Two-frequency timing of the pulsar B1937+21 in Kalyazin and Kashima in 1997–2002     

Yu. P. Ilyasov  M. Imae  Y. Hanado  V. V. Oreshko  V. A. Potapov  A. E. Rodin  M. Sekido 《Astronomy Letters》2005,31(1):30-36

We present the results from our timing of the millisecond pulsar B1937+21, performed jointly since 1997 on two radio telescopes: the RT-64 in Kalyazin (Russia) at a frequency of 0.6GHz and RT-34 in Kashima (Japan) at a frequency of 2.15 GHz. The rms value of the pulse time of arrival (TOA) residuals for the pulsar at the barycenter of the Solar system is 1.8 μs (the relative variation is ≈10^?14 over the observing period). The TOA residuals are shown to be dominated by white phase noise, which allows this pulsar to be used as an independent time scale keeper. The upper limit for the gravitational background energy density Ω_gh² at frequencies ≈6.5 × 10^?9 Hz is estimated to be no higher than 10^?6. Based on the long-term timing of the pulsar, we have improved its parameters and accurately determined the dispersion measure and its time variation over the period 1984–2002, which was, on average, ?0.00114(3) pc cm^?3 yr^?1.  相似文献   

Parameters of the spiral structure of the galaxy from data on open star clusters     

M. E. Popova  A. V. Loktin 《Astronomy Letters》2005,31(3):171-178

We use data on open star clusters (OSCs) from the Homogeneous Catalog of OSC Parameters to determine some of the parameters of the spiral structure of our Galaxy: the pitch angle of the spiral arms \(i = 21\mathop .\limits^ \circ 5\), the pattern speed Ω_p = 20.4 ± 2.5 km s^?1 kpc^?1, and the initial phase of the spiral θ₀ = 206°. The spiral pattern of the Galaxy proves to have been virtually unchanged over the last billion years, and signatures of the concentration of objects toward the spiral arms can be traced back to this age. However, the number of spiral arms in the structure cannot be determined from OSCs.  相似文献   

Hard spectra of X-ray pulsars from INTEGRAL data     

E. V. Filippova  S. S. Tsygankov  A. A. Lutovinov  R. A. Sunyaev 《Astronomy Letters》2005,31(11):729-747

We present spectra for 34 accretion-powers X-ray pulsars and one millisecond pulsar that were within the field of view of the INTEGRAL observatory over two years (December 2002–January 2005) of its in-orbit operation and that were detected by its instruments at a statistically significant level (> 8σ in the energy range 18–60 keV). There are seven recently discovered objects of this class among the pulsars studied: 2RXP J130159.6-635806, IGR/AX J16320-4751, IGR J16358-4726, AX J163904-4642, IGR J16465-4507, SAX/IGR J18027-2017, and AX J1841.0-0535. We have also obtained hard X-ray (>20 keV) spectra for the accretion-powered pulsars RX J0146.9+6121, AX J1820.5-1434, and AX J1841.0-0535 for the first time. We analyze the evolution of spectral parameters as a function of the intensity of the sources and compare these with the results of previous studies.  相似文献   

XPer的新发射相：光谱与红外观测   总被引：1，自引：0，他引：1  

杭恒荣  夏剑萍 《天文学报》1995,36(4):438-441

ＸＰｅｒ的新发射相：光谱与红外观测杭恒荣，夏剑萍中国科学院紫金山天文台，南京２１０００８中国科学院光学天文联合实验室关键词Ｂｅ星／Ｘ射线双星，发射线，ＪＨＫ测光１引言ＸＰｅｒ是一颗Ｂｅ／Ｘ射线双星（４Ｕ０３５２＋３０）的光学对应体［１－３］，中子星的...  相似文献   

Assessment of Workers’ Contamination Caused by Air Pollution Exposure in Industry Using Biomonitors     

M. Â. B. C. Menezes  C. V. S. Sabino  M. B. Franco  E. C. P. Maia  C. C. B. Albinati 《Journal of Atmospheric Chemistry》2004,49(1-3):403-414

The workers health service is guided to look for risks. There is not an evaluation of the onset of the disease linked to a long-term exposure to low levels of toxic agents. Besides, there are few records of the level of metal concentration in the environmental air in industry, as well as few records of the level of contamination of factory workers. To assess the level of pollution in workplace, galvanising industry was chosen as the object of this study. The worker exposure and contamination levels were assessed by means of airborne particulate matter collected in air filters and biomonitors. The analysis of the air filter, hair and toenail samples were carried out by Instrumental Neutron Activation Analysis, and urine samples by Graphite Furnace Atomic Absorption Spectrophotometry. The statistical multivariate analysis and ANOVA methods were applied to elemental concentration. Copper and iron elements were highlighted as the main contributors on the differentiation of the classes. The results point out the effectiveness of biomonitors in occupational studies.  相似文献   

