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B.R.N.O. Contributions #34
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| The N2K Consortium. VII. Atmospheric Parameters of 1907 Metal-rich Stars: Finding Planet-Search Targets
We report high-precision atmospheric parameters for 1907 stars in theN2K low-resolution spectroscopic survey, designed to identify metal-richFGK dwarfs likely to harbor detectable planets. Of these stars, 284 arein the ideal temperature range for planet searches,Teff<=6000 K, and have a 10% or greater probability ofhosting planets based on their metallicities. The stars in thelow-resolution spectroscopic survey should eventually yield >60 newplanets, including 8-9 hot Jupiters. Short-period planets have alreadybeen discovered orbiting the survey targets HIP 14810 and HD 149143.
| Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation
Orbital angular momentum (OAM, Jo), systemic mass (M) andorbital period (P) distributions of chromospherically active binaries(CAB) and W Ursae Majoris (W UMa) systems were investigated. Thediagrams of and logJo-logM were formed from 119 CAB and 102 WUMa stars. The logJo-logM diagram is found to be mostmeaningful in demonstrating dynamical evolution of binary star orbits. Aslightly curved borderline (contact border) separating the detached andthe contact systems was discovered on the logJo-logM diagram.Since the orbital size (a) and period (P) of binaries are determined bytheir current Jo, M and mass ratio, q, the rates of OAM loss(dlogJo/dt) and mass loss (dlogM/dt) are primary parametersto determine the direction and the speed of the dynamical evolution. Adetached system becomes a contact system if its own dynamical evolutionenables it to pass the contact border on the logJo-logMdiagram. The evolution of q for a mass-losing detached system is unknownunless the mass-loss rate for each component is known. Assuming q isconstant in the first approximation and using the mean decreasing ratesof Jo and M from the kinematical ages of CAB stars, it hasbeen predicted that 11, 23 and 39 per cent of current CAB stars wouldtransform to W UMa systems if their nuclear evolution permits them tolive 2, 4 and 6 Gyr, respectively.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Contact Binaries with Additional Components. II. A Spectroscopic Search for Faint Tertiaries
It is unclear how very close binary stars form, given that during thepre-main-sequence phase the component stars would have been inside eachother. One hypothesis is that they formed farther apart but were broughtin closer after formation by gravitational interaction with a thirdmember of the system. If so, all close binaries should be members oftriple (or higher order) systems. As a test of this prediction, wepresent a search for the signature of third components in archivalspectra of close binaries. In our sample of 75 objects, 23 show evidencefor the presence of a third component, down to a detection limit oftertiary flux contributions of about 0.8% at 5200 Å (consideringonly contact and semidetached binaries, we find 20 out of 66). In ahomogeneous subset of 59 contact binaries, we are fairly confident thatthe 15 tertiaries we have detected are all tertiaries present with massratios 0.28<~M3/M12<~0.75 and implied outerperiods P<~106 days. We find that if the frequency oftertiaries were the same as that of binary companions to solar-typestars, one would expect to detect about 12 tertiaries. In contrast, ifall contact binaries were in triple systems, one would expect about 20.Thus, our results are not conclusive but are sufficiently suggestive towarrant further studies.
| 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.
| Luminosity function of contact binaries based on the All Sky Automated Survey (ASAS)
The luminosity function for contact binary stars of the W UMa type isevaluated on the basis of the All Sky Automated Survey (ASAS)photometric project covering all stars south of δ=+ 28° withina magnitude range 8 < V < 13. Lack of colour indices enforced alimitation to 3374 systems with P < 0.562 d (i.e. 73 per cent of allsystems with P < 1 d) where a simplified MV(logP)calibration could be used. The spatial density relative to themain-sequence FGK stars of 0.2 per cent, as established previously fromthe Hipparcos sample to V= 7.5, is confirmed. While the numbers ofcontact binaries in the ASAS are large and thus the statisticaluncertainties small, derivation of the luminosity function required acorrection for missed systems with small amplitudes and with orbitalperiods longer than 0.562 d; the correction, by a factor of 3, carriesan uncertainty of about 30 per cent.
| 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.
