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1.
We present the results of our infrared observations of WR 140 (=V1687 Cyg) in 2001–2010. Analysis of the observations has shown that the J brightness at maximum increased near the periastron by about 0 m .3; the M brightness increased by ∼2 m in less than 50 days. The minimum J brightness and the minimum L and M brightnesses were observed 550–600 and 1300–1400 days after the maximum, respectively. The JHKLM brightness minimum was observed in the range of orbital phases 0.7–0.9. The parameters of the primary O5 component of the binary have been estimated to be the following: R(O5) ≈ 24.7R ⊙, L(O5) ≈ 8 × 105 L ⊙, and M bol(O5) ≈ −10 m . At the infrared brightness minimum, T g ∼ 820–880 K, R g ≈ 2.6 × 105 R ⊙, the optical depth of the shell at 3.5 μm is ∼5.3 × 10−6, and its mass is ≈1.4 × 10−8 M ⊙. At the maximum, the corresponding parameters are ∼1300 K, 8.6 × 104 R ⊙, ∼2 × 10−4, and ∼6 × 10−8 M ⊙; the mean rate of dust inflow (condensation) into the dust structure is ∼3.3 × 10−8 M ⊙ yr−1. The mean escape velocity of the shell from the heating source is ∼103 km s−1 and the mean dispersal rate of the shell is ∼1.1 × 10−8 M ⊙ yr−1.  相似文献   

2.
Airborne eclipse observations of the [Six] 1430.5 nm coronal emission line are reviewed, and new ground-based out-of-eclipse coronagraph observations obtained at NSO/Sacramento Peak are reported. We find that the [Six] 1430.5 nm coronal emission line brightness is less than 8 × 10−6 B⊙ in small active region corona which showed [Fexiii] 1074.7 nm emission (corrected for sky background) of about 20 × 10−6 B⊙. Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.  相似文献   

3.
On the basis of the published times of minima and our own observations, we analysed the period change of the Algol-type eclipsing binary CU Pegasi. Over almost seventy years of observations, the parabolic period change has been clearly seen as dP/dt = 1.38 × 10−6 d/year. The estimated mass transfer in the system is about 1 × 10−7 MM⊙/year.  相似文献   

4.
Hydrodynamic calculations of nonlinear radial oscillations of LBV stars with effective temperatures 1.5 × 104 K ⩽ T eff ⩽ 3 × 104 K and luminosities 1.2 × 106 L ⊙ ⩽ L ⩽ 1.9 × 106 L ⊙ have been performed. Models for the evolutionary sequences of Population I stars (X = 0.7, Z = 0.02) with initial masses 70M ⊙ ⩽ M ZAMS ⩽ 90M ⊙ at the initial helium burning stage have been used as the initial conditions. The radial oscillations develop on a dynamical time scale and are nonlinear traveling waves propagating from the core boundary to the stellar surface. The amplitude of the velocity variations for the outer layers is several hundred km s−1, while the bolometric magnitude variations are within ΔM bol ⩽ 0· m 2. The onset of oscillations is not related to the κ-mechanism and is attributable to the instability of a self-gravitating envelope gas whose adiabatic index is close to its critical value of Γ1 = 4/3 due to the dominant contribution of radiation in the internal energy and pressure. The interval of magnitude variation periods (6 days ≤ II ≤ 31 days) encompasses all currently available estimates of the microvariability periods for LBV stars, suggesting that this type of nonstationarity is pulsational in origin.  相似文献   

5.
We present multi-colour CCD observations of the low-temperature contact binaries, V453 Mon and V523 Cas. Their light curves are modelled to determine a new set of stellar and orbital parameters. Analysis of mid-eclipse times yields a new linear ephemeris for both systems. A period decrease (dP/dt=2.3×10−7 days/yr) in V453 Mon is discovered. V523 Cas, however, is detected to show a period increase (dP/dt=9.8×10−8 days/yr) because of the mass transfer of a rate of 1.1×10−7 M⊙ yr−1, from a less massive donor. Using these findings we can determine the physical parameters of the components of V523 Cas to be M 1=0.76 (3)M ⊙, M 2=0.39 (2)M ⊙, R 1=0.74 (2)R ⊙, R 2=0.55 (2)R ⊙, L 1=0.19 (3)L ⊙, L 2=0.14 (3)L ⊙, and the distance of system as 46(9) pc.  相似文献   

