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恒星進化の理論の現状 とアストロメトリ

『 高密度アストロメトリ観測時代を迎えた２１世紀の天文学 』 （国立天文台、 Sep. 19-20 、 2007 ）. 恒星進化の理論の現状 とアストロメトリ. 藤本正行 須田拓馬・勝田豊（北大理） 小宮悠（東北大理）. contents. Parallaxes ⇒ 距離 ⇒ 光度 + spectroscopy → 恒星の半径、表面温度、質量、組成 ⇒ Age-Metallicity relation ⇒ star formation history of solar neighborhood 2. 恒星進化の理論的課題

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恒星進化の理論の現状 とアストロメトリ

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  1. 『高密度アストロメトリ観測時代を迎えた２１世紀の天文学』『高密度アストロメトリ観測時代を迎えた２１世紀の天文学』 （国立天文台、Sep. 19-20、 2007） 恒星進化の理論の現状とアストロメトリ 藤本正行 須田拓馬・勝田豊（北大理） 小宮悠（東北大理）

  2. contents • Parallaxes ⇒ 距離 ⇒ 光度+ spectroscopy → 恒星の半径、表面温度、質量、組成 ⇒ Age-Metallicity relation ⇒ star formation history of solar neighborhood 2. 恒星進化の理論的課題 • Mass Loss • Internal (Extra) Material Mixing ～ convective overshooting 非球対称効果（rotation, magnetic fields) 3. 銀河系の構造・進化への探査手段としての恒星 • 惑星を持つ恒星（Planet Hoboring Stars PHS） • 銀河系ハロー星（Extremely Metal-Poor Stars EMP, UMP, EMP）

  3. １．HR diagram from Hipparcos Hyades near-by stars

  4. Model fitting (Perryman et al. 1998, A&Ap) ZAMS: Metallicity and effective temperature from high resolution spectroscopy: [Fe/H]=0.14 Solar mixing length: l=1.64 resultant helium abundance: Y = 0.26 Isochrones: Age 625 ±50 Myr Asplund, Grevesse & Sauval . (2004) Decrease of metal abundance in solar by almost a factor of two as compared with a compilation by Anders & Grevesse (1989)

  5. Physical parametersfor Evolved stars (de Silva et al 2006 A&A) Mass-metallicity relation Age-metallicity relation Color-Magnitude Diagram

  6. Star Formation History of solar neighborhood CMD of near-by stars SFR vs. Age with the evolutionary models Luminosity Function (Cignoni et al 2006 A&A)

  7. 2. 恒星進化の理論的な課題 2.1 mass loss １） Massive Stars ⇒ Supernova neutron stars black hole ２） Intermediate- & Low-mass Stars ⇒ white dwarfs

  8. 2.1.a Mass loss from Massive Stars by the central exhaustion of helium wind mass loss Wolf Rayet WNL WC Limongi ＆ Chieffi （2006）

  9. SN Explosions Core Mass at SNe

  10. ηcarina (binary) VY Cannis Majoris Wolf-Rayet Stars WR124 WR１０４ (binary)

  11. 2.1.b Low- & Intermediate mass stars -- from AGBs to PNe and to WDs Super wind Fast wind Hydrogen deficient CSPNe ~20% Wind mass loss Born-again AGB Ignition of Very Late Thermal Pulse Hydrogen is mixed and burnt by He-flash convection Non-DA (hydrogen deficient) WDs ~20% Herwig 2005, ARA$AP

  12. End of Low- and Intermediate –mass stars

  13. Cat EyePlanetary Nebulae

  14. X-ray from PNe Guerrero, Chu & Gruendl Mem. S. A. It. 76,446 (2005)

  15. Suzaku observation of BD+30°3639 Murashima, Kokubun, Makishima et al. 2006, ApJL,647, L131 村島未生、天文学会2006年春季年会講演

  16. X-ray spectra from BD +30°3639 Large enhancement of C and Ne Fast wind ejects the matter from the Helium Flash Convective Zone XIS-1 spectra background Spectra with the solar abundance ratio

