asteroseismology of gamma doradus, beta cephei, delta scuti and other ‘heat-engine’stars

Asteroseismology of Gamma Doradus, Beta Cephei, Delta

Scuti and other ‘heat-engine’stars

Jørgen Christensen-Dalsgaard

Institut for Fysik og Astronomi, Aarhus Universitet

Dansk AsteroSeismologisk Center

Mode excitation or damping

Growth rate: amplitude / exp( t), with

In nonadiabatic region, L ' constant

Simplified excitation

Too hot

(J. P. Cox 1964)

Simplified excitation

Too cold

Simplified excitation

Just right!!

Location of instability region

Note: Decreasing Teff ! increasing mb ! increasing for a given opacity bump

Opacity bumps

Pamyatnykh (1999; Acta Astron. 49, 119)

Double-mode Cepheids

! tdyn / (R3/M)1/2

Double-mode Cepheids

! R, M???

Petersen diagram (J.O. Petersen 1973; Astron. Astrophys 27, 89)

! tdyn / (R3/M)1/2

Track along instability strip

Old opacity

New (OPAL) opacity

Massive pulsators

Excitation calculation

Pamyatnykh (1999; Acta Astron. 49, 119)

Work integralsCephei SPB Scuti

Asteroseismologi of Ceph stars Eridani

l = 1

l = 1

l = 0

De Ridder et al. (2004; MNRAS 351, 324)

Models of Eridani

Pamyatnykh et al. (2004; 350, 1022)

Avoided crossings

Scuti stars

ExcitationCephei Scuti

Pamyatnykh (2000; ASP. Conf. Ser. 210, 215)

Excited modesCephei Scuti

Instability regions

Pamyatnykh (2000; ASP. Conf. Ser. 210, 215)

Mode selection

Analysis techniques

Breger (1995; ASP Conf. Ser. 76, 596)

FG VirginisBreger et al. (2005; Astron. Astrophys. 435, 955)

FG Virginis frequencies

Breger et al. (2005)

FG Virginis frequencies

Breger et al. (2005)

FG Virginis amplitude distribution

Breger et al. (2005)

FG Virginis frequency interpretationNo rotation

With rotation, nlm = nl0 + m /2

Templeton et al. (2001; ApJ 563, 999)

Altair: the brightest Scuti star

Buzasi et al. (2005; ApJ 619, 1072)

Observations with the WIRE satellite

Doradus stars

Very slow pulsations

Poretti et al. (2002; Astron. Astrophys. 384, 513)

Very extended observations

Aerts et al. (2004; Astron. Astrophys. 415, 1079)

Instability region

Warner et al. (2003; ApJ 593, 1049)

Convective blocking

Guzik et al. (2002; ASP Conf. Ser. 259, 502)