1. The Sun in its Youth Alicia Aarnio

2. Outline Stellar evolution timeline – TTS: pre-main sequence Suns – dM/dt – dL/dt Solar-stellar connection – Coronae – Activity – Magnetic fields

3. Stellar evolution in 1 slide Hayashi track Henyey track Main sequence Iben (1965) t [Myr] 0.3 1.0 3.2 10.0 31.8 100.0 5.5 6.0 6.5 7.0 7.5 8.0 log(t [Myr]) Siess, Dufour & Forestini (2000) 1.4 M  0.4 M  0.6 M  0.2 M  10 5 yr 10 6 yr 10 7 yr 10 8 yr 2e7 yr 5e7 yr 2e6 yr 4e6 yr

4. Circumstellar disks SEDs – Observations – RT modeling Interferometry breaks degeneracies – Inclination – Revealed inner gap Whitney+2003b JHK, late Class I 873 Myr 881 Myr 1.2 Gyr Booth+2009

5. Long-baseline IR interferometry: resolution~ λ /b – 2 μ m, 100m baseline  resolution ~4mas (0.6AU at 140pc) Can presently measure visibilities (size), closure phase (shape- asymmetry?) Tuthill, Monnier & Danchi (2001) Dust-free inner cavity Dullemond & Monnier (2010) Inner disk measurements

6. Interferometry Transiting circumstellar disk observed with MIRC Hot Jupiter atmosphere measurements Zhao+2011 Kloppenborg+2010 Stencel+2008

7. Mass transfer in star-disk system Hadean Archean Preterozoic Phanerozoic  Hartigan+1995 - Cranmer & Saar 2011 Haisch & Lada 2 2001 Meyer+2008 - Wood+2005

8. Evolution of radiation field Hadean Archean Preterozoic Phanerozoic  Ingleby+2011 ✕ Getman+2005 Wright+2011 - Siess+2000  Ribas+2005 − Mamajek & Hillenbrand, 2008

9. Solar-stellar connection: X-ray properties X-rays – X-ray emission properties like the Sun Adapted from Schmitt (1997) Figures from Peres+2004 From Marino+2002b Solar min Solar max X9 flare QC AR AR cores Flares Flares: Reale+2001 All else: Orlando+2001 Stellar and solar data

10. Magnetic activity – Flares much like the Sun, but more frequent, energetic Classifying TTS flares like solar, COUP flares = X300-X40,000! Solar-stellar connection: flares, fields Getman+2005 ----- 1-8Å ----- 0.5-4Å E. Flaccomio for COUP collaboration Aarnio, Stassun & Matt (in prep)

11. Ramifications for planet formation Activity can impact planet formation – Chondrule formation via shock heating of CME hitting disk- Miura & Nakamoto (2007) – Composition of disk Strong early winds, frequent CMEs – Atmospheric stripping – oxidation, chemistry changes – Understanding young exoplanet magnetospheres Tidal forces on hot Jupiters- Trammell, Arras & Li (2011) Star-planet magnetospheric interaction causing chromospheric variability- Shkolnik et al. (2008)

12. Aarnio et al. (2012) Magnetic loops ~10R * – Cool plasma: prominences, ``clouds’’ (A. Collier Cameron, AB Dor) – Confining hot plasma: post-reconnection loops (UCL model, Reale+1997; applied to COUP Favata+2005) Large-scale magnetic structure Collier Cameron & Robinson (1989a)

13. Stellar CMEs Post-flare loops: 10 19 -10 22 g Our stellar CME mass loss rates: ~10 -9 – 10 -11 M  /yr Aarnio, Stassun & Matt (in prep)

14. Summary Sun-as-a-star and stars-as-suns valuable for better understanding both Stellar evolution generally understood, but many issues remain – Rotation/activity relationship – B – Initial conditions in protosolar system Chemistry Disk structure – Angular momentum evolution

15. Collaborators UM: John Monnier, Nuria Calvet, Chuck Cowley VU: Keivan Stassun CEA Saclay: Sean Matt BU: Jeff Hughes, Sarah McGregor Cal Tech: Scott Gregory St Andrews: Moira Jardine, Joe Llama

16. Hidden slides! In case questions arise, or I have extra time.

17. Magnetic field measurements – ~kG surface fields – Complex topology Hussain et al. (2007) – Contemporaneous DZI, X-ray Spectroscopy to reveal field structure at surface, in corona – O VII triplet used as density diagnostic – Surface field maps extrapolated outward; met by X-ray derived density/temperature constraints – X-ray corona likely only extends to 0.4 R  – Correlation found between active region indicators at surface (spots) and in corona (X-ray bright plasma) Field strength, G Spot coverage Observations Prominence (EUV absorption) Mapping the corona of AB Dor

18. Solar-stellar connection: flares, fields Magnetic activity – Flares just like the Sun, but much more energetic, frequent Aarnio+2011

19. Skumanich (1972) used data from multiple open clusters –Pleiades (70 Myr) –Ursa Major (120 Myr) –Hyades (600 Myr) –…and the Sun (4.5 Gyr) As a function of age, Li abundance, surface rotation rate, and Ca + emission decay as t -½ Li appears to begin to decay exponentially around the age of the Hyades Evolution of activity

20. Pizzolato+2003 Gudel, Guinan & Skinner (1997)

21. Herbig Ae/Be stars Inner rim models fit both TTS, HAeBe SEDs, interferometry Stability of puffed-up inner rim potentially explicable by: – Hot, optically thin gas interior to rim – Higher refractory index of grains than previously thought Dullemond, Dominik & Natta (2001)

22. NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA), the Hubble Space Telescope Orion Treasury Project Team and L. Ricci (ESO)