| Times of Minima for Neglected Eclipsing Binaries in 2005
Times of minima obtained at Rolling Hills Observatory during 2005 for anumber of neglected eclipsing binaries are presented.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| New Minima of Selected Eclipsing Close Binaries
We present 180 CCD and photoelectric times of minima of selected closeeclipsing binaries.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Deep, Low Mass Ratio Overcontact Binary Systems. III. CU Tauri and TV Muscae
New CCD photometric light curves in the B and V bands of the neglected WUMa-type eclipsing variable star CU Tauri are presented. The O'Connelleffect in the V light curve obtained in 2001 by Yang and Liu was aboutΔV=+0.015, but it vanished in our 2004 observations. Thevariations in the levels of both minima were seen. Our two epochs oflight minimum and others compiled from the literature were used for theperiod study. It is shown that the types of some eclipse times wereincorrect and the values of the period obtained by previousinvestigators were aliases that prevented formation of a plausible O-Ccurve. A new linear ephemeris was derived, and it is discovered that theorbital period of CU Tau shows a continuous decrease at a rate ofdP/dt=-1.81×10-6 days yr-1. The presentsymmetric light curves were solved with the 2003 version of theWilson-Devinney (W-D) code. Both our solutions and those derived by Yangand Liu reveal that CU Tau is a deep (f=50.1%+/-3.2%), low mass ratio(q=0.1770+/-0.0017) overcontact binary system.Meanwhile, the photoelectric light curves in the B, V, R, and I bands ofTV Muscae published by Hilditch and coworkers were reanalyzed with the2003 version of the W-D code. It is shown that the low mass ratio binaryturns out to be a deep overcontact system with f=74.3%+/-11.3%. A periodanalysis with all collected times of light minimum revealed acombination of a long-term period decrease(dP/dt=-2.16×10-7 days yr-1) and a possiblecyclic change with a period of 29.1 yr. The rapid long-term perioddecreases of both systems can be explained as a combination of the masstransfer from the more massive component to the less massive one and theangular momentum loss due to mass outflow from the L2 point. In thatway, the overcontact degrees of the two systems will become deeper astheir periods decrease, and finally they will evolve into a singlerapid-rotation star. However, for CU Tau, the rate of the secular perioddecrease is very large when compared with the other systems of the sametype. This suggests that the long-term period decrease may be part of along-period periodic change, which we need more data to check.
| Physical Parameters of Components in Close Binary Systems: IV
The paper presents new geometric, photometric and absolute parameters,derived from combined spectroscopic and photometric solutions, for tencontact binary systems. The analysis shows that three systems (EF Boo,GM Dra and SW Lac) are of W-type with shallow to moderate contact. Sevensystems (V417 Aql, AH Aur, YY CrB, UX Eri, DZ Psc, GR Vir and NN Vir)are of A-type in a deep contact configuration. For six systems (V417Aql, YY CrB, GM Dra, UX Eri, SW Lac and GR Vir) a spot model isintroduced to explain the O'Connell effect in their light curves. Thephotometric and geometric elements of the systems are combined with thespectroscopic data taken at David Dunlap Observatory to yield theabsolute parameters of the components.
| Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation
We study the kinematics of 129 W UMa binaries and we discuss itsimplications on the contact binary evolution. The sample is found to beheterogeneous in the velocity space. That is, kinematically younger andolder contact binaries exist in the sample. A kinematically young (0.5Gyr) subsample (moving group) is formed by selecting the systems thatsatisfy the kinematical criteria of moving groups. After removing thepossible moving group members and the systems that are known to bemembers of open clusters, the rest of the sample is called the fieldcontact binary (FCB) group. The FCB group is further divided into fourgroups according to the orbital period ranges. Then, a correlation isfound in the sense that shorter-period less-massive systems have largervelocity dispersions than the longer-period more-massive systems.Dispersions in the velocity space indicate a 5.47-Gyr kinematical agefor the FCB group. Compared with the field chromospherically activebinaries (CABs), presumably detached binary progenitors of the contactsystems, the FCB group appears to be 1.61 Gyr older. Assuming anequilibrium in the formation and destruction of CAB and W UMa systems inthe Galaxy, this age difference is treated as an empirically deducedlifetime of the contact stage. Because the kinematical ages (3.21, 3.51,7.14 and 8.89 Gyr) of the four subgroups of the FCB group are muchlonger than the 1.61-Gyr lifetime of the contact stage, the pre-contactstages of the FCB group must dominantly be producing the largedispersions. The kinematically young (0.5 Gyr) moving group covers thesame total mass, period and spectral ranges as the FCB group. However,the very young age of this group does not leave enough room forpre-contact stages, and thus it is most likely that these systems wereformed in the beginning of the main sequence or during thepre-main-sequence contraction phase, either by a fission process or mostprobably by fast spiralling in of two components in a common envelope.
| On the properties of contact binary stars
We have compiled a catalogue of light curve solutions of contact binarystars. It contains the results of 159 light curve solutions. Theproperties of contact binary stars were studied using the cataloguedata. As is well known since Lucy's (\cite{Lucy68a},b) and Mochnacki's(\cite{Mochnacki81}) studies, primary components transfer their ownenergy to the secondary star via the common envelope around the twostars. This transfer was parameterized by a transfer parameter (ratio ofthe observed and intrinsic luminosities of the primary star). We provethat this transfer parameter is a simple function of the mass andluminosity ratios. We introduced a new type of contact binary stars: Hsubtype systems which have a large mass ratio (q>0.72). These systemsshow behaviour in the luminosity ratio- transfer parameter diagram thatis very different from that of other systems and according to ourresults the energy transfer rate is less efficient in them than in othertypes of contact binary stars. We also show that different types ofcontact binaries have well defined locations on the mass ratio -luminosity ratio diagram. Several contact binary systems do not followLucy's relation (L2/L1 =(M2/M1)0.92). No strict mass ratio -luminosity ratio relation of contact binary stars exists.Tables 2 and 3 are available in electronic form athttp://www.edpsciences.org
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Key parameters of W UMa-type contact binaries discovered by HIPPARCOS
A sample of W UMa-type binaries which were discovered by the HIPPARCOSsatellite was constructed with the aid of well defined selectioncriteria described in this work. The selection process showed up thatseveral systems of which the variability types have been assigned as EBin HIPPARCOS catalogue are genuine contact binaries of W UMa-type. Thelight curves of the 64 selected systems based on HIPPARCOS photometrywere analyzed with the aid of light curve synthesis method by Rucinskiand their geometric elements (namely mass ratio q, degree of contact f,and orbital inclination i) were determined. The solutions were obtainedfor the first time for many of the systems in the sample and would be agood source for their future light curve analyses based on more precisefollow-up observations.Based on observations made with the ESA HIPPARCOSastrometry satellite.