  17. Empirical Mass Loss Rates Reimers formula (1977) Nieuwenhuijen & Jager (1990) Fast wind

  18. Mass Loss Theory (Massive Stars) Radiation Pressure (Line-Driven) + Multiple Scattering eg., (A&A, 2000) may subject to Large overestimation by Clumps in Wind (Bouret etal. A&A 2005) Foullerton et al. ApJ 2006 (mass loss rate ∝d1.5)

  19. Mass Loss Theory; Cool stars Pulsation-driven wind model + Radiation Pressure on Dusts But, for Oxygen-rich Chemistry; Shortage of radiation pressure on dusts (Woitke A&A, 2006) Carbon-rich Chemistry (Watcher et al. A&A, 2002) +Superwind +AGB RGB

  20. Large Mass Loss at Later Stages Reimers formula Mira variables Fast wind (Pulsation period) Lawlor & MacDonald 2006

  21. 2.2 Mixing in Stars Current standard framework = spherical symmetry + thermal convection + chemical diffusion (mixing length theory) Rotation, magnetic fields ⇒ instabilities = turbulence ⇒ transport of Angular momentum + internal material mixing

  22. Results Surface metal pollution shifts the evolutionary track to the lower effective temperature. Polluted: Z=0.02 at interior, Z=0.04 at Surface convection 0.8Msun Z=0.04 Z=0.02 Log (L/Lsun) 1.0Msun log Teff

  23. ZAMS for He-enriched model ZAMS for Basic model He enriched model Log (L/Lsun) Z=0.04, homogeneous log Teff

  24. ZAMS for Basic model ZAMS for Mixing-Length enlarged model Mixing-length enlarged model Log (L/Lsun) log Teff

  25. Ages of basic model and other models Ages of He enriched and large mixing-length models are underestimated if treated as a basic model. Age of changed free-parameter models [Gyr] 1:1 Age of the basic model [Gyr]

  26. 3. Stellar Evolution as a Probe 3.1 PHS with Hot Jupiters Stars without planets PHS

  27. Extra-solarplanetsdiscovered 質量の分布 軌道半径と離心率 （ １AU=地球の軌道半径） （１MJUP＝木星の質量）

  28. ○惑星の母星

  29. Polluted? Arguments against Metal-Pollution No-correlation with the depth of surface convection No or weak correlationｓ with the condensation temperatures Ecuvillon et al. (2006)

  30. Giants with Planets Planets with Giants are metal-poorer than those with Dwarfs (Pasquini et al. 2007) Metallicity Distribution ＆ Metal-Age relation Giant PHSs(G and K) Dwarf PHSs

  31. Possible explanations 1) Formation mechanism depending on the mass of host stars 2) Metal dependence of Migration: metal-rich host  smaller orbits 3) Surface pollution ∵ dilution due to deep surface convection

  32. 3.2 Stars in the Galactic Halo Deep survey of metal-poor stars in the Galactic Halo: HK survey （Beers et al. 1992） [2800 deg2 (North) + 4100 deg2 (South), 11.0 < B < 15.5] Hamburg/ESO (Christlieb et al. 2000) [8225 deg2 (South), 10.0 < B < 17.5] [Fe/H]<-2の星　 ~2700個 [Fe/H]<-3の星　 ~400個 (Beers et al. ARA&Ap 2005)

  33. 2 stars below [Fe/H] <-5, HE0107-5240 （-5.3, 2003) HE1327-2426 (-5.4, 2005) 1 star between[Fe/H] = -4 ~-5 HE0557-4840 (-4.8, 2007) Beers & Christlieb (2005) + Norris et al. (2007)

  34. 3.2.1 EMP population のIMF と Binary origin （Komiya et al. 2007） Mmd=10 M, Δm=0.4とすると mξ(m) 主星のIMF 白色矮星 +CEMP 超新星 鉄, r-process 元素合成 伴星のIMF EMP starとして残る 低質量星 中質量星 大質量星 0.1 1 10 100 m (M)

  35. Binary ― Probe into missing more massive EMP stars― H Evolution of a primary star affects abundances of a secondary star. How to estimate the IMF from observation of CEMP star. C,O He H CEMP star is formed in a binary system. Observed feature of a CEMP star Mass of a primary star. Estimate of the IMF Observation peculiarities of surface abundance of CEMP stars. Theoretical knowledge of the evolution process of EMP star. Relation between observed abundance and mass of primary. Estimation of IMF.

