1. Astrometric Observations of Mira variables with VERA A.Nakagawa ( 中川亜紀治 ), D.Nyu, M.Matsui, T.Omodaka, H.Imai, S.Kameno (Kagoshima University), T.Kurayama (KASI), H.Kobayashi, K.M.Shibata (NAOJ), VERA Project Team East Asia VLBI WS, Mar, 2009 the LG Convention Hall at the Ewha Woman’s University, Seoul, Korea 1

2. Outline “Mira variables project” as a sub-project of VERA Observations Results & Discussion  Internal motions of masers  Parallax measurement  Tentative Galactic Mira PL-relation  Application of our result Summary 2

3. → Mk determination : Distance obtained with VERA → Calibration of a distance ladder PL relation of the Galactic Miras Milky Way Galaxy Absolute magnitude obtained with Hipparcos results Large errors of distances ? PL relation of Miras in LMC LMC Using apparent magnitudes Ita et al. 2004 PL relation of the Mira variables 3

4. Advantage HIPPARCOS D~100pc VERA D~10kpc VERA HIPPARCOS Observable Region with <10% Distance error. VERA vs HIPPARCOS

5. Observation, Data Reduction Mira variables with H2O/SiO maser emission  O-rich AGB stars Phase referencing VLBI monitoring Wide period range to determine the PL-relation  Ideally, 100 – 1000 days → Actually, 215 days (VX UMa) – 654 days(AW Tau) Bright phase : maser time variability Parallax and linear motions （ α, δ)→π 、 μα 、 μδ α: Right Ascension of the source δ: Declination of the source r : Radius vector of the sun l : Celestial longitude of the sun ε: Obliquity of the ecliptic g : Mean anomaly of the sun π π π π （ μα, μδ ） We extract parallax and two dimensional motions from multi-epoch data. PL-relation :100 – 1000 days 5

6. Results S Crt Pulsation Period = 155day Δm V = 0.8 Semiregulra variable : SRa 22GHz water maser 6

7. Circumstellar masers of S Crt Bipolar Outflow Inclination angle of flow axis = 43° Photosphere 260±20R 。 ～ Lower limit of Mira size Maser distribution 9 ～ 10AU VERA Pi = 2.33 mas err 0.13 mu_a -3.17 mas/yr err 0.22 mu_d -5.41 mas/yr err 0.22 HIPPARCOS Pi = 1.27 mas err 0.92 mu_a -3.37 mas/yr err 1.00 mu_d -4.67 mas/yr err 0.75 Nakagawa et al.2008 7

8. Parallax of S Crt (Semiregular : SRa) Parallax 2.33±0. １ 3 mas ↓ Distance 430+25-23pc Nakagawa et al. 2008 HIPPARCOS Parallax = 1.27 mas err 0.92 8

9. π = 0.76 ± 0.03 [mas] D = 1.319 +.047 -.043 [kpc] ( μ x, μ y ) = (6.41, -6.90 )[mas/yr] Parallax of SY Scl Pulsation period 411day Internal motions of maser spots around SY Scl Nyu et al. 2009 (Submitted to PASJ) 9

10. (Us,Vs,Ws)=(-5.2±0.3,-53.8±2.1,-33.3±0.3)[km s ] SYScl 太陽 10

11. 過去 10 億年の SY Scl と太陽の運動 動径方向 Y-Z 平面 X-Z 平面 SY Scl [Mira Variable] The Sun [Main Sequence] Amplitude (R) [kpc] 1.00.5 Velocity [km/s/kpc] 44.436.7 Amplitude (Z) [kpc] 1.50.07 Period (Z) [Myr] 8634 SY Scl ・ Oscillation Amplitude (Z-direction) 1.5 kpc Thick Disk (Gies & Helsel 2005) (Feast & Whitelock 1997) (Gies & Helsel 2005) (Stothers 1998) 11

12. R Uma, T Lep Pulsation period 301d (LogP=2.48) Parallax 1.72±0.09mas (preliminary) Pulsation period 368d （ LogP=2.57 ） Parallax 2.62±0.33mas （ preliminary ） Distance 381±48pc （ preliminary ） R UMa 12

13. Very recent study of T Lep

14. Central star 1AU (208R 0 ) → 2.5AU (475R 0 ) Molecular layer 2.5AU (520R 0 ) → 5.7AU (1080R 0 )

15. Example : Phase Referenced Image RX Boo Period 340d （ LogP=2.53 ） Peak = 7Jy/beam Y Lib Period 276d （ LogP=2.44) Peak = 280mJy/beam J0113+13 WX Psc Period 660d （ LogP=2.82 ） QSO phase-referened image RX Boo Y Lib 13

16. Source : SY Scl, T Lep, R UMa, S Crt* (* Semiregular) PL-relation of the Galactic Mira variables (preliminary, Weighted least-squares fit) Mk = a*(LogP-P 0 ) + b a = -3.73 +/- 0.53 b = -7.58 +/- 0.03 S Crt T Lep SY Scl R UMa (Nakagawa et al. in prep) 14

17. LMC ： a = -3.520±0.034 (Ita et al. 2004) Source : SY Scl, T Lep, R UMa, S Crt* (* Semiregular) PL-relation of the Galactic Mira variables (preliminary, Weighted least-squares fit) 15

18. Observation plan VERA catalog (~300 Galactic sources)  Contains ~40 Mira variables  Monthly VLBI monitoring at 22GHz  Period coverage 215 – 654 day Y Cas, V524 Cas, omi Cet, IK Tau, R Tau, U Ori, GX Mon, S Gem, X Hya, VX UMa, T UMa, V2108 Oph, AH Oph, RW Lyr, R Aql, YZ Dra, RT Aql, BR Del, UU Peg, KZ Peg, R Cas, V Cam, U Lyn, R Cnc, IW Hya, R Leo, U Cvn, T Com, RU Hya, RS Vir, S Crb, S Ser, WX Ser, SW Lib, FS Lib, R Dra, IRC+10374, IRC-20540, R Peg, RY And 16

19. AP LynGX MonZ PupY Lib Now Observing ! VX UMaRX BooU Lyn S Crt T Lep SY Scl R UMa 17

20. Discussion Parallax measurement  Lifetime of maser emission : ~1month  Structure changes  Acceleration of maser emission Apparent magnitude  Calibration for an extinction effect  Calibration of m k obtained with different optical system Calibration of the distance ladder Distance estimator using SR & OH/IR star masers Stellar evolution : SR → Mira ???  Kinematics from revised HIPPARCOS catalog  Semiregular variables have masers 18

21. Summary VERA astrometric observations of the Galactic Miras have started since 2003. 2008 : Parallax measurement of 4 sources Bimodal morphorogy in S Crt 3D-motion of SY Scl in the Galaxy Tentative result of the Galactic Mira PL-relation Application of the Galactic PL-relation 19