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1.
TheSpectrophotometric Catalogue of the Sternberg State Astronomical Institute contains 875 stars; 8 of them are standards.TheCatalogue of the Fessenkov Astrophysical Institute consists of 1123 stars. The data on the spectral energy distribution for about a half of these stars are published.A comparison of energy distribution data for 473 common stars in the range 3200–7600 Å was made. Calibration of Alpha Lyr from Hayes (1985) was used for all the stars of both catalogues.In difference of the previous publications the comparison includes much more stars and energy distribution data were corrected where necessary. The agreement between the corrected data is better than in the case of the earlier comparison. Reductional factors due to the instrumental effects were taken into account for 275 stars from theSternberg Institute Catalogue. These factors are in the limits 1.01–1.04 and their mean value is 1.03.The reductional factors for the stars from theFessenkov Institute Catalague are much larger: 1.06–1.12 with the mean 1.06–1.07. In this case the reduction factors were taken into account for all the stars of the catalogue except the brightest ones withV<2.0.The values of the differences between spectral energy distribution data for common stars in dependence of magnitude, spectral type, and wavelength are presented.  相似文献   

2.
It is shown that during contact eclipsing binaries evolution under the influence of stellar wind, magnetic stellar wind and with matter transfer by gas flow, in binary stellar systems there may take place a process of star merger (low mass stars) within 105–107 yr and a fast increase of distance between stars of massive binaries. W UMa-type stars are a finite evolutionary stage of very close and low mass binary pairs. As for contact systems of early spectral types (CE-systems), they are more varied in evolution.  相似文献   

3.
G. Alecian 《Astrophysics》1995,38(4):294-299
A short review on diffusion processes in atmospheres of stars is given. The diffusion model and its application for interpretation of spectral features of Am and Ap stars are described schematically. The building of abundance stratification and the case of calcium in Am stars are described briefly.Published in Astrofizika, Vol. 38, No. 4, pp. 533–542, October–December, 1995.  相似文献   

4.
The H emission is searched for 67 spectroscopic binaries of the spectral types B0–B9 and of the orbital period 1–1000 days. Among them the H emission is detected in 13 stars with various intensity. The results of this inspection are presented. When combined with the previous data, our results show that the Be-star frequency in spectroscopic binaries along the orbital periods exhibits a sharp maximum in the period range 100–300 days, and that the stars of strong H emission concentrate in the same period range.  相似文献   

5.
A survey of emission-line stars was carried out in the CMa star formation region, based on spectral observations with the Kiso Schmidt telescope. In total, 128 emission-line stars were detected, ranging fromV=6 to 15, and the majority are found withV between 11 and 14. A comparison with the existing catalogues shows that some emission-line stars are common with ours, while some exhibit no detectable emission line on our plates, suggesting the variability of emission-line strength. The two-colour (U–B, B–V) diagram is also shown for the detected stars.Paper presented at the IAU Third-Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.On leave from the Bosscha Observatory, Institute of Technology Bandung, Indonesia.  相似文献   

6.
The spectral subtypes and luminosity classes are given for 15 comparatively faint M stars found on plates of the First Byurakan Spectroscopic Survey. Two of them are classified as M dwarfs. Most of the new M stars are probably Mirids.Translated from Astrofizika, Vol. 37, No. 1, pp. 73–82, January–February, 1994.  相似文献   

7.
Spatial density parameters ofz-distribution and luminosity dispersion in the HR diagram for nine stellar spectral groups (A-K III, A-G IV, A-F V) were determined. It was shown that all stars considered can be divided into two subsets according to their scale-height . For the younger stars is of the order of 100–150 pc, and for older ones of 300–400 pc. The accuracy of the parameters derived was evaluated with use of numerical simulations. We found that for subgiants and dwarfs the relative error in the local density makes 10 to 15%, and for giants it is a little higher (20 to 25%). For other parameters the typical error is of the order of 20–30%.  相似文献   

8.
Preliminary measurements of rotational velocities of pre-main sequence stars indicate that stars evolving into early F or late A spectral type have rotational velocities which are consistent with present Main-Sequence stars of similar spectral type. Stars evolving into G type, however, have rotational velocities which are as high as 100 km s–1 and would reach the Main Sequence with velocities of 150 km s–1. This requires the presence of a strong stellar wind to carry off considerable angular momentum in order to slow down the Sun to its present low rotational velocity.Paper presented at the Conference on Protostars and Planets, held at the Planetary Science Institute, University of Arizona, Tucson, Arizona, between January 3 and 7, 1978.  相似文献   

