The Origin Of The Soft X-ray Excess In Active Galactic Nuclei

The soft X-ray excess is a major component of many type1active galacticnuclei(AGN), especially Narrow Line Seyfert1(NLS1) galaxies. The radiation ofActive galactic nuclei can cover all band. Below1keV in the X-ray band, theX-ray data are above the low energy extrapolation of the best ftting2-10keVpower law by index about Γ～2.0. This is so-called soft X-ray excess. However,the origin of the soft X-ray excess is unclear and difcult to explain. In someprevious works that consider the black body radiation from accretion disc canemit the soft X-ray like as the”Big Blue Bump”. But according to the standardaccretion disc model, if the soft X-ray can be radiated from accretion disc, themass of black hole must be small as well as the accretion rate should be close orexceed the Eddington accretion rate. However, the observation shows that thesample of AGNs with soft X-ray excess do not obey those conditions. So that itis difcult to use the standard accretion disc model to explain the origin of thesoft X-ray excess. At the same time, the blackbody temperature of the soft X-ray excess remains remarkably constant at0.1-0.2keV. Since then, many modelsare present to explain the origin of the soft X-ray excess, such as refection andabsorption model,”Slim disc”, disc wind model, thermal comptonization and soon. But those models more or less have some difcult, so the origin of the softX-ray excess is still controversial.So we can quest a new scenario to explain the Soft X-ray excess in AGNs.Because magnetic feld exist in plasma generally, so it is necessary to considermagnetic feld into the radiative processes of the soft X-ray. Under the efect ofdiferential rotation of the accretion disc and turbulence, magnetic feld shouldbe tangled to generate magnetic reconnection. Then, electrons are acceleratedby shock wave and turbulence triggered by magnetic reconnection, then theytake place inverse Compton scattering with the soft photon which generate fromaccretion disc that contributes soft X-rays. We then apply the model to ft thespectra of AGNs with strong soft X-ray excess.