The Big Questions Stellar Flares

2. The Big Questions Stellar Flares particle acceleration in flares chromospheric heating coronal heating irradiation of protoplanetary disk outflow and wind acceleration

3. Questions Are stellar flares different ? What can we learn from stellar flares? Flares in star and planet formation? Role of flares in early solar system?

4. Thermal Flare Emission (soft X-rays)

5. Solar X-ray spectrum RHESSI non-thermal relativistic XMM-Newton Chandra thermal

6. Thermal soft X-rays of Orion sfr Chandra, Feigelson & Getman

7. X-ray flare on Algol solar radii Ness, 2009 solar radii

8. dM0. UV Cet B (dM6.0Ve, zero main-sequence star) Audard et al. 2003

9. Audard, 2000

10. Quiescent thermal X-ray emission Güdel, 2004

11. Quiescent emission of binaries YY Gem Güdel et al. 2001 AR Lac Siarkowski et al. 1996

12. When does magnetic activity start? Quiet and quiescent soft X-ray emission Güdel, 2004

13. Non-thermal Flare Emission (hard X-rays and gyro-synchrotron radio)

14. Sun Kosugi et al. 1988

15. Sun non-thermal gyro-synchrotron (> 100 keV) non-thermal bremsstrahlung < 100 keV

16. UV Ceti B dM6e Radio gyro- synchrotron Neupert effect ROSAT/HRI 0.1 – 2.4 keV Güdel et al. 1996

17. UV Cet B (dM6e) VLBA 3.6 cm

18. Proxima Centauri dM5.5e Neupert effect Güdel et al. 2002

19. Radio - X-ray Correlation

20. Flare peak fluxes Lx = 1015.5Lr

21. How Large Can a Flare Be? Flare on EQ Peg (dM4e): 3·1033 erg in soft X-rays Largest flare in stars: 2·1041 erg in soft X-rays (Grosso et al. 1997) Largest flare in solar-type stars: 2·1038 erg in optical (Ashbrook 1959, Schaefer et al. 2000) Largest flare in single solar-type stars: 6·1035 erg in optical (Kepler data, Maehara et al. 2012; Candelaresi et al., poster)

22. How Large Can a Flare Be? Energy in large solar active region B = 2000 – 4000 G < nkT (photosphere) h= 2·109 cm r = 1010 cm B2 8π r2π h = 1035 erg Free magnetic energy: 20% Released free energy: 50% → Max flare energy: 1034 erg The maximum flare energy is dominated by the size. Large stellar flares must involve large active regions.

23. Applications of Radio/X-ray Correlation Prediction of radio flux from X-ray luminosity -> Discovery of radio emission of K, G, and F stars Güdel 1994 Güdel et al. 1994 Güdel et al. 1995 Search for magnetic activity in embedded protostars (X-ray emission absorbed)

24. 8 - 12 GHz EVLA L 1527, Class 0 protostar

25. 8 - 12 GHz EVLA Spectral index at peak flux: +0.82

26. 8 - 12 GHz EVLA

27. Summary L 1527 300σ peak deconvolved radius < 7 AU thermal free-free (corona+wind?) No radio flare detected in 60 minutes ΔFradio < 80 µJy (5σ) radio/X-ray relation Lx = 1015.5Lradio → Lx < 6 1030 erg/s Very young protostars are less active than zero main sequence M stars, but need more observations

28. 12 deeply embedded young (< 105 y) stellar objects in OH+ absorption (Herschel Space Obs./HIFI, 1.1 THz)

29. abundance → age →

30. Observed: Very high X-rax flux or FUV

31. Summary Herschel/HIFI Enhanced irradiation in all protostars (low and high mass) Irradiation increases from Class 0 to Class I (> 105 y) The nature of the irradiation is not clear FUV, EUV, X-rays, particles? flares or shocks?

32. Flare Impact on Accretion Disks and Protoplanety Atmospheres

33. FUV energetic particles X-rays Protostar Class 0

34. Protostar Class I (105 – 106 y) Armitage

35. CME in planet and star forming region Shibata & Matsumoto 1996

36. Conclusions • Flares make up the quiescent X-ray emission in active stars. • Huge stellar flares require larger volumes than solar flares. • Enhanced irradiation found in molecular abundances in early star and planet formation. • No evidence (yet) for X-rays and magnetic activity in Class 0 protostars • Flare (and CME) X-ray and energetic particles are relevantin early planet evolution.

37. Thank you !

38. X-ray Radio Correlation Observations Theory Gyro-synchrotron emissivity: Conversion efficiencies: Dulk + Marsh 1982 G+B 1993 B+G 1994