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1.
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2.
The Grüneisen ratio, γ, is defined as γy=αK TV/Cv. The volume dependence of γ(V) is solved for a wide range in temperature. The volume dependence of αK T is solved from the identity (? ln(αK T)/? ln V)T ≡ δ T-K′. α is the thermal expansivity; K T is the bulk modulus; C V is specific heat; and δ Tand K′ are dimensionless thermoelastic constants. The approach is to find values of δ T and K′, each as functions of T and V. We also solve for q=(? ln γ/? ln V) where q=δ T -K′+ 1-(? ln C V/? ln V)T. Calculations are taken down to a compression of 0.6, thus covering all possible values pertaining to the earth's mantle, q=? ln γ/? ln V; δ T=? ln α/? ln V; and K′= (?K T/?P)T. New experimental information related to the volume dependence of δ T, q, K′ and C V was used. For MgO, as the compression, η=V/V 0, drops from 1.0 to 0.7 at 2000 K, the results show that q drops from 1.2 to about 0.8; δ T drops from 5.0 to 3.2; δ T becomes slightly less than K′; ? ln C V/? In V→0; and γ drops from 1.5 to about 1. These observations are all in accord with recent laboratory data, seismic observations, and theoretical results.  相似文献   

3.
We have performed speckle interferometry with the 6-m telescope of the Special Astrophysical Observatory and spectroscopy (at 3700–9200 Å) with the 2-m telescope at Peak Terskol of the spectroscopic and interferometric binary 9 Cyg, which is a composite-spectrum star with an orbital period of 4.3 yrs. The atmosphere of the system’s primary component is analyzed in detail. The luminosities of both components estimated to be L 1 = 103.8 L ⊙, L 2 = 55.2 L ⊙, where L ⊙ is the solar luminosity, and their effective temperatures to be T e (1) = 5300 K and T e (2) = 9400 K. The abundances of C, N, O, Fe, and other elements in the primary’s atmosphere have been derived. The chemical composition shows signatures of mixing of material from its atmosphere and the region of nuclear reactions. The evolutionary status of 9 Cyg has been determined. The binary’s age is about 400 million years; the brighter star is already in the transition to becoming a red giant, while the secondary is still in the hydrogen-burning stage near the zero-age main sequence. We suggest an evolutionary model for the binary’s orbit that explains the high eccentricity, e = 0.79.  相似文献   

4.
We use a lattice vibrational technique to derive thermophysical and thermochemical properties and phase equilibria in the system MgO-SiO2 at pressures and temperatures relevant to Earth’s mantle. The technique is based on an extension of Kieffer’s model to incorporate details of the phonon spectrum, and it includes treatment of intrinsic anharmonicity. We use a least squares inversion technique applied to available experimental data, and show that it results in an accurate representation of thermodynamic properties and sound wave velocities of high-pressure phases in the system MgSiO3. The vibrational method has been validated against laboratory experimental data in the temperature range between 0 and 2500 K and at pressures between 1 bar and 30 GPa. The technique results in a phase diagram consistent with the majority of thermophysical and thermochemical data. It is shown that intrinsic anharmonicity affects significantly slopes and positions of the phase boundaries. Our analysis indicates inconsistencies in a number of data sets of thermophysical properties for stishovite, majorite and ortho-enstatite necessitating new measurements. For akimotoite elasticity data at high-pressure and high-temperature conditions and 1 bar heat capacity measurements are needed. For stishovite elasticity measurements are necessary to reconcile elasticity data with V-P-T measurements. Additionally V-P-T measurements at pressures higher than 10 GPa are needed, which should be reconciled with V-P-T data at lower pressures. Raman and infrared spectroscopic data are necessary for both clino-enstatite and majorite. Additionally structural data are needed to resolve the discrepancy between values for the degree of disorder in majorite. Volume expansion data for ortho-enstatite are needed and effects causing differences in measured volume expansion should be elucidated.  相似文献   

