Fan-beamed X-Ray Emission from 1 to above 130 keV from the Ultraluminous X-Ray Pulsar RX J0209.6-7427 in the Small Magellanic Cloud

Abstract We present detailed timing and spectral analyses of the transient X-ray pulsar RX J0209.6−7427 in Small Magellanic Cloud during its 2019 giant outburst. With a better known distance than most galactic pulsars, peak luminosity is determined to be (1.11 ± 0.06) × 10 39 erg s −1 ; it thus bona fide pulsating ultraluminous source (PULX). Owing broad energy band Insight-HXMT, pulsed emission was detected from 1 keV up 130–180 band, which highest any PULXs outside Milky Way. This allows us conclude that main fan beam accretion column, intrinsic. also estimate magnetic field (4.8–8.6) 12 or (1.7–2.2) 13 G, spin evolution transition column structure outburst; we suggest two values strength correspond dipole multipole fields neutron star, similar recent discovery Galactic PULX Swift J0243.6+6124. Therefore, nature star ULX can understood within current theoretical frame accreting stars. may have implications for understanding those farther away extragalactic PULXs.