| New Parameters of the Contact Binary Systems YY CRB and EQ Tau
The new photoelectric l U,B,V light curves of the eclipsing contactbinary systems, YY CrB and EQ Tau, are presented and used to calculatethe photometric and, together with the published spectroscopic data, theabsolute parameters of the systems. 3D models of the systems arepresented.
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 25 minima times of 12 eclipsing binaries.
| Photoelectric Minimum Times of Some Eclipsing Binary Stars
We present 15 minimum times of 8 eclipsing binaries observed in theyears from 2001 to 2003 and in 1998 only for V436 Per.
| The Hamburg/RASS Catalogue of optical identifications. Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources
We present the Hamburg/RASS Catalogue (HRC) of optical identificationsof X-ray sources at high-galactic latitude. The HRC includes all X-raysources from the ROSAT Bright Source Catalogue (RASS-BSC) with galacticlatitude |b| >=30degr and declination delta >=0degr . In thispart of the sky covering ~ 10 000 deg2 the RASS-BSC contains5341 X-ray sources. For the optical identification we used blue Schmidtprism and direct plates taken for the northern hemisphere Hamburg QuasarSurvey (HQS) which are now available in digitized form. The limitingmagnitudes are 18.5 and 20, respectively. For 82% of the selectedRASS-BSC an identification could be given. For the rest either nocounterpart was visible in the error circle or a plausibleidentification was not possible. With ~ 42% AGN represent the largestgroup of X-ray emitters, ~ 31% have a stellar counterpart, whereasgalaxies and cluster of galaxies comprise only ~ 4% and ~ 5%,respectively. In ~ 3% of the RASS-BSC sources no object was visible onour blue direct plates within 40\arcsec around the X-ray sourceposition. The catalogue is used as a source for the selection of(nearly) complete samples of the various classes of X-ray emitters.
| CCD Times of Minima of Some Eclipsing Binaries in 2002
We present CCD observations of minima of 11 eclipsing binaries.
| Catalogue of the field contact binary stars
A catalogue of 361 galactic contact binaries is presented. Listedcontact binaries are divided into five groups according to the type andquality of the available observations and parameters. For all systemsthe ephemeris for the primary minimum, minimum and maximum visualbrightness and equatorial coordinates are given. If available,photometric elements, (m1+m2)sin3i,spectral type, parallax and magnitude of the O'Connell effect are alsogiven. Photometric data for several systems are augmented by newobservations. The quality of the available data is assessed and systemsrequiring modern light-curve solutions are selected. Selectedstatistical properties of the collected data are discussed.
| The First Eclipsing Binary Observations at the Ulupinar Astrophysics Observatory
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| High-Precision UBVRI Photometry with a New 50 CM Telescope at Stará Lesná
The paper presents the experience, observations and results obtainedwith the new 50 cm photometric telescope at the StaráLesná Observatory equipped with an SBIG ST10MXE CCD camera. Thetelescope time is devoted to observations of variable stars of varioustypes. Prospects for further improvement of the instrument,observational and reduction techniques are discussed.
| New Photoelectric and CCD Minima and Updated Ephemerides of Selected Eclipsing Binaries
This report presents minima times and updated ephemerides of selectedeclipsing binaries
| Photoelectric photometry of eclipsing contact binaries: U Peg, YY CrB, OU Ser and EQ Tau
New photoelectric UBV observations of the eclipsing contact binarysystems U Peg, YY CrB, OU Ser and EQ Tau obtained from August 2000 toOctober 2001 are presented and analyzed. The (O-C) diagram of U Pegindicates a decrease of the orbital period combined with aquasi-periodic variation. In the case of EQ Tau the long-term periodchanges can be interpreted by the presence of a third body on a 50 yearorbit. The present ephemerides for the studied systems were determined.The primary minimum of OU Ser, according to the Hipparcos photometry, isfound to be the shallower one and hence the system belongs to the Wsubgroup. The photometric elements determined from our light curvescombined with published spectroscopic elements yielded the absoluteparameters of the systems.
| UBV Photometry of The Newly Found Active Star YY Coronae Borealis
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Corona Boreale |
| Ascensione retta: | 15h50m32.44s |
| Declinazione: | +37°50'07.5" |
| Magnitudine apparente: | 8.696 |
| Distanza: | 88.028 parsec |
| Moto proprio RA: | -73.2 |
| Moto proprio Dec: | 9.2 |
| B-T magnitude: | 9.413 |
| V-T magnitude: | 8.756 |
Cataloghi e designazioni:
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