Seismology of Herbig stars with SIAMOIS

1. Seismology of Herbigstars with SIAMOIS Torsten Böhm, Marc-Antoine Dupret Claude Catala, Marie-Jo Goupil, Evelyne Alecian Observatoire de Paris-Meudon Observatoire Midi-Pyrénées

2. Let’s talk about… • Main observational properties of Herbig stars • Seismic potential of Herbig stars: probing the internal structure of PMS stars • HD 104237 : a very good target for SIAMOIS • Discovery of 8 pulsating modes in HD 104237 • Preliminary seismic study of HD 104237 • Improvements expected with SIAMOIS

3. Herbig Ae/Be stars • very young pre-main sequence objects • observational definition (Herbig, 1960): - spectral type earlier than F0 • presence of emission lines • embedded region • proximity of reflection nebula • intermediate masses (1.5 - 8 solar masses) • signs of intense activity and strong stellar winds • In addition: jets, outflows, IR excess, X-ray sources, presence of CS disks, detection of magnetic fields, ….

4. HR diagram ZAMS

5. Herbig Ae/Be stars • very young pre-main sequence objects • observational definition (Herbig, 1960): - spectral type earlier than F0 • presence of emission lines • embedded region • proximity of reflection nebula • intermediate masses (1.5 - 8 solar masses) • signs of intense activity and strong stellar winds • In addition: jets, outflows, IR excess, X-ray sources, presence of CS disks, detection of magnetic fields, ….

6. Discovery of pulsating Herbig Ae stars • - the d Scuti instability strip crosses the location of HAeBes in the HR diagram • Until now, only some Herbig stars between A2 and F0 have been • identified pulsating: • V588 Mon & • V599 Mon P < 3h (multip.) (Breger,1972) • HR5999 P approx 6 hrs (Kurtz & Marang 1995) • HD 104237 P approx 40 minutes (Donati, 1997) • … • + some recent discoveries (approx 15 stars as of today)

7. Potential of Herbig stars for asteroseismology Probing the internal physics of stars in the early stages of evolution Location of the convective core Initial nuclear burning (CNO cycle)

8. Probing the convective core in the early stages of evolution Evolution tracks Brunt Vaisala freq.

9. Comparison PreMS – PostMS frequencies Small separation

10. Internal rotation Transport of angular momentum Potential of Herbig stars for asteroseismology Probing the internal physics of stars in the early stages of evolution Location of the convective core Initial nuclear burning (CNO cycle)

11. HD 104237 - a PMS prototype star • Emission line star (Herbig Ae *) • Southern hemisphere (-78°) • mV approx 6.5 • Mass: 2.3 solar masses • Luminosity: 35 solar lum • Log Teff: 3.93 • Spectral type: A4IVe+sh • Vsini 12km/s • Highly active and variable (spectro) • Stellar wind 500km/s • Multiple system (+spectrosc. binary)

12. Previous work…

13. High resolution spectroscopic data base SAAO 04/1999 1 week SAAO 04/2000 1 week GIRAFFE… SAAO 05/2000 2 weeks Mt Stromlo 04/00 1 week data reduction ESPRIT/ LSD (multiplex information) + cross-correllation of telluric lines 100m/s precision on vrad (per spectrum) • 1888 spectra • - total of 42 nights

14. SAAO Avril 1999 D Amplitude! Orbital analysis SAAO Avril Mt Stromlo Avril 2000 SAAO Mai 2000

15. 5 ascertained +3 probable frequencies Böhm et al. 2004, A&A 427, 907

16. 5 ascertained +3 probable frequencies

17. 1999

18. 1999: 3 probables frequencies…?

19. 2000 (total)

20. Observations and modelisation 1999 SAAO

21. Rotational Modulation - 95 hrs Period Halpha

22. Van den Ancker et al. Teff=8500 K Grady et al. Teff=7500 K Bohm et al. (in prep.) Teff=8250 K Preliminary seismic study ZAMS A: primary B: secondary

23. Preliminary seismic study M=2.7 M0 M=2.2 M0

24. Preliminary seismic study Observed frequencies

25. Preliminary seismic study M=2.7 M0 M=2.2 M0

26. Preliminary seismic study

27. Preliminary seismic study M=2.7 M0 M=2.2 M0

28. Rot. Splitting ? (~ 3mHz)

29. Second order effect More splittings could be detected by SIAMOIS

30. Small separation (mHz)

31. Small separation (mHz) M=2.3 M0 Y=0.27 [Fe/H]=0 M=2.23 M0 Y=0.29 [Fe/H]=0 M=2.41 M0 Y=0.27 [Fe/H]=0.2 ( Dif. ~ 0.1 mHz) Possible with SIAMOIS

32. Stochastic excitation No convection zone d Scuti type k-driving Too high frequencies RoAp type driving ? Helium settling, winds, magnetic f. In collaboration with S. Theado, Liège Enhanced k-driving in the H partial ionization zone Preliminary seismic study Excitation mechanism Unknown up to now

33. Noise level : 0.8-1 m/s (120h) 3 – 4 months Duty cycle: 90-95 % Frequency precision : 0.1 mHz Many new modes Rotational splittings Internal rotation Small difference Constraining the Internal physics Excitation mechanisms Improvements with SIAMOIS

36. Major results on HD 104237 • -Orbital study: mass ratio primary/secondary 1.29 +/- 0.02 • Palla & Staler’s evolutionary tracks: secondary K3, 0.5 Lsol • Multi-periodic pulsations (5 frequencies ascertained + 3 potential) • frequences characteristical of d Scuti stars • Strong variation of amplitudes between seasons • Coherence of the modes on at least 2 month (resolved periodogram) • Rotational modulation of 95hrs (to be confirmed) • Separation between frequencies indicates presence of • non-radial modes; first asterosismological models

37. Next steps • -Modeling -Internal structure of HD 104237? • -model of pulsating HD 104237 -> modes -> frequencies • -need for precise Teff, log g, metallicities • Activity -Confirm rotational modulation • Search for correlation of HeI5876A, H alpha with orbital period • Search for accretion tracers CS environment - star • -study of the wind • -study of the forbidden lines, tracers of CS environment • Pulsation -systematic search for patterns (dynamical spectra) • -2D Periodicity analysis • -moment method • -Selectif LSD for specific elements (D phase, A?)

38. First asterosismological models (1) • Teff = 8250 K • « low » radial modes • large separation not matching

39. First Asterosismological models (2) • Teff = 7650 K (?) • « high » radial modes • large separation « matching » Model by Marc Antoine Dupret, OBSPM, Paris, France