A ground-based velocity campaign on Procyon Tim Bedding (Univ. Sydney) and about 50 others

Procyon A angular diameter = 5.40±0.03 mas (1%; VLTI) parallax = ± 0.9 mas (0.5%; Hipparcos) radius = 2.04±0.02 (1%) mass = 1.46±0.03 (2%; binary orbit)

Brown et al. (1991) Martic et al. (2004) Eggenberger et al. (2005) Leccio et al. (2006) Previous velocity observations Fourier power spectra of Doppler measurements. All have power centred at about 1 mHz (15-20 minutes) 0123 Frequency (millihertz)

n =18 What are stellar oscillations?

p-mode oscillations are standing sound waves n =1 n =3 n =2 frequencies tell us about internal sound speed

Power Fourier power spectrum of solar velocities: n increases →

radial modes (ℓ =0)

ℓ=1 ℓ= 2 ℓ= 3 ℓ > 0 (non-radial)

Power Fourier power spectrum of solar velocities: n increases →

ℓ=2 20 ℓ=0 ℓ=1 ℓ=3 3 n increases →  = 135  Hz

Brown et al. (1991) Martic et al. (2004) Eggenberger et al. (2005) Leccio et al. (2006) Previous velocity observations Fourier power spectra of Doppler measurements. All have power centred at about 1 mHz (15-20 minutes) 0123 Frequency (millihertz)  ≈ 55  Hz

2004

What we knew in 2007 there is a power excess in velocity amplitude is lower than predicted theoretically agreement on  ≈ 55  Hz. no agreement on frequencies, presumaby due to daily aliases/mixed modes/short mode lifetime?

The Velocity Campaign Arentoft et al. (2008, ApJ)

11 telescopes at 8 observatories over 25 days PROCYON P

HARPS CORALIE McDonald Lick UCLES Okayama Tautenburg SOPHIE EMILIE SARG FIES 11 telescopes at 8 observatories over 25 days 10 days

HARPS SOPHIE SARG

combined

Note: broad envelope

Bedding et al. (ApJ,in press)

ℓ=2 20 ℓ=0 ℓ=1 ℓ=3 3  = 135  Hz What is an echelle diagram? Here is the solar power spectrum divided into segments of width .

 Hz Sun

BISON freq. échelle diagram l=3 l=1 l=0l=2l=0l=2     Frequency mod  

Echelle diagram of Procyon (noise-optimized weights)

Reducing sidelobes

possible mixed mode (narrow peak)

Noise-optimized Sidelobe-optimized

l=3 l=1 l=0l=2 which ridge is which?

Do we have the correct ridge identification? l=3,1l=2,0

Ridge structure: l=3,1l=2,0 YES!

l=2,0l=1 Absolute model frequencuies: model (Christensen-Dalsgaard) NO!

A new method: scaled echelle diagrams Bedding & Kjeldsen (2010, Comm. Asteroseismology)

greyscale =  Cen A Δ = Sun  0.78

greyscale = Procyon ○=HD x (Benomar et al. 2010) ●=HD x (Deheuvels et al. 2010) l=1l=2,0 YES!

500  Hz acoustic glitch at  =1000s (He ionization zone) Asteroseismology using ridge spacings

Extracting the mode frequencies

Extracted peaks (“CLEAN”)

The mixed mode in Procyon

l=3, 1 l=2,0 model with 1.6Msun and Z=3% (Christensen-Dalsgaard 2004) Avoided crossings in subgiants

Bedding et al. (in prep.)

“C-D diagram” “p-g diagram” Christensen-Dalsgaard (1988,2004) Bedding et al. (in prep.)

Procyon: mass = 1.46±0.03 (2%; binary orbit) Bedding et al. (in prep.)

Lessons for SONG combining data from multiple sites works well (adjust weights to optimize noise and sidelobes) cannot afford to take 2-3 years to analyse each star! low stellar background in velocity allows detection of wider range of frequencies than may be possible with Kepler. In Procyon, broad envelope allowed us to measure He ionization glitch Kepler may not give many sun-like stars (18 Sco) or lower-mass stars (  Cen B, tau Cet) SONG will observe nearby stars with good parameters let’s SING!