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

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 high- velocity 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.

S106 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 SiO Masers can probe the kinematics and dynamics of the circumstellar shell April 22, 2004 U. Wash. Astron.

OH H2OH2O SiO AU 100s of AU

Photosphere SiO Masers and Dust Condensation Zone A few stellar radii

SiO Masers in TX Camelopardalis SiO 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 SiO 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.

6 – 10 thousand A.U.

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

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

2000 AU

10 AU

VLBA Observations of Water Masers in IRAS 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

Expanded Very Large Array Phase I Improved sensitivity by a factor of 5 below 10 GHz to more than a factor of 20 between 10 and 50 GHz Operation at any frequency between 1 and 50 GHz New correlator to handle wide-band data transmission, also improving flexibility and spectral resolution. Project began in 2002, test antenna outfitting in 2003 First light with newly outfitted test antenna 28 October 2003 First fringes between test antenna and VLA antennas on March 24, 2004

EVLA Phase I Schedule Start installation prototype system on VLA antenna for testingApr 2003 Start production of new electronics systemsDec 2003 Start installation of new systems on VLA antennas at rate 4 ant/yearMay 2004 Start installation of new correlator in new screened roomApr 2006 First “shared risk” science with new correlator subsetApr 2007 New correlator fully operationalFeb 2009 Last antenna converted to EVLA designOct 2010 Last EVLA receiver installedApr 2012

Student / Visitor Programs at NRAO Undergraduate Summer Student Research Program (REU) Graduate Summer Student Research Assistantships like REU, but for 1 st and 2 nd year grad students Co-op program undergraduate engineering / computing students 2-3 semesters Graduate Student Internship Program first / second year graduate students for pursuing a research program (not summer, see above) Pre-Doctoral Research Program Ph. D. candidates in radio astronomy in residence at NRAO

Student / Visitor Programs at NRAO Pre-Doctoral Research Program Ph. D. candidates in radio astronomy in residence at NRAO GBT Student Support Program Visiting Scientist Program Ph.D. Scientists / Engineers – Faculty Terms of visit negotiable, weeks – months & sabbaticals