A search for soft X-ray emission from stellar sources

With the soft X-ray detector (0.2–0.284 keV) aboard the Astronomical Netherlands Satellite (ANS) we have searched for X-ray emission from hot star coronae and peculiar stars. On Sirius ( CMa) and Capella ( Aur) X-ray emission has been measured at 6 and 5 level, respectively, above background. In all other cases the search revealed no evidence for soft X-ray emission. Upper limits to the luminosities of about 25 star coronae (main-sequence stars, (sub)giants, and supergiants) and of 4 peculiar stars ( Sco, Lyr, P Cyg, and Car) have been obtained.Paper presented at the COSPAR/IAU Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Sur les solutions Lagrangiennes et euleriennes du probleme generalise des trois corps en axes absolus

Résumé Le présent travail est une continuation d'un autre, publié plus tôt (Doubochine, 1970). On montre ici, que les propriétés des mouvements Lagrangiens et Euleriens établies en mécanique céleste classique sont vraies aussi dans les cas plus généraux, envisagés dans le travail indiqué. On montre de plus, que les trajectoires des points en ces mouvements en axes absolus sont les spirales infinies s'enroulant sur les surfaces des cylindres curvilignes infinis.

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-- , (, 1970). , , , , , , , . , , , , .

     

Поле излучения в полубесконечной атмосфере, содержащей источники энергии

, , , , . , , . , , - - ( , ..). - .     

Chromospheric variability in late-type dwarfs from high-resolution spectra of Caii H

Precise photometric observations of stars in the double cluster h and Persei reveal a large spread in the colours and magnitudes of the upper Main-Sequence; half of the stars are variables that are Be stars or related stars. The reported age difference between both clusters is found to be spurious. Rotation apparently affects both the intrinsic and the observed colours of the early-type stars in h and Persei. This result questions the validity of photometric calibrations that heavily rely on h and Persei or similar clusters.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

F stars: Evidence for ‘two-dimensional’ age-metallicity relation and a new light on the enrichment history of the solar neighbourhood

From theuvby photometry and proper motions for about 5500 nearby F stars we have found the following: (i) F stars, taken in narrow ranges of metallicity, show at [Fe/H]<0 rather distinct cut-off in their distribution along the Main Sequence (MS) at the blue side, which is suggested to be an indication for the MS turn-off in stellar groups of fixed metallicity; (ii) the corresponding turn-off age from theoretical isochrones strongly correlates with the mean peculiar velocity of the turn-off stars; (iii) the sub-groups of stars of different colours have essentially the same mean peculiar velocity at low metallicity, but at high metallicity the velocities of the red subgroups are much larger than those of the blue ones. We argue that these properties of F stars lead to a two-dimensional age-metallicity relation with the following main features: (i) a very large spread of metal abundance for old stars, (ii) narrowing of the metallicity range toward younger ages, (iii) increase of mean metallicity toward younger ages. This AMR seems to require a major revision of current models of the chemical evolution of the Galaxy: it suggests that the spatial distribution of metal abundance in the interstellar medium was initially highly inhomogeneous, the inhomogeneities being smoothed out and the mean metallicity being increased as the time went on.We also find an evidence for the evolution of the gaseous matter, from which the open clusters are formed, to be somehow decoupled from the evolution of the overall ISM.     

Narrow-band photometry of Wolf-Rayet stars and planetary nebulae

We present observational data in the (16)(9)(25)-photometric system for 11 Wolf-Rayet stars and 7 planetary nebulae. The results show anomalous (16)(9)-indices for these emission objects. Six W-R stars show possible variations in the strength of the HeII line at 6560 Å, perhaps none in the strength of the HeI line at 10830 Å. In spite of these misconstrued (16) and (9)-indices, most WC stars are separated from WN stars in the (16)(9)-array; and PN, in this diagram lie far apart from all kind of stellar objects. The results, yielded by the (25)-index, indicate that the HeI and HeII lines at 10830 Å and 10124 Å, respectively, are probably well suited for photometric examination in W-R stars, PN and other peculiar objects.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Повевхное магнитосферное течение С силяными разрывами

=qm . . ¶, I . — , ¶, 5. , . : , , . =ah 4. . . , -, ( ). .     

Horizontal-branch star models

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.     

О механззме оптического, рентгеновского и гамма-излучения пульсара в краБе

, , . , . ( , , ), - qqi . - ; , - . , , .     

An Improved Method of Photometric Mode Identification: Applications to Slowly Pulsating B, β Cephei, δ Scuti and γ Doradus Stars

We present an improved version of the method of photometric mode identification based upon the inclusion of non-adiabatic eigenfunctions determined in the stellar atmosphere, according to the formalism recently proposed by Dupret et al. (2002).We apply our method to Cephei, Slowly Pulsating B, Scuti and Doradus stars. Besides identifying the degree of the pulsatingstars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on the metallicity for Cephei and SPBs, the characteristics of the superficial convection zone for Scuti and Doradus starsand the limb-darkening law.     

On the stability of small quasiperiodic motions in the hamiltonian systems

Orbital stability of quasiperiodic motions in the many dimensional autonomic hamiltonian systems is considered. Studied motions are supposed to be not far from equilibrium, the number of their basic frequencies may be not equal to the number of degrees of freedom, and the procedure of their construction is supposed to be converged. The stability problem is solved in the strict nonlinear mode.Obtained results are used in the stability investigation of small plane motions near the lagrangian solutions of the three-dimensional circular restricted three-body problem. The values of parameters for which the plane motions are unstable have been found.

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εлектроны космических лучей радиогало галактики

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Слектры релятивистских эиектронов и изиучения, формируемьЫе комптоновским рассеянием лри отличном от нуля потоке

. , , . , ( ) . ( =2) ( ) .     

