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51.
Astronomy Letters - The reduction of all the available photometry for the Cepheid V420 Cen has allowed its $$O-C$$ diagram spanning a time interval of 131 years to be constructed. The data obtained... 相似文献
52.
Goryachev N. A. Sotskaya O. T. Astakhov A. S. Xuefa Shi Mikhalitsyna T. I. Aksentov K. I. Berdnikov N. V. 《Doklady Earth Sciences》2020,491(2):220-223
Doklady Earth Sciences - A mineralogical–geochemical study of Late Pleistocene bottom sediments of the LV 77-10 core collected in the central part of Long Strait was carried out. Two horizons... 相似文献
53.
L. N. Berdnikov A. A. Belinskii N. I. Shatskii M. A. Burlak N. P. Ikonnikova E. O. Mishin D. V. Cheryasov S. V. Zhuiko 《Astronomy Reports》2020,64(4):310-318
For the first time, BVIc observations of the Cepheid V811 Oph were obtained by using a new 60‑cm telescope at the Caucasus Mountain Observatory, Sternberg Astronomical Institute, Moscow State University (SAI MSU). An $$O{-}C$$ diagram covering a time span of 124 years was plotted using photometry from old photographic and modern sky surveys. The diagram has a parabola shape, which made it possible to determine for the first time the quadratic elements of the brightness variations. Furthermore, it made it possible to calculate the rate of an evolutionary decrease in the period of V811 Oph $$dP{\text{/}}dt = - 0.00375( \pm 0.00177)$$ s/year, which is consistent with the theoretical calculation results for the second intersection of the instability strip if this Cepheid is a classical one. The pulsation stability test proposed by Lombard and Koen confirmed the actual decrease in the period. 相似文献
54.
L. N. Berdnikov A. Yu. Kniazev V. V. Kravtsov E. N. Pastukhova 《Astronomy Letters》2017,43(7):489-500
In 2012–2014 we obtained 3641 CCD frames of the fields of the RR Lyrae (AB subtype, P = 0.583 days) variable DU Mon with BV I c filters using the 76-cm telescope of the South African Astronomical Observatory (SAAO) and the 1-m telescopes of the Las Cumbres Observatory Global Telescope Network (LCOGT). Our observations confirmed the presence of the Blazhko effect that we suspected previously and allowed its period to be determined, \({P_{Bl}} = 60_ \cdot ^d52 \pm 0_ \cdot ^d03\). Using all of the available observations, we constructed an O–C diagram spanning a time interval of 86 years that revealed at least one abrupt change in the pulsation period (a decrease by 15.26 s). 相似文献
55.
Based on balance calculations with the use of a spatially detailed mathematical model for transport and sedimentation of the particulate matter adjusted to the conditions of the Sea of Azov, particular spatiotemporal features of the terrigenous sedimentation in the second half of the 20th century are recognized. The general tendency for the deceleration of the accumulation of terrigenous sediments and for the decrease in the areas with a negative balance of the terrigenous matter is related to the 2.5-fold fall in the volumes of the matter supplied from land. During the period considered, the intensity of the sedimentation decreased from 1000 to 400 g/m2/year. The accumulation of terrigenous sediments proceeds in the regions where the sources of the matter supply are concentrated and where features of the bottom morphology and hydrodynamical activity are favorable for the sedimentation: in Taganrog and Temryuk bays. In the central part of the sea, the intensity of the sedimentation comprises a value of about 300 g/m2/year. In Taganrog Bay and in the sea proper, areas with a negative balance of terrigenous sedimentary matter increased up to 30%. 相似文献
56.
L. N. Berdnikov A. Yu. Kniazev I. A. Usenko V. V. Kovtyukh V. V. Kravtsov 《Astronomy Letters》2010,36(7):490-497
We present the results obtained by analyzing 20 spectra of six bright Cepheids taken with the 1.9-m telescope at the South
African Astronomical Observatory. The chemical composition and atmospheric parameters have been determined for XX Sgr, AP
Sgr, RV Sco, RY Sco, V482 Sco, and V636 Sco. 相似文献
57.
58.
