1 Accretion onto Stars with Complex Fields and Outflows from the Disk-Magnetosphere Boundary Marina Romanova Cornell University May 18, 2010 Min Long (University of Illinois) Richard Lovelace (Cornell University) Akshay Kulkarni (Harvard University) J.-F. Donati (CNRS, Toulouse France COLLABORATORS:

2 Disk-magnetosphere Interaction I. Accretion to stars with complex fields (3D MHD) II. Outflows from disk-magnetosphere boundary (2D) Uchida & Shibata 1985 Camenzind 1990 Konigl 1991; Lovelace et al Matt & Pudritz 2005

I. Accretion to Stars with Complex Fields B=B dip +B quad +B oct + … 3D simulations Cubed sphere grid N=40,50,60 Koldoba, et al. 2002

4 3D simulations of accretion to Tilted Dipoles Romanova, Ustyugova, Koldoba & Lovelace 2003,2004 Different tilts 2 funnel streams High-latitude spots Ang. Momentum – inner disk

5 The dipole may off-center Long, Romanova, Lovelace 2008 Both poles are misplaced to the right

6 Aligned Quadrupole and Dipole Fields Dipodrupole Long, Romanova, Lovelace 2007

7 Misaligned dipole and quadrupole Long, Romanova, Lovelace 2008

8 Octupole Field Hot spots – 2 rings Long, Romanova, Lamb, Kulkarni, Donati 2009

9 V2129 oph BP Tau Magnetic field of V2129 Oph & BP Tau Dipole: 0.35 kG Octupole: 1.2 kG Dipole: 1.2 kG Octupole: 1.6 kG Potential (vacuum) extrapolations Donati, Jardine, Gregory et al., 2007, 2008

10 Model, Initial field, V2129 Oph M=1.35 M_Sun R=2.4 R_Sun P=6.35 days Rcor=6.8 R_star M_dot=6.3 10^10 Donati et al., 2007)

11 Accretion to V2129 Oph Romanova, Long et al. 2009

12 Comparison with a pure dipole field case Dipole field determines the funnel flow and disk-star interaction Octupole field shapes spots Observed chromospheric spot in CaII line Romanova, Long et al. 2009

13 Light curves V2129 Oph BP Tau V2129 Oph BP Tau Romanova et al. 2009Long et al. 2010

14 Magnetic field of V2129 Oph Romanova et al Magnetic field distribution near the star (top) and at larger distances

15 Matter flux problem Dipole field with 350G polar field can not stop the disk at 7 R unless accretion rate is very small Mdot =3x10^-8 (Eisner 05) Mdot=4x10^-9 (Mohanty Mdot=10^-8 (Donati 07) Mdot=6x10^-10 (Donati 09) Simulations: 3x10^-11 Theory: 4x10^-11 Romanova et al. 2009

16 Matter flux problem Disk comes closer – octupolar belt spots dominate Probably, the dipole component is 2-3 times larger Romanova et al. 2009

17 Modeling accretion to BP Tau Dipole: 1.2 kG Octupole: 1.6 kG Long et al 2010

18 II. Outflows: Different Possibilities Shu et al Blandford & Payne 1982 Konigl & Pudritz 2000 Matt & Pudritz 2005,… Ferreira, Dougados, Cabrit 2006 Configuration favorable for outflows Bunching,  v >  d

19 Disk-Magnetosphere Interaction c  star c  disk

V = V Keplerian X-type winds (Shu et al. 1994) but: Star may rotate slowly – no fine-tuning Matter flows into cones Magnetic force Conical Winds Romanova et al. 2009

21 Background – matter flux, arrows – velocity. Young stars: T=2 years Stars of any spin: Conical Winds

22 Rapidly-rotating stars: Propeller regime Slow Conical Wind Poynting Jet Slow Conical Wind Two-component outflow forms Conical winds carry most of matter outwards Poynting jet carries energy and ang. momentum Romanova et al. 2005; Ustyugova et al. 2006; Romanova et al. 2009

23 Outflows at the Propeller Stage: Conical Winds + Axial Jet A star spins-down due to axial magnetic jet

24 Winds from Stars with Complex Fields Different initial configurations of the field Different quadrupole moments Lovelace et al. 2010

25 Wind is Asymmetric:

26

27 Flip-Flop Outflows in Pure Dipole case Lovelace et al. 2010

28 HST Observations: Cycle of inflation Cycle of inflation Simulations: Simulations: 7 years Major outbursts: 2 months HH30 Propeller Case Ustyugova et al. 2010

29 MRI-driven Accretion (large-scale turbulence) Long simulations: T=2,500 days = 7 years A star is in the propeller regime turbulent cells and centrifugal force prevent funnel accretion Spikes of accretion are observed (few months – one year) Accumulation and penetration of matter B Another study of episodic outbursts: Caroline D’Angelo & Spruit, H. BB Romanova et al. 2010

30 If a star with very complex field has a notable dipole component then it determines the disk-star interaction Complex field determines the shape of spots Conical outflows may form if magnetic flux is bunched Propeller-driven outflows carry angular momentum out of the star Outflows may be episodic Outflows from star with complex fields are asymmetric Summary

31 References: Camenzind, M. 1990, Reviews in Modern Astronomy, v. 3, (1990), p. 234 D’Angelo, C. & Spruit, H. 2010, MNRAS, eprint arXiv: Ferreira, J., Dougados, C., Cabrit, S. 2006, A&A, 453, 785 Koldoba, A.V., Romanova, M.M., Ustyugova, G.V., Lovelace, R.V.E. 2002, ApJL, 576, L53 Konigl, A. 1991, ApJ, 370, L39 Konigl, A. & Pudritz, R. 2000, Protostars and Planets IV, p.759 Long, M., Romanova, M.M., & Lovelace, R.V.E. 2007, MNRAS, 374, 436 “—”—” 2008, MNRAS, 386, 1274 Long, M., Romanova, M.M., Lamb, F.K., Kulkarni, A.K., Donati, J.-F. 2009, MNRAS, in press, eprint arXiv: Lovelace,R.V.E., Romanova, M.M., & Bisnovatyi-Kogan, G.S. 1995, MNRAS, 274, 244 Lovelace, R.V.E., Romanova, M.M., Ustyugova, G.V., Koldoba, A.V. 2010, MNRAS, in press Matt, S. & Pudritz, R. 2005, ApJ, 632, L135 Romanova, M.M., Ustyugova, G.V., Koldoba, A.V., Lovelace, R.V.E. 2003, ApJ, 595, 1009 “—”—” 2004, ApJ, 610, 920 “—”—” 2009, MNRAS, 399, 1802 Romanova, M.M.,Long, M., Lamb, F.K., Kulkarni, A.K., Donati, J.-f. 2009, in press, eprint arXiv: Shu, F.H. et al. 1994, ApJ, 429, 797 Uchida, Y. & Shibata, K. 1985, PASJ, 37, 515 Ustyugova, G.V., Koldoba, A.V., Romanova, M.M., Lovelace, R.V.E. 2006, ApJ., 646,304