A Birth and Growth of a Collimated Molecular Jet from an AGB Star

1
A Birth and Growth of a Collimated Molecular Jet
from an AGB Star
Future Directions in High Resolution Astronomy
A Celebration of the 10th Anniversary of the VLBA

• Hiroshi Imai
• (Joint Institute for VLBI in Europe, NL)
• Philip J. Diamond
• (Jodrell Bank Observatory, UK)

• Water fountains cites of stellar jets birth
• W43A an AGB star having a jet and an envelope
• Implication of the W43A jet

The Great Barrier Dam, the Netherlands
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Jet formation in final stellar evolution

• Central objects of planetary nebulae (PNe)
  post-AGB stars
• Bipolar jets (gt100 km/s, gtgt 1000K, ionized)
• Producing complicated PN morphology

Jet from a planetary nebula Henize 2-90 (Sahai
Nyman 2000)
3
Jet formation in final stellar evolution

• When such stellar jets are launched ?
• How to launch such stellar jets ?

Jet from a planetary nebula Henize 2-90 (Sahai
Nyman 2000)
4
High velocity stellar molecular flows
Jet
Outflow

• Before finding
• optical jet
• Dragged by a
• (unseen) collimated jet

Outflow in OH 231.84.2 (Alcolea et al. 2001)
5
High velocity stellar molecular flows

• What is
• the central star?
• White dwarf ?
• Mira star ?
• or young star ?

Outflow in OH 231.84.2 (Alcolea et al. 2001)
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Transition from AGB to post-AGB

• A Mira variable (AGB star)
• Pulsation
• Spherical envelope
• Small bipolarity
• Slow wind (10 km/s)

Spherical circumstellar envelope around RT
Virginis (Imai et al. 2003, see poster no
.62
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Transition from AGB to post-AGB
A Mira-star envelope is transformed to a
collimated jet smoothly ?
Spherical circumstellar envelope around RT
Virginis (Imai et al. 2003, see poster no
.62
8
Water fountains cites of on-going jet
formation
W43A

• V(H2O) gt 100 km/s gtgt V(OH) lt 30 km/s
• Clear double peaks
• Symmetric with respect to the systemic velocity

IRAS 191342131
IRAS 16342-3814
High velocity H2O maser sources (Likkel et al.
1992)
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Water fountains cites of on-going jet
formation
W43A

• Newly-formed jets or extreme super winds ?
• How old ?
• How to produce ?
• Young stellar objects ?

IRAS 191342131
IRAS 16342-3814
High velocity H2O maser sources (Likkel et al.
1992)
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VLBA observations of the W43A H2O/OH masers

• H2O masers
• Jun. 1994, Oct. 1994, Mar. 1995, Apr.
  2002, Jul. 2002, Nov. 2002, Apr. 2003,
  ..... (now going on) Synthesized beam 0.5
  mas
• Velocity resolution 0.2 km/s
• OH masers (1612, 1665 1667MHz) Jun. 1994,
  Oct. 1994, Mar. 1995, Dec. 2001, Aug. 2002,
  ..... (now going on) Synthesized beam 9
  mas
• Velocity resolution 0.45 km/s

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History of the W43A jet
Birth of the molecular jet (at my
birthday?)
Destruction of the molecular jet (at the end of
my life?)
Discovery of the high-velocity masers
(Genzel Downes 1977)
Discovery of the molecular jet
(Imai et al. 2002)
VLBA operation (Since 1993)
H2O maser observations (7 epochs)
OH maser observations (5 epochs)
1970 1980 1990 2000
2010 2020 2030....
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Highly-collimated jet of molecular gas
The first one year Imai, Obara, Diamond,
Omodaka, Sasao 2002
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Jet parameters (1994 - 1995)
Imai et al. (2002)
21 proper motions

• 3D jet speed 145 /-20 km/s in major axis
• Standard deviation ratio V(jet)/V(internal)
  9.5 /-4.1 (variance-covariance analysis)

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Jet parameters (1994 - 1995)
Imai et al. (2002)
21 proper motions

