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Stellar water fountains Hiroshi Imai (Kagoshima University)

Stellar water fountains Hiroshi Imai (Kagoshima University). Contents Discovery and identification of the water fountains Properties of the water fountains and circumstellar envelopes Stellar evolution and the water fountains Corkscrew jets? Equatorial flows?

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Stellar water fountains Hiroshi Imai (Kagoshima University)

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  1. Stellar water fountainsHiroshi Imai (Kagoshima University) Contents • Discovery and identification of the water fountains • Properties of the water fountains and circumstellar envelopes • Stellar evolution and the water fountains • Corkscrew jets? Equatorial flows? • Precursors of water fountains? • Stellar kinematics in the Galaxy • Earlier than the water fountain phase • Summary

  2. Betelgeuse ⓒ NASA From spherically symmetric to asymmetric mass loss flow Egg Nebula ⓒ NASA When/how is a bipolar jet launched in the final stellarevolution?

  3. First high velocity flow seen in water maser emission W43A (Genzel & Downes 1977) “This is an extremely interesting source, probably a late-type star.” but might be a young stellar object?

  4. “Water fountains” in AGB/post-AGB phases W43A • Associated with evolved stars • Faster than expansion velocity of OH maser shell (Vexp >> 30 km/s) IRAS 19134+2131 IRAS 16342-3814 High velocity H2O maser sources (Likkel et al. 1992)

  5. 10 water fountains identified to date • W43A (Diamond et al. 1985; Imai et al. 2002, 2005; Vlemmings et al. 2006) • IRAS19134+2131 (Imai et al. 2004; 2007) • IRAS16342-3814 (Sahai et al. 1999; Morris et al. 2003; Claussen et al. 2004) • OH 12.8-0.9(Boboltz & Marvel 2005) • IRAS18286-0959 (Imai et al. 2007) • IRAS18460-0151 (Imai et al. 2007) • IRAS18596+0315 (Deacon et al. 2007) • IRAS15445-5449 (Deacon et al. 2007) • IRAS15544-5332 (Deacon et al. 2007) • IRAS18043-2116 (Deacon et al. 2007)

  6. W43A: First identification ofa water fountain in maser images Imai et al. 2002 Nature 417, 829 Periodic OH maser variation (P~360 days) (Hertman & Habing 1985) Jet velocity =145 km/s, dynamical age ~50 yr

  7. Quenching water fountainwithin < 1000 years Photodissociation destroying H2O molecules Collimated jet before full photoionization Dispersing water fountain in Pre-PN phase 5000 AU Continuum radio emission (=planetary nebula) and H2O/OH masers in K3-35 (Miranda et al. 2001)

  8. HST image IRAS 19134+2131 -23 - -10 km/s -121- -117 km/s • Optically visible → in pre-planetary nebula (PPN) phase • Flow dynamical age ~50 years Imai et al. (2007)

  9. Dynamical ages < 100 years IRAS 16342-3814 (Morris, Sahai & Claussen 2003) OH 12.8-0.9 (Boboltz & Marvel 2005)

  10. W43A: AGB phase • No nebulosity, detected by SPITZER GLIMPSE (Deguchi et al. 2007) • OH maser shell (R~500 AU, Vexp=9km/s) • SiO maser detection (Nakashima & Deguchi 2002) • Dust envelope radius < 3000 AU • Dynamical age T~ 260 yr (OH), 1600 yr (dust)

  11. W43A details: Jet precession • Precession period ~55 years • Precession angle amplitude ~5° • (10-year scale) length growth speed≈ (1-year scale) maser feature proper motions Imai et al. 2005

  12. Magnetohydrodynamical (MHD) jet • Zeeman effect and linear polarization (Vlemmings, Diamond & Imai 2006, Nature 440, 58)

  13. Bow shock?Spiral flow? (VLA) (VLBA) (VLBA) 500 AU at 8 kpc Imai et al. (2004) IRAS19134+2131 Imai et al. (2007)

  14. Corkscrew jets?Bow shocks? IRAS16342-3814 (Sahai et al. 2005) W43A (Imai & Diamond in prep)

  15. SiO/H2O and continuum locations Equatorial flow? Biconical SiO maser flow (~15 km/s) | within 10 AU | H2O maser jet (Imai et al. 2005) (Imai et al. in prep.) Where is a disk?

  16. Proper motion in the equatorial flow • Flow velocity ~30 km/s W43A (Imai & Diamond in prep)

  17. New water fountains IRAS 18286-0959 (Deguchi et al. in prep.)

  18. New water fountains IRAS 18460-0151 (Deguchi et al. in prep.) Equatorial flow ? (see Miyaji’s talk)

  19. Maser source astrometry with position-reference QSO Galactic rotation H2O masers in IRAS 19134+2131 (Imai et al. 2007)

  20. Annual parallax and Galactic rotation

  21. Location and velocity in the Galaxy IRAS 19134+2131 (Imai et al. 2007) • Annual parallax distance = 8.0+0.9-0.7 kpc • Location: (R, θ, z)=(7.4 kpc, 62deg, 650 pc) • 3D velocity (VR, Vθ, Vz) =(3, 125, 8)[km/s] • Travel time from the Galactic plane > 7.7 x 107 years >> M*< 5 Msun c.f. Progenitors of bipolar nebulae may be higher mass stars located near the Galactic plane.

  22. Summary Magneto-hydrodynamical Corkscrew/precessing jet V> 100 km/s, T~100 years M*< 5 Msun single AGB/post-AGB star (or binary <10 AU?) Equatorial flow V~ 20-30 km/s Evolution from AGB flow? Only 10 water fountains in the whole Galaxy?

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