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61.
Gosselin Jeremy M. Dosso Stan E. Askan Aysegul Wathelet Marc Savvaidis Alexandros Cassidy John F. 《Journal of Seismology》2022,26(4):781-821
Journal of Seismology - Seismic site characterization attempts to quantify seismic wave behavior at a specific location based on near-surface geophysical properties, for the purpose of mitigating... 相似文献
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Microfossils in isolation basin sediments are frequently used to reconstruct sea‐level change, but preservation problems and non‐analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (δ13C) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment δ13C and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high δ13C and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low δ13C and high C/N. The application of δ13C and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
65.
Y.-F. Yuan Jeremy S. Heyl † 《Monthly notices of the Royal Astronomical Society》2005,360(4):1493-1505
We study the evolution of a rigidly rotating protoneutron star (PNS) with hyperons and nucleons or solely nucleons in its core due to the escape of trapped neutrinos. As the neutrinos escape, the core nucleonic neutron star (NS) expands and the stellar rotation slows. After the neutrinos escape, the range of the spin periods is narrower than the initial one, but the distribution is still nearly uniform. A PNS with hyperons, at the late stage of its evolution, keeps shrinking and spinning up until all the trapped neutrinos escape. Consequently, the distribution of the stellar initial spin periods is skewed towards shorter periods. If the hyperonic star is metastable, its rotational frequency accelerates distinguishedly before it collapses to a black hole. 相似文献
66.
J. A. Yates E. M. L. Humphreys A. M. S. Richards 《Astrophysics and Space Science》1997,251(1-2):285-288
The combination of a time-dependent spherically symmetric hydrodynamic model of stellar atmosphere pulsation and a radiation
transport code, which incorporates maser saturation theory, enabled us to synthesise maps and spectra of H2O maser emission from the circumstellar envelopes of long period variable stars.
The synthetic maps and spectra compare favourably with observed 22, 321 and 325 GHz H2O maser emission. As is observed in H2O maser regions the peak emission occurs between 3–8 stellar radii from the star. The calculated H2O maser regions are in conditions of nH2 = 106 − 108 cm−3, assuming a fractional abundance of 10−4; kinetic temperatures of 550–3000 K; dust ensemble temperatures of 500–1200 K and an accelerating velocity field. The IR
radiation field is explicitly included in the radiation transport model, incorporating the latest absorption efficiency data
for silicates from Draine. We reproduce the features seen in high angular resolution MERLIN spectral line datacubes. This
shows that a mass outflow model which extends the photosphere using pulsations and incorporates radiation pressure on silicate
based dust particles can produce the observed data on small (10-mas) angular scales.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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Drake Deming † L. Jeremy Richardson Joseph Harrington 《Monthly notices of the Royal Astronomical Society》2007,378(1):148-152
We report infrared photometry of the extrasolar planet HD 209458b during the time of secondary eclipse (planet passing behind the star). Observations were acquired during two secondary eclipses at the NASA Infrared Telescope Facility (IRTF) in 2003 September. We used a circular variable filter (1.5 per cent bandpass) centred at 3.8 μm to isolate the predicted flux peak of the planet at this wavelength. Residual telluric absorption and instrument variations were removed by offsetting the telescope to nearby bright comparison stars at a high temporal cadence. Our results give a secondary eclipse depth of 0.0013 ± 0.0011, not yet sufficient precision to detect the eclipse, whose expected depth is ∼0.002 –0.003 . We here elucidate the current observational limitations to this technique, and discuss the approach needed to achieve detections of hot Jupiter secondary eclipses at 3.8 μm from the ground. 相似文献
69.
Jeremy S. Heyl 《Astrophysics and Space Science》2007,308(1-4):101-107
Owing to effects arising from quantum electrodynamics (QED), magnetohydrodynamical fast modes of sufficient strength will break down to form electron-positron pairs while traversing the magnetospheres of strongly magnetised neutron stars. The bulk of the energy of the fast mode fuels the development of an electron-positron fireball. However, a small, but potentially observable, fraction of the energy (~1033 erg) can generate a non-thermal distribution of electrons and positrons far from the star. This paper examines the cooling and radiative output of these particles. Small-scale waves may produce only the non-thermal emission. The properties of this non-thermal emission in the absence of a fireball match those of the quiescent, non-thermal radiation recently observed non-thermal emission from several anomalous X-ray pulsars and soft-gamma repeaters. Initial estimates of the emission as a function of angle indicate that the non-thermal emission should be beamed and therefore one would expect this emission to be pulsed as well. According to this model the pulsation of the non-thermal emission should be between 90 and 180 degrees out of phase from the thermal emission from the stellar surface. 相似文献
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