6.
The density of the white dwarf stars is reconsidered from the point of view of the theory of the poly tropic gas spheres, and gives for themean density of a white dwarf (under ideal conditions) the formula ρ=2.162 × 106 × (M/⊙)2. The above formula is derived on considerations which are a much nearer approximation to the conditionsactually existent in a white dwarf than the previous calculations of Stoner based on uniform density distribution in the star and which gave for the limiting density the formula ρ=3.977 × 106 × (M/⊙)2.  相似文献   

7.
Four series of coronal images have been obtained by the expedition of Abastumani Astrophysical Observatory during the August 11, 1999 total solar eclipse with the help of a photographic mirror–lens polarimeter (D = 100 mm, F = 1000 mm). Each series include three images corresponding to three positions of the polarization analyzer. The position of the solar disk center relative to the Moon's center has been determined beforehand. In addition, the background skylight polarization and intensity are calculated. All measurements are absolute given in units of the Sun's average surface brightness. A new technique for separation of the F- and K-coronae is used. It was found that in the equatorial regions the model of hydrostatic distribution of the density with T = constant is not quite accurate for the August 11, 1999 corona and there is a temperature gradient in this region. For r1 = 1.3R⊙ and r2 = 1.8R⊙ we derived T1 = 1.25×106 K and T2 = 1.07×106 K, respectively. The average polarization degree in the equatorial regions changes from 10 to 40%, while in the polar regions the maximum value reaches only 10%. The values of electron densities Ne(r) vary from 1.32×108 cm−3 (r = 1.1R⊙) to 2.0×106 cm−3 (r = 2.0R⊙). Our data are compared with previous measurements.  相似文献   

8.
More than 635 thousand positional observations of planets and spacecraft of various types (mostly radiotechnical ones, 1961–2010) were used to estimate possible changes in the gravitational constant, Sun’s mass, and semi-major axes of planetary orbits, as well as the associated value of the astronomical unit. The observations were analyzed based on the EPM2010 ephemerides constructed at the Institute of Applied Astronomy (Russian Academy of Sciences) in a post-Newtonian approximation as a result of simultanious numerical integration of the equations of motion of nine major planets, the Sun, the Moon, asteroids, and trans-Neptunian objects. The heliocentric gravitational constant GM ⊙ was found to vary with a rate of (GṀ ⊙/GM ⊙ = (−5.0 ± 4.1)) × 10−14 per year (at the 3σ level). The positive secular changes in the semimajor axes ȧ i /a i were found for Mercury, Venus, Mars, Jupiter, and Saturn provided by high-precision observations. These changes also correspond to the decrease in the heliocentric gravitational constant. The changing of GM ⊙, itself is probably caused by the loss of the mass M ⊙ of the Sun due to its radiation and solar wind; these effects are partly compensated by the material falling onto the Sun. Allowing for the maximum bounds on the possible change in the Sun’s mass M ⊙, it has been found from the change obtained in GM ⊙ that the annual change Ġ/G of the gravitational constant G falls within the interval −4.2 × 10−14 < ȧ/G < +7.5 × 10−14 with a 95% probability. The astronomical unit (AU) is connected by its definition only with the heliocentric gravitational constant. The decrease of GM ⊙ obtained in this paper should correspond to a secular decrease in the AU. It is shown, however, that the modern level of accuracy does not allow us to determine a change in the AU. The attained posibility of determining changes in GM ⊙ using high-accuracy observations encourages us to have a relation between GM ⊙ and the AU fixed for a certain moment in time, since it is inconvenient to have a time-dependent length for the AU.  相似文献   

9.
The ionizing star BD+60°2522 is known as the central star of Bubble Nebulae NGC 7635—wind-blown bubble created by the interaction of the stellar wind of BD+60°2522 (O6.5 IIIef, V=8.7 mag, mass loss rate 10−5.76 M ⊙/year) with the ambient interstellar medium. From the evolutionary calculations for the star with mass loss and overshooting, we find that the initial mass of the star is 60M ⊙, its present age is 2.5×106 years, and the present mass is 45M ⊙.  相似文献   

10.
We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 9 Metis (1.03 ± 0.24 × 10-11 M⊙), 17 Thetis (6.17 ± 0.64 × 10-13 M⊙), 19 Fortuna (5.41 ± 0.76 × 10-12 M⊙), and 189 Phthia (1.87 ± 0.64 × 10-14 M⊙) appear to be new. The resulting bulk porosities of 11 Parthenope (12±4%) and 16 Psyche (46±16%) are smaller than previously-reported values. Empirical expressions modeling bulk density as a function of mean radius are presented for the C and S taxonomic classes. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications.  相似文献   

