![Kepler 63: 40-80 days ! ! (G2, P=5d)!
Sun: 115 days !! ! ! ! (G2, P=25d)!
!
AB Dor: 110 days ! ! ! ! (K0, P=0.5d)!
Speedy Mic: 191 days ! ! (K3, P=0.4d)!
!
GJ 1243: 700-1200 days ! (M4, P=0.6d)!
HK Aqr: [-1449-449] days ! (M0, P=0.4d)
Expectation: lap times increase with
later spectral type
e.g. Kueker (2011), Barnes (2005)
See excellent recent paper by
Timo Reinhold et al. (2013)
Equator-Lap-Pole time comparisons
!54](https://image.slidesharecdn.com/bu-2014-davenport-140318013053-phpapp01/85/Spots-and-Flares-Stellar-Activity-with-Kepler-James-R-A-Davenport-2014-54-320.jpg)
Uploaded byJames Davenport
Spots and Flares, Stellar Activity with Kepler (James R. A. Davenport, 2014)
The document discusses stellar activity, focusing on spots and flares, using data from Kepler to analyze the magnetic fields and behavior of solar-type stars. It highlights the significance of studying flares for understanding stellar dynamics, habitability, and stellar ages, presenting a comprehensive dataset of flares and starspot evolution over time. Key questions regarding the relationship between stellar properties, flare morphology, and differential rotation remain to be explored.
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Spots and Flares, Stellar Activity with Kepler (James R. A. Davenport, 2014)
- 1. Spots & Flares StellarActivity with Kepler Leslie Hebb (Hobart & William Smith) James R. A. Davenport (University of Washington) !1 Suzanne L. Hawley (University of Washington) Boston University — 2014 February 25
- 2. Spots & Flares Observablebyproducts of magnetic fields "If the Sun did not have a magnetic field, it would be as uninteresting a star as most astronomers believe it to be." -R.B. Leighton (or E. Parker) !2
- 3. Spots & Flares Buildour intuition from the Sun !3
- 4. Source of solarB field? Convective Envelope (differential rotation) Radiative Zone (solid body rot.) Tachocline (interface) !4
- 5. Evolution of theB field with mass, age, rotation? !5
- 6.
- 7.
- 8. Flares - whywe care? A few reasons… • Insight into properties of stellar dynamo/interior • Habitability (of our planet, and others) • Potential age-tracer for stars !8
- 9. Martens & Kuin(1989) Standard Solar Flare Model !9
- 10. Martens & Kuin(1989)!10
- 11. Martens & Kuin(1989)!11
- 12. Kepler: Stellar FlareMachine • Long continuous light curves (up to ~4years) • Very precise photometry (~0.01%) • Enormous sample (>100,000 solar-type stars) !12
- 13. Kepler: Stellar FlareMachine • Long continuous light curves (up to ~4years) • Very precise photometry (~0.01%) • Enormous sample (>100,000 solar-type stars) • Look for outliers (super-flares) • Complete samples! !13
- 14. (Walkowicz+ 2010) Flares Observedby Kepler 4 M-dwarfs !14
- 15. Davenport in prep GJ1243 M4, Prot=0.59 days, ~300days 1-min data !15
- 16. Davenport in prep GJ1243 M4, Prot=0.59 days, ~300days 1-min data !16
- 17. Flares By EYE(FBEYE) Davenport in prep!17
- 18. Davenport in prep CompareUsers !18
- 19. Massive Flare Sample! •6107 flares, spanning 300 days • most of any star besides the Sun! • 15% complex • energy range: Log E = 27-33 erg • complete to Log E ~31 !19
- 20. tstart tstop Determined bypeople for every flare !20
- 21. Amplitude t1/2 (FWHM) Place inscale units for time & flux tpeak !21
- 22. Davenport in prep MedianCombine: Flare Template !22
- 23. Rise Phase DecayPhase Davenport in prep e-1t e-0.3t Fit with 4th order polynomial Energy budget: rise=20%, decay1=41%, decay2=39% !23
- 24. Davenport in prep ComplexFlare Fitting !24
- 25. Davenport in prep ComplexFlare Fitting Objective way to determine complex vs classical !25
- 26. RelativeFlux Some flares notwell fit by template Davenport in prep Caused by different physical morphology (e.g. arcade)? Active region rolling off limb? !26
- 27. Hawley in prep Nocorrelation between flares & spot 1 month short cadence !27
- 28. Big questions stillawait us! • Dependence of morphology on stellar properties? • Does decay rate depend on total flare energy? • Can we resolve peak shape? • More detailed understanding of complex events !28
- 29. GJ 1245 AB(C): anovel system for spots & flares 2 distinct periods Lurie in prep!29
- 30. GJ 1245 AB(C): anovel system for spots & flares 2 distinct periods !30
- 31. GJ 1245 AB(C): anovel system for spots & flares HST 2” Kepler Pixel !31
- 32. GJ 1245 AB(C): anovel system for spots & flares HST 2” Kepler Pixel !32
- 33.
- 34. Flux Time (days) Preliminary separatedlight curves Lurie in prep!34
- 35.
