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1.
Based on high-latitude molecular clouds with highly accurate distance estimates taken from the literature, we have redetermined the parameters of their spatial orientation. This systemcan be approximated by a 350 × 235 × 140 pc ellipsoid inclined by the angle i = 17° ± 2° to the Galactic plane with the longitude of the ascending node l Ω = 337° ± 1°. Based on the radial velocities of the clouds, we have found their group velocity relative to the Sun to be (u 0, v 0, w 0) = (10.6, 18.2, 6.8) ± (0.9, 1.7, 1.5) km s?1. The trajectory of the center of the molecular cloud system in the past in a time interval of ~60 Myr has been constructed. Using data on masers associated with low-mass protostars, we have calculated the space velocities of the molecular complexes in Orion, Taurus, Perseus, and Ophiuchus. Their motion in the past is shown to be not random.  相似文献   

2.
The mean diameter D = 147 ± 3 km of (106) Dione is derived from visual observations in Denmark, Germany and the Netherlands of the occultation of AGK3 + 25°0989 on 1983 January 19. Photoelectric magnitudes are: B(1, 2°.4) = 8m.51 ± 0m.06 and B – V = 0m.65 ± 0m.07. The visual albedo is pv = .064. Constraints on the axis of rotation are derived from the observed elliptical contour.  相似文献   

3.
A fine structure related to the kinematic peculiarities of three components of the Scorpius-Centaurus association (LCC, UCL, and US) has been revealed in the UV-velocity distribution of Gould Belt stars. We have been able to identify the most likely members of these groups by applying the method of analyzing the two-dimensional probability density function of stellar UV velocities that we developed. A kinematic analysis of the identified structural components has shown that, in general, the center-of-mass motion of the LCC, UCL, and US groups follows the motion characteristic of the Gould Belt, notably its expansion. The entire Scorpius-Centaurus complex is shown to possess a proper expansion with an angular velocity parameter of 46 ± 8 km s?1 kpc?1 for the kinematic center with l 0 = ?40° and R 0 = 110 pc found. Based on this velocity, we have estimated the characteristic expansion time of the complex to be 21 ± 4 Myr. The proper rotation velocity of the Scorpius-Centaurus complex is lower in magnitude, is determined less reliably, and depends markedly on the data quality.  相似文献   

4.
We measured the radial velocity of the star θ1 Ori D from IUE spectra and used published observations. Based on these data, we determined the period of its radial-velocity variations, P=20.2675±0.0010 days, constructed the phase radial-velocity curve, and solved it by least squares. The spectroscopic orbital elements were found to be the following: the epoch of periastron passage Ep=JD 2430826.6±0.1, the system's center-of-mass velocity /Gg=32.4±1.0 km s?1, K=14.3±1.5 km s?1, Ω=3.3±0.1 rad, e=0.68±0.09, a1 sin i = 3 × 1010 km, and f1 = 0.0025M⊙. Twice the period, P=40.528±0.002 days, is also consistent with the observations.  相似文献   

5.
A laboratory study was performed using the Visible Oxford Space Environment Goniometer in which the broadband (350–1250 nm) bidirectional reflectance distribution function (BRDF) of the Winchcombe meteorite was measured, across a range of viewing angles—reflectance: 0°–70°, in steps of 5°; incidence: 15°, 30°, 45°, and 60°; and azimuthal: 0°, 90°, and 180°. The BRDF dataset was fitted using the Hapke BRDF model to (1) provide a method of comparison to other meteorites and asteroids, and (2) to produce Hapke parameter values that can be used to extrapolate the BRDF to all angles. The study deduced the following Hapke parameters for Winchcombe: w = 0.152 ± 0.030, b = 0.633 ± 0.064, and hS = 0.016 ± 0.008, demonstrating that it has a similar w value to Tagish Lake (0.157 ± 0.020) and a similar b value to Orgueil (0.671 ± 0.090). Importantly, the surface profile of the sample was characterized using an Alicona 3D® instrument, allowing two of the free parameters within the Hapke model φ and θ ¯ , which represent porosity and surface roughness, respectively, to be constrained as φ = 0.649 ± 0.023 and θ ¯ = 16.113° (at 500 μm size scale). This work serves as part of the characterization process for Winchcombe and provides a reference photometry dataset for current and future asteroid missions.  相似文献   

