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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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.

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

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

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

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...

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

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.