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21.
M. G. Revnivtsev 《Astronomy Letters》2003,29(6):383-386
Analysis of the RXTE slew data in October 1996 revealed a weak X-ray burst from the millisecond pulsar SAX J 1808.4-3658. The 3–20-keV energy spectrum of the source can be described by a power law with an index of 2.0 and a(3-to 20 keV) luminosity of ~1.4×1035 erg s?1 (the distance to the source was taken to be 2.5 kpc). Because of the short exposure time, we failed to detect weak pulsations at a frequency of 401 Hz in the source. The (2σ) upper limit of the pulse fraction is ~13%. 相似文献
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Qing-Yao Liu Yu-Lan Yang National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 《中国天文和天体物理学报》2006,6(3):331-337
The variation in the orbital period of the W UMa type contact binary V502 Oph is analyzed. The orbital period exhibits a wavelike variation with a periodicity of 23.0 years and an amplitude of △P = 1.24×10~(-6) days superimposed on secular decrease of dP/dt = 1.68×10-7 day per year. The long-term decrease may be accompanied by the contraction of the secondary at a rate of 83 m per year and a mass transfer rate from the primary to the secondary of 4.28×10~8 M per year. The short-term oscillation may be explained by the presence of a third component. Orbital elements of the third body and its possible mass are presented. 相似文献
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We present H2CO observations of young protostar candidates in the Serpens Cloud Core. We find evidence for dense molecular gas in the cores of these objects that is warmer than the surrounding dust. The strong emission and gas properties support the premise that many of these sources may be very young protostars. 相似文献
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在综合的科学考察船上以异步通讯口实现的IBM-PC局部网具有较好的性能价格比。本文介绍了该网的联网环境、网络系统的组成及其拓扑结构、网络的服务功能以及网络软、硬件的安装和配置。 相似文献
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Abstract. The reproductive cycle of the comatulid crinoid Nemaster rubiginosa from Discovery Bay, Jamaica is described histologically. The cycle is annual and may be divided into (1) a "resting" phase (summer) in which most adults possess immature, unsexable gonads, (2) a recovery phase (early fall) marked by the re-initiation of gametogenesis and rapid gonadal growth, (3) a breeding phase (late fall and winter) during which the gonads are mature and repeated spawning likely takes place, and (4) a post-spawning phase (spring) during which relict gametes are removed from the shrinking gonads. Although unsexable individuals predominate during the "resting" phase, a small proportion of the adult population is unsexable at all times of the year. The reproductive condition of animals in the same month in two successive years was very similar, suggesting that the timing of reproduction is quite predictable from year to year. The re-initiation of gametogenesis in the early fall is correlated with both rising sea temperature and shortening daylength, and the October to March breeding season corresponds to the period of short daylengths at the study site. The well-defined and synchronized annual reproductive cycle of Nemaster rubiginosa contrasts with the more prolonged and variable reproductive cycles reported for other tropical crinoids and points to a diversity of breeding patterns among tropical crinoids. 相似文献
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We have started a program of high-resolution (0.4/pixel) 10m imaging of bipolar outflow sources using the 10m camera CAMIRAS. We present recent results obtained at the Canada France Hawaii Telescope which reveal extended emission or IR companions in several luminous objects. The extended emission we detected probably arises from transiently heated very small grains, while the newly discovered companions could contribute significantly to the outflow activity and extended far-IR emission usually attributed to the main optical source. 相似文献