贫金属星整体元素丰度分布的研究
摘要
贫金属星被称为是恒星演化历史的"化石"。研究其核合成元素丰度,对检验核合成理论和探索恒星形成具有十分重要的意义。S-过程的理论已经相对完善,但对r-过程的理解还相对模糊。
本文以元素核合成基本理论为基础,采用参数化方法将r-过程分为弱r-过程和主要r-过程。用以从理论角度预言元素丰度,探索元素丰度分布的特征和规律,从而进一步讨论r-过程核合成的分量过程及可能的场所。此文分别把HD 122563和CS 22892-001作为弱r-过程和主要r-过程的典型星,采用了用最小二乘法找最小开方的方法,对98颗r-过程超丰贫金属星进行了计算去预言它们的元素丰度。并将误差详细的分为了贫金属星观测误差和典型星观测误差,使我们的模型最大限度的优化。通过计算结果来研究r-过程的两个组成。参数化模型是将具体的物理过程数学化,将这两个过程辅以两个分量系数。从而也可以很直观的看出弱r-过程和主要r-过程所占的比例。
通过本文的计算,可以很直观的从图中看出我们模型的准确性。从而证明我们提出的弱r-过程和主要r-过程是相当可信的。
r过程与恒星的形成和演化密切相关。通过对核合成的研究,可以了解元素的起源、恒星的形成及星系的化学演化过程。近年来对贫金属星r-过程的研究越来越多。但是,到目前为止还没有一种成熟的理论,对其形成场所也存在许多争议。因此本文的工作对于r-过程,以及核合成的研究都具有非常重要的意义。
The metal-poor stars are known as the stellar evolution history of the "fossil." Studying the nucleosynthesis element abundances to test nucleosynthesis theories and exploration of star formation have great significance. S-process theory has been relatively well, but the understanding of r-process are relatively vague.
In this paper, based on element nucleosynthesis theory, using parametric method to divide r-process into a weak r-process and a main r-process. Predict from a theoretical point to view for the element abundances, and explore the distribution of element abundances characteristics and laws,so as to further discuss the r-process nucleosynthesis process and the possible site. This article use HD 122563 and CS 22892-001 as a typical star of weak r-process and main r-process.The way is using the least square method to find the smallest prescribing . 98 r-process enhancde metal-poor stars were calculated to predict the abundance of their elements. And the error is detailed into metal-poor stars observation error and the typical satellite observation error, so that our model for maximum optimization. By calculating the metal-poor stars to study two composition of r-process. Parameterized model is the specific physical processes mathematically, and these two processes supported by two-component coefficients.Thus can see intuitively the proportion of the weak and main r-process in the r-process.
By this calculation, the accuracy of our model can be intuitively seen from the figure. Thus the weak and main r-process of we mading is quite credible.
R- process is closely linked with formation and evolution of the star. Through the study of nuclear synthesis, we can understand the origin of elements, star formation and chemical evolution of galaxies. In recent years, study of the r-process nuclear synthesis on metal-poor stars are more and more。However, there does not have a mature theory so far, and there are also lot of controversy on place of their formation . Therefore, the work for the r-process of this article, as well as for the nucleosynthesis of the studies have very important significance.
本文以元素核合成基本理论为基础,采用参数化方法将r-过程分为弱r-过程和主要r-过程。用以从理论角度预言元素丰度,探索元素丰度分布的特征和规律,从而进一步讨论r-过程核合成的分量过程及可能的场所。此文分别把HD 122563和CS 22892-001作为弱r-过程和主要r-过程的典型星,采用了用最小二乘法找最小开方的方法,对98颗r-过程超丰贫金属星进行了计算去预言它们的元素丰度。并将误差详细的分为了贫金属星观测误差和典型星观测误差,使我们的模型最大限度的优化。通过计算结果来研究r-过程的两个组成。参数化模型是将具体的物理过程数学化,将这两个过程辅以两个分量系数。从而也可以很直观的看出弱r-过程和主要r-过程所占的比例。
通过本文的计算,可以很直观的从图中看出我们模型的准确性。从而证明我们提出的弱r-过程和主要r-过程是相当可信的。
r过程与恒星的形成和演化密切相关。通过对核合成的研究,可以了解元素的起源、恒星的形成及星系的化学演化过程。近年来对贫金属星r-过程的研究越来越多。但是,到目前为止还没有一种成熟的理论,对其形成场所也存在许多争议。因此本文的工作对于r-过程,以及核合成的研究都具有非常重要的意义。
The metal-poor stars are known as the stellar evolution history of the "fossil." Studying the nucleosynthesis element abundances to test nucleosynthesis theories and exploration of star formation have great significance. S-process theory has been relatively well, but the understanding of r-process are relatively vague.