5.
We have carried out photometry and spectroscopy of the star V1327 Aql (R = 16 m ) as part of our program of observations of poorly studied cataclysmic variables using the 1.5-m optical Russian—Turkish telescope (RTT-150, Turkey) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. After analyzing our photometry, we have re-classified the variable as an RR Lyrae star. Our BV R photometry during 10 nights reveals brightness variations with the period 12h49m, with the B, V, and R amplitudes being 1.36 m , 1.13 m , and 1.11 m , respectively. We derived the first estimates of the star’s atmospheric parameters from our moderate-resolution spectra: T eff = 6280 K, log g = 3.3, [M/H] = ?1.05. The extremely high radial velocity of the star’s motion (V R = ?470 km/s) and the star’s large distances to the Galactic center (13.1 kpc) and disk (4.2 kpc) testify to a probable extragalactic origin of this object.  相似文献   

6.
The following hardsphere modified Redlich-Kwong (HSMRK) equation of state was obtained by least squares fitting to available P-V-T data for methane (P in bars; T in Kelvins; v in cm3 mol?1; b = 60.00 cm3 mol?1; R = 83.14 cm3barmol?1K?1): PRT(1 + y + y2?y3v(1?y)3)-c(T) + d(T)v + e(T)v2/v(v + b)T12y = b4vc(T) = 13.403 × 106 + (9.28 × 104)T + 2.7 T2d(T) = 5.216 × 109 ? (6.8 × 106)T + (3.28 × 103)T2e(T) = (?2.3322 × 1011) + (6.738 × 108)T + (3.179 × 105)T2 For the P-T range of experimental data used in the fit (50 to 8600 bars and from 320 to 670 K), calculated volumes and fugacity coefficients for CH4 relative to experimentally determined volumes and fugacity coefficients have average percent deviations of 0.279 and 1.373, respectively. The HSMRK equation, which predicts linear isochores over a wide P-T range, should yield reasonable estimates of fugacity coefficients for CH4 to pressures and temperatures well outside the P-T range of available P-V-T data. Calculations for the system H2O-CO2-CH4, using the HSMRK equations for H2O and CO2 of Kerrick and Jacobs (1981) and the HSMRK equation for CH4 of this study, indicate that compared to the binary H2O-CO2 system, small amounts of CH4 in the ternary system H2O-CO2-CH4 slightly increases the activity of H2O, and significantly decreases the activity of CO2.  相似文献   

7.
The atmospheric abundances of 30 chemical elements in the halo star HD 221170 are analyzed by fitting synthetic spectra to observed spectra (i) with a resolution of 60 000 and signal-to-noise ratios of about 200 taken with the 1.93-m telescope of the Observatoire de Haute Provence and (ii) with a resolution of 35 000 and signal-to-noise ratios of more than 100 taken with the 2-m telescope of the Terskol Peak Observatory. The derived parameters of the stellar atmosphere are Teff=4475 K, log g=1.0, [Fe/H]=?2.03, Vmicro=1.7 km/s, and Vmacro=4 km/s. The parameters Teff, log g, [Fe/H], and Vmicro can be determined by analyzing the variations of the rms error of the mean iron abundance derived using different model atmospheres. The chemical composition of the star’s atmosphere is analyzed. The abundances of a total of 35 elements in HD 221170 have been derived in this paper and in previous studies. Overall, the abundances of elements lighter than praseodymium are consistent with the elemental abundances in the atmospheres of stars with similar metal deficits. Copper and manganese are underabundant by ?2.9 and ?2.6 dex, respectively, relative to the Sun (when the analysis includes the effects of hyperfine structure). Heavy r-process elements (starting from praseodymium) are overabundant compared to iron-group elements. This can be explained by an enrichment in r-process elements of the material from which the star was formed.  相似文献   

8.
We report H2O maser line observations of the bright-rimmed globule IC 1396 N using a ground-space interferometer with the 10-m RadioAstron radio telescope as the space-based element. The source was not detected on projected baselines >2.3. Earth diameters, which indicates a lower limit on the maser size of L > 0.03 AU and an upper limit on the brightness temperature of 6.25 × 1012 K. Fringe-rate maps are prepared based on data from ground-ground baselines. Positions, velocities and flux densities of maser spots were determined. Multiple low-velocity features from ?4.5 km/s to +0.7 km/s are seen, and two high-velocity features of V LSR = ?9.4 km/s and V LSR = +4.4 km/s are found at projected distances of 157 AU and 70 AU, respectively, from the strongest low-velocity feature at V LSR = ~+0.3 km/s. Maser components from the central part of the spectrum fall into four velocity groups but into three spatial groups. Three spatial groups of low-velocity features detected in the 2014 observations are arranged in a linear structure about ~200 AU in length. Two of these groups were not detected in 1996 and possibly are jets which formed between 1996 and 2014. The putative jet seems to have changed direction in 18 years, which we explain by the precession of the jet under the influence of the gravity of material surrounding the globule. The jet collimation can be provided by a circumstellar protoplanetary disk. There is a straight line orientation in the “V LSR-Right Ascension” diagram between the jet and the maser group at V LSR = ~+0.3 km/s. However, the central group with the same position but at the velocity V LSR ~ ?3.4 km/s falls on a straight line between two high-velocity components detected in 2014. Comparison of the low-velocity positions from 2014 and 1996, based on the same V LSR-Right Ascension diagram for low-velocity features, shows that the majority of the masers maintain their positions near the central velocity V LSR = ~0.3 km/s during the 18 year period.  相似文献   