Некоторые асимптотические решения в ограниченной задаче трех тел

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Some asymptotic solutions in the restricted problem of three bodies by L. G. Lukjanov.

Some particular solutions of the plane restricted problem of three bodies in the form of Liapunov's series are obtained. These solutions asymptotically approach the Lagrange solutions. Convergence is proved.

     

Оπорная селенодезическая система координат по гелиометрическим наБлюдениям луны В казани

, 1969–1975 .., 32 . , .     

Структура и эволюция Сверхмассивных вращающихся магнитных политроп

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The structure of rotating magnetic polytropes is considered in Roche approximation. Investigation of the influence of poloidal as well as toroidal magnetic fields on the conditions of the beginning of matter outflow due to rotational instability is carried out. The influence of the turbulent convection and twisting of magnetic force-lines on the time of smoothing of differential rotation is considered. The estimate of the magneto-turbulence energy generated by differential rotation is presented. Both maximum possible energy output and duration of the quasi-statical evolution phase up to the appearance of hydrodynamic instability due to the effects of general relativity are calculated for supermassive magnetic polytropes of index three with uniform or differential rotation. The radius-mass relation is obtained for supermassive differentially-rotating magnetic polytropes referring to the longest part of the quasi-statistical evolution stage; some consequences are pointed out, including the period-luminosity relation.The evolution of the considered models of supermassive rotating magnetic polytropes with different character of rotation and different geometry of a magnetic field is discussed.The results obtained are summarized in the last section.

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English translation will appear in the next issue ofAstrophys. Space Sci.

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Receipt delayed by postal strike in Great Britain     

Околозвездньiе облака поданньiм ультрафиолетовьiх спектров свезл

, ii (2000–3000 Å) i . , i . i (. 2). i i i i + ( 7–10). ii (. 13). ii i i (, 2400 Å) (. 14 15). i i i , iu , i (. 1). i i ii i i . .     

Имп␣льсное γ-излучение нейтронных, коллапсирующих qiх qi qsверхновых qzвезд

qp qz : (1) -, qi , (2) - (R=0.01–0.1R ) (3) - . qs. (1) - 0.1 10^–4 cm ^–2, . - . (2) 10⁸ . . 10^42–43 , (25 ). 10% - (0.1 ). , , , , , . . (3) , , - . . (2×10⁴¹ ) (10²¹ ). - 10³⁸–10³⁹ , 0.25 . , , qq . - , , .

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The following three mechanisms of generation of gamma-ray bursts at advanced phases of stellar evolution are considered; (1) gamma-ray bursts as a result of absorption of neutrino propagating through the envelope of a collapsing star, (2) gamma-ray burst due to thermal radiation of external layers of a compact star (R=0.01–0.1R ) heated by powerful shock wave, and (3) gamma-ray burst as a consequence of possible ejection of matter from neutron star at some active phases of its evolution. In the case (1) the gamma-ray flux at the top of the Earth's atmosphere is about 10^–4 (0.1 MeV photons) cm^–2, if a collapsing star is at Galactic distance (10 kpc). It is considerably less than observed one. The observations of such gamma-bursts however would be an important supplement to the direct detection of neutrino radiation from collapsing stars. In the case (2) external layers of a star are heated up to 10⁸ K. As a result we have a short pulse of thermal radiation with total energy of the order of 10^42–43 erg. The main fraction of the radiation is in the X-ray ( 25 keV), about 10% of total energy being radiated in gamma-ray ( 0.1 MeV). The energy of such a burst is sufficient for explaining observed gamma-bursts provided the supernova outburst probably takes place in our Galaxy and as a result we have some trouble with explanation of observed frequency and spectra of gammabursts. In the case (3) ejection from neutron star of chemically nonequilibrium matter results in the intensive gamma-radiation in consequence of superheavy nuclei fission followed by beta-decays and radiative captures of free neutrons. The ejection of matter from neutron stars may be connected with observed jumps of pulsar's periods. The total ejected mass ( 10²¹ g) can be evaluated from increase of kinetic energy ( 2×10⁴¹ erg.) of Crab nebula filaments. The resulting theoretical energy of gammabursts is of the order of 10^38–39 erg. It is in accordance with observations provided the mean distance of gamma-ray sources is about 0.25 kpc. Contrary to the supernova-outburst mechanism in this case we have probably no troubles with frequency and spectra of gamma-bursts. Among the three mechanisms considered above ejection of matter from neutron stars seems to be a more suitable one for explanation of observations.

     

О наблю дениях вспышек звезд в инфракрасных лучах

(Kilyachkoet al., 1978) , . l ( I II). (Kilyachkoet al., 1978) : (1) 800 Å , , UV Cet. EV Lac; (2) UV Cet EV Lac 8000 Å , ; (3) 8000 Å . — MO-KS; (4) 1–3 m.     

Variability of Circumstellar Emission from Dust Envelopes Around Carbon Stars

The main constituents of the dust, produced around late-type carbon stars, are thought to be carbon and silicon carbide (SiC), although their exact nature is not yet well established. This subject has been addressed by several authors and good fits of a large number of IRAS sources (chosen among the carbon stars exhibiting the SiC feature at about 11.3 m) were obtained. In this work we use the same procedure on a limited number of objects, of the same type, taking into account the variability of such sources and the changes induced in their IR spectra. For this purpose, the chosen stars have been observed with a spectral resolution higher than that available for the IRAS data (/ 50), using the CGS3 instrument of the UKIRT telescope, both in the low ( / 160) and in the high ( / 500) resolution configuration. The results are discussed and some preliminary conclusions are drawn.