Context : Stellarpulsationsinmain-sequenceB-typestarsaredrivenbythe \kappa -mechanismduetotheFe-groupopacitybump.ThecurrentmodelsdonotpredictthepresenceofinstabilitystripsintheBspectraldomainatverylowmetallicities.AsthemetallicityoftheSMCislowerthan Z = 0.005 , itconstitutesaverysuitableobjecttotestthesepredictions .

Aims : ThemainobjectiveistoinvestigatetheexistenceofB-typepulsatorsatlowmetallicities , searchingforshort-termperiodicvariabilityinabsorption-lineBandBestarsintheSMC.Theanalysishasbeenperformedinasampleof313BandBestarswithfundamentalastrophysicalparametersaccuratelydeterminedfromhigh-resolutionspectroscopy .

Methods : PhotometriclightcurvesoftheMACHOprojecthavebeenanalyzedusingstandardFouriertechniquesandlinearandnon-linearleastsquaresfittingmethods.ThepositionofthepulsatingstarsintheHRdiagramhasbeenusedtoascertaintheirnatureandtomaptheinstabilityregionsintheSMC .

Results : Wehavedetected9absorption-lineBstarsshowingshort-periodvariability , twoamongthembeingmultiperiodic.Onestarismostlikelya \beta Cepheivariableandtheremaining8areSPBstars.TheSPBinstabilitystripintheSMCisshiftedtowardshighertemperaturesthantheGalaxy.IntheBestarsample,32starsareshort-periodvariables,20amongthemmultiperiodic.4.9 % ofBstarsand25.3 % ofBestarsarepulsatingstars .

Conclusions : \beta CepheiandSPBstarsdoexistattheSMCmetallicity.ThefractionsofSPBstarsandpulsatingBestarsintheSMCarelowerthanintheGalaxy.ThefractionofpulsatingBestarsintheSMCismuchhigherthanthefractionofpulsatingabsorption-lineBstars , asintheGalaxy .