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91.
92.
Walter Winter 《Earth, Moon, and Planets》2006,99(1-4):285-307
Because the propagation of neutrinos is affected by the presence of Earth matter, it opens new possibilities to probe the
Earth’s interior. Different approaches range from techniques based upon the interaction of high energy (above TeV) neutrinos
with Earth matter, to methods using the MSW effect on the oscillations of low energy (MeV to GeV) neutrinos. In principle,
neutrinos from many different sources (sun, atmosphere, supernovae, beams etc.) can be used. In this talk, we summarize and
compare different approaches with an emphasis on more recent developments. In addition, we point out other geophysical aspects
relevant for neutrino oscillations. 相似文献
93.
H. M. Antia 《Journal of Astrophysics and Astronomy》2002,23(1-2):3-8
The interior of the Sun is not directly observable to us. Nevertheless, it is possible to infer the physical conditions prevailing
in the solar interior with the help of theoretical models coupled with observational input provided by measured frequencies
of solar oscillations. The frequencies of these solar oscillations depend on the internal structure and dynamics of the Sun
and from the knowledge of these frequencies it is possible to infer the internal structure as well as the large scale flows
inside the Sun, in the same way as the observations of seismic waves on the surface of Earth help us in the study of its interior.
With the accumulation of seismic data over the last six years it has also become possible to study temporal variations in
the solar interior. Some of these seismic inferences would be described. 相似文献
94.
95.
Dong Han Shuang-Nan Zhang Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing Department of Physics & Center for Astrophysics Tsinghua University Beijing Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(4)
Hilbert-Huang Transform (HHT) is a novel data analysis technique for nonlinear and non-stationary data. We present a time-frequency analysis of both simulated light curves and an X-ray burst from the X-ray burster 4U 1702-429 with both the HHT and the Windowed Fast Fourier Transform (WFFT) methods. Our results show that the HHT method has failed in all cases for light curves with Poissonian fluctuations which are typical for all photon counting instruments used in astronomy, whereas the WFFT method can sensitively detect the periodic signals in the presence of Poissonian fluctuations; the only drawback of the WFFT method is that it cannot detect sharp frequency variations accurately. 相似文献
96.
97.
98.
99.
J. A. McSaveney K. R. Pollard P. L. Cottrell 《Monthly notices of the Royal Astronomical Society》2005,362(1):331-336
In this paper we examine the problems of phasing using light curves and offer an alternate technique using the changes in acceleration to establish the zero point. We give astrophysical justification as to why this technique is useful and apply the technique to a selection of Type II Cepheids. We then examine some limitations of the technique which qualify its use. 相似文献
100.
G. Bono † F. Caputo M. Marconi 《Monthly notices of the Royal Astronomical Society》2001,325(4):1353-1358
We present a new set of Cepheid, full amplitude, non-linear, convective models which are pulsationally unstable in the second overtone (SO). Hydrodynamical models were constructed by adopting a chemical composition typical of Cepheids in the Small Magellanic Cloud (SMC) and for stellar masses ranging from 3.25 to 4 M⊙ . Predicted φ 21 Fourier parameters agree, within current uncertainties, with empirical data for pure first- and second-overtone variables as well as for first-/second-overtone (FO/SO) double-mode Cepheids collected by Udalski et al. in the SMC. On the other hand, predicted I -band amplitudes are systematically larger than the observed ones in the short-period range, but attain values that are closer to the empirical ones for log P SO ≥−0.12 and log P FO ≥0.1 . We also find, in agreement with empirical evidence, that the region within which both second and first overtones attain a stable limit cycle widens when moving towards lower luminosities. Moreover, predicted P SO / P FO and P FO / P F period ratios agree quite well with empirical period ratios for FO/SO and fundamental/FO double-mode SMC Cepheids.
Interestingly enough, current models support the evidence that pure SO Cepheids and SO components in FO/SO Cepheids are good distance indicators. In fact, we find that the fit of the predicted period–luminosity–colour ( V , V – I ) relation to empirical SMC data supplies a distance modulus ( DM ) of 19.11±0.08 mag . The same outcome applies to pure FO Cepheids and FO components in FO/SO Cepheids, and indeed we find DM =19.16±0.19 mag . Current distance estimates do not account for, within current uncertainties on photometry and reddening, the so-called short distance scale. 相似文献
Interestingly enough, current models support the evidence that pure SO Cepheids and SO components in FO/SO Cepheids are good distance indicators. In fact, we find that the fit of the predicted period–luminosity–colour ( V , V – I ) relation to empirical SMC data supplies a distance modulus ( DM ) of 19.11±0.08 mag . The same outcome applies to pure FO Cepheids and FO components in FO/SO Cepheids, and indeed we find DM =19.16±0.19 mag . Current distance estimates do not account for, within current uncertainties on photometry and reddening, the so-called short distance scale. 相似文献