1 / 14

超広帯域／高感度 VLBI が切り開く 変光星脈動による物質放出機構 の研究

大学 VLBI 連携・東アジア VLBI 観測網ワークショップ 2010 年 11 月 12 日. 超広帯域／高感度 VLBI が切り開く 変光星脈動による物質放出機構 の研究. Hiroshi Imai Graduate School of Science and Engineering Kagoshima University. Contents: Proposal as an EAVN key science project. What can we learn from stellar masers? Current trial observations

tiger
Download Presentation

超広帯域／高感度 VLBI が切り開く 変光星脈動による物質放出機構 の研究

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 大学VLBI連携・東アジアVLBI観測網ワークショップ 2010年11月12日 超広帯域／高感度VLBIが切り開く変光星脈動による物質放出機構の研究 Hiroshi Imai Graduate School of Science and Engineering Kagoshima University

  2. Contents:Proposal as an EAVN key science project • What can we learn from stellar masers? • Current trial observations • Acceleration in an H2O maser clump motion in RT Virginis (Imai et al. 2003) • Mapping SiO v=1, 2, 3 (J=1-0) lines in W Hydrae (Imai et al. 2010) • Possible observation plan with EAVN • H2O masers @13 mm with VERA+KVN+EAVN • SiO masers @7 mm (v=1, 2, 3 J=1-0) with VERA+KVN+NRO45m/NICT 34m 1GHz band width recording and spectroscopy

  3. Stellar maser: the movie― What can we learn from stellar masers? ― • Maser movie visualizes… • expansion • contraction /convection • rotation/ radial acceleration • ballistic and non-ballistic motions • Maser motions visualize • giant gas clumps floating from giant convective cells • jets or spurs • shock wave transfer (H2O) • Maser motions fascinate public people as well as astronomers! SiO masers around TX Cam (Gonidakis, Diamond & Kemball 2010, 75 epochs, every 2 weeks)

  4. From surface to envelope 20 AU • Inhomogeneity in stellar mass loss flow • Transfer of pulsation-driven shock waves Radio photosphere SiO masers H2O masers H2O velocity-integrated flux Optical magnitude • Observed phase lags • 0.7 ≦ Δφ(H2O—opt)≦1.5 (Shintani et al. 2008) • 0.5 ≦ Δφ(H2O—SiO)≦1.4 (Ueda et al. 2011 in prep.) Reid & Menten (2007) with VLA

  5. Open issues in stellar maser astrophysics • True kinematics and physical conditions in maser clumps/regions • SiO maser pumping mechanism (collisional, radiative) • Velocity gradient, acceleration, “Christmass tree effect” • Their relation of stellar pulsation and mass loss flow • Distance measurement • Extended atmosphere preventing from accurate astrometry

  6. Current trial observations Mapping SiO v=1, 2, 3 (J=1-0) lines in W Hydrae Imai et al., PASJ, 62, 431-439 (2010) Acceleration in an H2O maser clump motion in RT Virginis Imai et al., ApJ, 590, 460-472 (2003)

  7. SiO v=1, 2, 3 maser maps in W Hydrae Switching pumping schemes? 2009 February 27-28(with 4 VERA telescopes) ALMA band 10 beam Size of the star 2009 April 11-12 (with 6 JVN telescopes)

  8. True maser excitation model tells us true physical condition in the envelope. ーLine overlapping between SiO and H2O molecules ー IR H2O radiation Pump from SiO v=1 J=0 to v=2 J=1 resulting in … • excitation of v=2 J=1-0 maser • quench of v=2 J=2-1 maser

  9. Small difference in v=1,2 maser distributions between two major pumping schemes • Collisional pumping: resulting in larger difference between the v=3 and v=1/v=2 maser distribution • Line overlapping: resulting in coexistence among the three masers. (classical) radiative pumping model collisional pumping model Modeling v=1, 2, 3 SiO lines (Locket & Elitzur 1992)

  10. Detection of a pulsation-driven shock wave? RT Virginis (Imai et al. 2003) Constant radial acceleration

  11. Shock wave transfer in the envelope Acceleration by shock waves (ΔV~10 km s-1/2-3 months) Shock ignition Model of dust-induced pulsation-driven shock waves (Hofner et al. 1995 )

  12. EAVN array configuration Unique specifications 7 telescopes daily specialized in VLBI astronomy (VERA, KVN) compact configuration within 1000 km (>30 km) Capability of multiband mapping and astrometry

  13. Possible observation setups and scheduling • Biweekly monitoring VLBI mapping (≧ 5 telescopes) • SiO: KVN(3) +VERA(4) (7 tels.)+NRO 45m/NICT 34m • H2O: KVN (3) or VERA (4)+ EAVN (≧3) • Spanning 1—2 years, >20 epochs • 1GHz band width (4 Gbps) recording • ADS3000+ (A/D) / OCTAVIA (formatter)/ OCTADISK, • Multi-IF filtering and high resolution spectroscopy • e.g. 2048 ch in 32 MHz/IF × 4IFs = 8192 channels • Astrometry in multi-bands/IFs for map registration • Dual beam in VERA • Dual K/Q band receiving system in KVN • Annual parallax measurement

  14. Stellar pulsation explored in ALMA era • Direct imaging of stellar continuum and line emission • Asymmetric structures of evolved stars and their envelopes • Planet search around evolved stars • Movie of nearby Mira variables and their envelopes • Stellar pulsation and periodic mass ejection • Within reasonable hours of observation time (< 1 hr/epoch) • Exploration of binary systems belonging to AGB stars • Symbiotic stars • Stellar molecular jets (water fountains) • What VLBI can find before ALMA? • 3D velocity field of the envelope and its time variation • Trigonometric parallax distance measurement • Finding ALMA target candidates

More Related