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Comparative statistics and origin of triple and quadruple stars
The statistics of catalogued quadruple stars consisting of two binaries(hierarchy 2 + 2), is studied in comparison with triple stars, withrespective sample sizes of 81 and 724. Seven representative quadruplesystems are discussed in greater detail. The main conclusions are asfollows. (i) Quadruple systems of ? Lyr type with similar massesand inner periods are common, in 42 per cent of the sample the outermass ratio is above 0.5 and the inner periods differ by less than 10times. (ii) The distributions of the inner periods in triple andquadruple stars are similar and bimodal. The inner mass ratios do notcorrelate with the inner periods. (iii) The statistics of outer periodsand mass ratios in triples and quadruples are different. The medianouter mass ratio in triples is 0.39 independently of the outer period,which has a smooth distribution. In contrast, the outer periods of 25per cent quadruples concentrate in the narrow range from 10 to 100yr,the outer mass ratios of these tight quadruples are above 0.6 and theirtwo inner periods are similar to each other. (iv) The outer and innermass ratios in triple and quadruple stars are not mutually correlated.In 13 per cent of quadruples both inner mass ratios are above 0.85(double twins). (v) The inner and outer orbital angular momenta andperiods in triple and quadruple systems with inner periods above 30dshow some correlation, the ratio of outer-to-inner periods is mostlycomprised between 5 and 104. In the systems with small periodratios the directions of the orbital spins are correlated, while in thesystems with large ratios they are not. The properties of multiple starsdo not correspond to the products of dynamical decay of small clusters,hence the N-body dynamics is not the dominant process of theirformation. On the other hand, rotationally driven (cascade)fragmentation possibly followed by migration of inner and/or outerorbits to shorter periods is a promising scenario to explain the originof triple and quadruple stars.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| The long-period companions of multiple stars tend to have moderate eccentricities
We examined the statistics of an angle gamma between the radius vectorof a visual companion of a multiple star and the vector of its apparentrelative motion in the system. Its distribution f(gamma ) is related tothe orbital eccentricity distribution in the investigated sample. Wefound that for the wide physical subsystems of the 174 objects from theMultiple Star Catalogue f(gamma ) is bell-shaped. The Monte-Carlosimulations have shown that our f(gamma ) corresponds to the populationof the moderate-eccentricity orbits and is not compatible with thelinear distribution f(e)=2e which follows from stellar dynamics andseems to hold for wide binaries. This points to the absence of highlyelongated orbits among the outer subsystems of multiple stars. Theconstraint of dynamical stability of triple systems is not sufficient toexplain the ``rounded-off'' outer orbits; instead, we speculate that itcan result from the angular momentum exchange in multiple systems duringtheir early evolution.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Precise equatorial coordinates of double and multiple systems - an astronomical support to the HIPPARCOS mission
Results are presented on determinations of precise positions (to theaccuracy required for their possible inclusion in the Hipparcos InputCatalogue) of 623 double and multiple stars (126 of them newlydiscovered) from the measurement of 39 plates taken at the ESO and theAstronomical Observatory of Torino, obtained between 1984 and 1987. Thetable includes the index number, the name of the discoverer, binarycomponent according to the designation by the Catalogue de Composantesd'etoiles Doubles et Multiples (CCDM), the magnitude of the componentsas given in the CCDM, epoch of observation, right ascension referred tothe J2000.0 equinox, declination, position angle referred to the J2000.0North Pole, angular separation, and DM and ADS numbers.
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| Сазвежђа: | Хидра |
| Ректацензија: | 14h18m12.39s |
| Deклинација: | -27°31'17.3" |
| Apparent магнитуда: | 9.234 |
| Даљина: | 121.655 parsecs |
| Proper motion RA: | -33.8 |
| Proper motion Dec: | -5.3 |
| B-T magnitude: | 9.858 |
| V-T magnitude: | 9.286 |
Каталог и designations:
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