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1.
Time resolved spectroscopy of the dwarf nova IP Pegasi in the range 7670–8320Å shows absorption lines originating from the cool secondary. A radial velocity curve for this component has been derived by cross-correlation with a normal M star. The curve has semi-amplitude K2=288.3±4 km s–1, and is slightly distorted. This distortion is equivalent to an orbit with an apparent eccentricity of 0.075±0.024. The mass function of the primary is 0.394±0.016M. From this we derive constraints on the component masses of 0.621<1.14M and 0.172<0.71M. The red star has a radius in the range 0.322<0.51R and is probably on the main sequence.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986  相似文献   

2.
The Freundlich red shift of wavelengths in the solar spectrum is discussed. Born's approach on the photon-photon interaction is used in conjunction with Melvin's recalculation of Freundlich's universal constant in order to derive the cross-section for scattering in the solar atmosphere. The new cross-section appears to be = 1.58 × 10–18 cm2, which is about one thousand times Born's estimate for the effective cross-section. However, a modified value of the constant is in a good agreement with the one obtained by Ter Haar by scattering process methods, which leads to 10–18 cm2 for the photon-photon interaction cross-section of the solar atmosphere. A new expression for Freundlich's red shift formula is obtained. Some numerical examples are given and some interesting aspects of Freundlich's parameters are discussed.  相似文献   

3.
We have studied the thermonuclear runaways which develop on white dwarfs of 1.205M and 1.358M accreting hydrogen rich material at 10–10 M yr–1. It is found that ignition of this material occurs at densities in excess of about 104 gm cm–3 and that the critical accumulated mass required to initiate the runaway is 0.7(1.5)×10–4 M for a 1.358(1.205)M white dwarf.  相似文献   

4.
Summary In the solar neighborhood, approximately half of all intermediate mass main sequence stars with initially between 1 and about 5 Mbecome carbon stars with luminosities near 104 L for typically less than 106 years. These high luminosity carbon stars lose mass at rates nearly always in excess of 10–7 M yr–1 and sometimes in excess of 10–5 M yr–1. Locally, close to half of the mass returned into the interstellar medium by intermediate mass stars before they become white dwarfs is during the carbon star phase. A much greater fraction of lower metallicity stars become carbon-rich before they evolve into planetary nebulae than do higher metallicity stars; therefore, carbon stars are much more importan t in the outer than in the inner Galaxy.  相似文献   

5.
We present Very Large Array observations at wavelengths of 2, 3.5, 6, and 20 cm, of angular broadening of radio sources due to the solar wind in the region 2–16 solar radii. Angular broadening is anisotropic with axial ratios in the range 2–16. Larger axial ratios are observed preferentially at smaller solar distances. Assuming that anisotropy is due to scattering blobs elongated along magnetic field lines, the distribution of position angles of the elliptically broadened images indicates that the field lines are non-radial even at the largest heliocentric distances observed here. At 5R , the major axis scattering angle is 0.7 at =6 cm and it varies with heliocentric distance asR –1.6. The level of turbulence, characterized by the wave structure function at a scale of 10 km along the major axis, normalized to =20 cm, has a value 20±7 at 5R and varies with heliocentric distance asR –3. Comprison with earlier results suggest that the level of turbulence is higher during solar maximum. Assuming a power-law spectrum of electron density fluctuations, the fitted spectral exponents have values in the range 2.8–3.4 for scales sizes between 2–35 km. The data suggests temporal fluctuations (of up to 10%) in the spectral exponent on a time scale of a few tens of minutes. The observed structure functions at different solar distances do not show any evidence for an inner scale; the upper limits are 1 km at 2R and 4 km at 13R . These upper limits are in conflict with earlier determinations and may suggest a reduced inner scale during solar maximum.  相似文献   

6.
Doyle  J.G.  Keenan  F.P.  Ryans  R.S.I.  Aggarwal  K.M.  Fludra  A. 《Solar physics》1999,188(1):73-80
Using new close-coupling excitation rates for the C-like ion Siix, density-diagnostic ratios based on Siix lines have been re-evaluated and applied to a sequence of CDS observations taken above a polar coronal hole. The derived electron densities are in excellent agreement with previous values of Neestimated from the N-like ion Siviii for another coronal hole. The confirmed trend is for a fall-off of one order of magnitude within the first 0.3 Rabove the limb. These densities are well fitted with an analytic formula for the density profile out to at least 8 R, by which stage the electron density has fallen to 4×103 cm–3, from 1.5×108 cm–3at 1.0 R.  相似文献   