  36. 2種類のCEMP CEMP-s s-process元素過剰窒素も過剰 CEMP-nos s-process元素は少ない窒素は過剰な星と過剰でない星がある 3 21 0-1 -2 CEMP-s [Ba/Fe] CEMP-nos -1 -0.5 0 0.5 1 1.5 2 2.5 3 □：[C/Fe], ■:[N/Fe] （EMPではない炭素星は1種類）

  37. 3.2.2 Metallicity Distribution Function (MDF) Cut-off of MDF Hyper metal poor (HMP) stars Number100001000 100101 Salpeter IMF Assumptions Theoretical MDF for IMF with Mmd =10 M☉. One zone model.No infall/outflow.Instantaneous recycling. Fe yield: 0.07M☉ Effect of formation process of the Galaxy?Pop.III star ? observation -6 -5 -4 -3 -2 Results Derived top-heavy IMF is consistent with observation (for [Fe/H] > -4). [Fe/H]

  38. 銀河形成 Population III形成 2段階に分けて考える EMP形成 [Fe/H]=-4~-2.5 mstar~10M☉ 合体 MDM~106M☉Mgas~105M☉ 最初は小さなガス雲の中で星形成が起きる Population II形成Mgas~1011M☉ disk形成。 現在：Population I

  39. Hierarchical galaxy formation Galaxy is formed hierarchically. ⇒ 2nd star [Fe/H]~-4 [Fe/H]~-4 SN 1st mini-halo ~ 106-7 M☉ First star Stars formed after first supernova. After 1st SN explosion, merge MDF cut-off at [Fe/H]~-4 -∞-4[Fe/H] Pop.3 stars still alive ⇒HMP star. (Suda et al.2004) The cut-off is originate from structure formation process

  40. Merger tree mini-haloの質量(M☉) （実際は枝の数はこの1000倍） このようなtreeでの化学進化を計算 z 0.1 0.2 0.5 1 ( Big Bangからの時間Gyr)

  41. Effect of structure formation Assumptions number 100001000 1001010.1 Merging history: Press-Schechter (Somerville & Kollat1999) Theoretical MDF with merger tree. SFE: 10-10/yr Observed MDF Results Model predict cut-off at [Fe/H]~-4. Number of stars with Z = 0 is inconsistent. Z=0 -∞ -5 -4 -3 -2.5[Fe/H]

  42. First star Pair-Instability supernovae (Fe yield: 10M☉) ⇒iron overproduction Mmd =100 M☉ for Z=0. First star : supermassive not PISN.

  43. 初代星への表面汚染 • Mini-haloの中では恒星の運動速度が遅いために、星間ガスの恒星表面への降着が起きやすい 周囲の星間物質を降着[Fe/H]~-3 連星の場合は主星からの質量降着（炭素星に）[Fe/H]<-5 金属0で誕生 赤色巨星に[Fe/H]<-5 表面対流層の深化により[Fe/H]<-5に

  44. 汚染を考慮したMDF

  45. 3.3.3 Database of Galactic EMP Starsfor Galactic Archaeology Contents • Papers: 96 (covering since 2000) on high resolution spectroscopy • Stars: 1495(847) • Data • [X/Fe]: 24,498 • [X/H]: 26,090 • logε: 26,090 • Ｌog g, etc; atmospheric data, (DaGaAr: Suda et al. 2007) [Fe/H] Number(prev.) -1< 124 -1~-2 214 -2~-3 419 -3~-4 117 <-4 4 • 炭素星が多い • 20~25% • 炭素星に2種類 • S-procrss rich • S-process なし　→普通の星にはない

  46. Sample characteristics Metallicity distribution giants Teff - surface gravity Magnitude distribution among samples selection effects due to survey dwarfs

  47. Eu: neutron capture element r-process + s-process r-process only [Eu/Ba] > 0 [Eu/Fe] [Fe/H]

  48. Space distributions of EMP stars Distance ← surface gravity (assuming M=0.8 M) Astrometry ＋ Spectroscopy (e.g., WFMOS） ↓ 位置、運動、 光度、組成 ⇒ 年齢 銀河の恒星地図 銀河形成史の再構築 dwarfs giants

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