• Jet alignment length 1700 AU, P.A.
  69.30.3 deg.
• Cluster alignment length 250, 350 AU, width lt
  30 AU
• P.A. 54.6/-6.0 deg., 57.2/-0.3 deg. (red,
  blue clusters)

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H2O maser kinematics in 2002
Imai Diamond (2003)
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Growth of the molecular jet

• Growth rate of jet 300AU/ 8 years 180 km/s
• Birth of the jet around the year 1970

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A precessing jet model
Point symmetry Constant-velocity motion of each
maser cloud Interaction with the ambient envelope
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A precessing jet model
Straight alignments with axis offsets gtgtgt
lifetime of maser clouds 10 years
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The W43A jet is precessing !

• Period 55 years
• Amplitude 5 degrees
• Inclination 39 degrees

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The precession is true !

• A consistent model at every epoch gtgtgt
  direct estimation d (2.6 kpc),
• origin location, and jet ignition time (30 yr
  ago)

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What star is W43A ?
An AGB star!
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Signatures of an pulsating star
Periodic flux variation (P 400 d) in OH 1612 MHz
masers (Harman Habing 1985 van Langevelde et
al. 1990)
Dwingeloo 25-m telescope
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Spherically-expanding envelope

• The same systemic velocity of the H2O and OH
  masers (VLSR 34 km/s)
• Similar to Mira OH maser sources

OH masers
1612 MHz OH masers
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Spherically-expanding envelope

• The same systemic velocity of the H2O and OH
  masers (VLSR 34 km/s)
• Dynamical time scale of the envelope 260 years

OH masers
Distance - velocity diagram
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When is a stellar jet launched?
H2O masers and a jet in PPN (Miranda et al. 2001)

• Mira stars
• Elongation of circumstellar envelop (Elitzur et
  al. 2003)
• by jets ? or by others?
• OH/IR stars
• Super winds (1000 years)
• H2O maser jets lt 100 years
• Later outflows, optical jets
• H2O maser segments in PPNs

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Morphology of planetary nebulae

• Determined by
• the envelope morphology
• at AGB phase,
• created by a stellar jet !

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Water fountains Molecular jets
W43A
Imai, Diamond 2003
IRAS 191342131
IRAS 16342-3814
UH88Sirius image (Deguchi Nakashima 2002)
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Water fountains Molecular jets
W43A
IRAS 191342131
Morris, Sahai Claussen 2003
IRAS 16342-3814
HST image (Sahai et al. 1999)
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Water fountains Molecular jets
W43A
IRAS 191342131
Imai, Morris Sahai 2003
3-D jet speed 120 km/s Dynamical time scale
90 years
IRAS 16342-3814
2MASS All Sky Survey image
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Water fountains Molecular jets
W43A
Similar sizes (2000 - 4000 AU) and
dynamical time scales (lt 100 years) of the
molecular jets !
IRAS 191342131
IRAS 16342-3814
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Duration of molecular jetin the earliest phase
of stellar jets 100 years

• A molecular jet in W43A
• was born with me and
• will disappear with me!

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A sensational chance in my life!
The Prince Charles, visiting in the MERLIN
upgrade celebration on 28 April 2003 at Jodrell
Bank Observatory, UK
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Schematic cartoon of W43A
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Thank you !
Kasteel de Haar, the Netherlands
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Circumstellar envelope of W43A
Well developed, but compact ......

• Size lt 10000 AU
• Mass 15 Msun
• (including
• foreground cloud)
• Optically thin
• (spectral index3-4)

20000 AU at 2.6 kpc
H2O OH masers
2.7 mm dust continuum emission (NMA
observation) (Imai et al. 2003)
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Circumstellar envelope of W43A
Has not be ionized yet .....
20000 AU at 2.6 kpc
H2O OH masers
UH88Sirius JHK-band image (Deguchi
Nakashima 2002)
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Signatures of going mass loss
SiO maser emission (see Nakashima Deguchi 2003)
Rotating disk ? e.g. IRC -10414 (Imai et al.
1999) NML Cyg (Boboltz Marvel 1999) OH
231.84.2 (Sanchez Contreras et al. 2002)