M. V. Goroshko V. A. Gur’yanov N. V. Berdnikov V. E. Kirillov 《Russian Journal of Pacific Geology》2009,3(6):511-529
Numerous gold deposits and occurrences were recognized in the regions of tectonomagmatic activation in the southeastern Siberian
Platform. They are located in four metallogenic zones: the Ket-Kap (skarns, quartz veins, and stockworks; gold-bearing lodes
in silicitolites; and argillisite-sericite metasomatites), Ulkan (clayey-micaceous metasomatites, quartz veins), Preddzhugdzhur
(quartz veins, skarns, and sericite-hydromicaceous metasomatites), and Uda (sericite-hydromicaceous metasomatites). The skarn
mineralization is of Meosozoic age, while the mineralization in the quartz veins, quartz-hydromicaceous metasomatites, and
quartz-sulfide veins may have a Meosozoic, Paleozoic, or Late Paleozoic age.
The highest temperatures were determined for the ore formation in the Preddzhugdzhur skarns (500–715 °C) and the hydrothermal-metasomatic
rocks of the Ket-Kap zone (510–530 °C). The composition of gas-liquid inclusions in the minerals of these rocks is dominated
by aqueous Na, K, and Ca chloride solutions with salinity up to 40 wt % NaCl equiv; fluid contains CO2. Quartz veins and stockworks of the Ket-Kap zone were formed under high (up to 465°C) and moderate temperatures and salinity
up to 32 wt % NaCl equiv. Sometimes, the minerals in these rocks contain inclusions of low-density CO2. The gold-bearing veins of the Preddzhugdzhur zone formed at 225–230°C and salinity of 1–2 wt % NaCl equiv. The ore-bearing
solutions in the gold-bearing veins of the Ulkan zone are characterized by a potassium-sodium-chlorine composition and salinity
of 2–10 wt % NaCl equiv., and the temperature of their formation was 220–280 °C. 相似文献
59.
N. R. Tanvir M. A. Hendry A. Watkins S. M. Kanbur L. N. Berdnikov C. C. Ngeow 《Monthly notices of the Royal Astronomical Society》2005,363(3):749-762
We describe techniques to characterize the light curves of regular variable stars by applying principal component analysis (PCA) to a training set of high-quality data, and to fit the resulting light-curve templates to sparse and noisy photometry to obtain parameters such as periods, mean magnitudes etc. The PCA approach allows us to efficiently represent the multiband light-curve shapes (LCSs) of each variable, and hence quantitatively describe the average behaviour of the sample as a smoothly varying function of period, and also the range of variation around this average.
In this paper we focus particularly on the utility of such methods for analysing Hubble Space Telescope ( HST ) Cepheid photometry, and present simulations which illustrate the advantages of our PCA template-fitting approach. These are: accurate parameter determination, including LCS information; simultaneous fitting to multiple passbands; quantitative error analysis; objective rejection of variables with non-Cepheid-like light curves or those with potential period aliases.
We also use PCA to confirm that Cepheid LCSs are systematically different (at the same period) between the Milky Way and the Large and Small Magellanic Clouds, and consider whether LCS might therefore be used to estimate the mean metallicities of Cepheid samples, thus allowing metallicity corrections to be applied to derived distance estimates. 相似文献
In this paper we focus particularly on the utility of such methods for analysing Hubble Space Telescope ( HST ) Cepheid photometry, and present simulations which illustrate the advantages of our PCA template-fitting approach. These are: accurate parameter determination, including LCS information; simultaneous fitting to multiple passbands; quantitative error analysis; objective rejection of variables with non-Cepheid-like light curves or those with potential period aliases.
We also use PCA to confirm that Cepheid LCSs are systematically different (at the same period) between the Milky Way and the Large and Small Magellanic Clouds, and consider whether LCS might therefore be used to estimate the mean metallicities of Cepheid samples, thus allowing metallicity corrections to be applied to derived distance estimates. 相似文献
60.
For the classical Cepheid U Sgr, we have constructed an O - C diagram spanning a time interval of 144 years. The O - C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary increase in the period, dP/dt = 0.39 (±0.10) s yr?1, in agreement with the results of theoretical calculations for the third crossing of the instability strip. The available data reduced by the Eddington-Plakidis method reveal small random period fluctuations that do not distort the evolutionary trend in the O - C residuals. 相似文献