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1.
Using high signal-to-noise ratio spectra of extrasolar planet-hosting stars, we obtained the atmospheric parameters, accurate metallicities and the differential abundance for 15 elements (C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Ni and Ba). In a search for possible signatures of metal-rich material accreting onto the parent stars, we found that , for a given element, there is no significant trend of increasing [X/H] with increasing condensation temperature Tc. In our sample of planet-harboring stars, the volatile and refractory elements behave similarly, and we can not confirm if there exists any significant dependence on the condensation temperature Tc.  相似文献   

2.
An estimate of the period of the rotation of the line of apsides of the double-star system Phe is obtained by representing the density function as a product of a normal Gaussian distribution and an associated Legendre polynomial .The asymptotic behaviour of this function coincides with the results obtained by Zeldovichet al. (1981).The period of motion of the line of apsides of Phe (about 63 years) obtained in this way comes close to the period determined by an empirical formula for of Batten (1973).  相似文献   

3.
The initial period of a pulsar is an important factor in our understanding of the formation of neutron stars and of the nature of the equation of state of neutron star matter.Up to now this quantity can only be obtained for a few pulsars for which accurate age and braking index are known.Based on the theory of the offcenter dipole emission,in which pulsars obtain theiry high velocities depending on the initial periods,we calculate the initial period using the proper motion data,Because the orbital velocity of the progenitor and asymmetric kick in the supernova explosion may also contribute to the observed velocity of the pusar,the derived values of initial periods are lower limits.For normal pulsars,the initial periods are in the range of 0.6～2.6ms.For the millisecond pulsars,the initial periods are comparable to their current periods,and the ratio between the initial period and the current period increases with the decrease of the current period.For PSR B1937 21 with the shortest period of 1.56ms,the ratio is 0.77.  相似文献   

4.
We propose a method to determine the thickness of non-edge-on disk galaxies from their observed structure of spiral arms, based on the solution of the truly three-dimensional Poisson‘s equation for a logarithmic disturbance of density and under the condition where the self-consistency of the density wave theory is no longer valid. From their measured number of arms, pitch angle and location of the innermost point of the spiral arms, we derive and present the thicknesses of 34 spiral galaxies.  相似文献   

5.
We summarize studies of helical properties of solar magnetic fields such as current helicity and twist of magnetic fields in solar active regions (ARs), that are observational tracers of the alpha-effect in the solar convective zone (SCZ). Information on their spatial distribution is obtained by analysis of systematic mag-netographic observations of active regions taken at Huairou Solar Observing Station of National Astronomical Observatories of Chinese Academy of Sciences. The main property is that the tracers of the alpha-effect are antisymmetric about the solar equator. Identifying longitudinal migration of active regions with their individual rotation rates and taking into account the internal differential rotation law within the SCZ known from helioseismology, we deduce the distribution of the effect over depth. We have found evidence that the alpha-effect changes its value and sign near the bottom of the SCZ, and this is in accord with the theoretical studies and numerical simulations. We discuss  相似文献   

6.
We present X-ray spectral analyses of the low-mass X-ray binary Cir X-1 dur- ing X-ray dips,using the Rossi X-ray Timing Explorer(RXTE)data.Each dip was divided into several segments,and the spectrum of each segment was fitted with a three-component blackbody model,in which the first two components are affected by partial covering and the third one is unaffected.A Gaussian emission line is also included in the spectral model to represent the Fe Kαline at～6.4 keV.The fitted temperatures of the two partially covered components are about 2 keV and 1 keV,while the uncovered component has a temperature of～0.5-0.6 keV.The equivalent blackbody emission radius of the hottest component is the smallest and that of the coolest component is the largest.During the dips the fluxes of the two hot components are linearly correlated,while that of the third component does not show any significant variation.The Fe line flux remains constant,within the errors,during the short dips.However,during the long dips the line flux varies significantly and is positively correlated with the fluxes of the two hot components.These results suggest:(1)that the tem- perature of the X-ray emitting region decreases with radius,(2)that the Fe Kαline emitting region is close to the hot continuum emitting region,and(3)that the size of the Fe line emit- ting region is larger than that of the obscuring matter causing the short dips but smaller than the region of that causing the long dips.  相似文献   