9.
A new list of reference stars for differential meridian observations is proposed. The list inclides 905 stars of stellar magnitude 7–9 with 3–5 stars in each area of 252 compact extragalactic radio sources, available for high precision measurements in radio and optics.  相似文献   

10.
Far-ultraviolet photometric data for early type stars in Orion, in the 1050–1180 and 1230–1350 Å wavelength ranges, were obtained in an Aerobee rocket flight on 30 January 1969. The results corrected for interstellar extinction, appear in good agreement with model atmospheres in the case of main-sequence stars. Bright giant and supergiant stars, however, appear to be up to one magnitude fainter than main-sequence stars of similar spectral class in the 1050–1180 Å range.The present results indicate that the detectors used in a previous flight were lower in sensitivity than was thought, so the results from that flight have been corrected using the present data for stars in common with the previous flight.The far-ultraviolet extinction law for Orionis is shown to be abnormal, with the observed extinction far less than predicted on the basis of ultraviolet extinction measurements of other stars, and the observedE(B-V).  相似文献   

11.
A system for obtaining high-precision radial velocities of solar-type stars by spectral cross-correlation has been established at the Mt John University Observatory. The use of a fibre-feed between the telescope and échelle spectrograph has enabled a stability such that we can achieve a precision of better than 50 m s–1.A programme of radial-velocity observations of 29 southern solar-type stars—of which two are IAU radial velocity standard stars—is under way with the prime objective being a search for low-mass companions to the stars. Ten further IAU radial-velocity standard stars are also being monitored.  相似文献   

12.
We demonstrate here the possibility of using very low dispersion (10000 Å mm–1) slitless spectroscopy of stars for a fairly accurate spectral classification. The technique is shown to be very useful in studies of star clusters.  相似文献   

13.
We studied the spectra of 24 flare stars of the Pleiades cluster region obtained on the 2.6m telescope of the Byurakan observatory in the years 1986–1989. From the spectral indices of titanium oxide (TiO) and other chemical elements of the stars investigated we determined their spectral classes and luminosities (absolute visual stellar magnitudes). The agreement of these moduli of the stars with the distance modulus of the Pleiades cluster confirms that 21 of them belong to the cluster. Only three of them (FSP 169, FSP 377, and FSP 435) are possibly not members of the cluster. This indicates that the flare activity of a star is a reliable criterion for its membership in a nearby stellar system (cluster or association).Translated fromAstrofizika, Vol. 37, No. 4, 1994.  相似文献   

14.
It is shown that the observed variety in macrostructures of continuous spectra in the ultraviolet (2000–3000 Å) of hot stars is a result of the presence of circumstellar clouds around such stars. A method for calculations of synthetic spectra, originating as a result of passage of central star photospheric radiation through its own circumstellar cloud, is developed. It introduces a new idea of spectral class for circumstellar cloud, and a recommended method for its determination depending from the spectral class of central star and cloud's parameters (Figure 2). The results of calculations of synthetic spectra for the four combinations of system star+cloud are presented (Figures 7-10). The strongest influence of circumstellar cloud in ultraviolet is discovered on A-class stars (Figure 13). Graphic relations are introduced for determination of cloud power by observed parameters of synthetic spectra (Figures 14 and 15).It establishes an important fact for an understanding of the nature of circumstellar clouds and processes occurring in them, according to which the selective absorption in such clouds stimulatesresonance lines only, the largest number of which lies in the ultraviolet in the region of 2100–2600 Å (Figure 1). An absence of visible signs of the effect of circumstellar clouds on continuous spectra of stars in visual region can be explained by a very small number of resonance lines in this region.Lastly, the possibility of determination of physical and geometric parameters of circumstellar clouds from stellar continuous spectra in the ultraviolet is analysed.  相似文献   