7.
The analysis of a homogeneous sample of 108 Abell clusters has led to an average peculiar velocity for the center of mass motion of these clusters of 610±750 km s–1. From this result, an upper limit for the average mass of the Abell clusters of (1.6±2.4)×1015 M was obtained under the assumption that the peculiar motion is due to the excess of neighbours with respect to an uniform background. A lower limit of (2.42.9) x 1014 h -10.4 M was derived if one assumes that the peculiar velocity results from the mutual acceleration with the nearest neighbour.  相似文献   

8.
High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 109 M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN.  相似文献   

9.
It is suggested that the minimum mass of a star at the time of its formation is approximately 0.01M . Making use of this fact and the stellar mass functionF(M) M –, it is found that the hidden mass (or the missing mass) in the solar neighborhood may be explained by the presence of a large number of invisible stars of very low mass (0.01M M<0.07M ).  相似文献   

10.
By analysing a sample of 158 globular clusters belonging to the galaxy M 31 or Andromeda Nebula (AN) in the framework of a spherically symmetric model with constant circular velocity a value of 260 ± 40 kms–1 for this quantity is obtained. It is also found that the number density of AN globulars roughly decreases as the cube of the distance to the centre with a cutoff radius of about 40 kpc. The implied AN mass within this cutoff is about 0.6 TM (1 TM = 1012 M ). Bearing in mind the model limitations this mass is rather an upper limit. The present results suggest 1.5 as a probable value for the mass ratio of AN to the Milky Way unless their massive dark coronae are significantly different in size.The velocity distribution of AN globulars seems to be close to isotropic.  相似文献   

11.
A classical nova model was evolved through a complete cycle, i.e. accretion leading to cutburst, mass loss and again accretion, ending in another outburst, by means of an implicit Lagrangian hydrodynamic code, which included diffusion (concentration, pressure and thermal terms), as well as an extensive nuclear reactions network between 28 isotopes of C, N, O, F, Ne, Na, Mg and Al. The initial model was a 1.25 M C–O white dwarf (WD) and the accretion rate assumed was 10–11 M/yr. For more details of this calculation, see Prialnik (1986).The accreted matter was assumed to have normal composition (X=0.70, Z=0.03). Nevertheless, due to diffusion and convection, a significant amount of core material was mixed into the accreted matter, raising Z by a factor of 10. The model's evolution closely resembled that of a fast nova eruption, with a peak bolometric luminosity of 2.9×105 L, a time of decline by 3m of 25 days, an ejected mass of 6.5×10–6 M and a maximum velocity of 3800 km/sec.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables, Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.  相似文献   

12.
The results of a numerical investigation of the hydrostatic carbon burning in a degenerate carbon core withM=1.4M are presented. Convective heat transfer has been taken into account according to the mixing length formalism. It is shown that for small convection the effective (10–3) computational results are in agreement with the assumption of a hydrostatic evolution of the core. At 10–2 the burning times in successive mass zones become less than the hydrodynamic time for the core. In this case carbon burning starts with a rapidly propagating thermal instability. The connection between the convective and neutrino mechanisms of burning propagation is discussed.  相似文献   

13.
The published photometric and spectroscopic data of the symbiotic binary V 1329 Cyg are interpreted. It is shown, that V 1329 Cyg is an eclipsing binary with an elliptical orbit orbit (e=0.28). The cooler component fills up the Roche-lobe at periastron. A model of moving gaseous structures in the system is proposed and their influence on the radial velocity curve is shown. The following characteristics of the system are derived: the cooler component is an M6 giant with mass 7.9M , radius 339R and luminosityM bol=–5.42, the hot component is a white dwarf surrounded by an accretion disk. The mean distance between the components is 842R and in periastron it decreases to 605R .  相似文献   

14.
Within the cosmological standard models of the Universe, we inquire the 2-fluid radiation hydrodynamics during and before the recombination era. If we neglect all nonlinearities with exception of those contained in the coupling term between the two fluids via the degree of ionization, there exists a strong feedback mechanism on the instable modes which prevents them from growing if their relative amplitudes of the density contrast have values in the order of 10–1–10–2. The non-linear equations are numerically solved by adiabatic elimination technique used usually in self-organization problems. The effect depends very on the redshift z and become maximum atz1350. It depends also on the masses involved for the rangeM>1011 M . The lowest limits in the amplitudes (10–2) are imposed on the largest masses (1017 M ). In the range 106M/M 1011, the effect is independent of the mass.  相似文献   

