共查询到20条相似文献,搜索用时 15 毫秒
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For at all 24 stars in the field of the heavity reddened open cluster NGC 1502 we obtained UBV and uvby photometry. 19 of these stars we classified definitely as members. From the photometric results we derived 1·1 × 107 years as the cluster age, 960 pc as its distance, and <E(B—V)> = 0·78 mag as mean reddening of the cluster. From the reddening of the foreground stars we evaluated that the intracluster reddening has to be smaller than 0·2 mag. The value of the colour excess ratio E(b—y)/E(B—V) = 0·770 leads us to the conclusion that in the spectra of the cluster stars a very broadband structure (VBS) with a central depth of about 0·04 mag is present. 相似文献
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The W UMa system V758 Centauri has been observed photoelectrically in theUBV system at Bosque Alegre Station, and the comparison and check stars at Cerro Tololo Observatory. Full light curves were constructed from 1043 differentialUBV observations. A study of 11 photoelectric times of minimum light and of earlier photographic data shows that the period remained constant in the last century, V758 Cen shows a total occultation at secondary minimum, thus being an A-type W UMa system. Asymmetries are observed at primary minima whereas maxima are of different heights. Thermal decoupling of the components is suggested by the depth ratio of the minima; V758 Cen may be at the broken phase (or marginal contact) of a thermal relaxation oscillation. 相似文献
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We have used the integrated brightnesses from Mariner 9 high-resolution images to determine the large phase angle (20° to 80°) phase curves of Phobos and Deimos. The derived phase coefficients are β = 0.032 ± 0.001 mag/deg for Phobos and β = 0.030 ± 0.001 mag/deg for Deimos, while the corresponding phase integrals are qPhobos = 0.52 and qDeimos = 0.57. The predicted intrinsic phase coefficients of the surface material are βi = 0.019 mag/deg and βi = 0.017 mag/deg for Phobos and Deimos, respectively. The phase curves, phase coefficients and phase integrals are typical of objects whose surface layers are dark and intricate in texture, and are consistent with the presence of a regolith on both satellites. The relative reflectance of Deimos to Phobos is 1.15±0.10. The presence of several bright patches on Deimos could account for this slight difference in average reflectance. 相似文献
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Photoelectric magnitudes and colors on the UBV system are presented for 65 minor planets, including four Mars crossers, six Trojans, and main-belt objects down to 6 km in diameter. The Trojans all have very similar colors not characteristics of the main-belt population. A paucity of S-type asteroids at the smallest diameters, predicted from trends seen at larger sizes, is not observed. The newly available color data for small objects ranging from 1.0 to 5.2 AU in heliocentric distance show the main belt to be a transition zone between predominantly silicate and carbonaceous compositions. 相似文献
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Some basic equations pertaining to the accretion of perfect magnetofluid on compact objects are derived without assuming that the flow is purely circular or purely radial. In addition, we assume that the magnetofluid exerts negligible self-gravitation and that its flow is stationary and axisymmetric. We restrict ourselves to the case of ‘stiff’ or ‘incompressible’ fluid with an equation of state: pressure = energy-density. 相似文献
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Hamid M. K. Al-Naimiy Ali A. A. Mutter Hassan A. Flaih 《Astrophysics and Space Science》1985,108(2):227-236
Photoelectric observations of the eclipsing variable β Per, were obtained inUBV standard system, and new elements for the primary minimum were determined as $$J.D. = 2445641.5135,O - C = 0_.^d 0.009.$$ The light curves of the system were analysed using Fourier techniques in the frequency-domain. The fractional radii of both components are $$r_1 = 0.217 \pm 0.002,r_2 = 0.233 \pm 0.002andi = 85.5 \pm 0.5.$$ Absolute elements were derived and the effective temperatures are $$T_1 = 11800K,T_2 = 5140K.$$ 相似文献
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V. T. Doroshenko 《Astrophysics》1988,28(1):1-9
P. K. Shternberg State Astronomical Institute. Translated from Astrofizika, Vol. 28, No. 1, pp. 5–17, January–February, 1988. 相似文献
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V. T. Doroshenko 《Astrophysics》1988,28(2):135-141
P. K. Shternberg State Astronomical Institute. Translated from Astrofizika, Vol. 28, No. 2, pp. 233–242, March–April, 1988. 相似文献
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R.L. Millis 《Icarus》1977,31(1):81-88
Measurements of the brightness and B-V color index of the leading and trailing hemispheres of Iapetus during the past five apparitions of Saturn are presented. The dependence of brightness on solar phase angle is determined for the two faces of the satellite. After correction for solar phase angle and distance effects, the brighter trailing hemisphere of Iapetus was found to be constant in brightness and color index throughout the interval covered by the observations. The brightness of the dark leading hemisphere, however, decreased by about 0.2 mag over the same period, and its B-V color index reddened by 0.05 mag. These changes are interpreted as evidence for the existence of a bright southern pole cap on Iapetus. 相似文献
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We presentUBV photometry and some spectroscopic observations of an anomalous SS Cyg outburst. A comparison of the photometric and spectroscopic properties of normal and anomalous outbursts gives evidence that the differences between them are caused by different behaviour of the Balmer discontinuity. 相似文献
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Byurakan Astrophysical Observatory. Translated from Astrofizika, Vol. 36, No. 3, pp. 315–332, July–September, 1993. 相似文献