15.
We have derived the real and imaginary indices of refraction for 10 phyllosilicate minerals—montmorillonite, beidellite, nontronite, hectorite, saponite, illite, illite–smectite (60/40 interlayered) kaolinite, halloysite, and serpentine—from 100–2000 cm−1 (5–100 μm) at 2 cm−1 spectral sampling using classical Lorentz–Lorenz dispersion theory. We present the real and imaginary indices and the oscillator parameters with which they were modeled. Use of these optical constants will aid in the modeling of thermal infrared spectra of planets, asteroids, interplanetary and interstellar dust, and protoplanetary disks around nearby stars.  相似文献   

16.
All hot stars are observed to have X-ray emission: O stars haveL X /L bol 10–7, whilst B stars' emission drops off with spectral subtype. Dynamical instability of OB star radiatively driven winds generates shocked regions which may be responsible for the bulk of the X-rays observed. The wind-compressed disc model of Bjorkman & Cassinelli (1993) presents another site for X-ray emission. The disc formed in the equatorial plane of a fast rotating Be star from equatorward drift of wind streamlines is confined on both sides by a shock which may also generate X-rays. As the X-ray emission originating from the wind shocking is ubiquitous amongst B and Be stars then the wind-compressed disc model näively predicts that Be stars should generate more X-rays than B stars of equivalent spectral subtype.The X-ray emission from the shocks confining compression discs has been calculated and compared to a limited set of observations. The excess X-ray emission from the Be star disc shocks is found to be undetectable over the inherent wind shocking emission.  相似文献   

17.
The bright stellar content for fifteen binary star clusters and their adjoining fields in the Large Magellanic Cloud (LMC) were studied here. Film copies of plates taken with the 1.2 U.K. Schmidt telescope were used for deriving the spectral types of the stars in the studied regions. All classified stars are brighter thanV=17.5 mag and situated in large areas around each pair and in a neighbouring field. Seven of the pairs, the brightest and most populous are young clusters (located mainly at the north part of the parent galaxy). The derived distributions of spectral types of their stars give strong evidence that each pair consists of similar stellar content with ages 0.6–8×107 yr.Eight more binary star clusters were studied as well, selected among the rest of the binaries in the LMC. It is found that their stars were faint for our limit of detection so the poor statistics did not allow a comparison among the two cluster members of each pair. However the bright limit of their stars implies ages >6×108 yr. Considering that these objects were randomly selected it is unlikely that all are projected pairs. So it seems that binarity in star clusters is a phenomenon (favourable in the LMC) which did not happen only once in the life of this galaxy.  相似文献   

18.
In a total of 181 photographic spectrograms, obtained at the Manuel Foster Observatory of the Catholic University in Santiago (Chile), the equivalent widths of the absorption lines HeI 4471 and MgII 4481 have been determined for 10 selected southern Be stars and 4 normal B-type stars. The mean equivalent widths of each star are compared to published mean values from largers samples of B stars. On the average, Be stars coincide with normal B-type stars in their equivalent width. However, a striking difference between rapidly and slowly rotating stars in their line ratios (HeI/MgII) was found, which is probably an artifact due to a systematic misclassification of spectral types of rapidly rotating B stars (v sini>200 km s–1). Six of the ten Be stars show evidence for variability in HeI and/or MgII with time-scales shorter than a few days and amplitudes up to a factor 2 in equivalent width. Line variability occurs in the entire range of projected rotation velocity (70 km s–1<v sini<350 km s–1), but seems to be restricted to spectral types B2-B4. In addition, variations at longer time-scales (years) were observed in two cases. Three of the variable stars (HR 4074, HR 4537, and Ara) present correlated variations in both lines, one ( Cen) anti-correlated variability. We interpret our results in terms of nonradial pulsations and stress the importance to study the HeI/MgII lines and their variability in a larger sample of Be, Bn, and normal B stars, including archival material in order to follow-up line variability for several decades in the past.  相似文献   

19.
The results of electrophotometric observations of the 19 components of six Trapezium multiple star systems with primary stars of class M are presented. The Strömgren spectral intervals are determined. Of the 19 components, 18 belong to interval 3 ("late group").Translated fromAstrofizika, Vol. 39, No. 3, pp. 407–410, July–September, 1996.  相似文献   

20.
Here we present the results of 1.3 millimetre continuum measurements for intermediatemass stars in the Chamaeleon system of dark clouds. The detected millimetre radiation is most probably thermal emission from cold circumstellar dust grains. The measured millimetre fluxes are combined with infrared observations to model the broad-band spectral energy distribution (SED). In this way the parameters of the emission regions are determined.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

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