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B.R.N.O. Times of minima
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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.
| Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple systems.
| Times of Maxima for Selected Delta Scuti Stars
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| Radial Velocity Studies of Close Binary Stars. X.
Radial velocity measurements and sine-curve fits to orbital velocityvariations are presented for the ninth set of 10 close binary systems:V395 And, HS Aqr, V449 Aur, FP Boo, SW Lac, KS Peg, IW Per, V592 Per, TUUMi, and FO Vir. The first three are very close, possibly detached,early-type binaries, and all three require further investigation.Particularly interesting is V395 And, whose spectral type is as early asB7/8 for a 0.685 day orbit binary. KS Peg and IW Per are single-linebinaries, with the former probably hosting a very low mass star. We havedetected a low-mass secondary in an important semidetached system, FOVir, at q=0.125+/-0.005. The contact binary FP Boo is also a very smallmass ratio system, q=0.106+/-0.005. The other contact binaries in thisgroup are V592 Per, TU UMi, and the well-known SW Lac. V592 Per and TUUMi have bright tertiary companions; for these binaries, and for V395And, we used a novel technique of arranging the broadening functionsinto a two-dimensional image in phase. The case of TU UMi turned out tobe intractable even using this approach, and we have not been able toderive a firm radial velocity orbit for this binary. Three systems ofthis group were observed spectroscopically before: HS Aqr, SW Lac, andKS Peg.Based on the data obtained at the David Dunlap Observatory, Universityof Toronto.
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| TU UMi: A Contact Binary in a Triple System
We present 4 CCD times of minimum of the contact binary TU UMi. Linearephemeris for the orbit is given. Spectra have revealed that it belongsto a triple system.
| Is TU UMi a W UMa-type system
TU UMi is catalogued as a delta Scuti star, it was discovered byHipparcos (ESA 1997). Analysis of photometric observations carriedthrough the years 2001 and 2002 is presented. We obtain one onlyfrequency that it is in agreement with it listed in the HipparcosCatalogue. Using the derived uvbybeta indices, the most relevantphysical parameters of TU UMi are also determined. We suggest that thisstar is a W UMa-type eclipsing binary system.
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| True and Possible Contact Binaries in the Hipparcos Catalogue
A comprehensive list of contact binaries included in the HIPPARCOScatalogue is given.
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