Precisionstellar physicsfrom the ground • Andrzej Pigulski • University of Wrocław, Poland Special Session #13: High-precision tests of stellar physics from high-precision photometry
Asteroseismology:satellite observatories * 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
Aliasing problem Ground-based observing campaigns NGC 6910 campaign: single-site data, 81 observing nights
LIGHT CURVE SPB star HD 43317, CoRoT Pápics et al. (2012) FREQUENCY SPECTRUM 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 ?
Constraints on internal rotation, overshooting, ... Mode ID of the remaining modes • Photometric • observations provide: • frequencies, • amplitudes, • phases. global parameters Stability check ASTEROSEISMOLOGY Evolutionary & puls. models, theoretical frequencies Mode identification: quantum numbers ℓ,m,n RVs line profiles Asteroseismology:how it works? Frequency matching
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)
solar-like oscillations Mode ID:asymptotic relations 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 J.Christensen-Dalsgaard
Mode ID:asymptotic relations The Sun SOHO/VIRGO Bedding & Kjeldsen (2003)
Δν = large separation δν02 = small separation Mode ID:asymptotic relations Chaplin et al. (2010)
ℓ= 2 0 1 2 0 3 1 Mode ID:asymptotic relations echelle diagram: frequency vs. frequency modulo large separation White et al. (2011) Bedding et al. (2010)
pulsating (pre)white dwarfs + hot subdwarfs Mode ID:asymptotic relations asymptotic relations (for a given ℓ): p modes: equidistant in frequency g modes: equidistant in period solar-like oscillations rotational splitting: multiplets with (2ℓ+1) components J.Christensen-Dalsgaard
Mode ID:asymptotic relations PG 1159 star RXJ 2117+3412 Average period spacing = 21.618 s ℓ = 1 modes Vauclair et al. (2002)
Mode ID:asymptotic relations Pulsating hot subdwarf KIC 5807616 Average period spacing = 242.12 s ℓ = 1 modes Average period spacing = 139.13 s ℓ = 2 modes blue = observed Reed et al. (2011)
Mode ID:rotational splitting Pulsating hot subdwarf KIC 10139564 ℓ = 2 ℓ = 1 Baran et al. (2012)
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)
classical pulsators pulsating (pre)white dwarfs + hot subdwarfs Mode ID:period ratios period ratios: double/triple-mode pulsators, radial modes solar-like oscillations J.Christensen-Dalsgaard
3O/2O 2O/1O 1O/F 3O/1O Mode ID:period ratios Data: OGLE (LMC) Soszyński et al. (2008, 2010), Poleski et al. (2010) CEPHEIDS HADS RRd
single-band (satellite) photometry is sufficient for applying 1 and 2 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)
main-sequence pulsators + hot subdwarfs classical pulsators pulsating (pre)white dwarfs + hot subdwarfs Mode ID:multicolour photometry & spectroscopy driving mechanism: - self-excited pulsations, - stochastically excited pulsations (solar-like) character: - p modes (acoustic) - g modes (gravity) multicolour photometry & spectroscopy main-sequence pulsators + hot subdwarfs solar-like oscillations J.Christensen-Dalsgaard
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)
0 1 1 1 1,2 0,1,3 1,2,3 1 2,5 Mode ID:multicolour photometry & spectroscopy Diagnostic diagrams: β Cephei star ν Eridani: goodness-of-fit parameter χ2 vs. ℓ Daszyńska-Daszkiewicz & Walczak (2010)
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.
Rudolph et al. 2006 An example: Z-effect Pamyatnykh 1999
Physics to probe β Cephei star ν Eridani Daszyńska-Daszkiewicz & Walczak (2010)
Constraints on internal rotation, overshooting, ... Mode ID of the remaining modes • Photometric • observations provide: • frequencies, • amplitudes, • phases. global parameters Stability check ASTEROSEISMOLOGY Evolutionary & puls. models, theoretical frequencies Mode identification: quantum numbers RVs line profiles Asteroseismology:how it works? Frequency matching
Do we still need ground-based photometry ? YES, WE DO... 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.
Kepler field CoRoT „eyes” β Cephei stars: ASAS contribution (Southern) ASAS sky: δ < +28°, ~300 new β Cephei stars Pigulski & Pojmański (2010)
Conclusions • 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.
