Stellar Evidence of a Solar Dynamo in Transition · Stellar Evidence of a Solar Dynamo in...
Transcript of Stellar Evidence of a Solar Dynamo in Transition · Stellar Evidence of a Solar Dynamo in...
Travis Metcalfe (SSI)Travis Metcalfe (SSI)
with Ricky Egeland (HAO) and Jennifer van Saders (Carnegie)with Ricky Egeland (HAO) and Jennifer van Saders (Carnegie)
Stellar Evidence of aSolar Dynamo in Transition
Skumanich relation
Skumanich (1972)
Rotational evolution
Bouvier (2008)
M67
NGC6819
NGC6811
M44, M37
Gyrochronology
slide from Jen van Sadersvan Saders et al. (2016, Nature); Meibom et al. (2011, 2015); Barnes et al. (2016)
slide from Jen van Saders
ZAMS Teff ~6200-5100 K
Gyrochronology
van Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~6200-5100 K
Gyrochronology
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~6200-5900 K
Gyrochronology
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5900-5600 K
Gyrochronology
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5400-5100 K
Gyrochronology
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5900-5600 K
Gyrochronology revised
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5900-5600 K
Gyrochronology revised
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~6200-5900 K
Gyrochronology revised
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5900-5600 K
Gyrochronology revised
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
ZAMS Teff ~5400-5100 K
Gyrochronology revised
slide from Jen van Sadersvan Saders et al. (2016, Nature); Creevey et al. (2016, submitted)
Garcia et al. (2014)
Stellar rotation with Kepler
Metcalfe et al. (2012)
max
Asteroseismology with Kepler
Rotation-activity relation
Metcalfe et al. (2016)
Rotation-activity relation
Metcalfe et al. (2016)
Differential rotation
fast equator
fast poles
Gastine et al. (2014)
Vaughan-Preston gap
Vaughan & Preston (1980); Wright (2004)
Rapid magnetic evolution
Pace et al. (2009)
Rapid magnetic evolution
1.1 Gyr
1.7 Gyr
Metcalfe et al. (2016)
Spots and faculae
spot dominated
faculae dominated
Lockwood et al. (2007)
Breaking magnetic braking
Metcalfe et al. (2016)
Breaking magnetic braking
Metcalfe et al. (2016)
Breaking magnetic braking
Metcalfe et al. (2016)
Solar analogs
18 Sco
HD 76151
HD 30495
HD 20630
16 Cyg
Metcalfe et al. (2016)
Spindown and magnetic topology
Reville et al. (2015); see also Garraffo et al. (2015)
dipole quadrupole octupole
Petit et al. (2008)
Zeeman Doppler imaging
18 Sco
18 Sco
HD 76151
HD 76151
Zeeman Doppler imaging
• Young solar analog is dominated by a dipole (80% of poloidal field)
• Dipole (35%) is already disappearing in 18 Sco, with 55% in quadrupole
• Old solar analog has no Zeeman signatures, weak average line-of-sight field
Petit et al. (2008, + priv. comm.)
Stellar activity cycles
Metcalfe et al. (2016)
HD 30495
HD 76151
HD 2063018 Sco
TESS: all-sky asteroseismology
Summary
• A change in differential rotation at Ro ~ 1 pushes stars across the V-P gap, rapidly decreases spot area, then disrupts magnetic braking at Ro ~ 2
• The Sun is in a transitional evolutionary phase, and its 11-year activity cycle may represent a special case of stellar dynamo theory
• Future ZDI measurements, more constraints on differential rotation, and asteroseismology of the Mount Wilson sample will help test this scenario
Details: ApJ Letters, 826, L2 (arXiv:1606.01926)
Nature, 529, 181 (arXiv:1601.02631)