Horizontal branch stars should show significant differential rotation with depth. Models that assume systematic angular momentum exchange in the convective envelope and local conservation of angular momentum in the core produce HB models that preserve a ra

8S.Kawaler&S.Hostler

ofthecoresofsdBstarsthatevolveassinglestarsfromtheRGB.Couldthismeanthatthemechanismresponsibleforthepulsationofthesestarsmightbeconnectedwithrotation(r-modesoroverstableconvectivemodes)?

Acknowledgements

WeappreciatesupportfromtheUSNationalScienceFoundationthroughGrantAST-0205983,andtoNASAforsupportthroughtheAstro-physicsTheoryProgramviagrantNAG5-8352toIowaStateUniversity.

References

Behr,B.B.,Cohen,J.G.,&McCarthy,J.K.2000a,ApJL,531,L37

Behr,B.B.,Djorgovski,S.G.,Cohen,J.G.,McCarthy,J.K.,Cote,P.,Piotto,G.,&Zoccali,M.2000b,ApJ,528,849

Brassard,P.,Fontaine,G.,Bill`eres,M.,Charpinet,S.,Liebert,J.,&Sa er,R.2001,ApJ,563,1013

Charpinet,S.,Fontaine,G.,&Brassard,P.2001,PASP,113,775

Charpinet,S.,Fontaine,G.,Brassard,P.,&Dorman,B.2002,ApJS,139,487D’Cruz,N.,Dorman,B.,Rood,R.,&O’Connell,R.1996,ApJ,466,359Heber,U.,Reid,I.N.,&Werner,K.1999,A&A,348,L25

Kawaler,S.D.1987,PASP,99,1322

Kawaler,S.D.1998,in11thEuropeanWorkshoponWhiteDwarfs,ed.J.-E.Solheim&E.Meistas,(SanFrancisco:ASP),158.

Kawaler,S.D.,Sekii,T.,&Gough,D.1999,ApJ,516,349

Kilkenny,D.,Koen,C.,O’Donoghue,D.,VanWyk,F.,Larson,K.,Shobbrook,B.,Sullivan,D.,Burleigh,M.,Dobbie,P.,&Kawaler,S.1999,MNRAS,303,525Kilkenny,D.,Bill`eres,M.,Stobie,R.,Fontaine,G.,Shobbrook,R.,O’Donoghue,D.,Brassard,P.,Sullivan,D.,Burleigh,M.,&Barstow,M.2002,MNRAS,331,399Mengel,J.G.,Norris,J.,&Gross,P.1976,ApJ,204,488

Peterson,R.C.1983,ApJ,275,537

Peterson,R.C.1985a,ApJ,289,320

Peterson,R.C.1985b,ApJ,294,L35

Peterson,R.C.,Rood,R.T.,&Crocker,D.A.1995,ApJ,453,214

Reed,M.etal.(theWETcollaboration)2003,MNRAS,inpress

Sandquist,E.,Taam,R.,&Burkert,A.2000,ApJ,533,984

Sills,A.&Pinsonneault,M.2000,ApJ,540,489

Soker,N.&Harpaz,A.2000,MNRAS,317,861

Stobie,R.S.,Kawaler,S.D.,Kilkenny,D.,O’Donoghue,D.,&Koen,C.1997,MNRAS,285,651

Sweigert,A.&Gross,P.1976,ApJS,32,367

vanHoolst,T.,Dziembowski,W.A.,&Kawaler,S.D.1998,MNRAS,297,536Zahn,J.–P.1992, a,265,115