waves at the several-GHz frequency band. Thus, for a sufficiently low accretion-rate state (similar to 1032 erg s(-1)), the radio emission at the several-GHz band is not blocked by the plasma, and the radio pulsar can be detected in the favored "observational windows," i.e., the L band (1-2 GHz), S band (2-4 GHz), and C band (4-8 GHz). Furthermore, to evaluate the penetration characteristics of the outgoing radio wave of low frequency, we calculate its skin depth, which is found to be a couple of centimeters for the low X-ray luminosity of 10(34)-10(32) erg s(-1), a scale that is much shorter than the light cylinder radius of about 100 km for MSPs.