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A Hare and Hound in a Bag…

 Cephei Stars. A Hare and Hound in a Bag…. Why are they seismologically interesting ?. Structure of  Cephei Stars. Massive stars : M ~ 9 – 12 M . « Middle» main sequence stars : X c  0.3 ,  c /  150.

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A Hare and Hound in a Bag…

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  1.  Cephei Stars A Hare and Hound in a Bag… Why are they seismologically interesting ? Corot Week 4 Belgian Asteroseismology Group

  2. Corot Week 4 Belgian Asteroseismology Group

  3. Structure of  Cephei Stars • Massive stars : M ~ 9 – 12 M • « Middle» main sequence stars : Xc  0.3 , c/  150 • Simple structure : no convective envelope • Convective core : mc  0.20 • Solar metallicity : if Z < Z too few excited modes • Parameters : M,X,Z,ov,c/ Corot Week 4 Belgian Asteroseismology Group

  4. Oscillations of  Cephei Stars f, g- and p-modes but… low degree l and low order n excited modes  Sparse structure spectrum Excitation :  mechanism in the Fe opacity bump at ~ 2 105 K Avoided crossings : • frequencies parameter dependent • rare enough to take it easy… Corot Week 4 Belgian Asteroseismology Group

  5. BAG ground-based observations • 16 Lac  3 frequencies to appear in A&A – see Bag poster 1 • HD129929  5 frequencies Science Express, May 29, 2003  M,Z,ov,rotation law– see Bag poster 2 •  Eri  ? frequencies work in progress Corot Week 4 Belgian Asteroseismology Group

  6. BAG Hare & Hound Exercise • KU-Leuven • Ulg • ROB Site 1 : - Compute model HH1 and frequencies - Find Model HH2  Light curve  Site 2 : - Compute model HH2 and frequencies - Find Model HH1 Corot Week 4 Belgian Asteroseismology Group

  7. Time Sampling - Total time span: 150 days - Orbital period: 6092 s (= 1h42m) - Exposure time: 0.8 s - CCD frame transfer time: 0.2 s - Rebinning in time domain: 1 data point every 32 s - Data loss due to moon: none (if launch before 2007) - Data loss due to SAA: 6-8 orbits/day pass through SAA no data loss for seismo channel, but increased noise level - Data loss due to solar panel rotation + flat field calibration: 1 orbit per 10 days - Data loss due to SEUs: 0.15 % of (rebinned) dataset - Data loss due to eclipse entries/exits: 20 s per orbit - Data loss due to technical failures: the longer the more rare, longest: +/- 6 days, about once a year - Barycentric time correction applied Corot Week 4 Belgian Asteroseismology Group

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  12. Mode Identification Five high amplitude peaks  l = 0,1,2 • One isolated peak at f2 = 82.963 Hz  l = 0 • One quintuplet containing f3 and f5  f3 = 80.013 Hz is l = 2, m = 0 • One quintuplet containingf4  f4 = 43.704 Hz is l = 2, m = 0 Corot Week 4 Belgian Asteroseismology Group

  13. Method • Given : the error box in [log Te, log g] diagram log Te = [4.34,4.36] log g = [3.70,3.90] • On each sequence of evolution, i.e. for each (M,ov,Z,X), find the model which fits f2 fixes the age of the model • Among these, find models which also fit f3 and f4  Constraints on M,ov,Z,X • Finally, check that all peaks in the spectrum can be explained by unstable modes Corot Week 4 Belgian Asteroseismology Group

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  21. Conclusions • Frequencies given at a precision of 2 x 10–4  Error bars on parameters More precision on frequencies  smaller errors bars • Frequency analysis  output frequencies identical to input frequencies except where crowded Even there, most frequencies are recovered exactly down to very low amplitudes • Modes of high degree (example shown : l = 5)  discriminate between several solutions if in a crowded region  NOT detectable with ground-based telescopes  COROT Corot Week 4 Belgian Asteroseismology Group

  22. 31 frequencies BAG HH1-Frequency analysis Corot Week 4 Belgian Asteroseismology Group

  23. l=1 l=0 l=2 BAG HH1-Mode identification 5 or more multiplets Corot Week 4 Belgian Asteroseismology Group

  24. HH1 - Seismic analysis June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group Corot Week 4 Belgian Asteroseismology Group

  25. June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group Corot Week 4 Belgian Asteroseismology Group

  26. Corot Week 4 Belgian Asteroseismology Group June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group

  27. Corot Week 4 Belgian Asteroseismology Group June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group

  28. Corot Week 4 Belgian Asteroseismology Group June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group

  29. Conclusions • Ground-based observations : l = 0,1,2 • Observations from space : l >>> • More frequencies  more constraints on stellar parameters  COROT should observe B stars Corot Week 4 Belgian Asteroseismology Group

  30. Screenplay : Belgian Asteroseismology Group Starring : Aerts Conny – KU-Leuven Ausseloos Mario – Ulg Barban Caroline – KU-Leuven Briquet Maryline – KU-Leuven Bourge Pierre-Olivier – Ulg Cuypers Jan – ROB Daszynska Jadwiga – KU-Leuven De Cat Peter – KU-Leuven De Ridder Joris – KU-Leuven Dupret Marc-Antoine – Ulg Montalban Josefina – ULg Noels Arlette – Ulg Scuflaire Richard – Ulg Thoul Anne – Ulg Uytterhoeven Katrien – KU-Leuven Corot Week 4 Belgian Asteroseismology Group

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