In this paper, based on element nucleosynthesis theory, using parametric method to divide r-process into a weak r-process and a main r-process. Predict from a theoretical point to view for the element abundances, and explore the distribution of element abundances characteristics and laws,so as to further discuss the r-process nucleosynthesis process and the possible site. This article use HD 122563 and CS 22892-001 as a typical star of weak r-process and main r-process.The way is using the least square method to find the smallest prescribing . 98 r-process enhancde metal-poor stars were calculated to predict the abundance of their elements. And the error is detailed into metal-poor stars observation error and the typical satellite observation error, so that our model for maximum optimization. By calculating the metal-poor stars to study two composition of r-process. Parameterized model is the specific physical processes mathematically, and these two processes supported by two-component coefficients.Thus can see intuitively the proportion of the weak and main r-process in the r-process.
By this calculation, the accuracy of our model can be intuitively seen from the figure. Thus the weak and main r-process of we mading is quite credible.
R- process is closely linked with formation and evolution of the star. Through the study of nuclear synthesis, we can understand the origin of elements, star formation and chemical evolution of galaxies. In recent years, study of the r-process nuclear synthesis on metal-poor stars are more and more。However, there does not have a mature theory so far, and there are also lot of controversy on place of their formation . Therefore, the work for the r-process of this article, as well as for the nucleosynthesis of the studies have very important significance.
引文
[1]Cowan J J,Thielemann F K,Truran J W.The R-process and nucleochronology Phys,Rep,1991,208:267.
[2]Truran J W,Cowan J J,Pilachowski C A,Sneden C. Probing the neutron‐capture nucleosynthesis history of galactic matterpasp,2002,114:1293.
[3]Cowan J J,Sneden C,Lawler J E,Den Hartog E A.R-pocess enhanced halo stars.Science,2006,014.
[4]Kratz K L,Bitouzet J P,Thielemann F K,Moeller P,Pfeiffer B.Isotopic r-process abundances and nuclear structure far from stability:implications for the r-preocess mechanism.ApJ,1993,403:216.
[5]Woosley S E,Hoffman R D.Theα-process and r-process.ApJ,1992,395:202.
[6]Takahashi K,Witti J,Janka H–Th.Nucleosynthesis in neutrino-driven winds from protoneutron stars II:the r-process.A&A,1994,286:857.
[7]Wanajo S,Kajino T,Mathews,G J,Otsuki K.The r-process in neutrino-driven winds from nascent, "compact" neutron stars of core-collapse supernovae. ApJ,2001,554:578.
[8]Thompson T A,Burrows,Meyer B S.The physics of proto-neutron star winds: implications for r-process nucleosynthesis.ApJ,2001,562:887.
[9]Freiburghaus C.Rosswog S.Thielemann F K.R-process in neutron star mergers. ApJ,1999,525:121.
[10]Rosswog S,Liebendorfer M,Thielemann F K,Davies M B,Benz W,Piran T.Mass ejection in neutron star mergers.A&A,1999, 341:499.
[11]Goriely S,Demetriou P,Janka H–Th,Pearson J M,Samyn M.The r-process nucleosynthesis: a continued challenge for nuclear physics and astrophysics . Nucl.Phys.A,2005,758:587.
