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1.
Based on two high-dispersion spectra of the close binary BW Boo, we have detected lines of the secondary component whose contribution to the combined spectrum does not exceed 2%. We have determined the rotation velocities of the components and spectroscopic orbital elements. Numerous lines of neutral and ionized iron have been used to determine the effective temperature and surface gravity for the primary component. The photometric light curves for this binary have been solved for the first time. Its primary component is an A2Vm star with a mass of 2 ± 0.1M ⊙ and a radius of 1.9 ± 0.4R ⊙. Its rotation velocity is 2 km s−1, which is a factor of 18 lower than the pseudo-synchronous velocity for this component. The G6 secondary component, a T Tau star, has a rotation velocity of 17 km s−1, amass of 1.1M ⊙, and a radius of 1 R ⊙. The age of the binary has been estimated to be 107 yr.  相似文献   

2.
We have compared the frequency distribution of the dynamical observedquantity log (V z 2 r p), for a sample of 46 pairs of elliptical galaxies, to the distribution of this quantity obtained from numerical simulations of pairs of galaxies. From such an analysis, where we have considered the structure of the galaxies and its influence in the orbital evolution of the system, we have obtained the characteristic mass and the mass-luminosity ratio for the sample. Our results show that the hypothesis of point-mass in elliptical orbits is, for this sample, an approximation as good as the model that takes into account the structure of the galaxies. The statistical method used here gives an estimate of a more reliable mass, it minimizes the contamination of spurious pairs and it considers adequately the contribution of the physical pairs. We have obtained a characteristic mass to the 46 elliptical pairs of 1.68 × 1012 ± 7.01 ×1011 M⊙ with M/L = 17.6 ± 7.3 (H 0 = 60 km s-1Mpc-1). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
A unified picture of the photodissociation of theC 2 H radical has been developed using the results from the latest experimental and theoretical work. This picture shows that a variety of electronic states ofC 2 are formed during the photodissociation of theC 2 H radical even if photoexcitation accesses only one excited state. This is because the excited states have many avoided corssings and near intersections where two electronic states come very close to one another. At these avoided crossings and near intersections, the excited radical can hop from one electronic state to another and access new final electronic states of theC 2 radical. The complexity of the excited state surfaces also explains the bimodal rotational distributions that are observed in all of the electronic states studied. The excited states that dissociate through a direct path are limited by dynamics to produceC 2 fragments with a modest amount of rotational energy, whereas those that dissociate by a more complex path have a greater chance to access all of phase space and produce fragments with higher rotational excitation. Finally, the theoretical transition moments and potential energy curves have been used to provide a better estimate of the photochemical lifetimes in comets of the different excited states of theC 2 H radical. The photochemically active states are the 22+, 22II, 32II, and 32+, with photodissociation rate constants of 1.0×10–6, 4.0×10–6, 0.7×10–6, and 1.3×10–6s–1, respectively. These rate constants lead to a total photochemical lifetime of 1.4×105 s.  相似文献   

4.
We have detected new HD absorption systems at high redshifts, z abs = 2.626 and z abs = 1.777, identified in the spectra of the quasars J0812+3208 and Q1331+170, respectively. Each of these systems consists of two subsystems. The HD column densities have been determined: log N HDA = 15.70 ± 0.07 for z A = 2.626443(2) and log N HDB = 12.98 ± 0.22 for z B = 2.626276(2) in the spectrum of J0812+3208 and log N HDC = 14.83 ± 0.15 for z C = 1.77637(2) and log N HDD = 14.61 ± 0.20 for z D = 1.77670(3) in the spectrum of Q1331+170. The measured HD/H2 ratio for three of these subsystems has been found to be considerably higher than its values typical of clouds in our Galaxy.We discuss the problem of determining the primordial deuterium abundance, which is most sensitive to the baryon density of the Universe Ωb. Using a well-known model for the chemistry of a molecular cloud, we have estimated the isotopic ratio D/H=HD/2H2 = (2.97 ± 0.55) × 10−5 and the corresponding baryon density Ωb h 2 = 0.0205−0.0020+0.0025. This value is in good agreement with Ωb h 2 = 0.0226−0.00060.0006 obtained by analyzing the cosmic microwave background radiation anisotropy. However, in high-redshift clouds, under conditions of low metallicity and low dust content, hydrogen may be incompletely molecularized even in the case of self-shielding. In this situation, the HD/2H2 ratio may not correspond to the actual D/H isotopic ratio. We have estimated the cloud molecularization dynamics and the influence of cosmological evolutionary effects on it.  相似文献   