9.
Our high-resolution spectral observations have revealed variability of the optical spectrum of the cool star identified with the IR source IRAS 20508+2011. We measured the equivalent widths of numerous absorption lines of neutral atoms and ions at wavelengths 4300–7930 Å, along with the corresponding radial velocities. Over the four years of our observations, the radial velocity derived from photospheric absorption lines varied in the interval V r⊙ = 15–30 km/s. In the same period, the Hα profile varied from being an intense bell-shaped emission line with a small amount of core absorption to displaying two-peaked emission with a central absorption feature below the continuum level. At all but one epoch, the positions of the metallic photospheric lines were systematically shifted relative to the Hα emission: ΔV r = V r(met) ? V r(Hα, emis) ≈ ?23 km/s. The Na D doublet displayed a complex profile with broad (half-width ≈ 120 km/s) emission and photospheric absorption, as well as an interstellar component. We used model atmospheres to determine the physical parameters and chemical composition of the star’s atmosphere: T eff = 4800 K, log g = 1.5, ξt = 4.0 km/s. The metallicity of the star differs little from the solar value: [Fe/H]⊙ = ?0.36. We detected overabundances of oxygen [O/Fe]⊙ = +1.79 (with the ratio [C/O] ≈ ?0.9), and α-process elements, as well as a deficit of heavy metals. The entire set of the star’s parameters suggests that the optical component of IRAS 20508+2011 is an “O-rich” AGB star with luminosity M v ≈ ?3m that is close to its evolutionary transition to the post-AGB stage.  相似文献   

10.
The fine structure of the active region in the Orion KL gas-dust complex has been measured in polarized H2O maser emission (epoch December 12, 1998) with an angular resolution of 0.15 mas, or 0.07 AU, and a velocity resolution of 0.05 km/s. The maser emission is concentrated in a line with ΔV = 0.45 km/s, V LSR = 7.65 km/s, and a flux density of F = 2.1 MJy. The structure consists of a compact source (ejector), highly collimated bipolar outflow, and a toroidal component. The brightness temperature of the ejector is T b = 2 × 1016 K, and its degree of linear polarization reaches m ≈ 20%. The variation of the polarization angle across the profile is dX/dV = ?23°/(km/s), which considerably exceeds the Faraday rotation in the HII region foreground to the molecular cloud. The observed “rotation” is explained as an effect of different orientations for the polarization of the ejected outflows. The brightness temperature of the bipolar outflow is T b ≈ 1014 K, while that of individual components is T b ≈ 1015 K. The degree of polarization in the components exceeds that of the ejector and reaches m ≈ 50%. The position angle of the polarization is X ≈ 45° relative to the outflow. The torus, which is observed edge-on, has a diameter of 0.38 AU and a thickness of 0.08 AU. The brightness temperature of the tangential directions in the torus is T b ≈ 5 × 1015 K, and the rotational velocity is V rot ≈ 0.02 km/s. The degree of polarization is m ≈ 40%, and its position angle relative to the azimuthal plane is X ≈ 43°. The relative deviations of the polarization plane in the bipolar outflow and torus relative to the pumping direction are nearly the same and are determined by Faraday rotation within the HII region.  相似文献   

