Asymmetric%20Planetary%20Nebulae%20IV

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Water Fountains in Pre-Planetary Nebulae
Mark Claussen NRAO June 19, 2007
Hancock, New Hampshire VLBA Antenna

• Asymmetric Planetary Nebulae IV
• La Palma, Canary Islands

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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.
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June 19, 2007 APN IV
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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.
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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

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Late-Type Stars and Circumstellar Shells

• Mira variables, OH/IR stars, and red
  supergiants
• Pulsating stars
• Oxygen-rich shells harbor molecular masers
• OH, H2O, and SiO
• Masers can probe the kinematics and dynamics
  of the
• circumstellar shell

April 22, 2004 U. Wash. Astron.
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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 gt physical resolution of 0.2
  AU
• Masers roughly in a ring
• Significant asymmetry in the shell
• Gas motion show predominantly expansion, but
  local deviations

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Diamond Kemball TX Cam SiO Masers
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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.
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A few thousand A.U.
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6 10 thousand A.U.
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IRAS 16342-3814
Estimated Distance of 2 kpc Bipolar
protoplanetary nebula Water Fountain Nebula
1000 AU
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IRAS 16342-3814
Estimated Distance of 2 kpc Bipolar
protoplanetary nebula Water Fountain Nebula
1000 AU
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10 AU
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VLBA Observations of Water Masers in
IRAS16342-3814

• 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.
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VLBI using NRAOs 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_at_nrao.e
du
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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

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EVLA Phase I Schedule
Start installation prototype system on VLA
antenna for testing Apr 2003 Start production
of new electronics systems Dec 2003 Start
installation of new systems on VLA antennas at
rate 4 ant/year May 2004 Start installation of
new correlator in new screened room Apr 2006
First shared risk science with new correlator
subset Apr 2007 New correlator fully
operational Feb 2009 Last antenna converted
to EVLA design Oct 2010 Last EVLA receiver
installed Apr 2012
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Student / Visitor Programs at NRAO

• Undergraduate Summer Student Research Program
  (REU)
• Graduate Summer Student Research Assistantships
• like REU, but for 1st and 2nd 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

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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
• http//www.nrao.edu/students
• http//www.nrao.edu/astrores/visitors.shtml