5.
We consider the Newtonian planar three-body problem with positive masses m 1, m 2, m 3. We prove that it does not have an additional first integral meromorphic in the complex neighborhood of the parabolic Lagrangian orbit besides three exceptional cases ∑m i m j /(∑m k )2 = 1/3, 23/33, 2/32 where the linearized equations are shown to be partially integrable. This result completes the non-integrability analysis of the three-body problem started in papers [Tsygvintsev, A.: Journal für die reine und angewandte Mathematik N 537, 127–149 (2001a); Celest. Mech. Dyn. Astron. 86(3), 237–247 (2003)] and based on the Morales–Ramis–Ziglin approach.  相似文献   

6.
In this paper we present a detailed study of BCT Ist solution Tewari (Astrophys. Space Sci. 149:233, 1988) representing time dependent balls of perfect fluid with matter-radiation in general relativity. Assuming the life time of quasar 107 years our model has initial mass≈108 M Θ with an initial linear dimension≈1015 cm. Our model is radiating the energy at a constant rate i.e. L ∞=1047 ergs/sec with the gravitational red shift, z=0.44637. In this model we have 2GM(u)/c 2 R S (u))=0.3191 i.e. the model is horizon free.  相似文献   

7.
In this paper we propose a method for computing the equilibrium structure of differentially rotating polytropic models of the stars. A general law of differential rotation of the type 2=b 0+b 1 s 2+b 2 s 4, which can account for a reasonably large variety of possible differential rotations in the stars has been used. The distortional effects have been incorporated in the structure equations up to second order of smallness in distortion parametersb 0,b 1, andb 2 using Kippenhahn and Thomas' averaging approach in conjunction with Kopal's results on Roche equipotentials in manner similar to the one earlier used by Mohan and Saxena for computing the equilibrium structure of polytropes having solid body rotation. Numerical results have been obtained for various types of differentially rotating polytropic models of stars of polytropic indices 1.5, 3, and 4. Certain differentially rotating models of the Sun which are possible with such a type of law of differential rotation, have also been computed.  相似文献   

8.
Using theR-matrix approach new calculations have been made for the electron impact excitation of the fine structure transitions within the 1s 22s 22p 2 ground configuration of Mgvii. The computations have been made at a large number of energies in order to account for the contribution of resonances. All partial waves withL 9 are included in the calculations which are considered to be sufficient for the convergence of collision strengths in the energy range below 65 Ry. From this collision strength data, excitation rate coefficients have been calculated at a series of electron temperatures which are employed in the computation of population of the five lowest levels of Mgvii. The line intensity ratios for the transitions3 P 1 1 D 2 and3 P 2 1 D 2 to3 P 1 1 S 0 are then calculated in the temperature range of 105 to 107 K at electron densities in the range 106 to 1010 cm–3. The calculated values are in good agreement with the earlier available results.  相似文献   

9.
Bobylev  V. V.  Bajkova  A. T. 《Astronomy Letters》2019,45(9):580-592

We have studied the kinematic properties of the candidates for hot subdwarfs (HSDs) selected by Geier et al. from theGaiaDR2 catalogue. We have used a total of 12 515 stars with relative trigonometric parallax errors less than 30%. The HSDs are shown to have different kinematics, depending on their positions on the celestial sphere. For example, the sample of low-latitude (|b| < 20°) HSDs rotates around the Galactic center with a linear velocity V0 = 221 ± 5 km s?1. This suggests that they belong to the Galactic thin disk. At the same time, they lag behind the local standard of rest by ΔV☉ ~ 16 km s?1 due to the asymmetric drift. The high-latitude (|b| ≥ 20°) HSDs rotate with a considerably lower velocity, V☉ = 168 ± 6 km s?1. Their lagging behind the local standard of rest is already ΔV☉ ～ 40 km s?1. Based on the entire sample of 12 515 HSDs, we have found a positive rotation around the x axis significantly differing from zero with an angular velocity ω1 = 1.36±0.24 km s?1 kpc?1. We have studied the samples of HSDs that are complete within r < 1.5 kpc. Based on them, we have traced the evolution of the parameters of the residual velocity ellipsoid as a function of both latitude |b| and coordinate |z|. The following vertical disk scale heights have been found: h = 180 ± 6 and 290 ± 10 pc from the low- and high-latitude HSDs, respectively. A new estimate of the local stellar density Σout = 53 ± 4 M☉ kpc?2 has been obtained for zout = 0.56 kpc from the high-latitude HSDs.

