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1.
We develop an automatic, computer controlled procedure to select and to analyze the Network Bright Points (NBPs) on solar images. These have been obtained at the Sac Peak Vacuum Tower Telescope by means of the Universal Birefringent Filter and Zeiss H filters, tuned, respectively, along the profiles of the H, Mg-b1, Na-D2, and H lines.A structure is identified as an NBP if at the wavelength H- 1.5 A its maximum intensity is greater than I + 3 and its area is greater than 1.5 arc sec2 at I + 1.5, where I is the mean value and the standard deviation of the intensity distribution on the image. Each detected NBP is then searched and confirmed in all the remaining 31 images at different wavelengths.For each NBP several parameters are measured (position, area, mean and maximum contrast, Dopplergram velocity, compactness, and so on) and some identification constraints are applied.The statistical analysis of the various parameter distributions, for NBPs present within an active region and its surroundings, shows that two types of NBPs can be identified according to the value of their mean contrast C min the H- 1.5 Å image (C m 0.1 type I, C m> 0.1 type II). The type I NBPs (all occurring on the boundaries of the supergranular network) appear to be much more frequent (180/26) than the type II ones.The size A of type I NBPs is less than 1.0 arc sec for H/H wings but of the order of 1.2 arc sec for Na-D2 and Mg-bl. The mean contrast C m is around the value of 10% along the Na-D2 and Mg-bl profiles and of 20% along the H/H wings.The C m - A scatter diagrams show, for the photospheric radiation (h < 100 km), a narrow range of variability for C min correspondence with a wide range for A. For radiation orginated at higher levels (h > 200 km), the C m- A scatter diagrams seem to indicate, even if with a large variance, that the highest C m's tend to correspond to the highest A values.The mean Doppler shift is close to zero for Na-D2 and Mg-bl lines but negative (downward motion) for H and H lines.The type II NBPs tends to be preferentially located in the neighbourhood of small, compact sunspots and their detectability is almost constant through all the 4 studied line profiles. No conclusions can be derived on the mean size, contrast and Doppler shift values because their distributions are too dispersed. The only positive information is that its C m- A scatter diagram, in H and H wings, indicates a wide range of variability for C m in correspondence with very narrow range of variability for A.  相似文献   

2.
The equivalent widths of the oxygen lines at 7774 and 8446 and of H (and some H) have been measured for 22 early-type, emission-line stars. A strong correlation between H and 8446 intensities has been found, although there is no such correlation between H and 7774. This confirms the probability that Bowen's mechanism is operative (the neutral oxygen 33 D state is overpopulated because the excitation energy of Ly- nearly coincides with that of theOi 1025 line). The possibility of using 8446 and H equivalent widths for a comparison of oxygen to hydrogen abundances in these stars is discussed.  相似文献   

3.
The stars in the Main Sequence are seen as a hierarchy of objects with different massesM and effective dynamical radiiR eff=R/ given by the stellar radii and the coefficients for the inner structure of the stars.As seen in a previous work (Paper I), during the lifetime in the Main SequenceR eff(t) remains a near invariant when compared to the variation in the time ofR(t) and (t).With such an effectiveR eff one obtains the amounts of actionA c(M), the effective densities eff(M)=(M)3(M), the densities of action and of energy (or mean presures in the stellar interior)a c(M),e c(M), and the potential energiesE p(M).The amounts of action areA cM k withk1.87 for the M stars,k5/3 for the KGF stars, andk1.83 for the A and earlier stars, representing very simples conditions for the other dynamical parameters. For instancek5/3 means a near invariant effective density eff for the KGF stars, while for such stars the mean densities and coefficients present the strongest variations with masses (M)M –1.81, (M)M0.6.The cases for the M stars (e c(M)M –1) and for the A and earlier stars (betweena c(M)=constant and eff(M)M –1) and also discussed. These conditions for the earlier stars also represent reasonable mean values for the whole stellar hierarchy in the range of masses 0.2M M25M .With all this, one can build dynamical HR diagrams withA c(M), Ep(M), eff M –p , etc., whose characteristics are analogous to these in the photometrical HR diagram. A comparison is made betweenA c(M) from the models here and the HR diagram with the best known stars of luminosity classes IV, V, and white dwarfs.The comparison of the potential energiesE p(M)M –p according to the stellar models used here and the observed frequency function (MM –q (number of stars in a given interval of masses) from different authors suggests the possibility that the productE p(M)(M) is a constant, but this must be confirmed with further studies of the function (M) and its fine structure.There are analogies between the formulation used here for the stellar hierarchy and other physical processes, for instance, in modified forms of the Kolmogorov law of turbulence and in the formulation used for the hierarchy of molecular clouds in gravitational equilibrium. Besides, the function of actionA c(M) for the stars has analogous properties to the relations of angular momenta and massesJ(M) for different types of objects. The cosmological implications of all this are discussed.  相似文献   

