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June 3-7 2003Corot Week 4 Belgian Asteroseismology Group A Hare and Hound in a Bag… Why are they seismologically interesting ?  Cephei Stars.

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Presentation on theme: "June 3-7 2003Corot Week 4 Belgian Asteroseismology Group A Hare and Hound in a Bag… Why are they seismologically interesting ?  Cephei Stars."— Presentation transcript:

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

2 June Corot Week 4 Belgian Asteroseismology Group

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

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

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

6 June Corot Week 4 Belgian Asteroseismology Group 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

7 June Corot Week 4 Belgian Asteroseismology Group 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

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12 June Corot Week 4 Belgian Asteroseismology Group Mode Identification Five high amplitude peaks  l = 0,1,2  One isolated peak at f 2 =  Hz  l = 0  One quintuplet containing f 3 and f 5  f 3 =  Hz is l = 2, m = 0  One quintuplet containing f 4  f 4 =  Hz is l = 2, m = 0

13 June Corot Week 4 Belgian Asteroseismology Group 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 f 2  fixes the age of the model  Among these, find models which also fit f 3 and f 4  Constraints on M,  ov,Z,X  Finally, check that all peaks in the spectrum can be explained by unstable modes

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21 June Corot Week 4 Belgian Asteroseismology Group 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

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

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

24 June Corot Week 4 Belgian Asteroseismology Group June Corot Week 4 Belgian Asteroseismology Group HH1 - Seismic analysis

25 June Corot Week 4 Belgian Asteroseismology Group June Corot Week 4 Belgian Asteroseismology Group

26 June Corot Week 4 Belgian Asteroseismology Group June Corot Week 4 Belgian Asteroseismology Group

27 June Corot Week 4 Belgian Asteroseismology Group June Corot Week 4 Belgian Asteroseismology Group

28 June Corot Week 4 Belgian Asteroseismology Group June Corot Week 4 Belgian Asteroseismology Group

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

30 June Corot Week 4 Belgian Asteroseismology Group 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


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