基于星型结构的虚拟参考站网络实时动态测量关键算法研究     

沈雪峰  高成发  潘树国 《测绘学报》2012,41(1):33-0

构建一种星型结构的VRS网络RTK基线解算方式,提出适用于星型结构VRS网络RTK模糊度解算方法。针对这种星型结构分别对VRS网络RTK中电离层、对流层改正数的算法进行深入研究。最后通过两个试验对星型VRS网络与传统VRS三角形网络在网络模糊度解算与VRS网络改正数计算两方面进行了验证分析。试验结果表明所提出的星型结构...  相似文献   

Tayler instability with Hall effect in young neutron stars     

G. Rüdiger  D.A. Shalybkov  M. Schultz  M. Mond 《Astronomische Nachrichten》2009,330(1):12-19

Collapse calculations indicate that the hot young neutron stars rotate differentially so that strong toroidal magnetic field components should exist in the outer shell where also the Hall effect appears to be important when the Hall parameter = ω_Bτ exceeds unity. The amplitudes of the induced toroidal magnetic fields are limited by the current‐induced Tayler instability. An important characteristics of the Hall effect is its distinct dependence on the sign of the magnetic field. We find for fast rotation that positive (negative) Hall parameters essentially reduce (increase) the stability domain. It is thus concluded that the toroidal field belts in young neutron stars induced by their differential rotation should have different amplitudes in both hemispheres which later are frozen in. Due to the effect of magnetic suppression of the heat conductivity also the brightness of the two hemispheres should be different. As a possible example for our scenario the isolated neutron star RBS 1223 is considered which has been found to exhibit different X‐ray brightness at both hemispheres (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

PSR J1753−2240: a mildly recycled pulsar in an eccentric binary system     

M. J. Keith  M. Kramer  A. G. Lyne  R. P. Eatough  I. H. Stairs  A. Possenti  F. Camilo  R. N. Manchester 《Monthly notices of the Royal Astronomical Society》2009,393(2):623-627

We report the discovery of PSR J1753−2240 in the Parkes Multibeam Pulsar Survey data base. This 95-ms pulsar is in an eccentric binary system with a 13.6-d orbital period. Period derivative measurements imply a characteristic age in excess of 1 Gyr, suggesting that the pulsar has undergone an episode of accretion-induced spin-up. The eccentricity and spin period are indicative of the companion being a second neutron star, so that the system is similar to that of PSR J1811−1736, although other companion types cannot be ruled out at this time. The companion mass is constrained by geometry to lie above 0.48 solar masses, although long-term timing observations will give additional constraints. If the companion is a white dwarf or a main-sequence star, optical observations may yield a direct detection of the companion. If the system is indeed one of the few known double neutron star systems, it would lie significantly far from the recently proposed spin-period/eccentricity relationship.  相似文献   

Age and metallicity of compact stellar systems in Virgo and Fornax     

P. Firth  E. A. Evstigneeva  M. J. Drinkwater 《Monthly notices of the Royal Astronomical Society》2009,394(4):1801-1811

From high signal-to-noise ratio GMOS-N and AAOmega spectra, we have measured line-strength indices in the Lick/IDS system for several luminous and spatially dispersed compact stellar systems (CSSs) located in the Virgo and Fornax galaxy clusters. We estimate their [α/Fe] ratios, ages and metallicities using a simple (single-burst) stellar population model. We confirm that the Virgo core region luminous CSSs (     ) contain ancient stellar populations with subsolar total metallicities, suggesting that they comprise the bright tail of M87's GC distribution. The two Virgo intracluster globular clusters have ages and metallicities consistent with the cluster core CSSs. Two Fornax luminous CSSs also have ancient stellar populations but are at the upper end of the Virgo CSS metallicity range, while the third (UCD3) appears to be relatively young, metal-rich and with a core + halo radial profile. Our results suggest that Fornax may contain an extra population of luminous CSSs formed more recently than the ancient GC-like systems found in both clusters.  相似文献   

An interference removal technique for radio pulsar searches     

R. P. Eatough  E. F. Keane  A. G. Lyne 《Monthly notices of the Royal Astronomical Society》2009,395(1):410-415

Searches for radio pulsars are becoming increasingly difficult because of a rise in impulsive man-made terrestrial radio-frequency interference. Here, we present a new technique, zero dispersion measure filtering, which can significantly reduce the effects of such signals in pulsar search data. The technique has already been applied to a small portion of the data from the Parkes multi-beam pulsar survey, resulting in the discovery of four new pulsars, so illustrating its efficacy.  相似文献