4.
, . N/E, E r, (E r)=1. , (, ) . .  相似文献   

5.
In the external layers of supermassive stars and thermal sources of X-ray radiation electron scattering contributes more to the opacity than free-free process. Therefore, the thermal radiation spectrum of supermassive stars must greatly differ from Planckian. The approximate formulae obtained for the radiation spectra are applicable to any objects with a predominant role of electron scattering in the opacity and power dependence of plasma temperature and density on geometrical depth of the layers.In thermal radiation sources with power dependence of plasma temperature on depth of the layer the formation of power radiation spectraF(v)v – with >0 with >0 is possible. Such spectra can imitate the presence of non-thermal radiation mechanisms. This effect takes place also in the case of small optical depth on the Thomson scattering. Possibly, this effect is of interest for the theories of X-ray sources and X-ray solar flares.This case was considered also in the final version of the paper (Felten and Rees, 1972).  相似文献   

6.
H emission objects were searched for, using the objective-prismSchmidt plates in a 36 deg2 sky area covering the Cepheus OB3 association.Hundred and eight emission stars have been found, 68 of which are newfindings to our knowledge. The properties of the IRAS point sourcesidentified with H emission stars indicate that most of theH emission stars are T Tauri stars or related objects. Hemission stars associated with IRAS sources and those unassociated havedifferent distributions, suggesting an age sequence among them.Altogether, they show a ring- or shell-like surface distribution, whichalmost coincides with that of heated dusts, and these distributionsappear to be encompassed by an HI shell.  相似文献   

7.
A model of a first generation intermediate star of 5M , with Z=0 has been considered. The model is at an advanced stage of its evolution and has a double shell burning. It burns helium in the inner shell, and hydrogen, via CNO cycle, in the outer shell. =(log/log) T and T =(log/logT) were computed allowing for the oscillations of the relative mass abundance of the reagents in nuclear reactions. Including =(log/log) T and =(log/logT) of mean molecular weight and the effect of the oscillations of abundances due to nuclear reactions, stability was studied. Contrary to the results of the static calculations, we found that instability due to the excitation mechanism provided by the high temperature sensitivity of energy generation rate propagates up to the surface. Thus the model in question was found to be unstable against radial adiabatic pulsations, in its fundamental mode.  相似文献   

8.
The time transformation dt/ds=r is studied in detail and numerically stablized differential equations are obtained for =1,2, and 3/2. The case =1 corresponds to Baumgarte's results.  相似文献   

9.
The results of the observations to search gamma-ray sources with the energy greater than 2×1012 eV, which were made in Crimean Astrophysical Observatory during the years 1969–73 are presented. A technique of the detection of the EAS Cerenkov flashes was used.The quality of the data obtained is analysed. The criteria for the selection of the data free from meteorological variations are considered.It was shown that two objects, namely, Cyg X-3 and Cas -1, may be the sources of high-energy gamma quanta. It is probable that the object with the coordinates =05h15m, =+1° is the source of gamma-rays as well. An unidentified object Cas -1 is variable: gamma-ray flux was observed twice — in Sepember–October 1971 and in December 1972. It is possible that the flux from Cyg X-3 has a period of 4.8 hr.
I I , I I , - >2.1012 . I . I , I I, I ., - -1 Cyg -3- -I . , =0515 ·=+1° -.I -1 I: I J I- - 1971 1972 . Cyg -3, , - T=4.8 .
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10.
The flare of 11 November, 1980, 1725 UT occurred in a magnetically complex region. It was preceded by some ten minutes by a gradual flare originating over the magnetic inversion line, close to a small sunspot. This seems to have triggered the main flare (at 70 000 km distance) which originated between a large sunspot and the inversion line. The main flare started at 172320 UT with a slight enhancement of hard X-rays (E > 30 keV) accompanied by the formation of a dark loop between two H bright ribbons. In 3–8 keV X-rays a southward expansion started at the same time, with - 500 km s –1. At the same time a surge-like expansion started. It was observable slightly later in H, with southward velocities of 200 km s–1. The dark H loop dissolved at 1724 UT at which time several impulsive phenomena started such as a complex of hard X-ray bursts localized in a small area. At the end of the impulsive phase at 172540 UT, a coronal explosion occurred directed southward with an initial expansion velocity of 1800 km s–1, decreasing in 40 s to 500 km s–1.Now at Fokker Aircraft Industries, Schiphol, The Netherlands.  相似文献   

