ϵ-mechanism driven pulsations in hot subdwarf stars with mixed H-He atmospheres

BATTICH, T.; ALTHAUS, L. G.; A. H. CÓRSICO; M .M. MILLER BERTOLAMI

Cracovia

Congreso; Eighth Meeting on Hot Subdwarfs and Related Objects; 2017

Pedagogical University of Cracow

The ϵ mechanism is a self-excitation mechanism of stellar pulsations which acts in regions where nuclear burningtakesplace.Ithasbeenshownthattheϵmechanismcanexcitepulsationsinhotpre-horizontalbranchstars beforetheysettleintothestableheliumcore-burningphaseandthattheshortestperiodsofLSIV-14∘116couldbeexplainedthatway.Weaimtostudytheϵmechanisminstellarmodelsappropriateforhotpre-horizontalbranchstarsto predicttheirpulsationalproperties.Weperformdetailedcomputationsofnon-adiabaticnon-radialpulsationsonsuch stellarmodels.Wepredictanewinstabilitydomainoflong-periodgravitymodesinthelogg−logTeff planeatroughly 22000K . Teff . 50000Kand4.67 . logg . 6.15,withaperiodrangefrom∼ 200to∼ 2000s.Comparisonwith thethreeknownpulsatingHe-richsubdwarfsshowsthattheϵmechanismcanexcitepulsationsinmodelswithsimilar surfacepropertiesexceptformodeswiththeshortestobservedperiods.Basedonsimpleestimatesweexpectatleast3 starsinthecurrentsamplesofhot-subdwarfstarstobepulsatingbytheϵmechanism.Ourresultscouldconstitutea theoreticalbasisforfuturesearchesofpulsatorsintheGalacticfield