june 3-7 2003corot week 4 belgian asteroseismology group a hare and hound in a bag… why are they...
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June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
A Hare and Hound in a Bag…
Why are they seismologically interesting ?
Cephei Stars
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 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 : mc 0.20
« Middle» main sequence stars : Xc 0.3 , c/ 150
Parameters : M,X,Z,ov,c/
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
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…
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
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
June 3-7 2003 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
June 3-7 2003 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
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
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 containing f4
f4 = 43.704 Hz is l = 2, m = 0
June 3-7 2003 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 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
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 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
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
BAG HH1-Frequency analysis31 frequencies
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
BAG HH1-Mode identification
l=0l=1 l=2
5 or more multiplets
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
HH1 - Seismic analysis
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
June 3-7 2003 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
June 3-7 2003 Corot Week 4 Belgian Asteroseismology Group
Screenplay : Belgian Asteroseismology Group
Starring : Aerts Conny – KU-LeuvenAusseloos Mario – UlgBarban Caroline – KU-LeuvenBriquet Maryline – KU-LeuvenBourge Pierre-Olivier – UlgCuypers Jan – ROBDaszynska Jadwiga – KU-LeuvenDe Cat Peter – KU-LeuvenDe Ridder Joris – KU-LeuvenDupret Marc-Antoine – UlgMontalban Josefina – ULgNoels Arlette – UlgScuflaire Richard – UlgThoul Anne – UlgUytterhoeven Katrien – KU-Leuven
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