Soft X-Ray Absorption Due to the Photo-Ionized Plasma in the Low-Mass X-Ray Binary EXO 0748a?’676 Observed with XMM-Newton Observatory

摘要

Weanalyzedaneffectofthephoto-ionizationonthecontinuumspectrausingtheXMM-Newtonarchivedataofthelow-massX-raybinaryEXO0748$$-$$676.Wefoundthattheionizationdegreeofthecircumstellarplasma,whichmodifiesthesoftX-rayspectrumthroughabsorption,changeslargelyinassociationwiththeX-rayburstsandthedips.Theburstlightcurvebelow$$sim1,mathrm{keV}$$isfoundtohaveamajorcontributionfromthepersistentemission,whichtemporaryincreasedduringtheburstduetoareductionoftheopacityoftheabsorber.Weutilizedacorrelationdiagramofthecountrates(0.5a€“1.0a€‰keVvs.2.0a€“4.0a€‰keV)tostudytheeffectofphoto-ionizationduringthedips.Wefoundthatthecorrelationcanbemuchbetterreproducedifwetakeintoaccountthephoto-ionizationoftheabsorber.Nopartialcoveringabsorptionwasrequired,exceptfortheresidualfluxinthedeepestdips.