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A catalogue of close binaries located in the δ Scuti region of the Cepheid instability strip
A catalogue of close eclipsing binary systems (detached andsemidetached) with at least one of the components located in the δScuti region of the Cepheid instability strip is presented. Thepositions of the stars in the instability strip are determined by theiraccurate temperatures and luminosities. Observationally detectedbinaries (20 semidetached, four detached and one unclassified) withoscillating components were included in the catalogue as a separatetable. The primaries of the oscillating Algols tend to be located nearthe blue edge of the instability strip. Using reliable luminosities andtemperatures determined by recent photometric and spectroscopic studies,we have found that at least one or two components of 71 detached and 90semidetached systems are located in the δ Scuti region of theCepheid instability strip. In addition, 36 detached or semidetachedsystems discovered by the Hipparcos satellite were also given as aseparate list. One of their components is seen in the δ Scutiregion, according to their spectral type or B - V colours. They arepotential candidate binaries with the δ Scuti-type pulsatingcomponents which need further photometric and spectroscopic studies inbetter precision. This catalogue covers information and literaturereferences for 25 known and 197 candidate binaries with pulsatingcomponents.
| The connection between the pulsational and orbital periods for eclipsing binary systems
Considering a sample of 20 eclipsing binary systems with δ Scutitype primaries, we discovered that there is a possible relation amongthe pulsation periods of the primaries and the orbital periods of thesystems. According to this empirical relation, the longer the orbitalperiod of a binary, the longer the pulsation period of its pulsatingprimary. Among the sample, the masses of the secondaries and theseparations between the components are known for eight systems for whicha logPpuls versus logF (the gravitational pull exerted pergram of the matter on the surface of the primaries by the secondaries)diagram also verifies such an interrelation between the periods. So, asthe gravitational force applied by the secondary component onto thepulsating primary increases, its pulsation period decreases. Thedetailed physics underlying this empirical relation between the periodsneeds further confirmation, especially theoretically. However, one mustalso consider the fact that the present sample does not contain asufficiently large sample of longer period (P > 5 d) binaries.
| Detection of a classical δ Scuti star in the new eclipsing binary system HIP 7666
HIP 7666 is a variable star newly discovered during the Hipparcosmission and classified as of unknown type (ESA 1997, The Hipparcos andTycho Catalogues, ESA SP-1200). During 23 nights between July 2000 andNovember 2000, over 2300 CCD observations in the V band were obtained.These data show that the new variable is a detached eclipsing binarysystem with an orbital period of 2.37229 days. In addition, one of thecomponents undergoes very short-period oscillations with a mainpulsation frequency of 24.46 or 25.47 c/d. HIP 7666 is therefore a newmember of the rare group of detached eclipsing binary systems with aδ Scuti type component.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| UBV photometry of stars whose positions are accurately known. II
The present report on the UBV observations of stars with favorableastrometric history gives attention to stars of the BD zones lyingbetween 50 and 54 deg. These observations and their reductions wereperformed from August 1983 to August 1984, as described by Oja (1984).Results are presented as tables for both the standard stars and theprogram stars. Comparisons are conducted between the present Vmagnitudes and those of the NPZT (1982) and AGK3R (1978) catalogs.
| The improvement of the star positions of the Potsdam PZT catalog
Regular determinations of the right ascension and declination of starswith the aid of a photographic zenith tube (PZT) were begun in ageodetic-astronomical observatory of the German Democratic Republic in1972. Results obtained during the years 1972 and 1973 were used for afirst improvement of stellar positions listed in the Third Catalog(Katalog) of the 'Astronomische Gesellschaft' (Astronomical Society)AGK3. The corrections resulted in a distinct improvement of the accuracyof the positional values. However, the possibility could not be excludedthat the results were still affected by remaining errors with systematiccharacteristics. In order to eliminate the considered deficiencies, newstellar coordinate corrections were computed on the basis of aconsiderably larger data set. The new catalog containing the reviseddata has been called PZT 80, while the data obtained on the basis of thefirst observations are listed in PZT 74. The new catalog is presented inthe appendix.
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