1. Precision stellar physics from the ground Andrzej Pigulski University of Wrocław, Poland Special Session #13: High-precision tests of stellar physics from high-precision photometry

2. Asteroseismology: satellite observatories Satellite WIRE (tracker) MOSTCoRoTKepler Launch1999200320062009 Tel. diam. [cm]5.2152790/140 V range< 4< 6 5.5 - 9 (sei.) 11.5 - 16 (plan.) 9 - 16 Typical precision* (single meas.) [ppm] 20070150200 Detection threshold [ppm]** 802033 * bright star, ~1-min (stacked) integration, ** for one-month long observations

3. Ground-based observing campaigns DUTY CYCLE DETECTION THRESHOLD < 60%, typically ~20% > 0.08 mmag, typically ~1 mmag In comparison with satellite data: lower duty cycle, worse detection threshold

4. Ground-based observing campaigns NGC 6910 campaign: single-site data, 81 observing nights Aliasing problem

5. Observations: satellite vs. ground-based SATELLITE DATA: high duty cycle (up to ~100%), outstanding precision, low noise at low frequencies. Do we still need ground-based photometry ? LIGHT CURVE FREQUENCY SPECTRUM Pápics et al. (2012) SPB star HD 43317, CoRoT

6. Evolutionary & puls. models, theoretical frequencies global parameters Asteroseismology: how it works? Photometric observations provide: frequencies, amplitudes, phases. Mode identification: quantum numbers ℓ,m,n RVs line profiles Frequency matching Constraints on internal rotation, overshooting,... Mode ID of the remaining modes Stability check ASTEROSEISMOLOGY

7. Asteroseismology: how modes are identified? How modes are identified? 1. asymptotic relations & rotational splitting 2. period ratios 3. multicolour photometry and/or spectroscopy (many mode ID methods)

8. Mode ID: asymptotic relations J.Christensen-Dalsgaard driving mechanism: - self-excited pulsations, - stochastically excited pulsations (solar-like) character: - p modes (acoustic) - g modes (gravity) asymptotic relations (for a given ℓ ): p modes: equidistant in frequency g modes: equidistant in period solar-like oscillations

9. Mode ID: asymptotic relations Bedding & Kjeldsen (2003) The Sun SOHO/VIRGO

10. Mode ID: asymptotic relations Chaplin et al. (2010) Δ ν = large separation δ ν 02 = small separation

11. Mode ID: asymptotic relations White et al. (2011) echelle diagram: frequency vs. frequency modulo large separation Bedding et al. (2010) ℓ= 2 0 1 2 0 3 1

12. Mode ID: asymptotic relations J.Christensen-Dalsgaard asymptotic relations (for a given ℓ ): p modes: equidistant in frequency g modes: equidistant in period solar-like oscillations pulsating (pre)white dwarfs + hot subdwarfs rotational splitting: multiplets with (2 ℓ+1 ) components

13. Mode ID: asymptotic relations PG 1159 star RXJ 2117+3412 Average period spacing = 21.618 s ℓ = 1 modes Vauclair et al. (2002)

14. Mode ID: asymptotic relations Pulsating hot subdwarf KIC 5807616 Reed et al. (2011) Average period spacing = 242.12 s ℓ = 1 modes Average period spacing = 139.13 s ℓ = 2 modes blue = observed

15. Mode ID: rotational splitting Pulsating hot subdwarf KIC 10139564 Baran et al. (2012) ℓ = 2 ℓ = 1

16. Asteroseismology: how modes are identified? How modes are identified? 1. asymptotic relations & rotational splitting 2. period ratios 3. multicolour photometry and/or spectroscopy (many mode ID methods)

17. Mode ID: period ratios J.Christensen-Dalsgaard solar-like oscillations pulsating (pre)white dwarfs + hot subdwarfs period ratios: double/triple-mode pulsators, radial modes classical pulsators

18. 3O/1O 2O/1O 3O/2O Mode ID: period ratios Data: OGLE (LMC) Soszyński et al. (2008, 2010), Poleski et al. (2010) HADS RRd CEPHEIDS 1O/F

19. Asteroseismology: how modes are identified? How modes are identified? 1. asymptotic relations & rotational splitting 2. period ratios 3. multicolour photometry and/or spectroscopy (many mode ID methods) single-band (satellite) photometry is sufficient for applying 1 and 2

20. Mode ID: multicolour photometry & spectroscopy J.Christensen-Dalsgaard driving mechanism: - self-excited pulsations, - stochastically excited pulsations (solar-like) character: - p modes (acoustic) - g modes (gravity) solar-like oscillations pulsating (pre)white dwarfs + hot subdwarfs classical pulsators multicolour photometry & spectroscopy main-sequence pulsators + hot subdwarfs main-sequence pulsators + hot subdwarfs

21. Mode ID: multicolour photometry & spectroscopy Diagnostic diagrams: Amplitude ratio vs. phase difference Cugier et al. (1994)

22. Mode ID: multicolour photometry & spectroscopy Diagnostic diagrams: Amplitude ratio (RV/phot.) vs. amplitude ratio (colour/band) Cugier et al. (1994)

23. Mode ID: multicolour photometry & spectroscopy Diagnostic diagrams: β Cephei star ν Eridani: goodness-of-fit parameter χ 2 vs. ℓ Daszyńska-Daszkiewicz & Walczak (2010) 0 1111,2 1 0,1,31,2,3 2,5

24. Mode ID: multicolour photometry & spectroscopy Kepler β Cephei/SPB hybrids Balona et al. (2011)

25. Mode ID: multicolour photometry & spectroscopy The methods using multicolour photometry and spectroscopy for mode ID require ground-based data. A lot of interesting physics to study: - internal (core) rotation, - amount of overshooting from the core, - diffusion, - testing stellar opacities.

26. An example: Z-effect Pamyatnykh 1999 Rudolph et al. 2006

27. Physics to probe Daszyńska-Daszkiewicz & Walczak (2010) β Cephei star ν Eridani

28. Evolutionary & puls. models, theoretical frequencies global parameters Asteroseismology: how it works? Photometric observations provide: frequencies, amplitudes, phases. Mode identification: quantum numbers RVs line profiles Frequency matching Constraints on internal rotation, overshooting,... Mode ID of the remaining modes Stability check ASTEROSEISMOLOGY

29. Ground-based vs. satellite SATELLITE: higher duty cycle (up to ~100%), better precision, low noise at low frequencies (?). GROUND-BASED: cheaper, multicolour photometry (exc. BRITE, however), spectroscopy, all sky available. Do we still need ground-based photometry ? YES, WE DO...

30. β Cephei stars: ASAS contribution (Southern) ASAS sky: δ < +28°, ~300 new β Cephei stars Pigulski & Pojmański (2010) CoRoT „eyes” Kepler field

31. Conclusions 1.Ground-based and satellite data are complementary. Ground-based data are crucial for characterization of all and asteroseismology of some stars. There are good prospects for testing stellar physics and stellar interiors with ground-based data.