11.
A new orbital period analysis for U Geminorum is made by means of the standard O–C technique based on 187 times of light minima including the three newest CCD data from our observation. Although there are large scatter near 70,000 cycles in its O–C diagram, there is strong evidence (>99.9% confidence level) to show the secular increase of orbital period with a rate  s−1. Using the physical parameters recently derived by Echevarría et al. (Astron. J. 134:262, 2007), the range of mass transfer rate for U Geminorum is estimated as from −3.5(5)×10−9 M ⊙ yr−1 to −1.30(6)×10−8 M ⊙ yr−1. Moreover, the data before 60,000 cycles shows the obvious quasi-period variations. The least square estimation of a ∼17.4 yr quasi-periodic variation superimposed on secular orbital period increase is derived. Considering the possibility that solar-type magnetic activity cycles in the secondary star of U Geminorum may produce the quasi-period variations of the orbital period, Applegate’s mechanism is discussed and the results indicate such mechanism has difficulty explaining the quasi-period variation for U Geminorum. Hence, we attempted to apply the light-travel time effect to interpret the quasi-period variation and found the perturbation of ∼17.4 yr quasi-period may result from a brown dwarf. If the orbital inclination is assumed as i∼15°, corresponding to the upper limit of mass of a brown dwarf, then its orbital radii is ∼7.7 AU.  相似文献   

12.
An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10±0.05) MK, (0.70±0.08) MK, and (0.98±0.12) MK, at 1.1 R ⊙ from Sun center in the solar north, east and west, respectively, and (0.93±0.12) MK, at 1.2 R ⊙ from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103±92) km s−1, (0+10) km s−1, (0+10) km s−1, and (0+10) km s−1. Since the observations were taken only at 1.1 R ⊙ and 1.2 R ⊙ from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 R ⊙ from Sun center is larger at the north (polar region) than the east and west (equatorial region).  相似文献   

13.
The spectral energy distributions and mid-infrared spectra of 44 carbon Mira variables are fitted using a dust radiative transfer model. The periods cover the entire range observed for carbon Miras. The luminosities are calculated from a period-luminosity relation. Parameters derived are the distance, the dust mass loss rate and the ratio of silicon carbide to amorphous carbon dust. The total mass loss rate is derived from a modified relation between the photon momentum (L/c) and the momentum in the wind (M υ∞). Mass loss rates between 1 × 10−8 and 4 × 10−5 M⊙ yr−1 are found. We find good correlations between mass loss rate and pulsation period, and mass loss rate and luminosity. The dust-to-gas ratio appears to be almost constant up to periods of about 500 days, corresponding to about 7900 L⊙, and then to increase by a factor of 5 towards longer periods and higher luminosities. A comparison is made with radiation-hydrodynamical calculations including dust formation. The mass loss rates predicted by these models are consistent with those derived in this paper. The main discrepancy is in the predicted expansion velocities for models with luminosities below ∼5000 L⊙. The radiation-hydrodynamical calculations predict expansion velocities which are significantly too large. This is related to the fact that these models need to be calculated with a large C/O ratio to get an outflow in the first place. This is contrary to observations. It indicates that a principle physical ingredient in these radiation-hydrodynamical calculations is still missing. Possibly the winds are ‘clumpy’ which may lead to dust formation on a local scale, or there is an additional outwards directed force, possibly radiation pressure on molecules. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

14.
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   

15.
Based on data from the Baksan underground scintillation telescope (BUST) for the period 2001–2004, we searched for cosmic gamma-ray bursts (GRBs) at primary photon energies of 0.5 TeV or higher. We obtained constraints on the rate of bursts with durations of 1–10 s for fluences within the range 4.6 × 10−3-1.8 × 10−2 erg cm−2 in the declination band 30° ≤ δ ≤ 80°. We searched for ultrahigh-energy gamma rays from GRBs detected on spacecraft during and within ±2 h of the burst. No statistically significant excesses above the background of random coincidences were found. The derived constraints on the ultrahigh-energy gamma-ray fluence during GRBs lie within the range 4.6 × 10−3-3.7 × 10−2 erg cm−2.  相似文献   

