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HL Aurigae: A pre-contact binary system with a solar-mass companion
Orbital period changes of the near-contact binary (NCB) system, HLAurigae, are analyzed based upon all the published CCD and photoelectrictimes of light minimum. It is found that the period of HL Aurigae showsa small-amplitude cyclic oscillation with a period of 6.5 years and anamplitude of 0.d0058 while it undergoes a secular decrease ata rate of dP/dt = ‑1.08 × 10‑7 days/year.The cyclic period oscillation can be interpreted either by thelight-time effect of a third body or by magnetic activity cycles of thecomponents. Since the third-body assumption is in agreement with thepresence of a large amount of third light in the system discovered by ,we think that HL Aurigae may be a true triple system. In order to deducea G2-type third companion as proposed by , the orbital inclination ofthe third body should be i′ = 40°, which is much smaller thanthat of the eclipsing pair (i = 85.°7). This suggests that the thirdcompanion is not coplanar with the eclipsing binary. This may indicatethat the solar-mass component may be captured by the eclipsing binarysystem in some previous stages of its formation and evolution. HLAurigae is a short-period NCB with a F1V-type primary and a G9V-typesecondary component and both of the components are filling or nearlyfilling their Roche lobes. As the period is decreasing, the shrinking ofthe Roche lobe will finally cause it to evolve into a contact binarysystem in the timescale of 2.1 × 106 years. Theperiod decrease may be caused by mass transfer or/and by angularmomentum loss via magnetic braking.
| Precise CCD Times of Minima of Selected Eclipsing Binaries
We present 135 precise CCD minima timings for 93 eclipsing binariesobtained at Ondrejov observatory during 2003-2004.
| 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.
| An Orbital Period Study of the W UMa-Type Binary RZ Comae Berenicis
New photoelectric and CCD photometry observations of a short-period WUMa-type binary system, RZ Com, are presented. The light curves ofBroglia (1960, Contr. Milano-Merate, 165) were symmetric in V band,while the present light curve shows a typical O'Connell effect, withMaximum I brighter than Maximum II by 0.015mag. It is found that thelight curve of the binary star has changed from W-subtype to A-subtypeaccording to Binnendijk's classification. This variation may be causedby the activity of dark spot on the primary component. Combining fournewly determined times of the light minimum with others published in theliterature, the orbital period change of the system was investigated. Asmall-amplitude oscillation (A = 0.0058 d), with a period of 44.8yr hasbeen discovered to be superimposed on a long-term period increase with arate of dP/dt = +4.12 × 10-8 d yr-1. Theperiod oscillation can be explained either by the light-time effect viathe presence of an unseen third body or by magnetic-activity cycles ofthe components. The mass ratio of RZ Com is q = 0.43. The secular periodvariation is in agreement with the conclusions of Qian (2001, MNRAS,328, 914; 2003, MNRAS, 342, 1260). This indicates that it is on theTRO-controlled stage of the evolutionary scheme proposed by Qian.
| The first CCD photometric study of the neglected W UMa-type binary PP Lacertae
The first complete charge couple device (CCD) photometric light curve inV band of the neglected W UMa-type binary star, PP Lacertae, ispresented. It is shown that the system is a complete eclipsing binaryand belongs to W type according to Binnendijk’s classificationwhere the occultation minimum is much deep than the transit one. Thelight curve is symmetric and no day-to-day variation of the light curvewas found. These properties enable good chance to determine photometricparameters of the binary system. Photometric solutions based on thecomplete light curve were derived with the 2003 version of the W D code.It is suggested that PP Lacertae is a W-type overcontact binary systemwith a mass ratio of q = 2.3000(±0.0044) and a median degree ofovercontact of f = 23.9%(±1.1%). The temperature of the lessmassive component is about 260 K higher than that of the more massiveone. Our four CCD times of light minimum, including others collectedfrom the literature, have been used for the period study. It is foundthat the period showed a small-amplitude cyclic oscillation with aperiod of 19.7 years and an amplitude of 0.d0058, which canbe explained as the light-time effect of an unseen third body.
| 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.