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The systematic UBV observations of six variable post-AGB supergiants in 1991–1999 are presented. Their variability is analyzed. The coolest stars V1027 Cyg and V354 Lac exhibit bimodal pulsations with variable amplitudes. Apart from pulsations, the hotter stars V887 Her and IRAS 19386+0155 show light variations associated with a stellar wind. A variable stellar wind appears to be mainly responsible for the photometric variations in the still hotter stars SAO 163075 and IRAS 20572+4919. Distinct trends in the yearly mean brightness have been found in three of the six supergiants studied, with the trend amplitude being independent of the spectral range. They are interpreted as the result of dust envelopes composed of large grains with R=A V /E(B?V)≥7 becoming optically thin. 相似文献
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In this paper we present the observations of the eclipsing binary LX Per, which were obtained in 1983. There is a wave-like distortion at outside eclipses with an amplitude ranging from 0.03 to 0.08 mag. The wave-like distortion was removed with a new approach. Then, the light curves were analyzed by the methods of Wood and Nelson, Davis, and Etzel. The absolute parameters of the components were also calculated. The physical parameters of the components indicate that the cooler star has seperated or has been departing from the Main Sequence. 相似文献
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We present a surface photometry of M 82 of medium spatial resolution. Special attention was paid to good systematic photometric accuracy. The results are discussed in terms of the distribution of intensity, colour, reddening free parameteer Q and colour excess b -V. The bright elongated body of the galaxy consists of a moderately old stellar population (1 – 3 · 109a) and is only slightly reddned with the exception of the central absorption lane and the southern central region. The chaotic fan-like disturbance south of the center shows the colours of a very young (106 – 107a) highly reddened group of stars; according to polarimetric data from the literature we see their light scattered by dust. The population index Q of the inner halo is bluer than that of the disc everywhere (with the possible exception of the extreme western part). Two sources must be responsible for the illumination of the halo; one of them is responsible for the light from the great disturbances near the minor axis. Both may be located near center but must be partly shadowed. A major contribution of the disc to the illumination is less probable because the population index is different in most places of the halo from that of the disc. In addition to the dusty halo, obscuring dust is probably located to the south of the galaxy. This can be interpreted as part of a thick disc of dust embedding the stellar disc or as beeing connected to a proposed strip of B stars at the southern boundary of the visible disc. Both these interpretations lead to opposite results concerning the direction of the inclination of the disc. The inclination itself is estimated to lie between 80° and 90°. 相似文献
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At least three large areas on the surface of Phobos are covered by a dark material of complex texture which scatters light according to the Hapke-Irvine Law. The average 20° to 80° intrinsic and disc-integrated phase coefficients of this material are βi = 0.020 ± 0.001 mag/deg and β = 0.033 mag/deg, respectively. These values are slightly greater than the values found for Deimos in Paper II (preceding article). On the largest scale the surface of Phobos is rougher than the surface of Deimos, perhaps accounting for the slightly greater phase coefficients. Contrary to the situation on Deimos, no definite regions of intrinsically brighter material are apparent on Phobos. This difference could account for the slightly lower average reflectance of Phobos relative to Deimos. No evidence for large exposures of solid rock has been found in the three areas studied. 相似文献
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To a good approximation the face of Deimos observed by Mariner 9 is covered uniformly by a dark, texturally complex material obeying a Hapke-Irvine scattering law. The intrinsic 20° to 80° phase coefficient of this material is βi = 0.017 ± 0.001 mag/deg, corresponding to a disc-integrated value of β = 0.030 mag/deg. There is also evidence of a slightly brighter (by ~30%) unit near some craters which may have been produced by the cratering events. Its texture appears to be identical to that of the average material. No evidence of quasi-specular reflection has been found, suggesting that large-scale exposures of unpulverized rock are absent. 相似文献
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J. J. Lockley Janet H. Wood S. P. S. Eyres T. Naylor Sergei Shugarov 《Monthly notices of the Royal Astronomical Society》1999,310(4):963-972
We have performed high-speed UBV photometric observations on the peculiar binary V Sagittae. Using three new eclipse timings we update the orbital ephemeris and convert it to a dynamical time-scale (TDB). We also searched for quasi-periodic oscillations but did not detect them. Using the Wilson–Devinney algorithm we have modelled the light curve to find the stellar parameters of V Sge. We find that the system is a detached binary but that the primary star is very close to filling its Roche lobe, while the secondary star fills 90 per cent of its Roche lobe volume. We find temperatures of the primary and the secondary star to be T 1 =41 000 K and T 2 =22 000 K. We find i =72° and masses of 0.8 M⊙ and 3.3 M⊙ for the primary and secondary stars respectively. De-archived Hubble Space Telescope ( HST ) spectroscopy of V Sge shows evidence of mass loss via a wind or winds. In addition we report radio observations of V Sge during an optical high state at 2 cm, 3.6 cm and 6 cm wavelengths. The 3.6 cm emission is increased by a factor of more than six compared with an earlier detection in a previous optical high state. 相似文献