Near-Infrared Spectra of 21 Wolfa€“Rayet Stars: Wind Clumping and Mass-Loss Rates

摘要

Wepresent0.9a€“2.4$$mu$$mspectraof21galacticWolfa€“Rayet(WR)starsthatwereobtainedbyusinganechellespectrographattachedtothe1.5a€‰minfraredtelescopeinTokyo.TheobservedWolfa€“Rayetstarscontain12WNE,3WNL,and6WCstars.Thenear-infraredcontinuumspectracanbefittedbythesuperpositionofstellarblackbodyradiationwithastellareffectivetemperatures,$$T_*$$,of30a€“60kKandfreea€“freeradiationfromthestellarwindwithanelectrontemperature,$$T_{ me}$$,of$$sim$$15kK.However,thesecalculatedspectrashowanexcessatcmwavelengthcomparedwiththecmdataforalmostallstars.Thismaybeinterpretedbyaninfraredexcessfluxpossiblyduetotheclumpingofthestellarwindgas.Assumingana€?enhancementfactora€?thatdependsonthedistancefromthecenterofthestarsas$$simr^{-omega}$$,wecanreproducebothournear-infraredspectraandthecmdatabythisclump-correctedfreea€“freeradiationwithmass-lossratessimilartothosederivedbyNugisetal.Ontheotherhand,wealsoestimatedthemass-lossratesfromourHei1.083andHeii1.012fluxeswithoutaconsiderationofclumping,althoughamoredetailedconsiderationshouldbenecessaryinordertoestimatemorereliablevaluesofthemass-lossratesfromtheHelinefluxes.