arXiv: Astrophysics最新文献_第5页

Modeling the Local Warm/Hot Bubble 模拟局部热/热气泡

arXiv: Astrophysics Pub Date : 2008-12-02 DOI: 10.1063/1.3211826

D. Breitschwerdt, M. Avillez, V. Baumgartner

引用次数: 4

Intergalactic Baryons in the Local Universe 本地宇宙中的星系间重子

arXiv: Astrophysics Pub Date : 2008-12-02 DOI: 10.1063/1.3154092

C. Danforth

{"title":"Intergalactic Baryons in the Local Universe","authors":"C. Danforth","doi":"10.1063/1.3154092","DOIUrl":"https://doi.org/10.1063/1.3154092","url":null,"abstract":"Simulations predict that shocks from large-scale structure formation and galactic winds have reduced the fraction of baryons in the warm, photoionized phase (the Lya forest) from nearly 100% in the early universe to less than 50% today. Some of the remaining baryons are predicted to lie in the warm-hot ionized medium (WHIM) phase at T=10^5-10^7 K, but the quantity remains a highly tunable parameter of the models. Modern UV spectrographs have provided unprecedented access to both the Lya forest and potential WHIM tracers at z~0, and several independent groups have constructed large catalogs of far-UV IGM absorbers along ~30 AGN sight lines. There is general agreement between the surveys that the warm, photoionized phase makes up ~30% of the baryon budget at z~0. Another ~10% can be accounted for in collapsed structures (stars, galaxies, etc.). However, interpretation of the ~100 high-ion (OVI, etc) absorbers at z<0.5 is more controversial. These species are readily created in the shocks expected to exist in the IGM, but they can also be created by photoionization and thus not represent WHIM material. Given several pieces of observational evidence and theoretical expectations, I argue that most of the observed OVI absorbers represent shocked gas at T~300,000 K rather than photoionized gas at T<30,000 K, and they are consequently valid tracers of the WHIM phase. Under this assumption, enriched gas at T=10^5-10^6 K can account for ~10% of the baryon budget at z<0.5, but this value may increase when bias and incompleteness are taken into account and help close the gap on the 50% of the baryons still \"missing\".","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80964011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

15 GHz VLBI detection of the HST-1 feature in the M87 jet M87喷气机中HST-1特征的15ghz VLBI检测

arXiv: Astrophysics Pub Date : 2008-12-01 DOI: 10.22323/1.072.0010

C. Chang, E. Ros, Y. Kovalev, M. Lister

引用次数: 1

Magnetic Fingerprints of Solar and Stellar Oscillations 太阳和恒星振荡的磁指纹

arXiv: Astrophysics Pub Date : 2008-11-29 DOI: 10.1007/978-3-642-11250-8_5

E. Khomenko

引用次数: 2

The open cluster Pismis 11 and the very luminous blue supergiant HD 80077 疏散星团双鱼座11和非常明亮的蓝超巨星HD 80077

arXiv: Astrophysics Pub Date : 2008-11-29 DOI: 10.1051/0004-6361:200810125

A. Marco, I. Negueruela

{"title":"The open cluster Pismis 11 and the very luminous blue supergiant HD 80077","authors":"A. Marco, I. Negueruela","doi":"10.1051/0004-6361:200810125","DOIUrl":"https://doi.org/10.1051/0004-6361:200810125","url":null,"abstract":"(Abridged) The very luminous blue supergiant HD 80077 has been claimed to be a member of the young open cluster Pismis 11, and hence a hypergiant. We obtained UBVRI photometry of the cluster field and low-resolution spectroscopy of a number of putative members. We derive spectral types from the spectra and determine that the reddening in this direction is standard. We then carry out a careful photometric analysis that allows us to determine individual reddening values, deriving unreddened parameters that are used for the main sequence fit. We identify 43 likely members of Pismis 11. We study the variation of extinction across the face of the cluster and find some dispersion, with a trend to higher values in the immediate neighbourhood of HD 80077. We estimate a distance of 3.6 kpc for the cluster. If HD 80077 is a member, it has M_bol<-10.5 and it is one of the three visually brightest stars in the Galaxy. Several early type stars in the vicinity of Pismis~11 fit well the cluster sequence and are likely to represent an extended population at the same distance. About 18 arcmin to the North of Pismis 11, we find a small concentration of stars, which form a clear sequence. We identify this group as a previously uncatalogued open cluster, which we provisionally call Alicante 5. The distance to Alicante 5 is also 3.6 kpc, suggesting that these two clusters and neighbouring early-type stars form a small association. Based on its proper motion, HD 80077 is not a runaway star and may be a member of the cluster. If this is the case, it would be one of the brightest stars in the Galaxy.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80644333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Spatial Distribution of Nucleosynthesis Products in Cassiopeia A: Comparison Between Observations and 3D Explosion Models 仙后座A核合成产物的空间分布:观测与三维爆炸模型的比较

arXiv: Astrophysics Pub Date : 2008-11-28 DOI: 10.22323/1.053.0020

P. Young, C. Ellinger, F. Timmes, D. Arnett, C. Fryer, G. Rockefeller, A. Hungerford, S. Diehl, M. Bennett, R. Hirschi, M. Pignatari, F. Herwig, Georgios Magkotsios The NuGrid Collaboration, Los Alamos National Laboratory, A. S. University, Keele University, U. Victoria, U. N. Dame, U. Arizona