[12]Cameron A G W.Some properties of r-process accretion disks and jets .APJ,2001,562:456.
[13]Surman R,McLaughlin G C.Prospects for obtaining an r process from gamma ray burst disk winds .Nucl.Phys.A,2005,758:189.
[14]Kappeler F,Beer H,Wisshak K,Clayton D D,Macklin R L,Ward R A.S-process studies in the light of new experimental cross sections - distribution of neutron fluences and r-process residuals.ApJ,1982,257:821.
[15]Raiteri C M,Gallino R,Busso M.S-processing in massive stars as a function of metallicity and interpretation of observational trends.ApJ,1992,387:263.
[16] Busso M,Gallino R, Lambert D L, et al. Nucleosynthesis and mixing on the asymptotic giant branch. III. predicted and observed s-process abundances [J]. ApJ,2001, 557: 802-821.
[17]Arlandini C,Kappeler F,et al.Neutron capture in low-mass ssymptotic giant branch stars: cross sections and abundance signatures.ApJ,1999,525:886.
[18]Travaglio C,Gallino R.Galactic evolution of Sr, Y, And Zr: a multiplicity of nucleosynthetic processes.ApJ,2004,601:864.
[19]Cristallo S,Straniero O,Gallino R.et al. Evolution, nucleosynthesis, and yields of low-Mass asymptotic giant branch stars at different metallicities[J].ApJ,2009,696:797-820.
[20] Clayton D D,Rassbach M E.Termination of the s-process.ApJ,1967,148:69.
[21]Travaglio C,Gallino R. Asymptotic giant branch production and galactic chemical evolution.ApJ,2001,549:346.
[22]Sneden C.The extremely metal-poor, neutron capture-rich star CS 22892-052: a comprehensive abundance analysis.ApJ,2003,591:936.
[23]Hill V.First stars. I. the extreme r-element rich, iron-poor halo giant CS 31082-001. implications for the r-process site(s) and radioactive cosmochronology.A&A.2002.387:560.
[24]Goriely S,Arnould M.Actinides: how well do we know their stellar production? A&A,2001,379:1113.
[25]Schatz H,Toenjes R,et al.Thorium and uranium chronometers applied to CS 31082-001.ApJ,2002,579:626.
[26]Honda S,Aoki W,Ishimaru Y.Spectroscopic studies of extremly metal-poor stars with subaru/HDS:II.The r-process Elements,Including Thorium.ApJ,2004,607:474.
[27]Barklem P S,Christlieb N,Beers T C.The hamburg/eso r-process enhanced star survey(heres)[J].A&A,2005,439:129.
[28]Pfeiffer B,Kratz K–L.Nuclear structure studies for the astrophysical r-process.Nucl.Phys.A,2001a,693:282.
[29]Pfeiffer B,Kratz K–L.Nuclear structure studies for the astrophysical r-process .Nucl.Phys.A,2001b,693:282.
[30]Wasserburg G J,Busso M,Gallino R.Abundances of actinides and short-lived nonactinides in the interstellar medium: diverse supernova sources for the r-processes.ApJ,1996,466:L109.
[31]Qian Y Z, Wasserburg G J.Stellar abundances in the early galaxy and two /r-process components. Phys.Rep,2000,333:77.
[32]Qian Y Z, Wasserburg G J.Prompt iron enrichment, two r-process components, and abundances in very metal-poor stars.ApJ,2000,529:L21.
[33]Kratz K–L,Farouqi K,Pfeiffer B,et al.Explorations of the r-processes: comparisonsbetween calculations and observations of low-metallicity stars.ApJ,2007,662:39.
[34]McWilliam A.Barium abundances in extremely metal-poor stars.AJ,1998,115:1640.
[35]Burris D L,Pilachowski C A.Neutron-capture elements in the early galaxy:insights from a large sample of metal-poor giants[J].ApJ,2000,544:302.
