Astrometry of Water Masers in Post-AGB Stars

Hiroshi ImaiGraduate School of Science and Engineering, Kagoshima

University

ContentsAstrometry with VLBA, and VERA (EVN for OH

masers) Results of astrometry

IRAS 19134+2131 K3-35 IRAS 19312+1950 IRAS 18286-0959 IRAS 22480+6002

Future perspectives

This talk is based on several researches with collaborators listed as follows.

Guillem Anglada, Philip J. Diamond, Shuji Deguchi, Yolanda Gómez, Tomoya Hirota, Mareki Honma, Murray B. Lewis, Sun Kwok,

Luis F. Miranda, Takeshi Miyaji, Mark Morris, Hiroyuki Nakanishi, Jun-ichi Nakashima, Nimesh Patel, Raghvendra Sahai,

Daniel Tafoya, Jose, M. Torrelles, Bosco Yung, and VERA collaboration

Astrometry with VLBA and VERA

(Sub) milli-arcsecond level angular resolution10-100 micro-arcseconds level astrometric accuracyradio astrometry for non-thermal sources, e.g. maserstrigonometric parallax measurement on kpc-scaleabsolute coordinates and secular motions

Dual beam system equipped for VERA

perfect compensation of atmospheric fluctuation and instrumental delay difference between position-reference and target sources separated by 0.3-2.2 deg.

measurement of atmospheric zenith delay residual using GPS data

Tracking motions of water maser features

Galacticrotation

Water masers in IRAS 19134+2131 (Imai et al. 2007)

Detection of annual parallax

Maser spot motion in IRAS 22480+6002 (Preliminary) π=~360 μas, D~2.8 kpc

Target sources and scientific goals

water fountains (AGB/post-AGB)IRAS 19134+2131IRAS 18286-0959

pre-planetary nebulaIRAS 19312+1950

planetary nebulaK3-35

K-type supergiantIRAS 22480+6002

trigonometric parallax distancessource luminositysource mass

secular motiondeviation from

circular Galactic rotation

birth point and ageInternal motion of

water maser sourcekinematic property

of bipolar jet, equatorial torus, and circumstellar envelope

IRAS 19134+2131 (water fountain)

Dynamical age of jet ~50 yearsWatching light from

central star

Imai, Sahai, & Morris (2007)

IRAS 19134+2131 (water fountain)

Travel time from the Galactic plane

1.1-7.7 x 107 yearsStellar mass M*< 5-5.8 M◉

Imai, Sahai, & Morris (2007)

IRAS 18286-0959 (water fountain, double helix)

Discovered in SPIZER/GLIMPS image

(Deguchi et al. 2007)

Dynamical age of jet ~60 yearsDiscontinuous mass ejection to form the double helix(Jet 1 is younger than Jet 2.)

Yung et al. (2011)

Location of 1612 MHz OH maser (Imai et al. 2008)

IRAS 18286-0959

D=3.9+1.1-0.7 kpc

(R,z)=(4.9±0.7 kpc, 22±2 pc)(VR, Vθ, Vz) [km s-1]= (64±30, 133±36, -17±31)

Preliminary results(will be revised) Imai et al. (in prep.)

Motions of spots in Jet 2:• large deviation from circular Galactic rotation• consistent with

jet motion (~100 km/s) + stellar motion (~30 km/s)?

IRAS 19312+1950(pre-planetary nebula)

Double peaks (ΔV~30 km/s) of H2O and SiO masersSmall relative proper

motionsBinary system?

or bipolar flow?

Enigmatic sourceC-rich/O-rich hybrid

chemistry in envelope

Nakashima et al. (2011)

IRAS 19312+1950

D=3.8+0.8-0.6 kpc

(R,z)= (7.1±0.1 kpc, 28±3 pc)(VR, Vθ, Vz) [km s-1]= (33±28, 214±4, -14±8)

L*~18,000 Lsun

dM/dt~10-4 Msun yr-1

Roughly following circular Galactic rotation,but it is not a YSO.

Imai et al. (2011)

K3-35 (planetary

nebula)Photo ionization time

scale ~50 yearsDynamical time scale of

the bipolar nebula ~1000 years

Tafoya et al. (2011)

Miranda et al. (2001)

K3-35 (planetary nebula)

D=3.9+0.7-0.5 kpc

(R,z) [kpc, pc]= (7.1±0.1, 140+25

-18)(VR, Vθ, Vz) [km s-1]= (33±16, 233±11, 11±2)

Following circular Galactic rotation

Tafoya et al. (2011)

IRAS 22480+6002 (K-type star)

First example of H2O maser source associated with K-type starBipolar flow traced by H2O maser motions

(Imai et al. 2008; Imai et al. in prep.)

2MASS image

IRAS 22480+6002

D=2.8+0.37-0.29 kpc

(R,z)=(9.7±0.2 kpc, 59±6 pc)(VR, Vθ, Vz) [km s-1]= (203±6, 54±4, -3±1)L*~45,000 Lsun

K-type supergiant harboring H2O/SiO maser emission

Preliminaryresults

Future perspectives

Upgrade in VLBA and VERAWider receiving band width for detecting fainter

position-reference sources closer to target stars. Higher dispersion spectroscopy for water fountains. Joint operation of VERA and KVN

Statistical analysis of astrometric information~15 water fountain sources~10 pre-planetary and planetary nebulaeEvolved stars with peculiar motionsDiagnostics of luminosities, masses, mass loss rates,

binarity, etc. to track the final stellar evolution Larger sample: GBT, Effelsberg, EVLA /ALMA

…..ASKAP/SKAOH masers in the Galactic disk, bulge, and haloKinematic study on maser sources in the Magellanic

Clouds