16.
The extensiveUBV observations of SV Camelopardalis by Patkos (1982) have been analysed to derive the orbital elements of the system. The data were corrected for the effect of third body (Sarma, Sarma & Abhyankar 1985) and for the ‘RS CVn’ distortion wave (Sarma, Vivekanandarao & Sarma 1988). The cleaned data were used to obtain a preliminary solution by a modified version of Wellmann method (Sarma & Abhyankar 1979) from which we concluded that the primary eclipse is a transit. The final orbital elements of SV Cam were obtained by the modified version (Sarma 1988; Sarmaet al. 1987) of WINK program by Wood (1972). The colour and median brightness variation are discussed. From the spectroscopic mass functionf(m) = 0.118 M⊙ (Hiltner 1953), the absolute dimensions of the components are found to be 0.826 Mbd & 0.592 M⊙ and 1.236 R⊙ & 0.778 R⊙ for the primary and secondary components, respectively. The age of the binary system is estimated to be 6.0 ± 1.0 × 108 years  相似文献   

17.
Complete UBV light curves of the W Ursae Majoris binary V839 Ophobtained in the year 2000 are presented. The available spectroscopic data of V839 Oph is new and we used the first radial velocity data of this system obtained by Rucinski and Lu (1999)for analysis. The radial velocity and light curves analysis was made with the latest version of Wilson programme (1998) and the geometric and physical elements of the system are derived. By searching the simultaneous solutions of the system we have determined the masses and radii of the components: 1.61M ⊙and 1.49402R ⊙ for the primary component; 0.50M ⊙and 0.90147R ⊙ for the secondary component. We estimate deffective temperatures of 6650±18 (K) for the primary and6554±15 (K) for the secondary component. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
Results from two-color VR photometry of the unique cataclysmic magnetic variable star V1432 Aql and a theoretical model of these data are presented. The accuracy is improved by using the “mean-weighted comparison star” method. The derivative of the rotational period is dP/dt = −1.11(±0.016)·10−8. The characteristic synchronization time for the rotational and orbital motions of the white dwarf is 96.7±1.5 years, in good agreement with theory for the acceleration of an asynchronous propeller owing to the angular momentum of accreting matter. A third type of minimum detected in the light curve is interpreted in terms of the presence of an arc, or ring, rather than an accretion disk. A theoretical model is developed for determining the capture radius of accreted matter by the magnetic field of the white dwarf using the phase difference between the two types of minima associated with the axial rotation. This parameter is estimated to be 16–28 times the radius of the white dwarf for an inclined column model. A dependence of the main characteristics of the system on the mass of the white dwarf is derived which yields better values for the range of this quantity than those determined by indirect methods. For the assumed masses (M1 = 0.9 M⊙ and M2 = 0.3 M⊙) the estimated accretion rate is ∼7×10−10 M⊙. It is shown that in a synchronizing polar the contribution to the change in the period by the variation in the angular momentum of the white dwarf is negligible compared to the accretion torque. In the future multicolor monitoring is needed for studying the spin-orbital synchronization and periodic changes in the accretion structure caused by “spinning” of the white dwarf. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 135–159 (February 2007).  相似文献   

19.
The tritium chain of the hydrogen cycle on the Sun including the reactions 3He(e−, ν e) 3H(p, γ)4He is considered. The flux of tritium neutrinos at a distance of 1 AU is 8.1 × 104 cm−2 s−1. It exceeds the neutrino flux from the (hep)-reaction by one order of magnitude. The radial distribution of the yield of 3H neutrinos inside the Sun and their energy spectrum, which has the form of a line at an energy of 2.5–3.0 keV, have also been calculated. The flux of thermal tritium neutrinos is accompanied by a very weak flux of antineutrinos (∼103 cm−2 yr−1) with an energy below 18.6 keV. These antineutrinos are produced in the URCA processes 3He ⇆ 3H.  相似文献   

20.
We have used the Very Large Array to image a single field in a set of adjacent frequency bands around 333.0 MHz in an attempt to detect 21 cm emission from large scale H I inhomogeneities at a redshift of z = 3.3. Following the subtraction of continuum radio sources, the absence of any spectral signals apart from that expected due to the system thermal noise has been used to derive constraints on the evolutionary scenario leading to the formation of the present day clusters of galaxies. The observations rule out the existence of H I protoclusters atz = 3.3 with masses ≃3.5 × 1014 M ⊙ in H I gas and space density exceeding (74 Mpc)−3. This indicates that the present day rich clusters of galaxies either formed as gaseous protocluster condensates prior toz = 3.3 or else they formed through the clustering of their constituent galaxies.  相似文献   

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