11.
We have determined the physical (T eff, logg, ζ) and kinematic (V e sini,V r ) parameters and abundances for 14 chemical elements in the atmosphere of the “antiflare” variable RZ Psc, using medium-resolution spectra obtained with the Coudé spectrographs of the 6-m telescope of the Special Astrophysical Observatory and the Crimean Astrophysical Observatory 2.6-m Shain telescope. The chemical composition of the star is characterized by a slight metal deficiency; however, the iron and calcium abundances are consistent with the solar values within the errors. We also detected a peculiar dip (depression) of the continuum level near the Hα line. Assuming that this depression and the photospheric Hα line have independent origins, we calculated the hydrogen abundance X in the atmosphere of RZ Psc. The resulting value X=0.70 (of the solar value) implies a relative deficiency of hydrogen. Together with the spatial location of the star, these properties provide evidence that RZ Psc is an evolved star, most likely belonging to population II.  相似文献   

12.
We used a photoelectric photometer designed by V.M. Lyutyi and the Zeiss-600 telescope of the Sternberg Astronomical Institute’s Crimean Observatory to acquire precise UBV brightness measurements (σ obs V ～ 0.007m) for the eclipsing binary system HS Her in 1984–1991. These measurements continue the homogeneous series of observations of this star commenced in 1969 by D.Ya. Martynov using the same equipment. Our detailed analysis of this homogeneous 22-year series of photoelectric observations has yielded a self-consistent set of physical and geometric parameters of the binary, and enabled us to establish the evolutionary stages of its components. The systems’s primary, M 1 = 5 M ⊙, is at the beginning of its main-sequence evolution, whereas its secondary, M 2 = 1.6 M ⊙, has not yet reached the main sequence. The binary’s age is estimated to be t = (17 ± 3) × 106 years.  相似文献   

13.
We have studied the relatively recently discovered object 2-7-0122, with a V magnitude of 17 m , and have confirmed that it is an SX Phe variable star. Our photometry at the 1.8 m telescope of the Boyhunsan Observatory and the 1.0 m telescope of the Mount Lemon Observatory has enabled us to refine the photometric elements and to perform a frequency analysis of the light curve. We demonstrate the presence of two close frequencies, f 1 = 24.6539 cycles/day and f 2 = 24.8173 cycles/day, one of them possibly non-radial, and of several combinational frequencies. The star’s metallicity is at least two orders of magnitude lower than that of the Sun, making the star the most metal-poor SX Phe object in the Galactic field. We confirm variability of another star in the field of view, and have determined its light elements and its possible variability type (RRc).  相似文献   

14.
The thermoelastic parameters of Ca3Cr2Si3O12 uvarovite garnet were examined in situ at high pressure up to 13 GPa and high temperature up to 1100 K by synchrotron radiation energy-dispersive X-ray diffraction within a 6-6-type multi-anvil press apparatus. A least-square fitting of room T data to a third-order Birch–Murnaghan (BM3) EoS yielded K0 = 164.2 ± 0.7 GPa, V0 = 1735.9 ± 0.3 Å3 (K’0 fixed to 4.0). P–V–T data were fitted simultaneously by a modified HT-BM3 EoS, which gave the isothermal bulk modulus K0 = 163.6 ± 2.6 GPa, K’0 = 4.1 ± 0.5, its temperature derivative (?K0,T/?T)P = –0.014 ± 0.002 GPa K?1, and the thermal expansion coefficients a0 = 2.32 ± 0.13 ×10?5 K?1 and b0 = 2.13 ± 2.18 ×10?9 K?2 (K’0 fixed to 4.0). Our results showed that the Cr3+ enrichment in natural systems likely increases the density of ugrandite garnets, resulting in a substantial increase of mantle garnet densities in regions where Cr-rich spinel releases chromium through a metasomatic reaction.  相似文献   

15.
We present a detailed analysis of the optical spectrum of the post-AGB star HD 56126 (IRAS 07134+1005) based on observations made with the echelle spectrographs of the 6-m telescope of the Special Astrophysical Observatory with resolutions of R = 25 000 and 60 000 at 4012-8790 Å. The profiles of strong lines (HI; FeII, YII, BaII absorption lines, etc.) formed in the expanding atmosphere at the base of the stellar wind display complex and variable shapes. To study the kinematics of the atmosphere, the velocities of individual features in these profiles must be measured. Differential line shifts of up to ΔV r = 15–30 km/s have been detected from the lines of metals and molecular fetures. The stellar atmosphere simultaneously contains both expanding layers and layers falling onto the star. A comparison of the data for different times demonstrates that both the radial velocity and the overall velocity pattern are variable. The position of the molecular spectrum is stable, implying stability of the expansion velocity of the circumstellar envelope around HD 56126 detected in observations in the C2 and NaI lines.  相似文献   

