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Astrometric Observations of Mira variables with VERA

East Asia VLBI WS, Mar, 2009 the LG Convention Hall at the Ewha Woman’s University, Seoul, Korea. 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),

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Astrometric Observations of Mira variables with VERA

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  1. East Asia VLBI WS, Mar, 2009 the LG Convention Hall at the Ewha Woman’s University, Seoul, Korea 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

  2. 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

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

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

  5. 5 π π π 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 We extract parallax and two dimensional motions from multi-epoch data. PL-relation :100 – 1000 days 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 （μα, μδ）

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

  7. 7 Nakagawa et al.2008 Circumstellar masers of S Crt • Bipolar Outflow • Inclination angle of flow axis = 43° • Photosphere260±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

  8. 8 Parallax of S Crt (Semiregular : SRa) • Parallax 2.33±0.１3 mas ↓ • Distance 430+25-23pc HIPPARCOS Parallax = 1.27 mas err 0.92 Nakagawa et al.2008

  9. 9 Parallax of SY Scl Nyu et al. 2009 (Submitted to PASJ) • Pulsation period411day π = 0.76 ± 0.03 [mas] Internal motions of maser spots around SY Scl +.047 [kpc] D = 1.319 - .043 (μx , μy) = (6.41 , -6.90 )[mas/yr]

  10. (Us,Vs,Ws)=(-5.2±0.3,-53.8±2.1,-33.3±0.3)[km s] -1 10 SYScl 太陽

  11. 11 動径方向 Y-Z平面 X-Z平面 過去10億年のSY Sclと太陽の運動 (Gies & Helsel 2005) (Feast & Whitelock 1997) (Gies & Helsel 2005) (Stothers 1998) SY Scl ・Oscillation Amplitude (Z-direction) 1.5 kpc Thick Disk

  12. 12 R Uma, T Lep • Pulsation period 368d（LogP=2.57） • Parallax2.62±0.33mas　（preliminary） • Distance381±48pc　 （preliminary） • Pulsation period301d (LogP=2.48) • Parallax 1.72±0.09mas (preliminary) R UMa

  13. Very recent study of T Lep

  14. Very recent study of T Lep Central star 1AU (208R0) → 2.5AU (475R0) Molecular layer 2.5AU (520R0) → 5.7AU (1080R0)

  15. 13 Example : Phase Referenced Image • Y Lib • Period 276d • （LogP=2.44) • Peak = 280mJy/beam • WX Psc • Period660d • （LogP=2.82） • QSO phase-referened image • RX Boo • Period 340d （LogP=2.53） • Peak = 7Jy/beam J0113+13 RX Boo Y Lib

  16. 14 PL-relation of the Galactic Mira variables(preliminary, Weighted least-squares fit) • Source : SY Scl, T Lep, R UMa, S Crt* (* Semiregular) Mk = a*(LogP-P0) + b a = -3.73 +/- 0.53 b = -7.58 +/- 0.03 T Lep R UMa SY Scl S Crt (Nakagawa et al. in prep)

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

  18. 16 Observation plan • VERA catalog (~300 Galactic sources) • Contains ~40 Mira variables • Monthly VLBI monitoring at 22GHz • Period coverage 215 – 654 day < 40 Mira variables > 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

  19. 17 Now Observing ! VX UMa Y Lib RX Boo U Lyn AP Lyn Z Pup GX Mon T Lep R UMa SY Scl S Crt

  20. 18 Discussion < Difficulties in parallax determination > • Parallax measurement • Lifetime of maser emission : ~1month • Structure changes • Acceleration of maser emission • Apparent magnitude • Calibration for an extinction effect • Calibration of mk obtained with different optical system < Scientific application > • 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

  21. 19 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

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