- 36. Strassmeier (1999) • Observedacross range of mass, evolutionary phase • Trace B field geometry, rotation, differential rotation ! • Evolve on timescales from days to years (perhaps longer!) Starspots a generic result of B fields SDO Carroll (2012) !36
- 37. – Stellar rotationrate – Spot sizes – Differential rotation rate – Spot Lifetimes – Spot evolution over stellar cycles – Evolution with stellar age Starspots: Parameters/Physics of Interest !37
- 38. Davenport in prep GJ1243: M4, Prot=0.59 days, 300days1-min data, 13 Quarters 30-min data !38
- 39. GJ 1243 Flatten withpolynomial fits !39
- 40. Davenport in prep GJ1243 !40
- 41. Phase Davenport in prep GJ1243 - spot evolution in phase !41
- 42. Phase Davenport in prep GJ1243 - spot phase map Primary Spot Secondary Spot(s) !42
- 43. Phase Davenport in prep GJ1243 Differential Rotation! !43
- 44. Phase Davenport in prep GJ1243 Differential Rotation! “Equator-Lap-Pole” time of 700-1200 days (assume Solar-like diff. rot.) !44
- 45. Phase Davenport in prep GJ1243 Differential Rotation! Spot lifetimes: 150-500 days for 2nd spot >4 years for 1st spot !45
- 46. Davenport in prep GJ1243 2-spot lightcurve model Phase 1-spot model preferredunclear !46
- 47. Time Time Phase Phase Some other Mdwarfs with Prot<2 day ! A wide range of starspot- phase evolution! ~20 other short P dM’s in Kepler 30-min data !47
- 48. Davenport & Hebbin prep Kepler 63 Differential Rotation transits !48 G2, Prot=5.4d
- 49. Kepler 63 Differential Rotation Davenport& Hebb in prep !49
- 50. Kepler 63 Differential Rotation Primary! Spot Secondary ! Spots Davenport & Hebb in prep !50
- 51. Kepler 63 Differential Rotation Davenport& Hebb in prep Different slopes: Likely 3 different spot latitudes Faster ! differential ! rotation Slower ! differential ! rotation !51
- 52. Kepler 63 Differential Rotation Davenport& Hebb in prep Faster ! differential ! rotation Slower ! differential ! rotation “Equator-Lap-Pole” times: 40-80 days Spot lifetimes: 100-500 days !52
- 53. Kepler 63 Davenport &Hebb in prep Faster ! differential ! rotation Slower ! differential ! rotation Might be Anti-Solar diff. rot., polar primary spot Solar diff. rot., equatorial primary spot !53
- 54. Kepler 63: 40-80days ! ! (G2, P=5d)! Sun: 115 days !! ! ! ! (G2, P=25d)! ! AB Dor: 110 days ! ! ! ! (K0, P=0.5d)! Speedy Mic: 191 days ! ! (K3, P=0.4d)! ! GJ 1243: 700-1200 days ! (M4, P=0.6d)! HK Aqr: [-1449-449] days ! (M0, P=0.4d) Expectation: lap times increase with later spectral type e.g. Kueker (2011), Barnes (2005) See excellent recent paper by Timo Reinhold et al. (2013) Equator-Lap-Pole time comparisons !54
- 55.
- 56. Hebb & Davenportin prep!56
- 57. Hebb & Davenportin prep!57
- 58.
- 59. Advantage: Spot lat/lonbetter constrained (if planet properties known) !59
- 60. Key: fit transit“bumps” & out-of-transit flux together !60
- 61. Hebb & Davenportin prep Spot contrast-radius-latitude degeneracy (partially) broken! vary both spot radius & contrast !61
- 62. Hebb & Davenportin prep Spot contrast-radius-latitude degeneracy (partially) broken! !62
- 63. Hebb & Davenportin prep Spot contrast-radius-latitude degeneracy (partially) broken! !63
- 64. Hebb & Davenportin prep Spot contrast-radius-latitude degeneracy (partially) broken! Finding 70-80% !64
- 65. Fitting challenges… • MCMC veryexpensive • Parameter space “target” very small • Need to run over many “windows” of time • Spots can evolve on few-transit (or few rotation) timescales !65
- 66. The future: measurecontrast from umbra & penumbra? NewSolarTelescope(2010) !66
- 67. Time PhaseThe future: automatethe diff. rot. & spot timescale measurement? !67
- 68. The future: comparedetailed spot properties with gyrochronology • Spot timescales • Spot contrast(s) • Differential rotation rate & direction (Prot spin down with stellar age) !68
- 69. The future: findflares in every Kepler target, learn about B fields en masse • Comparable to transit-finding (just inverted) • Tackle flare physics questions (e.g. dependence on star properties) • Include gyrochronology, flares as age indicator? (viable for LSST?) !69
- 70. Proposed K2 fields Idealto test flares as age-indicator! !70
- 71. Summary Thanks! • Largest sampleof flares on any star, create flare template • One of slowest differential rotation rates ever measured • Detailed starspot properties observable in transiting systems • Kepler opening door to statistical understanding of stellar activity! !71