16.
The pressure dependence of the Raman spectrum of forsterite was measured over its entire frequency range to over 200 kbar. The shifts of the Raman modes were used to calculate the pressure dependence of the heat capacity, C v, and entropy, S, by using statistical thermodynamics of the lattice vibrations. Using the pressure dependence of C v and other previously measured thermodynamic parameters, the thermal expansion coefficient, α, at room temperature was calculated from α = K S (?T/?P) S C V/TVK T, which yields a constant value of (? ln α/? ln V)T= 6.1(5) for forsterite to 10% compression. This value is in agreement with (? ln α/? ln V)T for a large variety of materials. At 91 kbar, the compression mechanism of the forsterite lattice abruptly changes causing a strong decrease of the pressure derivative of 6 Raman modes accompanied by large reductions in the intensities of all of the modes. This observation is in agreement with single crystal x-ray diffraction studies to 150 kbar and is interpreted as a second order phase transition.  相似文献   

17.
We have analyzed the broad-band light curve of the massive eclipsing binary BAT99-129, which is located in the Large Magellanic Cloud and consists of WN3(h) and O5V components. The light curve was obtained as part of the MACHO project. The dense extended atmosphere of the Wolf-Rayet (WR) star makes it impossible to apply a standard parametric model, such as that of Wilson and Devinney, to analyze the light curve. We reconstructed the distributions of the brightness and absorption across the disk of the WR component by directly solving the integral equations describing the eclipses in the system. Our analysis yields reliable estimates of the system’s orbital parameters and the parameters of its components. The orbital inclination is 78°, the size of the orbit 28.5 R ⊙, and the radius of the O component R O = 7.1 R ⊙. The size of the WR core, which is opaque in the optical continuum, is R WR = 3.4 R ⊙, and the brightness temperature at the center of the WR-component disk is T br = 45 000 K. We discuss possible uncertainties in the parameters obtained. The derived information is used to draw conclusions about the system’s evolutionary status.  相似文献   

18.
New spectroscopic observations obtained in 1998–2001 and published radial velocities of neutral helium absorption lines suggest that the Herbig Ae/Be star HD 200775 is a spectroscopic binary with a 1180±60 day period. We have determined the elements of the spectroscopic orbit. The presence of both rapid and long-time-scale spectral variability is demonstrated. The rapid variability is apparently due to a nonuniform circumstellar environment and modulation by the axial rotation of the system’s primary. Using data from the literature, we plot the V light curve of the system, which shows some brightening near the time of the minimum radial velocity, with its duration not exceeding 0.2 of the orbital cycle. We suggest that the system’s secondary is a low-mass (≥ 0.5M⊙) protostar, and that a semitransparent extended circumstellar envelope gives rise to eclipses in the system.  相似文献   

19.
Theoretical spectral energy distributions for Sakurai's object at 300–1000 nm are derived. A model-atmosphere grid with T eff=5000–6250 K and logg=0.0–1.0 is computed for the chemical composition of Sakurai's object using opacity sampling including molecular and atomic absorption. Opacity due to absorption in 20 band systems of diatomic molecules is computed using the JOLA technique. The theoretical fluxes are compared with the observed energy distribution in a spectrum of Sakurai's object taken in April 1997. It is shown that (a) the theoretical energy distributions agree well qualitatively with the observed spectrum and depend strongly on the effective temperature; (b) C2 and CN molecular bands are dominant in the visible and near-infrared spectrum, while atomic absorption is important at UV and blue wavelengths; and (c) comparison of the observed and computed spectra yields an effective temperature for Sakurai's object in April 1997 T eff≈5250–5500 K. The dependence of the computed spectra at 300–1000 nm on the input parameters and adopted approximations is also discussed.  相似文献   

20.
We report the results of a search for spatial and spectral fluctuations of the cosmic microwave background in the region of the North celestial pole carried out at 6.2 cm using the RATAN-600 radio telescope in 1999–2000. The spatial spectrum is flat and has no features exceeding ΔT/T =10?3 in a ～1 MHz frequency band for spatial periods from 0.5′ to 16′. If this estimate is adopted as an upper limit for emission associated with the first rotational transition of primordial LiH at z=90.7, we obtain an upper limit for the LiH abundance of about 3×10?14 for protocluster masses of about 1013 M ⊙.  相似文献   

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