6.
B. Buratti  J. Veverka 《Icarus》1984,58(2):254-264
Voyager imaging observations provide new photometric data on Saturn's satellites at large phase angles (up to 133° in the case of Mimas) not observable from Earth. Significant new results include the determination of phase integrals ranging from 0.7 in the case of Rhea to 0.9 for Enceladus. For Enceladus we find an average geometric albedo pv = 1.04 ± 0.15 and Bond albedo of 0.9 ± 0.1. The data indicate an orbital lightcurve with an amplitude of 0.2 mag, the trailing side being the brighter. For Mimas, the lightcurve amplitude is probably less than 0.1 mag. The value of the geometric albedo of Mimas reported here, pv = 0.77 ± 0.15 (corresponding to a mean opposition magnitude V0 = +12.5) is definitely higher than the currently accepted value of about 0.5. For Dione, the Voyager data show a well-defined orbital lightcurve of amplitude about 0.6 mag, with the leading hemisphere brighter than the trailing one.  相似文献   

7.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30%: (U, V,W)⊙ = (8.16, 11.19, 8.55)± (0.48, 0.56, 0.48) km s?1, Ω0 = 28.92 ± 0.39 km s?1 kpc?1, Ω'0 = ?4.087 ± 0.083 km s?1 kpc?2, and Ω″ 0 = 0.703 ± 0.067 km s?1 kpc?3, where the circular velocity of the local standard of rest is V0 = 231 ± 5 km s?1 (for the adopted R0 = 8.0 ± 0.15 kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, VR, residual tangential, ΔVcirc, and vertical, W, velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are fR = 7.1± 0.3 km s?1, fθ = 6.5 ± 0.4 km s?1, and fW = 4.8± 0.8 km s?1, respectively; the perturbation wavelengths are λR = 3.3 ± 0.1 kpc, λθ = 2.3 ± 0.2 kpc, and λW = 2.6 ± 0.5 kpc; and the Sun’s radial phase in the spiral density wave is (χ⊙)R = ?135? ± 5?, (χ⊙)θ = ?123? ± 8?, and (χ⊙)W = ?132? ± 21? for the adopted four-armed spiral pattern.  相似文献   

8.
Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have been used to determine the Galactic rotation parameters. The circular rotation velocity of the solar neighborhood around the Galactic center has been found from data on more than 2000 clusters of various ages to be V 0 = 236 ± 6 km s?1 for the adopted Galactocentric distance of the Sun R 0 = 8.3 ± 0.2 kpc. The derived angular velocity parameters are Ω 0 = 28.48 ± 0.36 km s?1 kpc?1, Ω’0 = ?3.50 ± 0.08 km s?1 kpc?2, and Ω″0 = 0.331 ± 0.037 km s?1 kpc?3. The influence of the spiral density wave has been detected only in the sample of clusters younger than 50 Myr. For these clusters the amplitudes of the tangential and radial velocity perturbations are f θ = 5.6 ± 1.6 km s?1 and f R = 7.7 ± 1.4 km s?1, respectively; the perturbation wavelengths are λ θ = 2.6 ± 0.5 kpc (i θ = ?11? ± 2?) and λ R = 2.1 ± 0.5 kpc (i R = ?9? ± 2?) for the adopted four-armed model (m = 4). The Sun’s phase in the spiral density wave is (χ⊙)θ = ?62? ± 9? and (χ⊙)R = ?85? ± 10? from the residual tangential and radial velocities, respectively.  相似文献   

9.
We present the results of the reduction of our observations for the spectroscopic binary ADS 2984A (B0 II–B0 III), which along with its visual component ADS 2984B (SZ Cam) are the brightest members of the open star cluster NGC 1502. The spectroscopic data were obtained with a fiber-fed echelle spectrograph (R = 15 000) at the 1.2-m telescope of the Astronomical Observatory of the Ural Federal University. The period of ADS 2984A (P orb = 57.24 ± 0.05 days) has been found for the first time. This spectroscopic binary is shown to belong to the SB1 type. We have determined the parameters of the radial velocity curve for the visible spectroscopic component, V 0 = ?5.5 ± 1.2 km s?1 and K = 41.5 ± 1.7 km s?1. The lower mass limit for the invisible spectroscopic component has been estimated to be ~\(5M_ \odot \). Evidence for the presence of a stellar wind outflowing from the surface of this blue giant is presented.  相似文献   

10.
A series of highly accurate photoelectric observations of the eclipsing binary MZ Lac was obtained with a 48-cm AZT-14 reflector at the Tien-Shan High-Altitude Station of the Sternberg Astronomical Institute from 1985 to 2004 to study its apsidal motion. We constructed a consistent system of physical and geometrical parameters of the components and the binary’s orbit: we determined their masses (M1 = 1.50M⊙, M2 = 1.29M⊙), radii (R1 = 1.86R⊙, R2 = 1.35R⊙), luminosities (L1 = 0.79L⊙, L2 = 0.45L⊙), surface gravities (logg1 = 4.06, logg2 = 4.27), age (t = 1.9 × 109 yr), and the distance to the binary (d = 510 pc). The binary exhibits apsidal motion with the period Uobs = 480 ± 40 yr, while its theoretically expected value is Uth = 450 ± 40 yr. Spectroscopic studies of MZ Lac and calculations of the absolute parameters of the components are required to test our conclusions.  相似文献   

