Asteroseismology of Gamma Doradus, Beta Cephei, Delta Scuti and other ‘heat-engine’stars
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Transcript of 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)