1. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO The Shape of Granulation Spectra: Simulations, Observations and Models Regner Trampedach

2. July 12th, 2011KASC4, HAO, Boulder, CO Why care about granulation “noise”? ● We can actually observe something unresolvable on other stars than Sun ● The fit, for p modes and background is more stable with good fitting functions....and fewer parameters. ● Something seems fishy with the Harvey law...

3. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Some Fourier Transforms

4. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Pulse in time Power Spectra

5. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO The Harvey Law – Generalized ● Harvey (1985): P(ν) = 1/[1 + (2πντ) 2 ] P(ν) = 1/[1 + (2πντ) 2 ] ● Generalized to: P(ν) = 1/[1 + (2πντ) α ] P(ν) = 1/[1 + (2πντ) α ] ● Different slopes: α ~ [1.5; 5] ⇒ different pulse width ● τ eff Measure actual width (Jérôme Ballot, priv. comm.)

6. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO One star, 6 fits, 6 realities!

7. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Fits to 6 Kepler Red Giants

8. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Fits to 6 Kepler Red Giants

9. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Fitting the time-series: The Good

10. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Remember the global fit?

11. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO And the bad and ugly one

12. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO And the global fit:

13. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO And the 3D convection simulations? ● Grid of 37 sims. ● Realistic EOS, opacities and radiative transf. ● [Fe/H]=0.0 ~GN93 ● Monochromatic intens.*Kepler filter ● ⇒ “obs. Time-series ● Fitted gran. “noise”

14. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Time-series of solar simulation

15. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Global spectrum of solar sim.

16. Regner Trampedach July 12th, 2011KASC4, HAO, Boulder, CO Conclusions ● Harvey law results from 1-sided Exp. Pulse ● Original Harvey (1985) =2-law rarely fit ● Time-series of Kepler stars and 3D conv. simulations show symmetric pulses. ● Well fit by Lorentzian pulses ⇒ Exponential power spectrum ⇒ 2 params. ● To fit spectrum well, need: 2 granulation-like components Gaussian envelope of p modes White noise ⇒ 8 parameters