Context : Boththeabsolutemass-lossratesandthemechanismsthatdrivethemasslossoflate-typesupergiantsarestillnotwellknown.Binariessuchas \alpha Scoprovidethemostdetailedempiricalinformationaboutthewindsofthesestars .

Aims : Thegoalwastoimprovethebinarytechniqueforthedeterminationofthemass-lossrateof $ α $ ~Sco~A byincludingarealisticdensitydistributionandvelocityfieldfromhydrodynamicandplasmasimulations .

Methods : Weperformed3Dhydrodynamicsimulationsofthecircumstellarenvelopeof \alpha Scoincombinationwithplasmasimulationsaccountingfortheheating , ionization , andexcitationofthewindbytheradiationof $ α $ ~Sco~B .Thesesimulationsservedasthebasisforanexaminationofcircumstellarabsorptionlinesinthespectrumof \alpha Sco Baswellasofemissionlinesfromthe Antaresnebula .

Results : Thepresentmodeloftheextendedenvelopeof \alpha Scoreproducessomeofthestructuresthatwereobservedinthecircumstellarabsorptionlinesinthespectrumof \alpha Sco B.Ourtheoreticaldensityandvelocitydistributionsoftheoutflowdeviateconsiderablyfromasphericallyexpandingmodel , whichwasusedinpreviousstudies.Thisresultsinahighermass-lossrateof ( 2 \pm 0.5 ) \times 10 ^ { -6 } M _ { \odot } \mathrm { yr } ^ { -1 } .ThehotH ii regionaroundthesecondarystarinducesanadditionalaccelerationofthewindatlargedistancesfromtheprimary , whichisseeninabsorptionlinesofTi ii andCr ii at -30 \mathrm { km s } ^ { -1 } .

Conclusions :