1. Astrometry of Water Masers in Post-AGB Stars Hiroshi Imai Graduate School of Science and Engineering, Kagoshima University

2. Contents Astrometry 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

3. Astrometry with VLBA and VERA (Sub) milli-arcsecond level angular resolution 10-100 micro-arcseconds level astrometric accuracy radio astrometry for non-thermal sources, e.g. masers trigonometric parallax measurement on kpc-scale absolute coordinates and secular motions

4. 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

5. Tracking motions of water maser features Galactic rotation Water masers in IRAS 19134+2131 (Imai et al. 2007)

6. Detection of annual parallax Maser spot motion in IRAS 22480+6002 (Preliminary) π=~360 μas, D~2.8 kpc

7. Target sources and scientific goals water fountains (AGB/post-AGB) IRAS 19134+2131 IRAS 18286-0959 pre-planetary nebula IRAS 19312+1950 planetary nebula K3-35 K-type supergiant IRAS 22480+6002 trigonometric parallax distances source luminosity source mass secular motion deviation from circular Galactic rotation birth point and age Internal motion of water maser source kinematic property of bipolar jet, equatorial torus, and circumstellar envelope

8. IRAS 19134+2131 (water fountain) Dynamical age of jet ~50 years Watching light from central star Imai, Sahai, & Morris (2007)

9. IRAS 19134+2131 (water fountain) Travel time from the Galactic plane 1.1-7.7 x 10 7 years Stellar mass M * < 5-5.8 M Imai, Sahai, & Morris (2007)

10. IRAS 18286-0959 (water fountain, double helix) Discovered in SPIZER/GLIMPS image (Deguchi et al. 2007) Dynamical age of jet ~60 years Discontinuous 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)

11. IRAS 18286-0959 D=3.9 +1.1 -0.7 kpc (R,z)=(4.9±0.7 kpc, 22±2 pc) (V R, V θ, V z ) [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)?

12. IRAS 19312+1950 (pre-planetary nebula) Double peaks (ΔV~30 km/s) of H 2 O and SiO masers Small relative proper motions Binary system? or bipolar flow? Enigmatic source C-rich/O-rich hybrid chemistry in envelope Nakashima et al. (2011)

13. IRAS 19312+1950 D=3.8 +0.8 -0.6 kpc (R,z)= (7.1±0.1 kpc, 28±3 pc) (V R, V θ, V z ) [km s -1 ]= (33±28, 214±4, -14±8) L * ~18,000 L sun dM/dt~10 -4 M sun yr -1 Roughly following circular Galactic rotation, but it is not a YSO. Imai et al. (2011)

14. K3-35 (planetary nebula) Photo ionization time scale ~50 years Dynamical time scale of the bipolar nebula ~1000 years Tafoya et al. (2011) Miranda et al. (2001)

15. K3-35 (planetary nebula) D=3.9 +0.7 -0.5 kpc (R,z) [kpc, pc]= (7.1±0.1, 140 +25 -18 ) (V R, V θ, V z ) [km s -1 ]= (33±16, 233±11, 11±2) Following circular Galactic rotation Tafoya et al. (2011)

16. IRAS 22480+6002 (K-type star) First example of H 2 O maser source associated with K-type star Bipolar flow traced by H 2 O maser motions (Imai et al. 2008; Imai et al. in prep.) 2MASS image

17. IRAS 22480+6002 D=2.8 +0.37 -0.29 kpc (R,z)=(9.7±0.2 kpc, 59±6 pc) (V R, V θ, V z ) [km s -1 ]= (203±6, 54±4, -3±1) L * ~45,000 L sun K-type supergiant harboring H 2 O/SiO maser emission Preliminary results

18. Future perspectives Upgrade in VLBA and VERA Wider 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 nebulae Evolved stars with peculiar motions Diagnostics of luminosities, masses, mass loss rates, binarity, etc. to track the final stellar evolution Larger sample: GBT, Effelsberg, EVLA /ALMA …..ASKAP/SKA OH masers in the Galactic disk, bulge, and halo Kinematic study on maser sources in the Magellanic Clouds