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Accretion onto Binary YSOs through Gap from Their Circumbinary Disk

Accretion onto Binary YSOs through Gap from Their Circumbinary Disk. Accretion rate of primary is larger than that of secondary. Accretion rate varies with a large amplitude. T. Hanawa, Y. Ochi, & K. Ando (Chiba Univ.). Majority of YSOs are multiple. UY Aur (Close et al. 1998). SPH model

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Accretion onto Binary YSOs through Gap from Their Circumbinary Disk

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  1. Accretion onto Binary YSOs through Gap from Their Circumbinary Disk Accretion rate of primary is larger than that of secondary. Accretion rate varies with a large amplitude. T. Hanawa, Y. Ochi, & K. Ando (Chiba Univ.)

  2. Majority of YSOs are multiple. UY Aur (Close et al. 1998) SPH model Artymowicz & Lubow (1996) Accretion from circumbinary disk should be important for evolution of YSO binaries. Q1: Does binary motion enhance the disk accretion? Q2: Which accretes more? Secondary or Primary?

  3. Fixed Binary orbit (no self-gravity) a = 1 (mean separation) q =M2/M1 (mass ratio) ω = 1 (mean angular velocity) e (eccentricity) cs: constant Δtouｔ Δtin= 2 Δtout 2D model • Corotation frame • Dual time step • 24002～ 34562 cells

  4. q = 0.8, cs = 0.2, e = 0, rin = 1.75, & rout =5.18

  5. Accretion onto Primary Frequency Spiral Shock Waves excited by Resonance

  6. Stationary Spirals and Traveling Spirals

  7. Shock Strength Resonances at Ω=Ω*/4, Ω*/6, …, Ω*/(2n) [different from the Lindblad and ultraharmonic resonances]

  8. Dependences on N and Rout

  9. Dependence on Cs Accretion rate is lower when Cs is lower.

  10. Dependence on rin Accretion begins later for a larger rin. N = 2400, rout = 4.2

  11. N = 2400, rin = 2.5, rout = 4.2 Main resonance at r = 3.30

  12. Qualitatively independent of q

  13. q = 0.9, e = 0.14, cs = 0.2 R: Primary L: Secondary

  14. Preferential accretion onto primary: origin of apparently different ages? • SVS 13 in NGC1333 • VLA4A is apparently more evolved than VLA4B (0”.3). • YLW 15 • VLA 1 (embedded) & VLA 2 (Class I) • IRAS 16293-2422 • Combinations of protostars with and without outflows

  15. Summary • Accretion rate of primary is larger than that of the companion, which implies decrease in the mass ratio by accretion. • Gas flow inside the Roche lobe is important. • Stationary and traveling spiral waves are excited and resonant with the binary through higher harmonics. • Accretion rate varies with a large amplitude at a timescale comparable to the rotation period, which denies quasi-stationary accretion flow.

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