7.
Infrared Characteristics of Associated Sources of Water Masers   总被引：2，自引：0，他引：2  
We present an analysis of the infrared properties of 1417 water masers collected from the literature published by December 2004. The associated infrared sources of the water masers were identified with IRAS and MSX (Midcourse Space Experiment) catalogues. There are 1252 water masers associated with IRAS sources within 1', which include 700 interstellar and 552 stellar sources. For 382 sources, the IRAS counterpart identification and the maser classification are new. We found the colors of the interstellar maser sources are much redder than those of the stellar ones at IRAS wavelength bands; 99% of the interstellar maser sources are above black body line, while 95% of the stellar masers are below. The distribution difference of the two kinds of masers shown in the color-color diagram is due to their different optical depths and temperature distributions of dust regions. There are 743 water masers with MSX counterparts, of which 552 are interstellar masers and 191 are stellar masers. MSX colors of the associated sources of water masers are here analyzed for the first time. The color differences among the MSX bands are small and the interstellar masers are redder than the stellar masers. There is a correlation between the intensity of the stellar water maser emission and that of the 12μm and 25μm emissions, while there is no correlation between the water maser emission and the 8 μm emission. The infrared intensity increases with increasing wavelength for the interstellar masers, while it is the opposite for stellar masers. These results may provide clues for the pumping of water maser and for the properties of the two kinds of maser emission regions.  相似文献   

8.
A performance study of several CCD cameras of the Chinese Joint Laboratory of Optical Astronomy (CJLOA) is presented. The main results are: 1) We propose a modified classical method to analyse the linearity of CCD cameras. This method is more sensitive and accurate as well as more intuitive, especially in measuring around the 0.1%-0.2% range of nonlinearity. 2) To illustrate the advantage of the method, the linearity performance of the CCD cameras at CJLOA has been measured and analysed. 3) For the CCD systems tested, there is no unique formula to represent the correlation over the entire CCD frame between the deviation from linearity and the pixel value, i.e., different pixel has different correction even though their pixel values are the same. 4) For the BFOSC (BAO Faint Object Spectrograph Camera) Loral CCD camera and the Tek CCD camera at the 1.56-m reflector, blooming (bleeding) happens long before saturation, and we suspect whether it could have resulted from the charge transfer efficiency (CTE) n  相似文献   

9.
We present a study of the β Cephei instability strip based on a sample of 49 stars of this type.After deriving their effective temperatures and luminosities from their observed(B-V),(U-B) colors and parallaxes we find their positions in the HR diagram to be mostly confined to the main sequence,and their masses to lie between 7 M and 30 M.Their distribution on the HR diagram matches well with our previous theoretical instability strip which has an upper bound in the luminosity and rather tight boundaries in the effective temperature.  相似文献   

10.
We investigate the Luminosity Function(LF)of the cluster of galaxies Abell 566.The photometric data of 15 intermediate-bands are obtained from the Beijing-Arizona- Taiwan-Connecticut(BATC)photometric sky survey.For each of the 15 wavebands,the LF of cluster galaxies is well modelled by the Schechter function,with characteristic luminosi- ties from-18.0 to-21.9 magnitude,from the a- to the p-band.Morphological dependence of the LF is investigated by separating the cluster members into‘red’and‘blue’subsamples. It is clear that late type galaxies have a steeper shape of LF than the early type galaxies.We also divided the sample galaxies by their local environment.It was found that galaxies in the sparser region have steeper shape of LF than galaxies in the denser region.Combining the results of morphological and environmental dependence of LFs,we show that Abell 566 is a well relaxed cluster with positive evidence of galaxy interaction and merger,and excess number of bright early type galaxies located in its denser region.  相似文献   

11.
RESEARCH PAPERS 1 INTRODUCTIONA spiraI gaIaxy inherently consists of a halo, a bulge and a thin disc with spiral structurewhich emerges from the central region or the end of a bright bar. Optical images of spirals, whichare projections on the celestial sphere, are dominated by the light from the stars, as modifiedby the extinction and reddening of dust. AIthough Lord Rosse first discovered that M51 hastwo spiral arms in 1845, the form of the spiral structure had not been investigat…  相似文献   

12.
A technique for obtaining a three-dimensional distribution of received pho- tons in Hα flares in the solar atmosphere is presented.It is well known that during flares hydrogen atoms in the chromosphere and photosphere are excited(even ion- ized)by the downward heating of non-thermal particles and then emit Hα photons. We trace back these Ha photons to their original layers by use of the contribution func- tion in the theory of spectral line formation,and so acquire their three-dimensional (3D)distribution.This technique is applied to the two-ribbon flare of 2002 January 20.The atmospheric models are obtained by fitting the“quasi-profiles”with the help of the generally used model atmospheres.Since the variety of the 3D images reflects the response of the atmospheric layers to the impact of energy transport,an analysis of the development of the flare is given through a comparison of the 3D images with the 2D temperature distribution.  相似文献   