[36]Norris J E,Ryan S G,Beers T C.Extremely metal-poor stars. VIII. high-resolution, high signal-to-noise ratio analysis of five stars with [Fe/H]<~-3.5.ApJ,2001,561:1034.
[37]Johnson J A,Bolte M.The r-Process in the Early Galaxy.ApJ,2002,579:616.
[38]Otsuki K,Honda S.Neutron-capture elements in the metal-poor globular cluster M15.ApJ,2006,641:L117.
[39]Aoki W.Spectroscopic studies of very metal-poor stars with the subaru high dispersion spectrograph. III. light neutron-capture elements.ApJ,2005,632:611.
[40]Wanajo S.The rp-process in neutrino-driven winds.ApJ,2006,647:1323.
[41]Qian Y Z, Wasserburg G J.Where, oh where has the r-process gone? Phys.Rep,2007,442:237.
[42]Lawer J,Sneden C.Erbium and the r-process in the sun and metal-poor stars.AAS,2007,21110410L.
[43]Sneden C.New rare earth element abundance distributions for the sun and five r-process-rich very metal-poor stars.ApJ,2009,182:80.
[44]Sneden C,Cowan J J.Evidence of multiple r-process sites in the early galaxy: new observations of CS 22892-052.ApJ,2000,533:L139.
[46]Honda S,Aoki W,Ishimaru Y.Neutron-capture elements in the very metal poor star HD 122563.ApJ,2006,643:1180.
[47]Qian Y Z, Wasserburg G J.Determination of nucleosynthetic yields of supernovae and very massive stars from abundances in metal-poor stars.APJ,2002,567:515.
[48] Izutani N,Umeda H,Tominaga N.Explosive nucleosynthesis of weak r-process elements in extremely metal-poor core-collapse supernovae[J].ApJ,2009, 692:1517-1531.
[49]Montes F,Beers T C,Cowan J.Nucleosynthesis in the early Galaxy. ApJ,2007,671:1685-1695.
[50]Sneden C,Cowan J,Gallino R.Neutron-capture elements in the early galaxy. ARA&A, 2008,46:241-288.
[51]Sneden C,McWilliam A.The ultra--metal-poor, neutron-capture--rich giant star CS 22892-052.ApJ,1996,467:819.
[52]Westin J,Sneden C.The r-process-enriched low-metallicity giant HD115444.ApJ,2000,530:783.
[53]Cowan J J.The chemical composition and age of the metal-poor halo star BD +17°3248.ApJ,2002,572:861.
[54]McWilliam A,Preston G W,Sneden C,Swarle L.Spectroscopic analysis of 33 of the most metal poor stars. II.A J,1995,109:2757.
[55]Ryan S G,Norris J E,Beers T C.Extremely metal-poor stars. II. elemental abundances and the early chemical enrichment of the galaxy.ApJ,1996,471:254.
[56]Cowan J J,Pfeiffer B.R-process abundances and chronometers in metal-poor stars.ApJ,1999,521:194.
[57]Christlieb N,Beers T C.The hamburg/eso r-process enhanced star survey(heres) I.project description,and discovery of two stars with strong enhancements of neutron-capture elements.A&A,2004,428:1027.
[2]Truran J W,Cowan J J,Pilachowski C A,Sneden C. Probing the neutron‐capture nucleosynthesis history of galactic matterpasp,2002,114:1293.
[3]Cowan J J,Sneden C,Lawler J E,Den Hartog E A.R-pocess enhanced halo stars.Science,2006,014.
[4]Kratz K L,Bitouzet J P,Thielemann F K,Moeller P,Pfeiffer B.Isotopic r-process abundances and nuclear structure far from stability:implications for the r-preocess mechanism.ApJ,1993,403:216.
[5]Woosley S E,Hoffman R D.Theα-process and r-process.ApJ,1992,395:202.
[6]Takahashi K,Witti J,Janka H–Th.Nucleosynthesis in neutrino-driven winds from protoneutron stars II:the r-process.A&A,1994,286:857.
