Suzaku Results on the Obscured Low-Luminosity Active Galactic Nucleus in NGC 4258

摘要

In2006June,theobscuredlow-luminosityactivegalacticnucleusinthenearbySeyfert1.9galaxyNGC4258wasobservedwithSuzakufor$$sim$$100ks.UtilizingtheXISandtheHXD,thenucleusemissionwasdetectedovera$$sim$$2to$$sim$$40keVrange,withanunabsorbed2a€“10keVluminosityof$$sim$$8$$ imes$$10$$^{40}$$ergs$$^{-1}$$;itvariedbyafactorof$$sim$$2duringtheobservation.Its2a€“40keVspectrumisreproducedbyasinglepowerlawwithaphotonindexof$$Gamma$$$$sim$$2.0,absorbedbyanequivalenthydrogencolumnof$$sim$$1.0$$ imes$$10$$^{23}$$cm$$^2$$.Thespectrumwithin$$4{}^{prime}$$ofthenucleusalsorequiredasofterthin-thermalemission,aswellasanintermediatehardnesscomponent,attributabletointegratedpointsources.AweakneutralFe-K$$alpha$$florescencelinewasdetectedatanequivalentwidthof$$sim$$40eV.Acoldreflectioncomponentwasnotrequiredbythedata,withthereflectorsolidangle$$Omega$$seenfromthenucleusconstrainedas$$Omega/$$2$$pi$$$$lesssim$$0.3,assumingageneralcaseof60$$^circ$$inclination.Theresultssuggestthatthecoldreflectingmaterialaroundthenucleusislocalizedalongourlineofsight,ratherthanformingathicktorus.