11.
, . : , . , . . ( ) . . . HZ Her=Her X1, . . , . , ., hv 15–30 . , . Sco X1 .  相似文献   

12.
The assumption of a linearly expanding universe for the JBD-cosmological equations generates a set of solutions for the barotropic equations of statep= (=const.). These solutions turn out to be valid for closed space-except in the casep= which is for open space. The gravitational constant which is inversely proportional to the scalar field increases with time if >–1/3 and decreases for <–1/3. No solution exists for =1/3. The Brans-Dicke parameter is negative if <–1/3.  相似文献   

13.
Analytic structure of high-density steady isothermal spheres is discussed using the TOV equation of hydrostatic equilibrium which satisfies an equation of state of the kind:P = K g , = g c 2.Approximate analytical solutions to the Tolman-Oppenheimer-Volkoff (TOV) equations of hydrostatic equilibrium in (, ), (,U) and (u, v) phase planes in concise and simple form useful for short computer programmes or on small calculator, have been given. In Figures 1, 2, and 3, respectively, we display the qualitative behaviours of the ratio of gas density g to the central density gc , g / gc ; pressureP to the gc ,P/ gc ; and the metric componente –, for three representative general relativistic (GR) isothermal configurations =0.1, 0.2, and 0.3. Figure 4 shows the solution curve (, ) for =0.1, 0.2, and 0.3 (=0 represents the classical (Newtonian) curve). Numerical values of physical quantitiesv (=4r 2 P *(r)), in steps ofu (=M(r)/r)=0.03, and the mass functionU, in steps of =0.2 (dimensionless radial distance), are given, respectively, in Tables I and II. Other interesting features of the configurations, such as ratio of gravitational radius 2GM/c 2 to the coordinate radiusR, mass distributionM(r)/M, pressure (or density) distributionP/P c , binding energy (B.E.), etc., have also been incorporated in the text. It has further been shown that velocity of sound inside the configurations is always less than the velocity of light.Part of the work done at Azerbaijan State University, Baku, U.S.S.R., and Mosul University, Mosul, Iraq, 1985-1986  相似文献   

14.
We investigate the near-ultraviolet high-resolution LWR spectra of the stars Cas, And, Tau, Gem, Cru, Boo, and Peg, obtained with the aid of the International Ultraviolet Explorer Satellite. We have given here a list of the strongest and most prevalent emission lines in the near-ultraviolet spectra of Boo, KlIIIp, and Peg, M2.5II-III which have the same luminosity class and different spectral type. The near-ultraviolet continuum flux measurements and integrated emission line fluxes of these stars for the 2500–3200 Å region are presented in order to compare the variations in the appearance of the near-ultraviolet flux distribution with the temperature structure of their chromospheres for K and M giant stars. We also discuss differences between observed and calculated fluxes found from the Planck function.  相似文献   

15.
The present observational status of the Sct stars, Dor stars and roAp stars is discussed. The Sct stars are the most intensively observed of the three groups, but it has become clear that there are severe problems in extracting asteroseismic information from them. Dozens of frequencies are observed, but hundreds of frequencies are predicted from the models; unique matches of observation and theory still elude us. The Sct stars are observationally complex – some recent `best case' campaigns are discussed. It is possible that substantial observational advances for Sct stars may need to await upcoming satellite missions. New Dor stars are beingdiscovered frequently, and new behaviour is being found for them. They constitutean observationally young field. Their pulsational frequency range is being expanded, their position in the HR diagram is becoming better known (but is yet to be fully constrained), and the possibility exists of hybrid Dor – Sct stars that have greatasteroseismic promise, although it is clear such stars are rare, if they do exist. It has been observationally challenging to extract more than a fewfrequencies for any Dor star so far. Exciting spectroscopic discoveries of new behaviour in roAp stars promise unprecedented information about the structure of the peculiar atmospheres ofthose stars – pulsation amplitude and phase in 3D, magnetic field structurein 3D, abundance stratification in 3D, realistic T- for the most peculiarstars – as well as entirely new information about the interaction of pulsation,rotation and magnetic fields. Recent theoretical work has led to new understandingof the previously inexplicable frequency spacing of HR 1217 with new Whole Earth Telescope observations supporting this theory. An `improved oblique pulsator model' has been developed in which the pulsationaxis is not the magnetic axis; this model has passed several observationaltests and new ones are being devised to examine it further.  相似文献   

16.
The H observations of a selected sample of bright Be stars are presented. The available infrared observations at K band (2.2 m) of these stars have been used to find the infrared excess emission. The analysis of the combined data show thatL H, the luminosity of the H emission line, is proportional toL IR, the luminosity of the infrared excess emission. The linear correlation betweenL IR andL H shows that both the infrared excess and the H line originate in a common region. It is also detected that the infrared excess emission is produced throughout the whole envelope whereas the H is emitted in some defined region of the circumstellar (CS) envelope.  相似文献   

