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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.
| delta Scuti-type pulsation in the eclipsing and spectroscopic binary HD 172189 in the cluster IC 4756.
The binary system nature of the HD 172189 as well as the presence of thepulsating delta Scuti-type component in the system have beendiscovered. The great interest of this object lies in that threeimportant characteristics coexist: membership of the cluster IC 47456,binary and pulsation. An orbital period of 5.702 d has been found. Afrequency analysis of all the uvby out-of-primary-eclipse measurementsreveals a dominant frequency of 19.5974 c/d as well as high values inthe range of 18-20 c/d. In addition, it is located in the FOV of COROTmission, being a good candidate for its observation from space.
| Preparing the COROT Space Mission: New Variable Stars in the Galactic Anticenter Direction
The activities related to the preparation of the asteroseismic,photometric space mission COROT are described. Photoelectricobservations, wide-field CCD photometry, uvbyβ calibrations, andfurther time series have been obtained at different observatories andtelescopes. They have been planned to complete the COROT program in thedirection of the Galactic anticenter. In addition to suitableasteroseismic targets covering the different evolutionary stages betweenzero-age main sequence and terminal-age main sequence, we discoveredseveral other variable stars, both pulsating and geometric. We comparedresults on the incidence of variability in the Galactic center andanticenter directions. Physical parameters have been obtained, andevolutionary tracks fitting them have been calculated. The peculiaritiesof some individual stars are pointed out.Based on observations collected at the San Pedro Martír, SierraNevada, Teide, La Silla, Haute-Provence, and Roque de Los Muchachos(Telescopio Nazionale Galileo and Mercator telescopes) observatories.
| HD 172189: an eclipsing and spectroscopic binary with a δ Sct-type pulsating component in an open cluster
We present a study based on more than 2500 uvby-measurements collectedon HD 172189, a new eclipsing binary system with a δ Sct-typepulsating component that belongs to the open cluster IC 4756. The greatinterest of this object lies in that three important characteristicscoexist: cluster membership, binarity and pulsation. Its binarity andthe δ Sct-type pulsations of one component were detected in thecourse of several Strömgren photometric campaigns. The frequencyanalysis of all the uvby out-of-eclipse data reveals a clear frequencyof 19.5974 cd-1as well as the existence of other high valuesin the range 18-20 cd-1. We have also carried out a firstevaluation of the binary parameters and determined a value of 5.702 dfor the orbital period. An additional potential interest of HD 172189resides in its location in the field of view of the COROT mission and,therefore, this star is an excellent candidate for becoming a target forasteroseismology.
| Amendment of our method for deriving stellar membership of an open cluster
Our method for determining statistically the members of an open clusterby means of the proper motions (Missana et al.) is amended and itsvalidity is verified by applying it to the cluster IC 4756 with the datagiven by Herzog et al. (1975), adding nothing to their results. In thecomputation of the dispersion ellipses of the samples and of theChi2 for deriving the significance levels, the weights of theproper motions have been taken into account. The results obtained by thecriterion of the Chi2 and those obtained by Herzog et al. bythe criterion of the maximum likelihood of Sanders (1971) areconcordant.
| A four-color and Hbet study of the galactic cluster IC 4756.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..157S&db_key=AST
| Membership and photometry of the open cluster IC 4756
Probabilities of membership, based on relative proper motions, for 464stars in the field of IC 4756 are given. The cluster proper motiondispersion (m.e.) of 0.09 sec of arc yields 173 probable members.Photographic UBV magnitudes of 471 stars in the field are presented. Thecolor excess of IC 4756 is E(B-V) equal to 0.19 min; the apparentdistance modulus equals 8.5 min, corresponding to the true distance of400 pc. The membership probabilities of 6 blue stragglers and of thesupergiant HD 172365 (F9 Ib) are discussed.
| Untersuchung der offenen Sternhaufen IC 4665, NGC 6633, IC 4756
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Miembro de los siguientes grupos:
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Datos observacionales y astrométricos
| Constelación: | Serpiente |
| Ascensión Recta: | 18h38m37.56s |
| Declinación: | +05°27'55.4" |
| Magnitud Aparente: | 8.788 |
| Movimiento Propio en Ascensión Recta: | 1.5 |
| Movimiento Propio en Declinación: | -1.2 |
| B-T magnitude: | 9.185 |
| V-T magnitude: | 8.821 |
Catálogos y designaciones:
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