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Kinematics of the CSE in VY CMa

Kinematics of the CSE in VY CMa. Yoon Kyung Choi (MPIfR). New Science Enabled by Microarcsecond Astrometry, Socorro. Masers in Evolved Stars.

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Kinematics of the CSE in VY CMa

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  1. Kinematics of the CSE in VY CMa Yoon Kyung Choi (MPIfR) New Science Enabled by Microarcsecond Astrometry, Socorro

  2. Masers in Evolved Stars • SiO, H2O and OH masers are formed in the extended stellar atmosphere & circumstellar envelopes of evolved stars (AGB stars, Red supergiants, PPNe) • VLBI high angular resolution study of circumstellar masers → Precise distance measurements; estimation of accurate astrophysical properties → Unique tool to study extended stellar atmosphere and circumstellar envelopes OH231.8+4.2 (Desmurs et al. 2007) TX Cam (Diamond & Kemball 2003) VX Sgr (Chen et al. 2005) New Science Enabled by Microarcsecond Astrometry, Socorro

  3. 5 arcsec Asymmetric mass loss by HST observations (Humphreys et al. 2007) VY Canis Majoris RA offset (mas) 1 year • Luminous red supergiant • Distance: 1.14+0.11-0.09 kpc measured with VERA (Choi et al. 2008) • Luminosity: 3.0 × 105 L⊙ (Humphreys et al. 2007; Choi et al. 2008) • Effective temperature: 3000 K (Smith et al. 2007), 3650 K (Massey et al. 2006) • Mass: 25 M⊙ (Choi et al. 2008) • Mass-loss rate: 3 × 10-4 M⊙ yr-1 (Danchi et al. 2004) Bipolar outflow SiO (v=0 J=1–0) emission by VLA (Shinnaga et al. 2004) New Science Enabled by Microarcsecond Astrometry, Socorro

  4. VY Canis Majoris • Re-estimated luminosity with our distance of 1.14 kpc L ~ (3±0.5) × 105 L ⊙ • When we adopt the effective temperature of 3650 K (Massey et al. 2006), our result is consistent with the theoretical evolutionary track of initial mass of 25 M⊙. (Choi et al. 2008) New Science Enabled by Microarcsecond Astrometry, Socorro

  5. 5 arcsec Asymmetric mass loss by HST observations (Humphreys et al. 2007) VY Canis Majoris RA offset (mas) 1 year • Luminous red supergiant • Distance: 1.14+0.11-0.09 kpc measured with VERA (Choi et al. 2008) • Luminosity: 3.0 × 105 L⊙ (Humphreys et al. 2007; Choi et al. 2008) • Effective temperature: 3000 K (Smith et al. 2007), 3650 K (Massey et al. 2006) • Mass: 25 M⊙ (Choi et al. 2008) • Mass-loss rate: 3 × 10-4 M⊙ yr-1 (Danchi et al. 2004) Bipolar outflow SiO (v=0 J=1–0) emission by VLA (Shinnaga et al. 2004) New Science Enabled by Microarcsecond Astrometry, Socorro

  6. Aim of this study • To reveal spatial distributions of 3 different frequencies of masers in VY CMA to study circumstellar envelopes of massive evolved star with high angular resolution. • To consider the 3-dimensional kinematic model of the circumstellar envelopes around VY CMa. New Science Enabled by Microarcsecond Astrometry, Socorro

  7. Maser source Quasar Atmospheric fluctuation VERA Observations • Phase-referencing VLBI observations with VERA • 15 epochs for 2 years since April 2006 • H2O masers (22 GHz) & SiO masers (43 GHz) • Simultaneous dual-beam observations Target source: VY CMa Reference source: J0725-2640 (S.A. 1.059 degrees) • Angular resolution (2270 km baseline) 1.2 mas at 22 GHz 0.6 mas at 43 GHz • Velocity resolution ~ 0.21 km s-1 Two receivers in each antenna uv coverage New Science Enabled by Microarcsecond Astrometry, Socorro

  8. Spatial distribution of masers H2O masers DEC offset 200 AU 20 AU R.A. offset (Choi et al. 2008) New Science Enabled by Microarcsecond Astrometry, Socorro

  9. Spatial distribution of masers H2O masers v=1 J=1-0 SiO masers DEC offset 40 AU 200 AU 20 AU R.A. offset R.A. offset New Science Enabled by Microarcsecond Astrometry, Socorro

  10. v=1 J=1-0 SiO masers v=2 J=1-0 SiO masers DEC offset DEC offset 20 AU 40 AU R.A. offset R.A. offset Spatial distribution of masers New Science Enabled by Microarcsecond Astrometry, Socorro

  11. Alignment of these masers • The circumstellar structure is revealed by phase-referencing VLBI observations with different frequencies of masers in detail. • The SiO masers are tools to estimate the stellar position in the obscured dusty region by mass-loss with the highest resolution. New Science Enabled by Microarcsecond Astrometry, Socorro

  12. Estimation of stellar position • Stellar position α2000 = 07h22m58.32645s δ2000 = -25d46’03”.0660 • (Preliminay) inner motions of SiO masers v=1 J=1-0 SiO masers DEC offset 40 AU R.A. offset New Science Enabled by Microarcsecond Astrometry, Socorro

  13. Inner Motions of H2O masers • Subtract averaged absolute proper motions • Average motion -3.24±0.16 mas yr-1 in right ascension 2.06±0.60 mas yr-1 in declination New Science Enabled by Microarcsecond Astrometry, Socorro

  14. 3-dimensinal Kinematics For H2O masers, we know ① positions on 2-dimension, and ② velocities on 3-dimension. X-axis： right ascension Y-axis： declination Z-axis： radial direction New Science Enabled by Microarcsecond Astrometry, Socorro

  15. 3-dimensinal Kinematics DEC offset R.A. offset Position on line of sight 100 mas 200 mas R.A. offset DEC offset • Our results show the bipolar outflow along to the line of sight. New Science Enabled by Microarcsecond Astrometry, Socorro

  16. 3-dimensinal Kinematics red DEC offset blue 1 arcsec R.A. offset Bipolar outflow SiO (v=0 J=1–0) emission with VLA (Shinnaga et al. 2004) Position on line of sight 100 mas 200 mas R.A. offset DEC offset • Our results show the bipolar outflow along to the line of sight. • This is consistent with the result from Shinnaga et al. (2004). New Science Enabled by Microarcsecond Astrometry, Socorro

  17. Summary • We obtained and compared the spatial distributions of 3 different masers with absolute phase-referencing. • We estimated stellar position with high accuracy. α2000 = 07h22m58.32645s, δ2000 = -25d46’03”.0660 • We measured the 3-dimensional motions of these masers. H2O masers show bipolar outflow with 25 km s-1 . SiO masers show expansion with ~5 km s-1 . New Science Enabled by Microarcsecond Astrometry, Socorro

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