15.
Internal models have been obtained for uniformly rotating synchronous close binary systems using a modified double approximation scheme. We have considered primaries of 10M , 5M , and 2M with mass ratios of 0.0 to 1.0 in steps of 0.1, and some results are given for a 1M primary with a mass ratio of 1.0. A maximum luminosity reduction of 2.3% was found for a 10M primary with a mass ratio of 1.0 and 7.7% for a mass ratio of 0.0. The corresponding values for 5M are 2.0% and 7.0%, and for 2M they are 1.6% and 5.3%, respectively. These values were not found to be sensitive to small changes in composition. The maximum equatorial velocity varies from 399 km s–1 for 2M to 567 km s–1 for 10M when the mass ratio is zero, but these velocities decrease by 200–300 km s–1 if the mass ratio is unity. The effect of gravity darkening on the apparent position of the primary in the theoretical H-R diagram was investigated. It was determined that an unresolved close binary of unit mass ratio can lie up to 0.9 magnitudes (depending on inclination) above the main sequence, whereas if the effects of distortion are ignored this number is at most 0.75 magnitudes. There seems to be some observational support for the larger value. Two models of the secondaries are given and their dimensions are compared with their critical Roche lobes.  相似文献   

16.
C12 stars in the range 1.04–1.55M are evolved to simulate the core evolution of the possible precursors of planetary nebulae. The nuclear shell burning in stars above 1.2M advances to within about 0.2M of the surface, where the intense radiation interacts with the surface matter and causes mass loss. Comparison between our theoretical results and observations suggests that this may be a mechanism by which planetary nebulae are formed.Presented at the Trieste Colloquium on Mass Loss from Stars, September 12–16, 1968.  相似文献   

17.
Egil Leer 《Solar physics》1974,35(2):467-480
A one-fluid model of the solar atmosphere is considered. The corona is heated by waves propagating out from the Sun, and profiles for temperature, flow speed and number density are obtained. For a relatively quiet Sun the inwards heat flux in the inner corona is constant in T 5–6 × 105 K and the temperature maximum is reached for r — R = 0.4 — 0.5 R where R is the solar radius. The number density in the inner corona decreases with an increasing particle flux.  相似文献   

18.
The study of supernova (SN) models with slow energy pumping is continued. At maximum luminosity the main characteristics of a SN are shown to be independent of the initial structure of the model (Table I, Figure 1). However, they depend on the massM e of the envelope, and on the intensity of energy pumpingL , with an increase ofM e leading qualitatively to the same changes in the SN parameters as a decrease inL (Table I, Figures 2 and 3). A simple relationship connecting the important SN parameters is obtained (Equation (6)). From the inflection of the color indexB-V curve, the possibility of deriving the characteristic time of energy pumping with intensityL 1044 erg s–1 is pointed out. The comparison of the extragalactic type I SN observations with the results of calculations leads to the estimate ofM e 0.3–0.7M.An investigation of the galactic type I SN remnants is carried out (Table III). The estimate ofM e 0.2–0.3M is obtained for the remnants of supernovae SN 1006, SN 1572, and SN 1604. It completely fits the results for the extragalactic type I SNs. The total initial mass of SN 1604 presupernova was shown to be at least about 7M .It was established that the Crab nebula resulted from the outburst of a peculiar SN. The unique properties of such SNs, including SN 1054, are due to the low intensity of energy pumping (L 1042 erg s–1). The mass of the envelope of the Crab nebula is evaluated to beM e 0.7M . SN 1054 was shown to have m max v =–4 m . 0 at maximum luminosity.  相似文献   

19.
Observations are presented of emission line resonance polarization in Fe xiii 10747 at the total solar eclipse of 12 November 1966. Useful data, with angular resolution 15, describe three quadrants of the corona from 1.08 R to a maximum of 1.6 R . The direction of the electric vector of observed polarization is perpendicular to the solar limb, to the limits of accuracy of measurement, in at least 74% of all cases. Departures in the other points are consistent with the magnetic depolarization expected from the non-radial fields of streamers. Polarizations observed range from near zero at the limb to 80 % and higher at 1.6 R . Averaged polarization is highest in non-streamer regions, where above 1.2 R it suggests pure radiative excitation of the 10747 line. Below 1.2 R , and in a dense streamer, the polarization is significantly depressed, indicating dominant collisional excitation of the line wherever the electron density exceeds 50 × 106 cm–3.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

20.
RecentUBV photometry of the RS CVn binary CF Tuc is discussed and analysed. If we combine the results with previously published spectroscopy we find radii of 1.63R for the hotter (6000 K) and 3.11R for the cooler (4500 K) component; both stars having a mass of about 1.3M . The distance to the system is put at 86±15 pc.Though the photometric data is incomplete in the coverage of some regions out of the minima, there is no significant evidence of the wave-type distortions — a known hallmark of RS CVn stars — and the data can be modeled by a standard eclipsing binary system in which the statistical test of goodness-of-fit (2) produces quite acceptable values for reasonable estimates of observational accuracy (0.01 mag). We, therefore, have no need to postulate any additional photometric complications, and feel entitled to some confidence in the reliability of the derived parameter set.  相似文献   

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