Astrometric Observations of Mira variables with VERA A.Nakagawa ( 中中中中中 ), D.Nyu, M.Matsui, T.Omodaka, H.Imai, S.Kameno (Kagoshima University), T.Kurayama (KASI), H.Kobayashi, K.M.Shibata (NAOJ), VERA Project Team sia VLBI WS, Mar, 2009 Convention Hall at the Ewha Woman’s University, Seoul, Korea 1
21
Embed
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), - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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
1
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
→ 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
3
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.
Source : SY Scl, T Lep, R UMa, S Crt* (* Semiregular)
PL-relation of the Galactic Mira variables (preliminary, Weighted least-squares fit)
15
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
16
AP Lyn GX MonZ PupY Lib
Now Observing !
VX UMa RX Boo U Lyn
S Crt
T Lep
SY Scl
R UMa
17
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
18
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-