Stellar water fountains Hiroshi Imai Kagoshima University Contents

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? – Precursors of water fountains? • Stellar kinematics in the Galaxy • Earlier than the water fountain phase • Summary

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

First high velocity flow seen in water maser emission W 43 A (Genzel & Downes 1977) “This is an extremely interesting source, probably a late-type star. ” but might be a young stellar object?

W 43 A IRAS 19134+2131 IRAS 16342 -3814 “Water fountains” in AGB/post-AGB phases • Associated with evolved stars • Faster than expansion velocity of OH maser shell (Vexp >> 30 km/s) High velocity H 2 O maser sources (Likkel et al. 1992)

10 water fountains identified to date – W 43 A (Diamond et al. 1985; Imai et al. 2002, 2005; Vlemmings et al. 2006) – IRAS 19134+2131 (Imai et al. 2004; 2007) – IRAS 16342 -3814 (Sahai et al. 1999; Morris et al. 2003; Claussen et al. 2004) – OH 12. 8 -0. 9 (Boboltz & Marvel 2005) – IRAS 18286 -0959 (Imai et al. 2007) – IRAS 18460 -0151 (Imai et al. 2007) – – IRAS 18596+0315 (Deacon et al. 2007) IRAS 15445 -5449 (Deacon et al. 2007) IRAS 15544 -5332 (Deacon et al. 2007) IRAS 18043 -2116 (Deacon et al. 2007)

W 43 A: First identification of a 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

Quenching water fountain within < 1000 years 5000 AU Photodissociation destroying H 2 O molecules Collimated jet before full photoionization Dispersing water fountain in Pre -PN phase Continuum radio emission (=planetary nebula) and H 2 O/OH masers in K 3 -35 (Miranda et al. 2001)

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

Dynamical ages < 100 years IRAS 16342 -3814 OH 12. 8 -0. 9 (Morris, Sahai & Claussen 2003) (Boboltz & Marvel 2005)

W 43 A: AGB phase • • • No nebulosity, detected by SPITZER GLIMPSE (Deguchi et al. 2007) OH maser shell (R~500 AU, Vexp=9 km/s) Si. O maser detection (Nakashima & Deguchi 2002) Dust envelope radius < 3000 AU Dynamical age T~ 260 yr (OH), 1600 yr (dust)

W 43 A details: Jet precession Imai et al. 2005 • Precession period ~55 years • Precession angle amplitude ~5° • (10 -year scale) length growth speed ≈ (1 -year scale) maser feature proper motions

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

(VLA) (VLBA) Bow shock? Spiral flow? (VLBA) 500 AU at 8 kpc Imai et al. (2004) IRAS 19134+2131 Imai et al. (2007)

Corkscrew jets? Bow shocks? IRAS 16342 -3814 (Sahai et al. 2005) W 43 A (Imai & Diamond in prep)

Equatorial flow? Si. O/H 2 O and continuum locations Biconical Si. O maser flow (~15 km/s) | within 10 AU | H 2 O maser jet (Imai et al. 2005) (Imai et al. in prep. ) Where is a disk?

Proper motion in the equatorial flow • Flow velocity ~30 km/s W 43 A (Imai & Diamond in prep)

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

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

Maser source astrometry with position-reference QSO Galactic rotation H 2 O masers in IRAS 19134+2131 (Imai et al. 2007)

Annual parallax and Galactic rotation

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, 62 deg, 650 pc) – 3 D 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.

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? ) Only 10 water fountains in the whole Galaxy? Equatorial flow V~ 20 -30 km/s Evolution from AGB flow?