共查询到20条相似文献，搜索用时 31 毫秒
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R. Caimmi 《New Astronomy》2009,14(3):254-263
The tensor virial theorem for subsystems is formulated for three-component systems and further effort is devoted to a special case where the inner subsystems and the central region of the outer one are homogeneous, the last surrounded by an isothermal homeoid. The virial equations are explicitly written under the additional restrictions: (i) similar and similarly placed inner subsystems, and (ii) spherical outer subsystem. An application is made to hole + vortex + bulge systems, in the limit of flattened inner subsystems, which implies three virial equations in three unknowns. Using the Faber-Jackson relation, , the standard - form is deduced from qualitative considerations. The projected bulge velocity dispersion to projected vortex velocity ratio, , as a function of the fractional radius, , and the fractional masses, and , is studied in the range of interest, [Escala, A., 2006. ApJ, 648, L13] and [Marconi, A., Hunt, L.H., 2003. ApJ 589, L21], consistent with observations. The related curves appear to be similar to Maxwell velocity distributions, which implies a fixed value of below the maximum corresponds to two different configurations: a compact bulge on the left of the maximum, and an extended bulge on the right. All curves lie very close one to the other on the left of the maximum, and parallel one to the other on the right. On the other hand, fixed or , and , are found to imply more massive bulges passing from bottom to top along a vertical line on the plane, and vice versa. The model is applied to NGC 4374 and NGC 4486, taking the fractional mass,, and the fractional radius, , as unknowns, and the bulge mass is inferred from the knowledge of the hole mass, and compared with results from different methods. In presence of a massive vortex , the hole mass has to be reduced by a factor 2–3 with respect to the case of a massless vortex, to get the fit. Finally, the assumptions of homogeneous inner bulge and isotropic stress tensor are discussed. 相似文献
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《Planetary and Space Science》2006,54(13-14):1425-1444
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This paper presents the results of the first high-resolution spectroscopic observations of the Southern W UMa type system IS CMa. Spectroscopic observations of the system were made at Mt. John University Observatory using a HERCULES fibre-fed échelle spectrograph in September 2007. The first radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The resulting orbital elements of IS CMa are: AU, AU, , and . The components were found to be in synchronous rotation taking into account the disentangled line profiles of both components of the system. The Hipparcos light curve was solved by means of the Wilson–Devinney method supplemented with a Monte Carlo type algorithm. The radial velocity curve solutions including the proximity effects give the mass ratio of the system as 0.297 ± 0.001. The combination of the Hipparcos light and radial velocity curve solutions give the following absolute parameters of the components: and . The distance to IS CMa was calculated as pc using the distance modulus with corrections for interstellar extinction. The position of the components of IS CMa in the HR diagram are also discussed: the system seems to have an age of 1.6 Gyr. 相似文献
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Four new CCD times of light minimum of T Aurigae are presented. The orbital period variation is analyzed by means of the standard O–C technique. The new times of light minimum indicate that a ～24 yr sine-like period variation superimposed on a secular orbital period decrease is obviously seen in the O–C diagram. However, the orbital period should increase because of mass transfer between components. In order to solve this apparent paradox, three possibilities including magnetic braking mechanism, which plays an important role in angular moment loss of binary, are proposed. The mass loss rate is derived by assuming that the Alfvén radius of secondary is the same as that of the sun (i.e. ). Using the observational relationship of (McDermott and Taam, 1989, Rappaport et al., 1983), the Alfvén radius of secondary is estimated as , which only requires a weak magnetic field in secondary. Since the brightness variations of T Aurigae caused by Applegate’s mechanism need large energy beyond the total radiant energy in the time interval of 24 yr, the third body light travel-time effect is the most likely explanation for the 24-yr variation. The third body may be a brown-dwarf star in case of the high orbital inclination. 相似文献
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《New Astronomy》2015
The absolute dimensions of the components of the eccentric eclipsing binary KL CMa have been determined. The solution of light and radial velocity curves of high ( Å) and intermediate ( Å) resolution spectra yielded masses M1 = 3.55 ± 0.27 M⊙, M2 = 2.95 ± 0.24 M⊙ and radii R1 = 2.37 ± 0.09 R⊙, R2 = 1.70 ± 0.1 R⊙ for primary and secondary components, respectively. The system consists of two late B-type components at a distance of 220 ± 20 pc for an estimated reddening of .The present study provides an illustration of spectroscopy’s crucial role in the analysis of binary systems in eccentric orbits. The eccentricity of the orbit () of KL CMa is found to be bigger than the value given in the literature (). The apsidal motion rate of the system has been updated to a new value of , which indicates an apsidal motion period of yrs, two times slower than given in the literature. Using the absolute dimensions of the components yielded a relatively weak relativistic contribution of . The observed internal-structure component () is found to be in agreement with its theoretical value ().Both components of the system are found very close to the zero-age main-sequence and theoretical isochrones indicate a young age ( Myr) for the system. Analysis of the spectral lines yields a faster rotation ( km s−1) for the components than their synchronization velocities ( km s−1, km s−1). 相似文献
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We present new differential, four-color photoelectric photometry for the eclipsing binary TV Cet. UBVR light curves and radial velocities published previously are solved simultaneously using the Wilson–Devinney computer program. Our solutions indicate that TV Cet includes a third light contribution with 2.3% in U, 1.9% in B, 1.3% in V and 1.6% in R. The masses of the component stars are and , while the radii are and for the primary and secondary components, respectively. Using new absolute properties and our previous results from period analysis, we calculated the observational and theoretical internal structure constants to be and , respectively. Taking into account the third light contribution from the Wilson–Devinney solution and properties of the third body orbit from period analysis, the mass of the third body is obtained as , corresponding to the inclination value . Evolutionary status of the component stars is also studied. We present the position of the stars in an H–R diagram for solar compositions. 相似文献
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A new intrinsic-colour calibration is presented for the uvby-β photometric system, making use of re-calibrated Hipparcos parallaxes and published reddening maps. This new calibration for , our Eq. (1), has been based upon stars with in the photometric catalogues of Schuster and Nissen (1988), Schuster et al., 2004, Schuster et al., 2006, provides a small dispersion, , and has a positive “standard” coefficient, which is not too different from the coefficients of Crawford (1975a, +1.11) and of Olsen (1988, +1.34). For 61 stars with spectra from CASPEC, UVES/VLT, and FIES/NOT databases, without detectable Na I lines, the average reddening value shows that any zero-point correction to our intrinsic-colour equation must be minuscule. 相似文献