Stellar water fountains Hiroshi Imai (Kagoshima University)

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

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From spherically symmetric to asymmetric mass
loss flow
Betelgeuse ? NASA
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 gtgt 30 km/s)

IRAS 191342131
IRAS 16342-3814
High velocity H2O maser sources (Likkel et al.
1992)
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10 water fountains identified to date

• W43A
• (Diamond et al. 1985 Imai et al. 2002, 2005
  Vlemmings et al. 2006)
• IRAS191342131
• (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)
• IRAS185960315 (Deacon et al. 2007)
• IRAS15445-5449 (Deacon et al. 2007)
• IRAS15544-5332 (Deacon et al. 2007)
• IRAS18043-2116 (Deacon et al. 2007)

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W43A First identification ofa water fountain in
maser images
Imai et al. 2002 Nature 417, 829
Periodic OH maser variation (P360 days)
(Hertman Habing 1985) Jet velocity 145
km/s, dynamical age 50 yr
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Quenching water fountainwithin lt 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)

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IRAS 191342131
HST image
-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

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Dynamical ages lt 100 years
IRAS 16342-3814 (Morris, Sahai Claussen 2003)
OH 12.8-0.9 (Boboltz Marvel 2005)
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W43A AGB phase

• No nebulosity, detected by SPITZER GLIMPSE
  (Deguchi et al. 2007)
• OH maser shell (R500 AU, Vexp9km/s)
• SiO maser detection (Nakashima Deguchi 2002)
• Dust envelope radius lt 3000 AU
• Dynamical age T 260 yr (OH), 1600 yr (dust)

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W43A 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

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Magnetohydrodynamical (MHD) jet

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

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Bow shock?Spiral flow?
(VLA)
(VLBA)
(VLBA)
500 AU at 8 kpc
Imai et al. (2004)
IRAS191342131
Imai et al. (2007)
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Corkscrew jets?Bow shocks?
IRAS16342-3814 (Sahai et al. 2005)
W43A (Imai Diamond in prep)
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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?
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Proper motion in the equatorial flow
W43A (Imai Diamond in prep)

• Flow velocity 30 km/s

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New water fountains
IRAS 18286-0959 (Deguchi et al. in prep.)
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New water fountains
IRAS 18460-0151 (Deguchi et al. in prep.)
Equatorial flow ? (see Miyajis talk)
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Maser source astrometry with position-reference
QSO
Galactic rotation
H2O masers in IRAS 191342131 (Imai et al. 2007)
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Annual parallax and Galactic rotation
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Location and velocity in the Galaxy
IRAS 191342131 (Imai et al. 2007)

• Annual parallax distance 8.00.9-0.7 kpc
• Location (R, ?, z)(7.4 kpc, 62deg, 650 pc)
• 3D velocity (VR, V?, Vz) (3, 125, 8)km/s
• Travel time from the Galactic plane
• gt 7.7 x 107 years gtgt Mlt 5 Msun
• c.f. Progenitors of bipolar nebulae may be higher
  mass stars located near the Galactic plane.

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Summary
Magneto-hydrodynamical Corkscrew/precessing
jet Vgt 100 km/s, T100 years
Mlt 5 Msun single AGB/post-AGB star (or binary
lt10 AU?)
Equatorial flow V 20-30 km/s Evolution
from AGB flow?
Only 10 water fountains in the whole Galaxy?