11.
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12.
Observations of Saturn's satellites and external rings during the 1980 edge-on presentation were obtained with a focal coronograph. A faint satellite traveling in the orbit of Dione and leading it by 72° has been detected, together with the two inner satellites already suspected (cf. J. W. Fountain and S. M. Larson, 1978,Icarus36, 92–106). The external ring has been observed on both east and west sides; it may extend up to ?8.3 Saturn radii, and appears structured.  相似文献   

13.
In 2003–2008, highly accurate photoelectric and CCD observations of the close binary system DI Her were performed in the V band. The light curves of three primary and three secondary eclipses were constructed. These observations, along with the highly accurate photoelectric observations of other authors obtained in different years from 1963 to 1986, have confirmed the difference between the observed (1 . o 3 ± 0 . o 1/100 yr) and theoretical (4 . o 3/100 yr) rates of apsidal motion. Our photometric data are indicative of a possible variability in the system with period P′ = 1.175 days and amplitude A′ = 0 . m 011, which is probably related to the pulsations of one of the components. There may be a third body in the system that produces in-phase variations in the times of primary and secondary minima with a period of 10.5 yr and an amplitude of 1 . m 5.  相似文献   

14.
We consider two samples of OB stars with different distance scales that we have studied previously. The first and second samples consist of massive spectroscopic binaries with photometric distances and distances determined from interstellar calcium lines, respectively. The OB stars are located at heliocentric distances up to 7 kpc. We have identified them with the Gaia DR1 catalogue. Using the proper motions taken from the Gaia DR1 catalogue is shown to reduce the random errors in the Galactic rotation parameters compared to the previously known results. By analyzing the proper motions and parallaxes of 208 OB stars from the Gaia DR1 catalogue with a relative parallax error of less than 200%, we have found the following kinematic parameters: (U, V)⊙ = (8.67, 6.63)± (0.88, 0.98) km s?1, Ω0 = 27.35 ± 0.77 km s?1 kpc?1, Ω′0 = ?4.13 ± 0.13 km s?1 kpc?2, and Ω″0 = 0.672 ± 0.070 km s?1 kpc?3, the Oort constants are A = ?16.53 ± 0.52 km s?1 kpc?1 and B = 10.82 ± 0.93 km s?1 kpc?1, and the linear circular rotation velocity of the local standard of rest around the Galactic rotation axis is V 0 = 219 ± 8 km s?1 for the adopted R 0 = 8.0 ± 0.2 kpc. Based on the same stars, we have derived the rotation parameters only from their line-of-sight velocities. By comparing the estimated values of Ω′0, we have found the distance scale factor for the Gaia DR1 catalogue to be close to unity: 0.96. Based on 238 OB stars of the combined sample with photometric distances for the stars of the first sample and distances in the calcium distance scale for the stars of the second sample, line-of-sight velocities, and proper motions from the Gaia DR1 catalogue, we have found the following kinematic parameters: (U, V, W)⊙ = (8.19, 9.28, 8.79)± (0.74, 0.92, 0.74) km s?1, Ω0 = 31.53 ± 0.54 km s?1 kpc?1, Ω′0 = ?4.44 ± 0.12 km s?1 kpc?2, and Ω″0 = 0.706 ± 0.100 km s?1 kpc?3; here, A = ?17.77 ± 0.46 km s?1 kpc?1, B = 13.76 ± 0.71 km s?1 kpc?1, and V 0 = 252 ± 8 km s?1.  相似文献   

15.
Speckle-interferometric observations of FU Ori are performed with the 6-m telescope of the Special Astrophysical Observatory with 600/40 nm and 800/100 nm (central bandwidth/halfwidth) filters. The companion star FU Ori S that was recently discovered at λ >-1.25µm was recorded in observations with the λ/Δλ==800/100 nm filter. The positional parameters and magnitude difference of the companion in the filter considered are found to be θ = (163.9 ± 1.0)°, ρ = (0.493 ± 0.007)″, Δm = 3.96 ± 0.28. An analysis of the spectral energy distribution of the companion implies that for the extinction A V toward FU Ori to be greater than about 1.6 m , i.e., the minimum value required by the available models of the fuor, the spectral type of the companion star must be no later than K3. The reliability of this conclusion and the possible ways for obtaining more accurate estimates of A V are discussed.  相似文献   

