The first and second order moments of the polarization profiles of hydrogen lines     

R. HCasini  E. Landi Degl'Innocenti 《Solar physics》1996,164(1-2):91-96

The main properties of the first- and second-order moments of polarized hydrogen lines, forming in the presence of stationary electric and magnetic fields, are reviewed. The analytical results presented here apply directly to the case of optically-thin emission lines in the LTE regime. Some applications of such results to electric- and magnetic-field diagnostics in (solar) plasmas are then briefly considered.On leave from the Dipartimento di Astronomia e Scienza dello Spazio, Università di Firenze, Largo E. Fermi 5, I-50125 Firenze, Italy  相似文献   

CCD astrometry of the solar system     

J. E. Arlot  F. Colas 《Celestial Mechanics and Dynamical Astronomy》1996,66(1):123-130

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2060 Chiron back to a minimum of brightness     

Daniela Lazzaro  Marcos A. Florczak  Alberto Betzler  Othon C. Winter  Silvia M. Giuliatti-Winter  Claudia A. Angeli  Dietmar W. Foryta 《Planetary and Space Science》1996,44(12):1547-1550

The results of photometric observations of comet/asteroid 2060 Chiron at the Observatório do Pico dos Dias (Brazil-OPD) and the Observatoire de Haute-Provence (France-OHP) during 1994 and 1995 are presented. The analysis of the data shows a decrease of 2060 Chiron brightness from its peak values of 1988–1991. The absolute magnitude, H_v, varies from a maximum of 6.6 in February 1994 up to a minimum of 6.8 in June 1995. Therefore 2060 Chiron is back to a minimum of activity close to that of 1983–1985. The slope parameter G is found to be G = 0.71 ± 0.15. It is suggested that the H-G magnitude system, generally adopted to present 2060 Chiron brightness, is not the most appropriate due to the cometary activity of this object.  相似文献   

Evidence in a glassy cosmic spherule from Antarctica for grazing incidence encounters with the Earth's atmosphere     

Matthew J. GENGE  Monica M. GRADY  Robert HUTCHISON 《Meteoritics & planetary science》1996,31(5):627-632

Abstract— Cosmic dust accreted by the Earth can be extensively reprocessed during atmospheric encounters. The textures and compositions of reprocessed material provide important constraints by which the processes affecting extraterrestrial matter in the Earth's atmosphere can be better understood. Here we report results on an unusual Antarctic glassy cosmic spherule that demonstrates strong textural evidence for at least two grazing incidence encounters with the Earth's atmosphere prior to final reentry. The particle consists of a central glassy core with four peripheral glass lobes that transect a silicate particle rim. The texture of the particle confirms previous theoretical speculations that some high velocity, low incidence angle interplanetary particles experience numerous encounters with the Earth's atmosphere and also indicates that micrometeorites demonstrating multiple melting episodes should be interpreted with caution.  相似文献   

measurement of noise power spectrum in photon counting PMT's and the effect of the observed (1/f) noise on astronomical photometry     

S. S. Raouf  A. R. Sadik  N. K. Wafi  K. M. Aboud 《Astrophysics and Space Science》1986,127(2):207-218

In astronomical photometry, the sensitivity of observations is limited by the dark counts of the photomultiplier tube. In the present work, the effect of dark count noise in photon counting systems is investigated by theory and experimental measurements. Dark counts are considered to be originating from two sources, namely: dc fluctuations and random pulses.Experimental measurements were carried out to determine noise effects in different operating regions of noise dominance. The results provide strong evidence that: in normal operating mode, where the effect of random pulses is dominant, dark counts do not follow Poisson statistics. The observed noise shows strong (1/f) power spectrum, where the observed noise power is found to increase with time of observation.The results are important in photon counting systems operating under dark count limited mode. The conclusions drawn can be useful in obtaining more accurate error estimates and in assessing astronomical photometric observations and data reduction techniques.  相似文献   

A highly automated moving object detection package   总被引：1，自引：0，他引：1  

J.-M. Petit  M. Holman  H. Scholl  J. Kavelaars  B. Gladman † 《Monthly notices of the Royal Astronomical Society》2004,347(2):471-480

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Introduction     

Jenna E. Beletic  James W. Beletic  Paola Amico 《Experimental Astronomy》2005,19(1-3):1-3

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Elm bark beetle in Holocene peat deposits and the northwest European elm decline     

Sarah H. E. Clark  Kevin J. Edwards 《第四纪科学杂志》2004,19(6):525-528

The elm decline of 5000 ¹⁴C yr ago has been the most widely discussed phenomenon in post‐glacial vegetation history. This pan‐European reduction of elm populations, echoed in the decimation of elmwoods in Europe during the twentieth century, has attracted a series of interrelated hypotheses involving climate change, human activity, disease and soil deterioration. The elm bark beetle (Scolytus scolytus L.) is an essential component of disease explanations. We present evidence for the presence of the beetle over a prolonged period (ca. 7950–4910 yr BP [8800–5660 cal. yr BP]) from a lowland raised mire deposit in northeast Scotland, with its final appearance at this site, and the first and only appearance in another mire of a single scolytid find, around the time of the elm decline. The subfossil S. scolytus finds are not only the first from Scotland, but they also represent the most comprehensive sequence of finds anywhere. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A reanalysis of the light curve of RT Persei with the W-D code     

M. T. Edalati  F. Zeinali 《Astrophysics and Space Science》1996,243(2):275-283

The UBV photometric observations of RT Per, from Sanwal and Chaubey (1981), were analyzed by the Wilson and Devinney code (1971). The light curves include reflection effects that for the first time has been suggested by Dugan (1911). RT Per has a semi-detached configuration where the lower-mass component is in contact with its respective Roche surface. The higher-mass component very nearly fills its Roche lobe. It has the characteristic of an Algol type system. The absolute dimensions for the primary and secondary of this system were calculated from its spectral types and by combining the photometric solution with inferred component radial velocities (Lu, 1990).  相似文献   

On the orthogonality of surface wave eigenfunctions in cylindrical coordinates     

M. G. Bostock 《Geophysical Journal International》1990,103(3):763-767

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