Water Fountains in PrePlanetary Nebulae Hancock New Hampshire

Water Fountains in Pre-Planetary Nebulae Hancock, New Hampshire VLBA Antenna Mark Claussen NRAO June 19, 2007 Asymmetric Planetary Nebulae IV La Palma, Canary Islands

Water Fountain Pre-Planetary Nebulae • Outflow velocity of water masers extremely high compared to AGB radial expansion velocities • More than ten known or candidate water fountain sources • Usually discovered serendipitously (i. e. not searching for highvelocity flows) • A recent targeted survey turned up only April 22, 2004 U. . Wash. Astron.

June 19, 2007 APN IV

Very Long Baseline Array • Limited brightness temperature sensitivity • Limits observations to non-thermal phenomena • Superb angular resolution allows proper motion studies • Also allows A. U. scale structure on nearby objects • Astrometric studies give basic astronomy data April 22, 2004 U. Wash. Astron.

S 106 • Bipolar HII Region • Distance 600 pc • Luminosity: 24 – 1000 Lsun • Dark lane in radio and optical --- not a massive disk • No large scale outflow known

Late-Type Stars and Circumstellar Shells • Mira variables, OH/IR stars, and red supergiants • Pulsating stars • Oxygen-rich shells harbor molecular masers: OH, H 2 O, and Si. O • Masers can probe the kinematics and dynamics of the circumstellar shell April 22, 2004 U. Wash. Astron.

OH 100 --- 10000 AU H 2 O 100 s of AU Si. O

Si. O Masers and Dust Condensation Zone Photosphere A few stellar radii

Si. O Masers in TX Camelopardalis • Si. O masers in extended atmospheres between photosphere and inner dust formation radius • Observations at approximately bi-weekly intervals over approximately 2 years from optical phase 0. 68 to 1. 82 • Angular resolution ~500 microarcseconds (43 GHz) • Distance = 390 pc => physical resolution of 0. 2 AU • Masers roughly in a ring • Significant asymmetry in the shell • Gas motion show predominantly expansion, but local deviations

Diamond Kemball TX Cam Si. O Masers

Pre-planetary and Planetary Nebulae • Direct descendants of AGB circumstellar shells • So why are many not spherical in shape ? • Interacting winds ? • Fast wind is launched late in the history of AGB • Interacts with remnant of circumstellar shell • Where does fast wind come from ? April 22, 2004 U. Wash. Astron.

A few thousand A. U.

10 – 6 d n a s thou . U. A

IRAS 16342 -3814 Estimated Distance of 2 kpc Bipolar protoplanetary nebula “Water Fountain” Nebula 1000 AU

2000 AU

10 AU

VLBA Observations of Water Masers in IRAS 16342 -3814 • Six monthly epochs of VLBA observations in 2002 • Simultaneous VLA observations to help with position registration • The line connecting the extreme velocities (some 2970 mas long) has increased its length by 3 mas • The separation corresponds to velocity of 175 km/s • Water maser emission quite likely arises in shocks where a jet hits some molecular gas. April 22, 2004 U. Wash. Astron.

VLBI using NRAO’s VLBA • Not just for extragalactic science ! • Can be vital for understanding • Star formation • Radio emission from stars • Stellar endpoints http: //www. aoc. nrao. edu/vlba/html mclausse@nrao. edu

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