中国科学院云南天文台机构知识库

We study the giant outbursts of SMC X-3 and RX J0209.6-7427 (hereafter RX J0209) to compare their super-Eddington accretion regime with that of Swift J0243.6+6124 (hereafter Swift J0243). The high double-peak profile of SMC X-3 is found to be 0.25 phase offset from that below 2.3 x 10(38) erg s(-1), which is similar to Swift J0243 (happened around 0.9 x 10(38) erg s(-1)). The profile of RX J0209 shows a similar 0.25 phase offset between high double-peak and low double-peak around 1.25 x 10(38) erg s(-1). The 0.25 phase offset corresponds to a 90 degrees angle change of the emission beam and strongly supports for a transition from a fan beam to a pencil beam. Their critical luminosities imply a surface magnetic field similar to 4 x 10(13) and 2 x 10(13) G for SMC X-3 and RX J0209, respectively, based on the recently measured cyclotron line of Swift J0243. The spin-up rate and luminosity of SMC X-3 follows a relation of (v)over dot proportional to L-0.94(+/- 0.0)3, while that of RX J0209 follows (v)over dot proportional to L-1.00 +/-(0.03), which are similar to Swift J0243 and consistent with the prediction of a radiation-pressure-dominated disc. These results indicate that accretion columns are indeed formed above Eddington luminosity, and the population of ultraluminous X-ray pulsars likely corresponds to X-ray pulsars of highest magnetic field.