[7]Wanajo S,Kajino T,Mathews,G J,Otsuki K.The r-process in neutrino-driven winds from nascent, "compact" neutron stars of core-collapse supernovae. ApJ,2001,554:578.
[8]Thompson T A,Burrows,Meyer B S.The physics of proto-neutron star winds: implications for r-process nucleosynthesis.ApJ,2001,562:887.
[9]Freiburghaus C.Rosswog S.Thielemann F K.R-process in neutron star mergers. ApJ,1999,525:121.
[10]Rosswog S,Liebendorfer M,Thielemann F K,Davies M B,Benz W,Piran T.Mass ejection in neutron star mergers.A&A,1999, 341:499.
[11]Goriely S,Demetriou P,Janka H–Th,Pearson J M,Samyn M.The r-process nucleosynthesis: a continued challenge for nuclear physics and astrophysics . Nucl.Phys.A,2005,758:587.
[12]Cameron A G W.Some properties of r-process accretion disks and jets .APJ,2001,562:456.
[13]Surman R,McLaughlin G C.Prospects for obtaining an r process from gamma ray burst disk winds .Nucl.Phys.A,2005,758:189.
[14]Kappeler F,Beer H,Wisshak K,Clayton D D,Macklin R L,Ward R A.S-process studies in the light of new experimental cross sections - distribution of neutron fluences and r-process residuals.ApJ,1982,257:821.
[15]Raiteri C M,Gallino R,Busso M.S-processing in massive stars as a function of metallicity and interpretation of observational trends.ApJ,1992,387:263.
[16] Busso M,Gallino R, Lambert D L, et al. Nucleosynthesis and mixing on the asymptotic giant branch. III. predicted and observed s-process abundances [J]. ApJ,2001, 557: 802-821.
[17]Arlandini C,Kappeler F,et al.Neutron capture in low-mass ssymptotic giant branch stars: cross sections and abundance signatures.ApJ,1999,525:886.
[18]Travaglio C,Gallino R.Galactic evolution of Sr, Y, And Zr: a multiplicity of nucleosynthetic processes.ApJ,2004,601:864.
[19]Cristallo S,Straniero O,Gallino R.et al. Evolution, nucleosynthesis, and yields of low-Mass asymptotic giant branch stars at different metallicities[J].ApJ,2009,696:797-820.
[20] Clayton D D,Rassbach M E.Termination of the s-process.ApJ,1967,148:69.
[21]Travaglio C,Gallino R. Asymptotic giant branch production and galactic chemical evolution.ApJ,2001,549:346.
[22]Sneden C.The extremely metal-poor, neutron capture-rich star CS 22892-052: a comprehensive abundance analysis.ApJ,2003,591:936.
[23]Hill V.First stars. I. the extreme r-element rich, iron-poor halo giant CS 31082-001. implications for the r-process site(s) and radioactive cosmochronology.A&A.2002.387:560.
[24]Goriely S,Arnould M.Actinides: how well do we know their stellar production? A&A,2001,379:1113.
[25]Schatz H,Toenjes R,et al.Thorium and uranium chronometers applied to CS 31082-001.ApJ,2002,579:626.
[26]Honda S,Aoki W,Ishimaru Y.Spectroscopic studies of extremly metal-poor stars with subaru/HDS:II.The r-process Elements,Including Thorium.ApJ,2004,607:474.
[27]Barklem P S,Christlieb N,Beers T C.The hamburg/eso r-process enhanced star survey(heres)[J].A&A,2005,439:129.
[28]Pfeiffer B,Kratz K–L.Nuclear structure studies for the astrophysical r-process.Nucl.Phys.A,2001a,693:282.
[29]Pfeiffer B,Kratz K–L.Nuclear structure studies for the astrophysical r-process .Nucl.Phys.A,2001b,693:282.
[30]Wasserburg G J,Busso M,Gallino R.Abundances of actinides and short-lived nonactinides in the interstellar medium: diverse supernova sources for the r-processes.ApJ,1996,466:L109.