17.
Light-element abundances are compiled for six peculiar A stars (3 CenA, 2 CVn, HR 1732,v For, Cnc, and 112 Her) with Heilines very weak for their colours. The abundances are interpreted on the theory that peculiar A stars were once secondaries in binary systems in which the primaries exploded as type II supernovae. During the explosions of the primaries, protons were accelerated to high energies (>20 MeV) in shock waves at the secondaries, and spallation of He, C, N, and O occurred. This was followed by the arrival of heavier elements from the primaries. Abundances on 2 CVn, HR 1732, andv For were subsequently modified by surface nuclear reactions involving protons and -particles accelerated to lower energies (10 MeV), probably by magnetic fields. Successive (, ) reactions formed Si28 from Ne20, and (p, ) reactions acting on A40 and Ca40 may have contributed to the excesses of Cl observed on 2 CVn and HR 1732. These proposals have interesting implications with regard to the relative abundances of the iron-peak elements found on peculiar A stars and in the Solar System.  相似文献   

18.
Periodic orbits of stars in axisymmetrical nearly spherical stellar systems have been investigated. Generating orbits have been found among periodic ones relating to the spherically-symmetrical field. The linear approximation appears to be insufficient for constructing periodic trajectories. Possible variants of the generating periodic solutions have been found, which give rise to disturbed periodic orbits in the second approximation.
, . - . , . , .
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19.
Evolutionary tracks of 0.9M , 0.7M and 0.6M models for Population II stars have been computed in the post-red giant phase. The stars are initially composed of a helium core containing a mass fraction equal to 0.9 and of a hydrogen-rich envelope. They represent hypothetical remnants of stars after substantial mass loss in previous evolutionary phases or/and at the helium flash.u 0,9M , 0,7M 0,6M . , 90% , . , .Riassunto È stata calcolata per modelli di stelle di 0,9M , 0,7M e 0,6M di Popolazione II l'evoluzione successiva allo stadio di gigante rossa. Inizialmente i modelli constano di un nucleo di elio contenente il 90% della massa totale e di un inviluppo idrogenico. Essi possono interpretarsi come i resti di stelle che abbiano perso una frazione di massa considerevole in fasi evolutive precedenti, o all'innesco violento dell'elio al centro.  相似文献   

20.
Ayres  Thomas R. 《Solar physics》2000,193(1-2):273-297
The solar–stellar connection bridges the daytime and nighttime communities; an essential link between the singular, but detailed, views of our Sun, and the broad, but coarse, glimpses of the distant stars. One area in particular – magnetic activity – has profited greatly from the two way traffic in ideas. In that spirit, I present an evolutionary context for coronal activity, focusing on the very different circumstances of low-mass main-sequence stars like the Sun, compared with more massive stars. The former are active mainly very early in their lives, whereas the latter become coronal only near the end of theirs, during the brief incursion into the cool half of the Hertzsprung–Russell diagram as yellow, then red, giants. I describe tools at the disposal of the stellar astronomer; especially spectroscopy in the ultraviolet and X-ray bands where coronae leave their most obvious imprints. I compare HST STIS spectra of solar-type dwarfs – Dor (F7 V), an active coronal source, and Cen A (G2 V), near twin of the Sun – to the SOHO SUMER UV solar atlas. I also compare the STIS line profiles of the active coronal dwarf to the corresponding features in the mixed activity hybrid chromosphere bright giant TrA (K2 II) and the archetype non-coronal red giant Arcturus ( Boo; K2 III). The latter shows dramatic evidence for a cool absorber in its outer atmosphere that is extinguishing the hot lines (like Siiv 1393 and Nv 1238) below about 1500 Å; the corona of the red giant seems to lie beneath its extended chromosphere, rather than outside as in the Sun. I present an early taste of the moderate resolution spectra we can expect from the recently launched Chandra X-ray Observatory (CXO), and contemporaneous STIS high resolution UV measurements of the CXO calibration star Capella ( Aur; G8 III + G1 III). Last, I describe preliminary results from a May 1999 observing campaign involving SOHO SUMER, TRACE, and the Kitt Peak Infrared Imaging Spectrometer (IRIS). The purpose was to explore the dynamics of the quiet solar atmosphere through the key magnetic transition zone that separates the kinetically dominated deep photosphere from the magnetically dominated coronal regime. Linking spatially and temporally resolved solar phenomena to properties of the average line shapes (widths, asymmetries, intensity ratios, and Doppler shifts) is a crucial step in carrying physical insights from the solar setting to the realm of the distant stars.  相似文献   

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