摘要:

The parameters of the binary system HD 121447, the coolest known barium star with the second shortest orbital period (P=185.7 d), have been derived from the spectroscopic orbit and the lightcurve indicating that the system is an ellipsoidal variable. A mass of about 1.6 M⊙andMbol∼−2.2 follow from the assumption that the barium star is located on the upper giant branch, with the companion mass (∼0.6 M⊙) compatible with that of a white dwarf. This analysis provides the first direct determination of these physical parameters for a barium star. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47348

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A numerical code is developed, which integrates the equation of non‐grey radiative transfer through a spherically symmetric dust shell around an evolved AGB star. The code computes, by an iterative method, a self‐consistent thermal structure of the envelope, for multiple grain components of carbon‐ and oxygen‐rich material. The emergent radial brightness distribution at different wavelengths is calculated taking into account the effect of non‐isotropic scattering, absorption, and thermal reemission by grains. Our model results, for different sets of stellar and nebular parameters, are compared with observational data on oxygen‐ and carbon‐rich AGB stars with envelopes of different optical depths. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47422

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The paper proposes a model in which the cosmic ray spectrum is formed by propagation processes in magnetic and photon fields of Galaxy, for energy range from JACEE to Fly’s Eye experiments. The turbulence effect of Galactic magnetic field on the propagation of cosmic ray nuclei has been investigated. We have found that the way of propagation of the protons (and nuclei respectively) is changed at the same energies where JACEE and Fly’s Eye experiments observe alteration in the spectrum of protons. The diffusion equations for the nuclei in field of soft photons and turbulent magnetic field have been solved. We argue that the anisotropy of secondary protons should follow the heavy nuclei one. A good agreement with the whole features in total cosmic ray energy spectrum was obtained for parameters widely accepted for the cosmic environment. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47349

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The EAS experiment KASCADE (KArlsruhe Shower Core and Array DEtector) (1) which is presently under construction at the Karlsrube Nuclear Research Center consists of an extended array of detectors for the electron/photon component and for muons far from the shower core and of a compact hadron calorimeter. In addition, close to the calorimeter a large area muon detector will be implemented employing streamer tubes and persuing the tracking concept. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47350

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An overview is given of direct and indicect measurements of thermonucl reaction rates in the vicinity of the Gamow peak. The article deals with direct capture or transfer reactions induced by low‐energy light charged particles such asp,d, or3He. Astrophysical applications are discussed. (AIP) ©1995 American Institute of Physics.©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47351

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In explosive astrophysical sites reactions involving shortlived unstable nuclei determine the timescale, energy production, and nucleosynthesis. Radioactive beam (RB) facilities have opened this area of considerable astrophysical interest to direct measurements of reaction rates. Experimental results obtained with RB are presented and the techniques used are discussed. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47352

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The interpretation of the s‐process abundances in the solar system, in stellar atmospheres, and in the form of isotopic anomalies in meteoritic material represents an important test for various He‐burning scenarios. The information obtained from such analyses depends to a large extent on the quality of the nuclear physics that is available. This contribution deals with (i) the status of the main neutron producing reactions for the s‐process, and (ii) the progress in the determination of stellar (n,&ggr;) rates, in particular for the unstable branch point isotopes, and the problems related to p‐process corrections and neutron captures from excited states. The analysis of s‐process branchings in the mass range 90<A<200 is briefly discussed including an update of the most important cases. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47411

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Within the ‘waiting‐point’ assumption, we have investigated the influence of nuclear properties far from stability on the prediction of solar‐system r‐process abundance (Nr,⊙) distributions. When using data sets for masses and &bgr;‐decay quantities from the Finite‐Range Droplet Model (FRDM) and the Extended Thomas‐Fermi plus Strutinski Integral (ETFSI) method, local deficiencies in theNr,⊙fits aroundA≊115 and 175 cannot be avoided. As pointed out in previous papers, they are due to model‐inherent weaknesses in the shell‐structure description very far from stability. New experiments at CERN/ISOLDE together with recent HFB calculations using the Skyrime P interaction, confirm our earlier qualitative predictions, in particular shell‐quenching and neutron‐skin effects in drip‐line nuclei. These new nuclear‐structure properties are shown to result in a considerable improvement of the globalNr,⊙fits. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47426

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The reaction sequences and the reaction flow in the CNO cycles and the rp‐process are important for the understanding of the energy generation and nucleosynthesis of heavy elements in hot and explosive stellar hydrogen burning. Many of the involved reaction rates in particular for the proton capture on unstable short lived nuclei are only approximated and have not been verified experimentally. New experimental approaches are therefore necessary to determine these rates more reliable. This requires either the use of intense radioactive beams to measure directly the reaction cross sections over a wide energy range, or in a more classical approach the study of the level structure of the involved compound nuclei in the corresponding excitation range. On particular examples of reactions in the hot CNO cycles and the rp‐process, indirect experimental approaches will be presented and discussed. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47412

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

I review available techniques for extraction of weak interaction rates in nuclei. The case for using hadron charge exchange reactions to estimate such rates is presented and contrasted with alternate methods. Limitations of the (p,n) reaction as a probe of Gamow‐Teller strength are considered. Review of recent comparisons between beta‐decay studies and (p,n) is made, leading to cautious optimism regarding the final usefulness of (p,n)‐ derived GT strengths to the field of astrophysics. ©1995 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.47413

出版商:AIP    

年代:1995

数据来源: AIP