[31]Qian Y Z, Wasserburg G J.Stellar abundances in the early galaxy and two /r-process components. Phys.Rep,2000,333:77.
[32]Qian Y Z, Wasserburg G J.Prompt iron enrichment, two r-process components, and abundances in very metal-poor stars.ApJ,2000,529:L21.
[33]Kratz K–L,Farouqi K,Pfeiffer B,et al.Explorations of the r-processes: comparisonsbetween calculations and observations of low-metallicity stars.ApJ,2007,662:39.
[34]McWilliam A.Barium abundances in extremely metal-poor stars.AJ,1998,115:1640.
[35]Burris D L,Pilachowski C A.Neutron-capture elements in the early galaxy:insights from a large sample of metal-poor giants[J].ApJ,2000,544:302.
[36]Norris J E,Ryan S G,Beers T C.Extremely metal-poor stars. VIII. high-resolution, high signal-to-noise ratio analysis of five stars with [Fe/H]<~-3.5.ApJ,2001,561:1034.
[37]Johnson J A,Bolte M.The r-Process in the Early Galaxy.ApJ,2002,579:616.
[38]Otsuki K,Honda S.Neutron-capture elements in the metal-poor globular cluster M15.ApJ,2006,641:L117.
[39]Aoki W.Spectroscopic studies of very metal-poor stars with the subaru high dispersion spectrograph. III. light neutron-capture elements.ApJ,2005,632:611.
[40]Wanajo S.The rp-process in neutrino-driven winds.ApJ,2006,647:1323.
[41]Qian Y Z, Wasserburg G J.Where, oh where has the r-process gone? Phys.Rep,2007,442:237.
[42]Lawer J,Sneden C.Erbium and the r-process in the sun and metal-poor stars.AAS,2007,21110410L.
[43]Sneden C.New rare earth element abundance distributions for the sun and five r-process-rich very metal-poor stars.ApJ,2009,182:80.
[44]Sneden C,Cowan J J.Evidence of multiple r-process sites in the early galaxy: new observations of CS 22892-052.ApJ,2000,533:L139.
[46]Honda S,Aoki W,Ishimaru Y.Neutron-capture elements in the very metal poor star HD 122563.ApJ,2006,643:1180.
[47]Qian Y Z, Wasserburg G J.Determination of nucleosynthetic yields of supernovae and very massive stars from abundances in metal-poor stars.APJ,2002,567:515.
[48] Izutani N,Umeda H,Tominaga N.Explosive nucleosynthesis of weak r-process elements in extremely metal-poor core-collapse supernovae[J].ApJ,2009, 692:1517-1531.
[49]Montes F,Beers T C,Cowan J.Nucleosynthesis in the early Galaxy. ApJ,2007,671:1685-1695.
[50]Sneden C,Cowan J,Gallino R.Neutron-capture elements in the early galaxy. ARA&A, 2008,46:241-288.
[51]Sneden C,McWilliam A.The ultra--metal-poor, neutron-capture--rich giant star CS 22892-052.ApJ,1996,467:819.
[52]Westin J,Sneden C.The r-process-enriched low-metallicity giant HD115444.ApJ,2000,530:783.
[53]Cowan J J.The chemical composition and age of the metal-poor halo star BD +17°3248.ApJ,2002,572:861.
[54]McWilliam A,Preston G W,Sneden C,Swarle L.Spectroscopic analysis of 33 of the most metal poor stars. II.A J,1995,109:2757.
[55]Ryan S G,Norris J E,Beers T C.Extremely metal-poor stars. II. elemental abundances and the early chemical enrichment of the galaxy.ApJ,1996,471:254.
[56]Cowan J J,Pfeiffer B.R-process abundances and chronometers in metal-poor stars.ApJ,1999,521:194.
[57]Christlieb N,Beers T C.The hamburg/eso r-process enhanced star survey(heres) I.project description,and discovery of two stars with strong enhancements of neutron-capture elements.A&A,2004,428:1027.