Talk slides

@ruthangus
Calibrating Gyrochronology with
Kepler Asteroseismic targets
Ruth Angus, S. Aigrain, A. McQuillan, D. Foreman-Mackey, W. Chaplin, T. Mazeh Ages of MS stars
Isochrone fitting
- Large uncertainties.
Clusters
- Improved precision but young.
Asteroseismology
- Only applicable to bright Solar-like oscillators.
Activity-age-rotation relations
- Still poorly calibrated at late ages.
Ruth Angus, Oxford University
Irwin & Bouvier (2009)
Ruth Angus, Oxford University
Period-Age-Colour Plane
P = An ⇥ a(B
V
ck )b
P vs t for Sun-like
stars from Hyades to Sun
(Skumanich, 1972)
Ruth Angus, Oxford University
P vs B-V for Hyades
(Kawaler 1988, Barnes 2007)
Asteroseismic Ages
- Frequency of oscillations related to integrated sound speed along path
(Chaplin et al. 2013)
-  505 stars with asteroseismic ages from Chaplin et al. (2013)
- Ages with ~ 35% uncertainties.
Ruth Angus, Oxford University
Rotation Period Measurement
via Auto-Correlation
McQuillan, Aigrain & Mazeh (2013)
Ruth Angus, Oxford University
Angus et al. (in prep)
Period vs Colour
McQuillan et al. (2014)
Garcia et al. (2014)
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Angus et al. (in prep)
Period vs Colour
McQuillan et al. (2014)
Garcia et al. (2014)
Metcalfe et al. (2014)
- AMP stars
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Angus et al. (in prep)
Period vs Colour
McQuillan et al. (2014)
Garcia et al. (2014)
Metcalfe et al. (2014)
- AMP stars
Collier Cameron et al.
(2009)
- Coma Ber
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Radick et al. (1987)
- Hyades
Kovacs et al. (2014)
- Praesepe
Meibom et al. (2011)
- NGC 6811
Angus et al. (in prep)
Period vs Colour
McQuillan et al. (2014)
Garcia et al. (2014)
Metcalfe et al. (2014)
- AMP stars
Collier Cameron et al.
(2009)
- Coma Ber
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Radick et al. (1987)
- Hyades
Kovacs et al. (2014)
- Praesepe
Meibom et al. (2011)
- NGC 6811
The Sun (4.568 Gyr)
16 Cyg B (3.66 Gyr)
18 Sco (6.4 Gyr)
Α Cen AB (6.0 Gyr)
Period vs Colour
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Period vs Colour
10 Gyr
5 Gyr
2 Gyr
1 Gyr
Period vs Age
Hierarchical Inference
Proper treatment of uncertainties on all 3 variables, using importance sampling.
Hogg, Myers & Bovy (2010)
Also see Foreman-Mackey et al. (submitted) and
Rogers et al. (submitted)
Marginalised likelihood of
Tˆn , Pˆn , Aˆn given model parameters, m
p({Tˆn }, {Pˆn }, {Aˆn }|m)
✓T
m
Tn
Pn
An
Tˆn
Pˆn
Aˆn
stars n = 1, · · · , N
Ruth Angus, Oxford University
✓A
Ruth Angus, Oxford University
Ruth Angus, Oxford University
Ruth Angus, Oxford University
Conclusions
• 
New gyrochronology relation providing ages for F, G and K stars.
– 
Shift towards higher ages.
• 
Calibrated using the best available data, properly accounting for observational
uncertainties.
• 
Typical gyro-age uncertainties ~20%
• 
Is the Sun an outlier?
• 
Should gyrochronology only be applied in a statistical sense?
• 
Continue to incorporate more precise asteroseismic ages.
Ruth Angus, Oxford University

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