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Rainger, Ronald; Harvey, Joy; Winsor, Mary P.; Cain, J. C.; Benson, Keith R.

doi:10.1023/a:1004208323283

Cited by 23 publications

(2 citation statements)

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“…Instead the absorption can be described as a continuous range of columns through which the source is seen, as expected for the pre-shock material. While the ionization structure of the column is outside of the scope of this paper (see Rainger et al 1997), the data are clearly consistent with a power law column-covering fraction distribution of neutral material, so we use this model in all the following fits. The continuum is also significantly better described by a multi-temperature α = 1 cooling shock model than by a single temperature plasma, so we use this to describe the plasma emission in all the following fits.…”

Section: Asca Datamentioning

confidence: 93%

Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam

Done

Magdziarz

1998

Monthly Notices of the Royal Astronomical Society

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We re‐analyse the ASCAGinga X‐ray data from BY Cam, a slightly asynchronous magnetic accreting white dwarf. The spectra are strongly affected by complex absorption, which we model as a continuous (power‐law) distribution of covering fraction and column of neutral material. This absorption causes a smooth hardening of the spectrum below ∼ 3 keV, and is probably produced by material in the pre‐shock column which overlies the X‐ray emission region. The ASCA data show that the intrinsic emission from the shock is not consistent with a single‐temperature plasma. Significant iron L emission coexisting with iron K shell lines from H‐ and He‐like iron clearly shows that there is a wide range of temperatures present, as expected from a cooling shock structure. The Ginga data provide the best constraints on the maximum temperature emission in the shocked plasma, with kTmax = 21+18−4 keV. Cyclotron cooling should also be important; it suppresses the highest temperature bremsstrahlung components, so the X‐ray data provide only a lower limit on the mass of the white dwarf of M ≥ 0.5 M⊙. Reflection of the multitemperature bremsstrahlung emission from the white dwarf surface is also significantly detected. We stress the importance of modelling all these effects in order to gain a physically self‐consistent picture of the X‐ray spectra from polars in general and BY Cam in particular.

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Section: Asca Datamentioning

confidence: 93%

Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam

Done

Magdziarz

1998

Monthly Notices of the Royal Astronomical Society

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“…Modelling including all these are being developed [9], but here we use a phenomenological description of this complex absorption in terms of a continuous (power law) distribution of neutral absorping column and covering fraction (C f ∝ N β H , see also [10]).…”

Section: Spectral Complexitymentioning

confidence: 99%

The X-ray spectrum of the polar BY Cam

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Magdziarz²

1999

Nuclear Physics B - Proceedings Supplements

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ASCA and GINGA X-ray data from the magnetic Cataclysmic Variable BY Cam show that the spectrum is strongly affected by complex absorption, probably from the pre-shock accretion column. The intrinsic emission from the shock is significantly better described by the theoretically expected multi-temperature structure rather than a single temperature plasma, but with cyclotron cooling probably suppressing the highest temperature bremsstrahlung components. Reflection of this multi-temperature emission from the white dwarf surface is also significantly detected. All these spectral complexities are required to gain a physically self-consistent picture of the X-ray spectrum.

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Evolution and the nature of science: On the historical discord and its implications for education

Rudolph

Stewart

1998

J. Res. Sci. Teach.

117

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Research in the teaching and learning of evolutionary biology has revealed persistent difficulties in student understanding of fundamental Darwinian concepts. These difficulties may be traced, in part, to science instruction that is based on philosophical conceptions of science that are no longer viewed as adequately characterizing the diverse nature of scientific practice, especially in evolutionary biology. This mismatch between evolution as practiced and the nature of science as perceived by researchers and educators has a long history extending back to the publication of Darwin's theory of natural selection. An examination of how this theory was received by the scientific community of the time may provide insight into some of the difficulties that students have today in learning these important biological concepts. The primary difficulties center around issues of metaphysics and scientific method, aspects of the nature of science too often ignored in science education. Our intent is not to offer a specific course of action to remedy the problems educators currently face, but rather to suggest an alternative path one might take to eventually reach a solution. That path, we argue, should include the use of broader models of science that incorporate these elements of scientific practice to structure teaching and education research in evolution. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 1069–1089, 1998

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Cited by 23 publications

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Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam

Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam

The X-ray spectrum of the polar BY Cam

Evolution and the nature of science: On the historical discord and its implications for education

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