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, 2009the LG Convention Hall at the Ewha Woman’s University, Seoul, Korea

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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

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→ Mk determination : Distance obtained with VERA→ Calibration of a distance ladder

PL relation of the Galactic Miras

Milky WayGalaxy

•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

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Advantage

HIPPARCOS　　 D~100pc

VERA　　 D~10kpc

VERA

HIPPARCOS

Observable Region with

<10% Distance error.

VERA vs HIPPARCOS

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 sourceδ: Declination of the source r : Radius vector of the sun 　 l : Celestial longitude of the sunε: Obliquity of the ecliptic g : Mean anomaly of the sun

ππ π

π

（ μα, μδ ）

We extract parallax and two dimensional motions from multi-epoch data.

PL-relation :100 – 1000 days

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Results　　S　Crt　

Pulsation Period = 155day ΔmV = 0.8 Semiregulra variable : SRa

22GHz water maser

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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

VERAPi = 2.33 mas err 0.13mu_a -3.17 mas/yr err 0.22mu_d -5.41 mas/yr err 0.22

HIPPARCOSPi = 1.27 mas err 0.92mu_a -3.37 mas/yr err 1.00mu_d -4.67 mas/yr err 0.75

Nakagawa et al.2008

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Parallax　of　S　Crt　(Semiregular　:　SRa)

Parallax 　　　 2.33±0. １ 3 mas ↓ Distance 　 430+25-23pc

Nakagawa et al. 　 2008

HIPPARCOSParallax = 1.27 mas err 0.92

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π　=　0.76　±　0.03　[mas]

D　=　1.319+.047

-　.043[kpc]

(μx　,　μy　)　　=　(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)

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

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SYScl

太陽

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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] 1.0 0.5

Velocity [km/s/kpc] 44.4 36.7

Amplitude (Z)[kpc] 1.5 0.07

Period (Z)[Myr] 86 34

SY　Scl

・ Oscillation　Amplitude　(Z-direction)　　　　1.5　kpc

Thick　Disk

(Gies　&　Helsel　2005)

(Feast　&　Whitelock　1997)

(Gies　&　Helsel　2005)

(Stothers　1998)

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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

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Very recent study of T Lep

Very recent study of T Lep Central star

1AU (208R0) → 2.5AU (475R0)

Molecular layer

2.5AU (520R0) → 5.7AU (1080R0)

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

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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-P0) + ba = -3.73 +/- 0.53b = -7.58 +/- 0.03

S Crt

T Lep

SY Scl

R UMa

(Nakagawa et al. in prep)

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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)

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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

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AP Lyn GX MonZ PupY Lib

Now Observing !

VX UMa RX Boo U Lyn

S Crt

T Lep

SY Scl

R UMa

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Discussion

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

< Difficulties in parallax determination >

< 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

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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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