Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Is V899 Herculis an unsolved quadruple system containing double close binary stars?
Orbital period variation of the W UMa-type eclipsing binary, V899Herculis, discovered by the Hipparcos satellite was investigated basedon all available photoelectric and CCD times of light minimum. It isdiscovered that the orbital period of the binary shows a cyclic changewith an amplitude of 0.0117 days. The cyclic period change can beexplained as the light-travel time orbit of a tertiary component in thesystem, which is in agreement with the spectroscopic result obtained byLu et al. [Lu, W., Rucinski, S.M., Ogloza, W., 2001. AJ 122, 402] whofound that the system, of which V899 Herculis is a fainter component(B), is a triple, even quadruple and with the photometric resultobtained by Özdemir et al. [Özdemir, S., Demircan, O., Erdem,A., Cicek, C., Bulut, I., Soydugan, E., Soydugan, F., 2002. A&A 387,240] who reported a large amount of third light (L3 ˜0.68) of the system. The third body (A) rotates around the eclipsingpair in a period of 3.7 years. Lu et al. [Lu, W., Rucinski, S.M.,Ogloza, W., 2001. AJ 122, 402] reported that the tertiary component isF5-type main-sequence star. However, the present analysis shows that themass of the third component is no less than 2.8 Mȯ,which is larger than the mass of an F5-type main-sequence starsuggesting that the tertiary component may be a non-eclipsing closebinary. Therefore, the system may be a possible unsolved quadruplesystem containing double close binary stars. It is a good astrophysicallaboratory to study the formation and evolution of binary and multiplesystem. The timescale for the formation of the G-type overcontact binary(V899 Herculis) via AML should be shorter than the main-sequence time ofan F5-type star.
| 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.
| Masses and angular momenta of contact binary stars
Results are presented on component masses and system angular momenta forover 100 low-temperature contact binaries. It is found that thesecondary components in close binary systems are very similar in mass.Our observational evidence strongly supports the argument that theevolutionary process goes from near-contact binaries to A-type contactbinaries, without any need of mass loss from the system. Furthermore,the evolutionary direction of A-type into W-type systems with asimultaneous mass and angular momentum loss is also discussed. Theopposite direction of evolution seems to be unlikely, since it requiresan increase of the total mass and the angular momentum of the system.
| The dynamical stability of W Ursae Majoris-type systems
Theoretical study indicates that a contact binary system would mergeinto a rapidly rotating single star due to tidal instability when thespin angular momentum of the system is more than a third of its orbitalangular momentum. Assuming that W Ursae Majoris (W UMa) contact binarysystems rigorously comply with the Roche geometry and the dynamicalstability limit is at a contact degree of about 70 per cent, we obtainthat W UMa systems might suffer Darwin's instability when their massratios are in a region of about 0.076-0.078 and merge into thefast-rotating stars. This suggests that the W UMa systems with massratio q <= 0.076 cannot be observed. Meanwhile, we find that theobserved W UMa systems with a mass ratio of about 0.077, correspondingto a contact degree of about 86 per cent would suffer tidal instabilityand merge into the single fast-rotating stars. This suggests that thedynamical stability limit for the observed W UMa systems is higher thanthe theoretical value, implying that the observed systems have probablysuffered the loss of angular momentum due to gravitational waveradiation (GR) or magnetic stellar wind (MSW).
| 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.
| 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.
| Photoelectric Minima of Eclipsing Binaries
Not Available
| 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.
| Some Photoelectric Minima of Eclipsing Binary Stars
Not Available
| Times of Minima for Neglected Eclipsing Binaries in 2004
Times of minima obtained during 2004 for a number of neglected eclipsingbinaries are presented.
| 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
| A photometric study of the recently discovered eclipsing binary V776 Cassiopei
Photoelectric UBV light curves of the recently discovered eclipsingbinary V776 Cas were studied for the first time toderive the physical parameters of the system. The light curves wereobtained at the TÜBİTAK National Observatory (TUG) during 8-9October 2002. Due to the proximity of the visual companion the lightcurves were contaminated by the third light effect which has arelatively small impact on the system parameters estimation. This effectdominantly changes only the degree of overcontact and orbit inclination.The solutions made by using Djuraševic's inverse-problem methoddescribe the V776 Cas system as a high overcontactconfiguration (fover~41% without, and 55% and 58% with twodifferent values of the third light effect - L3=0.091 andL3=0.136) with a relatively small temperature differencesbetween the components. Because of the large difference in masses of thecomponents (q=mc/mh=0.13) these solutions suggesta significant mass and energy transfer from the hotter - more massiveprimary onto the cooler - less massive secondary through the connectingneck of the common envelope. The obtained orbital inclination(i~53∘.9 without, and i~55∘ andi~56∘ with two different values of the third lighteffect - L3=0.091 and L3=0.136) explains thecharacteristic shape of the light curves with a relatively smallamplitude which is due to partial eclipses of the components in both ofthe photometric minima.
| 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.
| 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.
| A photometric study of the recently discovered eclipsing binary V899 Herculis
The radial velocity and UBV light curves of V899 Her as found in theliterature were studied for the first time to obtain the orbitalparameters and geometry of the system. The solutions obtained by usingthe Wilson-Devinney code reveal an over-contact system with a fill-outfactor of 23.7%. This solution is only possible with a large amount ofthird light (L3~0.68) which confirms the spectroscopic resultobtained by Lu et al. (\cite{lu}) who reported that the system of whichV899 Her is a fainter component is triple, or even quadruple. Thedistance of the system found by using absolute parameters is comparablewith the Hipparcos result.
| Radial Velocity Studies of Close Binary Stars. IV.
Radial velocity measurements and sine-curve fits to the orbital velocityvariations are presented for the fourth set of 10 close binary systems:44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph,Anon Psc (GSC 8-324), and HT Vir. All systems are double-linedspectroscopic binaries, with only two of them not being contact systems(SW Lyn and GSC 8-324) and five (FI Boo, V2150 Cyg, V899 Her, EX Leo,and V2377 Oph) being the recent photometric discoveries of the Hipparcosproject. Five of the binaries are triple-lined systems (44 Boo, V899Her, VZ Lib, SW Lyn, and HT Vir). Three (or possibly four) companions inthe triple-lined systems show radial velocity changes during the span ofour observations, suggesting that these are in fact quadruple systems.Several of the studied systems are prime candidates for combined lightand radial velocity synthesis solutions. Based on the data obtained atthe David Dunlap Observatory, University of Toronto.
| The First Ground-Based PhotometricObservations of V899 Her
Not Available
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Herkules |
| Rektaszcenzió: | 16h35m01.96s |
| Deklináció: | +33°12'47.8" |
| Vizuális fényesség: | 7.886 |
| Távolság: | 124.069 parszek |
| RA sajátmozgás: | 38 |
| Dec sajátmozgás: | -40.1 |
| B-T magnitude: | 8.412 |
| V-T magnitude: | 7.93 |
Katalógusok és elnevezések:
|
INHABITED SKY
