历史上新疆白鹳的地理分布区域考证     

马鸣 《干旱区地理》2002,25(2):139-142

经过实地考察和访问，以及结合中国古籍和近代的鸟类学文献，对曾经分布于我国新疆的中亚白鹳（Ciconia ciconia asiatica)种群的过去和现在有了比较清楚的认识。据Scully(1876)和Ludlow and Kinnear(1933-34)等记载，一百年前，这是一个比较常见的种类，曾广泛分布于新疆南部的莎车和喀什等地区。根据笔者自1985－2001年对新疆各地的调查和访问，中亚白鹳在新疆（或者说在全中国）消失的年代大约为1980年前后。其原因归结为人为因素和自然因素，如绿洲人口的增加、农业开垦、栖息环境（湿地）的破坏和丧失、种间竞争（自然因素）以及不应有的滥捕乱猎行为等。白鹳比较喜欢亲近人类（有“送子鸟”之美誉），这也是其遭受厄运的原因之一。目前，新疆还有十几种鸟类（如鹈鹕、琵鹭、黑鹳、鸿雁、疣鼻天鹅、云石斑鸭、白肩雕、马雕、猎隼、黄爪率、白鹤、斑胸田鸡、长脚秧鸡、大鸨、小鸨、波斑鸨、遗鸥、小鸥、中亚鸽等）亦正面临相同的命运。  相似文献   

A search for binarity using Far-Ultraviolet Spectroscopic Explorer observations of DAO white dwarfs     

S. A. Good  M. A. Barstow  M. R. Burleigh  P. D. Dobbie  J. B. Holberg 《Monthly notices of the Royal Astronomical Society》2005,364(3):1082-1090

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The masses, radii and luminosities of the components of U Geminorum     

T. Naylor  A. Allan  K. S. Long 《Monthly notices of the Royal Astronomical Society》2005,361(3):1091-1101

We present a phase-resolved spectroscopic study of the secondary star in the cataclysmic variable (CV) U Gem. We use our data to measure the radial velocity semi-amplitude, systemic velocity and rotational velocity of the secondary star. Combining this with literature data allows us to determine masses and radii for both the secondary star and white dwarf, which are independent of any assumptions about their structure. We use these to compare their properties to those of field stars and find that both components follow field mass–radius relationships. The secondary star has the mass, radius, luminosity and photometric temperature of an M2 star, but a spectroscopic temperature of M4. The latter may well be due to a high metallicity. There is a troubling inconsistency between the radius of the white dwarf inferred from its gravitational redshift and inclination and that inferred from its temperature, flux and astrometric distance.
We find that there are two fundamental limits to the accuracy of the parameters we can derive. First, the radial velocity curve of the secondary star deviates from a sinusoid, in part because of its asphericity (which can be modelled) and in part because the line flux is not evenly distributed over its surface. Secondly, we cannot be certain which spectral type is the best match for the lines of the secondary star, and the derived rotational velocity is a function of the spectral type of the template star used.  相似文献   

Heavy-element abundance patterns in hot DA white dwarfs     

M. A. Barstow  S. A. Good  J. B. Holberg  I. Hubeny  N. P. Bannister  F. C. Bruhweiler  M. R. Burleigh  R. Napiwotzki 《Monthly notices of the Royal Astronomical Society》2003,341(3):870-890

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Geometrical constraints upon the unipolar model of V407 Vul and RXJ0806.3+1527     

S. C. C. Barros  T. R. Marsh  P. Groot  G. Nelemans  G. Ramsay  G. Roelofs  D. Steeghs  J. Wilms 《Monthly notices of the Royal Astronomical Society》2005,357(4):1306-1312

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Measuring the Fundamental Parameters of Hot Hydrogen- Rich White Dwarfs     

M.A.Barstow 《中国天文和天体物理学报》2003,(4)

This review considers the observations of hot, hydrogen-rich white dwarf stars, with particular reference to measurements of temperature, surface gravity and composition. Spectroscopic data from a variety of wavelength ranges are required for this work and, in particular, the important contributions from optical, ultraviolet and extreme ultraviolet studies are discussed. Using the values of Teff and log g determined for an individual white dwarf, estimates of mass and radius might be derived from the theoretical mass-radius relation. The issue of the accuracy of the theoretical mass-radius calculations and the prospects for making empirical tests using observational data are outlined.  相似文献   

Remnant evolution after a carbon–oxygen white dwarf merger     

S.-C. Yoon  Ph. Podsiadlowski  S. Rosswog 《Monthly notices of the Royal Astronomical Society》2007,380(3):933-948

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Near-infrared spectroscopy of the very low mass companion to the hot DA white dwarf PG 1234+482     

P. R. Steele  M. R. Burleigh  P. D. Dobbie  M. A. Barstow 《Monthly notices of the Royal Astronomical Society》2007,382(4):1804-1808

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A search for radio pulsars around low-mass white dwarfs     

Joeri van Leeuwen  Robert D. Ferdman  Sol Meyer  Ingrid Stairs 《Monthly notices of the Royal Astronomical Society》2007,374(4):1437-1440

Low-mass white dwarfs can be produced either in low-mass X-ray binaries by stable mass transfer to a neutron star, or in a common envelope phase with a heavier white dwarf companion. We have searched eight low-mass white dwarf candidates recently identified in the Sloan Digital Sky Survey for radio pulsations from pulsar companions, using the Green Bank Telescope at 340 MHz. We have found no pulsations down to flux densities of 0.6–0.8 mJy kpc⁻² and conclude that a given low-mass helium-core white dwarf has a probability of  <0.18 ± 0.05  of being in a binary with a radio pulsar.  相似文献   

White dwarfs in the 2dF QSO Redshift Survey – I. Hydrogen-rich (DA) stars     

S. Vennes  R. J. Smith  B. J. Boyle  S. M. Croom  A. Kawka  T. Shanks  L. Miller  N. Loaring 《Monthly notices of the Royal Astronomical Society》2002,335(3):673-686

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