Speaker
Description
We report on the results of MAXI monitoring of X-ray binary pulsars (XBPs), which are mostly high-mass X-ray binaries hosted by Be stars or OB supergiants. So far, about a hundred of XBPs have been known in our Galaxy. More than a half of them appear as X-ray transients whose activity are limited within their short (< several months) outburst periods. The MAXI all-sky survey for 15 years discovered several new XBPs including MAXI J1409-619, MAXI J0903-531, and MAXI J0655-013, and revealed their comprehensive outburst behaviours. Be XBPs usually exhibit outbursts lasting a few weeks to several months, according to the mass accretion on to a neutron star from a Be circumstellar disk. We investigated correlations between X-ray intensity variations observed by MAXI/GSC and pulse-period changes observed be Fermi/GBM for all clearly detected Be-XBP outbursts, and found that all of them reasonably agree with those predicted by theoretical models about the mass accretion along the pulsar magnetosphere. The model-fit results suggest that some Be XBPs with a long pulse period, X Persei, MAXI J0655-013, and LS V +44 17 would have strong magnetic fields of > 10^13 G, higher than the typical ~10^12 G. On the other hand, that of the ultra-luminous X-ray pulsar, Swift J0243.6+6124 was estimated to be typical ~10^12 G. We also examined the validity of these model predictions by comparing the results of all (~15) Be-XBP sample.
