Download presentation

Presentation is loading. Please wait.

Published byJordy Sainsbury Modified over 2 years ago

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

8
June Corot Week 4 Belgian Asteroseismology Group

9
June Corot Week 4 Belgian Asteroseismology Group

10
June Corot Week 4 Belgian Asteroseismology Group

11
June Corot Week 4 Belgian Asteroseismology Group

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

14
June Corot Week 4 Belgian Asteroseismology Group

15
June Corot Week 4 Belgian Asteroseismology Group

16
June Corot Week 4 Belgian Asteroseismology Group

17
June Corot Week 4 Belgian Asteroseismology Group

18
June Corot Week 4 Belgian Asteroseismology Group

19
June Corot Week 4 Belgian Asteroseismology Group

20
June Corot Week 4 Belgian Asteroseismology Group

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

Similar presentations

© 2016 SlidePlayer.com Inc.

All rights reserved.

Ads by Google