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10.
We have calculated Einstein A-coefficients for electric dipole transitions in the ground vibrational state of the moleculesH 2 D + andD 2 H +, between the rotational levels up to 2200 and 2000 cm–1, respectively. These A-coefficients are used for computing the mean radiative life-times of the levels. These data play an important role in analysing the spectra from astronomical objects.  相似文献   

11.
We have mapped 16 molecular clouds toward a new OB association in the Pup-CMa region to derive their physical properties. The observations were carried out in the 12CO (J = 1 – 0) line with the Southern millimetre-wave Telescope at Cerro Tololo, Chile. Distances have been determined kinematically using the rotation curve of Brand with R⊙ = 8.5 kpc and V⊙ = 220 km/s. Masses have been derived adopting a CO luminosity to H2 conversion factor X = 3.8 . 1020 molecules cm-2 (K km/s)-1. The observed mean radial velocity of the clouds is comparable with the mean radial velocity of stars composing an OB association in Pup-CMa; it is in favor of the close connection of clouds with these stars. __________ Published in Astrofizika, Vol. 48, No. 4, pp. 491–501 (October–December, 2005).  相似文献   

12.
Rates of production of O(1 D) atoms in the upper atmosphere by photodissociation of O2, dissociative recombination of O2 +, NO+ and electron impact excitation of O(3 P) have been calculated for low, medium and high levels of solar activity. Variations with solar activity, of neutral and ionic composition, electron and neutral temperatures of the upper atmosphere and solar extreme ultraviolet fluxes incident on it have been taken into consideration.Emission rates ofOi red line (6300Å) have been computed taking into account the deactivation both by molecular oxygen and nitrogen. It has been shown that the integrated intensity from low to high activity period varies by approximately an order of magnitude in agreement with the results of experimental observations.  相似文献   

13.
The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their positions in the 2MASS and USNO-A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about 17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45 million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω x,y,z = (−0.06, 0.17, −0.84) ± (0.15, 0.14, 0.14) mas yr−1. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R UCAC2 > 16 m and J > 14 m . 7, for which the color and magnitude equation effects are negligible.  相似文献   

14.
Svensson  L. Å.  Ekberg  J. O.  Edlén  B. 《Solar physics》1974,34(1):173-179
The levels of the configuration 3s 23 p 53d of Fe ix have been experimentally determined from their combinations with 3s3 p 63d 3 D in the region 300–400 Å. Wavelengths can now be accurately predicted for all transitions within 3s 23 p 53d, and eight of these can be identified with coronal lines from 2042 to 4585 Å. Also, identifications of solar lines from 171 to 245 Å with electric-dipole and magnetic-quadrupole transitions to the ground state, 3s 23p 6 1 S, are confirmed and extended. Solar identifications with corresponding transitions in Ni xi, both within 3s 23 p 53d and to the ground state, are proposed on the basis of a short extrapolation.  相似文献   

15.
WARREN  G. A.  KEENAN  F. P.  GREER  C. J.  PHILLIPS  K. J. H.  BRUNER  M. E.  BROWN  W. A.  McKENZIE  D. L. 《Solar physics》1997,171(1):93-102
We have calculated intensity ratios for emission lines of Fexviii in the 13–94 Å wavelength range at electron temperatures characteristic of the solar corona, T e = 2–10 x 106 K. Our model ion includes data for transitions among the 2s 22p 5 , 2s2p 6, 2s 22p 43l, and 2s2p 53l (l = s, p, and d) states. Test calculations which omit the 2s2p 53l levels show that cascades from these are important. We compare our results with observed ratios determined from four solar X-ray instruments, a rocket-borne spectrograph, and spectrometers on the P78–1, OV1–17 and Solar Maximum Mission (SMM) satellites. In addition, we have generated synthetic spectra which we compare directly with flare observations from SMM. Agreement between theory and observation is generally quite good, with differences that are mostly less than 30%, providing limited support for the accuracy of the atomic physics data used in our calculations. However, large discrepancies are found for ratios involving the 2s 22p 5 2P3/2- 2s2p 6 2S line at 93.84 Å, which currently remain unexplained. Our analysis indicates that the FeXVIII feature at 15.83 Å is the 2s 22p 5 2P3/2 - 2s 22p 4(3P)3s 4P3/2 transition, rather than 2s 22p 5 2P3/2 - 2s 22p 4(3P)3s 2P3/2, as suggested by some authors.  相似文献   