引用次数: 3

Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid 来自NuGrid的大范围核生产场所的核合成模拟

arXiv: Astrophysics Pub Date : 2008-11-28 DOI: 10.22323/1.053.0023

F. Herwig, M. Bennett, S. Diehl, C. Fryer, R. Hirschi, A. Hungerford, G. Magkotsios, M. Pignatari, G. Rockefeller, F. Timmes, Patrick Young The NuGrid Collaboration, Los Alamos National Laboratory, A. S. University, Keele University, U. Victoria, U. N. Dame

{"title":"Nucleosynthesis simulations for a wide range of nuclear production sites from NuGrid","authors":"F. Herwig, M. Bennett, S. Diehl, C. Fryer, R. Hirschi, A. Hungerford, G. Magkotsios, M. Pignatari, G. Rockefeller, F. Timmes, Patrick Young The NuGrid Collaboration, Los Alamos National Laboratory, A. S. University, Keele University, U. Victoria, U. N. Dame","doi":"10.22323/1.053.0023","DOIUrl":"https://doi.org/10.22323/1.053.0023","url":null,"abstract":"Simulations of nucleosynthesis in astrophysical environments are at the intersection of nuclear physics reaction rate research and astrophysical applications, for example in the area of galactic chemical evolution or near-field cosmology. Unfortunately, at present the available yields for such applications are based on heterogeneous assumptions between the various contributing nuclear production sites, both in terms of modeling the thermodynamic environment itself as well as the choice of specifc nuclear reaction rates and compilations. On the other side, new nuclear reaction rate determinations are often taking a long time to be included in astrophysical applications. The NuGrid project addresses these issues by providing a set of codes and a framework in which these codes interact. In this contribution we describe the motivation, goals and first results of the NuGrid project. At the core is a new and evolving post-processing nuclesoynthesis code (PPN) that can follow quiescent and explosive nucleosynthesis following multi-zone 1D-stellar evolution as well as multi-zone hydrodynamic input, including explosions. First results are available in the areas of AGB and massive stars.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"257 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76120679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 11

High Energy Neutrino Astronomy: Status and Perspectives 高能中微子天文学:现状与展望

arXiv: Astrophysics Pub Date : 2008-11-28 DOI: 10.1063/1.3076635

C. Spiering

引用次数: 5

Results of MAGIC on Galactic sources 银河系源的MAGIC结果

arXiv: Astrophysics Pub Date : 2008-11-26 DOI: 10.1063/1.3076633

J. Rico, F. C. Collaboration

引用次数: 0

Search for Solar Axions with the CDMS-II Experiment 用CDMS-II实验寻找太阳轴子

arXiv: Astrophysics Pub Date : 2008-11-25 DOI: 10.22323/1.064.0104

T. Bruch, F. C. Collaboration

{"title":"Search for Solar Axions with the CDMS-II Experiment","authors":"T. Bruch, F. C. Collaboration","doi":"10.22323/1.064.0104","DOIUrl":"https://doi.org/10.22323/1.064.0104","url":null,"abstract":"The CDMS-II experiment operates 19 germanium detectors with a mass of 250g each in a very low background environment. Originally designed for the search for Dark Matter the experiment can also detect solar axions by Primakoff conversion to photons. The Bragg condition for X-ray momentum transfer in a crystal allows for coherent amplification of the Primakoff process. Since the orientation of the crystal lattice with respect to the Sun changes with daytime an unique pattern in time and energy of solar axion conversions is expected. The low background ~1.5 counts/kg/day/keV and knowledge of the exact orientation of all three crystal axes with respect to the Sun make the CDMS-II experiment very sensitive to solar axions. In contrast to helioscopes, the high mass region < 1 keV can also be probed effectively. The alternating orientations of the individual crystals in the experimental setup provide different patterns of solar axion conversion, making a false positive result extremely unlikely. The result of an analysis of 289 kg-days of exposure resulted in a null observation of solar axion conversion. This analysis sets an upper limit on the axion photon coupling constant of g_{agammagamma} < 2.6 x 10^{-9} GeV{-1} at a 95% confidence level.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82852034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2