16.
《Icarus》1986,65(1):122-128
The Amplitude-Magnitude (AM) method is used for the pole determination of the asteroid 511 Davida, using observations from six oppositions. The possible North poles are found to be λ1 = 92° ± 7°; β1 = 33° ± 6°, and λ2 = 303° ± 4°; β2 = 34° ± 5°, when scattering effect is not taken into account. When scattering is accounted for, solutions not significantly different from (λ1, β1) and (λ2, β2) are obtained. The moderately eccentric and inclined orbit of 511 Davida does not allow us to distinguish between the two pole solutions. A comparison with other methods is necessary in order to make a definitive choice.  相似文献   

17.
We have studied the simultaneous and separate solutions of the basic kinematic equations obtained using the stellar velocities calculated on the basis of data from the Gaia TGAS and RAVE5 catalogues. By comparing the values of Ω'0 found by separately analyzing only the line-of-sight velocities of stars and only their proper motions, we have determined the distance scale correction factor p to be close to unity, 0.97 ± 0.04. Based on the proper motions of stars from the Gaia TGAS catalogue with relative trigonometric parallax errors less than 10% (they are at a mean distance of 226 pc), we have found the components of the group velocity vector for the sample stars relative to the Sun (U, V,W)⊙ = (9.28, 20.35, 7.36) ± (0.05, 0.07, 0.05) km s?1, the angular velocity of Galactic rotation Ω0 = 27.24 ± 0.30 km s?1 kpc?1, and its first derivative Ω'0 = ?3.77 ± 0.06 km s?1 kpc?2; here, the circular rotation velocity of the Sun around the Galactic center is V0 = 218 ± 6 km s?1 kpc (for the adopted distance R0 = 8.0 ± 0.2 kpc), while the Oort constants are A = 15.07 ± 0.25 km s?1 kpc?1 and B = ?12.17 ± 0.39 km s?1 kpc?1, p = 0.98 ± 0.08. The kinematics of Gaia TGAS stars with parallax errors more than 10% has been studied by invoking the distances from a paper by Astraatmadja and Bailer-Jones that were corrected for the Lutz–Kelker bias. We show that the second derivative of the angular velocity of Galactic rotation Ω'0 = 0.864 ± 0.021 km s?1 kpc?3 is well determined from stars at a mean distance of 537 pc. On the whole, we have found that the distances of stars from the Gaia TGAS catalogue calculated using their trigonometric parallaxes do not require any additional correction factor.  相似文献   

18.
《Icarus》1992,99(1):63-69
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19.
The orbital dynamics of the single known planet in the binary star system HD 196885 has been considered. The Lyapunov characteristic exponents and Lyapunov time of the planetary system have been calculated for possible values of the planetary orbit parameters. It has been shown that the dynamics of the planetary system HD 196885 is regular with the Lyapunov time of more than 5 × 104 years (the orbital period of the planet is approximately 3.7 years), if the motion occurs at a distance from the separatrix of the Lidov–Kozai resonance. The values of the planet’s orbital inclination to the plane of the sky and longitude of the ascending node lie either within ranges 30° < i p < 90° and 30° < Ωp < 90°, or 90° < i p < 180° and 180° < Ωp < 300°.  相似文献   

20.
We present the results of the study of the eclipsing polar CRTS CSS081231 J071126+440405. Photometric observations allowed us to refine the orbital period of the system \(P_ \circ = 0_ \cdot ^d 0.08137673\). Considerable changes in the appearance of the object’s spectra have occurred over the period of September 20–21, 2001: the slope of the continuum changed from “red” to “blue”, and the variability of the line profiles over the duration of the orbital period has also changed. Doppler maps have shown a shift of the emission line-forming region along the accretion stream closer to the white dwarf. We measured the duration of the eclipse of the system and imposed constraints on the inclination angle \(78_ \cdot ^ \circ 7 < i < 79_ \cdot ^ \circ 3\). The derived radial velocity amplitude was used to obtain the basic parameters of the system: M1 = 0.86 ± 0.08M⊙, M2 = 0.18 ± 0.02 M⊙, q = 0.21 ± 0.01, RL2 = 0.20 ± 0.03 R⊙, A = 0.80 ± 0.03 R⊙. The spectra of the object exhibit cyclotron harmonics. Their comparison with model spectra allowed us to determine the parameters of the accretion column: B = 31–34 MG, Te = 10–12 keV, θ = 80–90°, and Λ = 105.  相似文献   

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