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

Hiroshi Imai (Joint Institute for VLBI in Europe, NL)

Philip J. Diamond(Jodrell Bank Observatory, UK)

Future Directions in High Resolution Astronomy: A Celebration of the 10th Anniversary of the VLBA

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

The Great Barrier Dam, the Netherlands

Jet formation in final stellar evolution

• Central objects of planetary nebulae (PNe) = post-AGB stars

– Bipolar jets (>100 km/s, >> 1000K, ionized)– Producing complicated PN morphology

Jet from a planetary nebula: Henize 2-90 (Sahai & Nyman 2000)

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)

High velocity stellar molecular flows

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

Outflow in OH 231.8+4.2 (Alcolea et al. 2001)

Jet Outflow

High velocity stellar molecular flows

What is the central star?

White dwarf ? Mira star ?

or young star ?

Outflow in OH 231.8+4.2 (Alcolea et al. 2001)

Transition from AGB to post-AGB

Spherical circumstellar envelope: around RT Virginis (Imai et al. 2003, see poster no .62

• A Mira variable (AGB star):

– Pulsation– Spherical

envelope– Small bipolarity– Slow wind

(~10 km/s)

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

High velocity H2O maser sources (Likkel et al. 1992)

Water fountains: cites of on-going jet formation

• V(H2O) >= 100 km/s >> V(OH) =< 30 km/s

• Clear double peaks• Symmetric with respect to

the systemic velocity

W43A

IRAS16342-3814

IRAS19134+2131

High velocity H2O maser sources (Likkel et al. 1992)

Water fountains: cites of on-going jet formation

• Newly-formed jets or extreme super winds ?

• How old ?

• How to produce ?

• Young stellar objects ?

W43A

IRAS16342-3814

IRAS19134+2131

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 masVelocity 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

History of the W43A jet

1970 1980 1990 2000 2010 2020 2030....

Birth of the molecular jet (at my birthday?)

Discovery of the high-velocity masers (Genzel & Downes 1977)

H2O maser observations(7 epochs)

OH maser observations(5 epochs)

Destruction of the molecular jet (at the end of my life?)

Discovery of the molecular jet (Imai et al. 2002)VLBA operation

(Since 1993)

Highly-collimated jet of molecular gas

The first one year: Imai, Obara, Diamond, Omodaka, & Sasao 2002

Jet parameters (1994 - 1995)

-300

-200

-100

0

100

-700-600-500-400-300-200-1000100

119 - 126 km/s114 - 117 km/s-3 - 0 km/s-8 - -7 km/s-50 - -46 km/s-57 - -50 km/s

Dec

l. o

ffse

t (m

as)

R.A. offset (mas)

Proper motion100 km/s

• 3D jet speed: 145 +/-20 km/s in major axis • Standard deviation ratio:

V(jet)/V(internal) = 9.5 +/-4.1 (variance-covariance analysis)

21 proper motions

Imai et al. (2002)

Jet parameters (1994 - 1995)

-300

-200

-100

0

100

-700-600-500-400-300-200-1000100

119 - 126 km/s114 - 117 km/s-3 - 0 km/s-8 - -7 km/s-50 - -46 km/s-57 - -50 km/s

Dec

l. o

ffse

t (m

as)

R.A. offset (mas)

Proper motion100 km/s

• Jet alignment: length = 1700 AU, P.A.= 69.3±0.3 deg.• Cluster alignment: length = 250, 350 AU, width < 30 AU

P.A.= 54.6+/-6.0 deg., 57.2+/-0.3 deg. (red, blue clusters)

21 proper motions

Imai et al. (2002)

H2O maser kinematics in 2002Imai & Diamond (2003)

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

Point symmetry

Constant-velocity motion of each

maser cloud

Interaction with the ambient envelope

A precessing jet model

Straight alignments with axis offsets

>>> lifetime of maser clouds ~ 10 years

A precessing jet model

The W43A jet is precessing !

-500

-250

0

250

500

-1000-50005001000

Maser spot (Oct. 1994)Precessing jet model (1994.8)

Y (

AU

)

X (AU)

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

The precession is true !

-500

-250

0

250

500

-1000-50005001000

Maser spot (Oct. 1994)Precessing jet model (1994.8)

Y (

AU

)

X (AU)

Maser spot (Apr. 2002)Precessing jet model (2002.3)

A consistent model at every epoch >>> direct estimation: d (~2.6 kpc),

origin location, and jet ignition time (~30 yr ago)

What star is W43A ?

An AGB star!

Periodic flux variation (P~ 400 d) in OH 1612 MHz masers(Harman & Habing 1985; van Langevelde et al. 1990)

Dwingeloo 25-m telescope

Signatures of an pulsating star

-300

-200

-100

0

100

-700-600-500-400-300-200-1000100

1994 October 10

118 - 126 km/s114 - 118 km/s-8 - 0 km/s-51 - -46 km/s-57 - -51 km/s

Dec

l. of

fset

(m

as)

R.A. offset (mas)

500 AU @2.6 kpc

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

-150

-100

-50

0

50

100

150

050100150200250300

1994 June-October

42 - 44 km/s38 - 42 km/s25 - 30 km/s

Dec

l. of

fset

(m

as)

R.A. offset (mas) 1612 MHz OH masers

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

-150

-100

-50

0

50

100

150

050100150200250300

1994 June-October

42 - 44 km/s38 - 42 km/s25 - 30 km/s

Dec

l. of

fset

(m

as)

R.A. offset (mas) Distance - velocity diagram

• 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: < 100 years

– Later outflows, optical jets

– H2O maser segments in PPNs

When is a stellar jet launched? H2O masers and a jet in PPN

(Miranda et al. 2001)

Morphology of planetary nebulae

Determined by

the envelope morphology

at AGB phase,

created by a stellar jet !

Water fountains = Molecular jets

UH88+Sirius image (Deguchi & Nakashima 2002)

Imai, & Diamond 2003

W43A

IRAS16342-3814

IRAS19134+2131

Water fountains = Molecular jets

HST image (Sahai et al. 1999)

Morris, Sahai & Claussen 2003

W43A

IRAS16342-3814

IRAS19134+2131

Water fountains = Molecular jets

2MASS All Sky Survey image

Imai, Morris & Sahai 2003

W43A

IRAS16342-3814

IRAS19134+2131

3-D jet speed: ~120 km/sDynamical time scale ~ 90 years

Water fountains = Molecular jetsW43A

IRAS16342-3814

IRAS19134+2131

Similar sizes (2000 - 4000 AU)

and dynamical time scales

(< 100 years) of the molecular jets !

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!

A sensational chance in my life!

The Prince Charles, visiting in the MERLIN upgrade celebrationon 28 April 2003 at Jodrell Bank Observatory, UK

Schematic cartoon of W43A

Kasteel de Haar, the Netherlands

Thank you !

Circumstellar envelope of W43A

+H2O & OH masers

2.7 mm dust continuum emission (NMA observation)(Imai et al. 2003)

20000 AU at 2.6 kpc

Well developed, but compact ......

•Size < 10000 AU •Mass ~ 15 Msun

(including foreground cloud)• Optically thin (spectral index~3-4)

Circumstellar envelope of W43A Has not be ionized yet .....

+H2O & OH masers

20000 AU at 2.6 kpc

UH88+Sirius JHK-band image (Deguchi & Nakashima 2002)

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 231.8+4.2 (Sanchez Contreras et al.

2002)