16.
In the present paper we have considered the problem of determining the equilibrium structure of differentially rotating stars in which the angular velocity of rotation varies both along the axis of rotation and in directions perpendicular to it. For this purpose, a generalized law of differential rotation of the type 2 =b 0+b 1 s 2+b 2 s 4+b 3 z 2+b 4 z 4+b 5 z 2 s 2 (here is a nondimensional measure of the angular velocity of a fluid element distants from the axis of rotation andz from the plane through the centre of the star perpendicular to the axis of rotation, andb's are suitably chosen parameters) has been used. Whereas Kippenhahn and Thomas averaging approach has been used to incorporate the rotational effects in the stellar structure equations, Kopal's results on Roche equipotentials have been used to obtain the explicit form of the stellar structure equations, which incorporate the rotational effects up to second order of smallness in the distortion parameters. The method has been used to compute the equilibrium structure of certain differentially rotating polytropes. Certain differentially rotating polytropes. Certain differentially rotating models of the Sun have also been computed by using this approach.  相似文献   

17.
The recent level population calculations for Ne v by Aggarwal are used to determine the theoretical emission line ratios R 1 = I(2s2p 3 1Do - 2s22p2 1De)/I(2s2p3 3D 2 0 - 2s22p2 3P 1 e ) and R 2 = I(2s2p 3 1Do-2s22p2 1De)/I(2s2p 3 3D 3 0 -2s22p2 3P 2 e ). A comparison of these with observational data for a solar flare and erupting prominence obtained with the NRL XUV spectrograph on board Skylab reveals that R 1 and R 2 are in their predicted high density limits. Although the ratios cannot be used as density diagnostics for values of n e typical of the solar transition region, it is shown that they are temperature sensitive and hence may be employed to determine the electron temperatures of Ne v line emitting regions.  相似文献   

18.
Einstein's field theory of elementary particles (Einstein 1919) yields black holes with a mass M ˜ G−1 Λ−1/2c2 and a charge Q ˜ G−1/2λ−1/2c2, their curvatu re radius is Λ−1/2. Here 4Λ is an integration constant of Einstein's ‘trace-less’ gravitation equations. The choice λ = G−1h−1c3 for this constant defines Planckions and implies “strong gravity”. The choice λ = λ = 3Hinf2c−2 (where Hinf means the Hubble parameter of a final de Sitter cosmos) involves “weak gravity” and describes an electro-vac spherical universe.  相似文献   

19.
We have investigated the influence of X-ray irradiation on the vertical structure of the outer accretion disk in low-mass X-ray binaries by performing a self-consistent calculation of the vertical structure and X-ray radiation transfer in the disk. Penetrating deep into the disk, the field of scattered X-ray photons with energy E ≳ 10 keV exerts a significant influence on the vertical structure of the accretion disk at a distance R ≳ 1010 cm from the neutron star. At a distance R ∼ 1011 cm, where the total surface density in the disk reaches Σ0 ∼ 20 g cm−2, X-ray heating affects all layers of an optically thick disk. The X-ray heating effect is enhanced significantly in the presence of an extended atmospheric layer with a temperature T atm ≈ (2–3) × 106 K above the accretion disk. We have derived simple analytic formulas for the disk heating by scattered X-ray photons using an approximate solution of the transfer equation by the Sobolev method. This approximation has a ≲10% accuracy in the range of X-ray photon energies E < 20 keV.  相似文献   

20.
We have discovered a giant radio halo in the massive merging cluster MACSJ0417.5-1154. This cluster, at a redshift of 0.443, is one of the most X-ray luminous galaxy cluster in the MAssive Cluster Survey (MACS) with an X-ray luminosity in the 0.1–2.4 keV band of 2.9×1045 erg s − 1. Recent observations from GMRT at 230 and 610 MHz have revealed a radio halo of ∼ 1.2 × 0.3 Mpc2 in extent. This halo is elongated along the North-West, similar to the morphology of the X-ray emission from Chandra. The 1400 MHz radio luminosity (L r) of the halo is ∼2 × 1025 W Hz − 1, in good agreement with the value expected from the L x − L r correlation for cluster halos.  相似文献   

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