13.
The continuum energy distributions of the luminous blue variables R127 and R110 in the outburst phase are fitted with a circumstellar envelope model.Both stars show two peaks in their continuum, one near 1250A and the other in the optical band. We suggest that their UV and optical fluxes may have different origins: the UV flux comes from the central star while the optical flux comes from an expanding circumstellar envelope. We construct a model for LBVs consisting of two LTE atmosphere models with different temperatures, and find it to be in agreement with the observed spectral energy distributions of R127 and R110.According to our numerical experiments, R127‘s continuum is composed of fluxes from a circumstellar envelope of Teff = 8000K, R = 485R⊙, and log g = 1,and from a central star of Tef = 17000K, R = 135R⊙, and log g = 2.5 with a permeating factor f = 0.5; while R110‘s continuum can be fitted by a circumstellar envelope of Teff =7000K, R = 350R⊙, and logg = 0.5, and a central star of Teff =25 000 K, R = 27R⊙, and log g 3.0 with a permeating factor f = 0.65.Both models show that the non-spherically symmetric, optically thick regions are formed surrounding the central star in the outburst phase. The light of the central star is shielded by the circumstellar envelope so that the visual brightness increases with the decrease/increase of the temperature/radius of the optically thick regions.  相似文献   

14.
We present the analysis of the morphology of the light curves of WZ Sge based on simultaneous multicolour highspeed photometry durings the superoutburst in 2001. Observations started around the middle of the main superoutburst and continued for several nights in each of the subsequent phases of its evolution. For the first time for WZ Sge in a superoutburst a significant difference between the morphology of the U and BVRI light curves was detected. This is interpreted as a consequence of a substantial distinction of the structure and radiation between the inner and outer parts of the accretion disc. Using the space observatory WSO-UV for UV monitoring of the WZ Sge-stars throughout the entire superoutburst cycle one would have an opportunity to explore innermost regions of the accretion discs in these systems, which is important for understanding the physics of accretion processes and the nature of their activity.  相似文献   

15.
Photometry of Persei was obtained during ingress and egress of its 1989 eclipse and analyzed using a simple geometrical model. The estimated depths of eclipse are 0.62, 0.43, and 0.23 mag inU, B, andV, respectively, which imply that all but 17% of the A-type secondary is covered by the G-giant primary at minimum light. When combined with observations from the 1984 eclipse, the data yield a photometric period of 1515.869±0.059 days.  相似文献   

16.
It is of great importance to study pulsar beam shape if we are concerned with emission theories and pulsar birth rate.Both observations and the ICS model show that different emission components are emitted from different heights.The relative longitude phase shifts due to different heights of the emission components and the toridal velocity of the electrons are considered in this paper.Several pos-sible observational effects arising from the phase shift are presented.The emission beams may not have circular cross section although the emission region may be symmetric with respect to the magnetic axis.  相似文献   

17.
We determined the relative stellar ages and metallicities of about 80 elliptical galaxies in both low and high density environments using the latest binary stellar population (BSP) synthesis model and tested the predictions of a recent hierarchical formation model that adopted the new ACDM cosmology. The stellar ages and metallicities were estimated from two high-quality published spectra line indices, the Hβand [MgFe] indices. The results show that the stellar populations of elliptical galaxies are older than 3.9 Gyr and more metal rich than 0.02. Most of our results are in agreement with the model predictions: (1) elliptical galaxies in denser environment are redder and have older populations than field galaxies; (2) elliptical galaxies with more massive stellar components are redder and have older and more metal rich populations than less massive ones; (3) the most massive galaxies have the oldest and most metal rich stars. However, some of our results differ from the model predictions on the metallicity distributions of low- and high-density elliptical galaxies and the dependence on the distance to the cluster center.  相似文献   

18.
We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period of 0.35d is examined. The mass fraction of the primary mixed with the matter of the secondary, qmix, determined by the chosen core-envelope transition point, ranges from 0.04 to 1.00 in our analysis. If as qmix< 0.8, none of the  相似文献   

19.
A model is proposed for the formation of clouds of the La forest. Earlier calculations have shown that the UV emission from hot stars must play an important role in the reionization of the pregalactic medium (PGM). The formation of galaxies therefore occurred simultaneously with PGM ionization, and the reionization process was nonlinear. With allowance for this fact, the Gunn-Peterson effect, and the fact that galaxies exist at z ≈ 5, which follows from observations, we can conclude that galaxies began to form earlier, perhaps at z ≥ 10. The observed presence of heavy elements in La -forest clouds is evidence that these clouds were formed later than galaxies — from interstellar clouds ejected by galactic wind. The next generation of galaxies might have resulted from an increase in the masses of La -forest clouds due to their merging. Translated from Astrofizika, Vol. 43, No. 1, pp. 5-12, January–March, 2000.  相似文献   

20.
Four plates,photographed on March 17,1986 by Oversea Observation Team of CAS at Mount John Observatory,show the rays of Comey Halley.We scanned and measured three of them by the PDS micro-densitometer of PMO.The folding speed (towards the tail's spine) of the rays and the motion of some matter in the tail were obtained.  相似文献   

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