| Improved astrophysical parameters for the overcontact binary FG Hydrae
Photometric data on FG Hya obtained in 2002 and 2004 are presented.Three data sets show the exchange between A-type, W-type and thevariable O'Connell effects. The photometric mass ratio (q= 0.1115 +/-0.0003) derived from B and V light curves is almost the same as thespectroscopic mass ratio (qsp= 0.112 +/- 0.004). The newphotometric solutions reveal that FG Hya is a deep overcontact binarysystem (f= 85.6 +/- 1.8 per cent) with a spotted massive component. Aperiod investigation, based on all available photoelectric or CCD timesof light minimum, shows that the O-C curve of FG Hya can be explained asa combination of a secular period decrease and a cyclic variation with aperiod of 36.4yr and an amplitude of 0.0289 d. By comparing thevariation of the depth of the primary minimum with the change of thecyclic period, it is discovered that both of them may vary with the samecycle length of 36.4yr and in the same phase. The variation of the lightcurve, the spotted primary component and the connection between thecyclic period change and the depth of the primary minimum, all maysuggest that the G0-type component displays solar-type magnetic activitywith a 36.4-yr cycle length. The long-time period decrease isinterpreted by mass transfer from the more massive component to the lessmassive one or/and angular momentum loss due to mass outflow from theouter Lagrangian point.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Some Eclipsing Binary Stars
We present 70 minima times of 35 eclipsing binaries.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Light-time effect in the eclipsing binary system AM Leonis
We report four new times of minimum light and the improved ephemeris forthe well known contact binary AM Leo. The O-C diagram, constructed withall reliable timings found in the literature was analyzed and the thelight-time effect in the system was confirmed. We found a periodicity of44.82 years in the O-C residuals with an amplitude of 0.0058 day. Theperiodic curve representing the O-C values is asymmetric indicating alarge eccentricity of 0.73 of the third body orbit. The mass of thethird body is found to be 0.175 Msun for the orbitalinclination of the eclipsing pair's orbit.
| Period Changes of AO Camelopardalis and AM Leonis and Their Implications for the Presence of Tertiary Components and the Evolutionary States of the Two Overcontact Binary Systems
AO Cam and AM Leo are two short-period overcontact binary systems whosephysical properties are nearly the same. In the present paper, three CCDtimes of minimum light for AO Cam and two photoelectric eclipse timesfor AM Leo are presented. Combining the new determined eclipse timeswith others compiled from the literature, the behavior of their O-Cvariations were investigated. For AO Cam, its orbital period is revised,and it is found that the period shows a cyclic variation with a periodof 20.1 yr and an amplitude of 0.0047 days. In AM Leo, a new periodincrease has occurred recently. Two possibilities of period variations,sudden and continuous changes, are discussed. The period changes of bothsystems cannot be explained by apsidal motion, since both the primaryand the secondary eclipse times vary in the same O-C trend. Of the threemechanisms of magnetic activity cycles, internal mass motions, and thepresence of a third body, we think that the last is more plausible.Assuming that the period changes are due to third bodies revolvingaround the eclipsing pairs, the parameters of the third-component starsare determined. If it exists, the third body in AO Cam is revolving in acircular orbit, whereas that in AM Leo is revolving in an eccentricorbit (e'=0.58). No secular period changes were discovered ineither overcontact binary star, which is in agreement with the recentstatistical relation of Qian. This may suggest that AO Cam and AM Leoare in transition between the angular momentum loss-controlled and thethermal relaxation oscillation-controlled stages of the evolutionaryscheme recently proposed by Qian.
| New Light Curves and Orbital Solution for AM Leonis
New UBVRI photometry has been obtained for the W UMa eclipsing system AMLeonis. The data have been used to derive nine times of minimum and toconstruct light curves. The minimum timings show that the systemrecently had a significant period increase. Modeling of the light curvesshows AM Leo to be an overcontact system with a mass ratio of 2.51. BothRucinski & Duerbeck's absolute magnitude calibration for W UMa starsapplied to our photometry and the radial velocity curve combined withour derived parameters indicate a distance near 125 pc, larger than the77 pc from the Hipparcos parallax.
| Times of Minima for Neglected Eclipsing Binaries in 2003
Times of minima for a number of neglected eclipsing binaries arepresented.
| GR Virginis: A Deep Overcontact Binary
Orbital period variations of the low-mass ratio (q=0.122) overcontactbinary system, GR Vir, were investigated by using two new CCD times ofminimum light and other photoelectric data compiled from literatures. Itis found that the O-C residuals of GR Vir show a cyclic variation with aperiod of 19.3 yr and an amplitude of 0.0140 days while they areundergoing a long-term decrease (dP/dt=-4.32×10-7 daysyr-1). Meanwhile, the 1988 photoelectric observations fromCereda et al. were analyzed using the Wilson-Devinney method. Like somelow-mass ratio overcontact binary stars (e.g., AW UMa), GR Vir is anA-type overcontact binary with a high degree of overcontact (f=78.6%).By combining the spectroscopic solutions with the photometric elements,the absolute parameters of the system are determined as follows:M1=1.36Msolar,M2=0.17Msolar, a=2.40Rsolar,R1=1.42Rsolar,R2=0.61Rsolar,L1=2.87Lsolar, andL2=0.48Lsolar. The long-term period decrease isinterpreted as the result of mass transfer from the more massivecomponent to the less massive one in combination with the angularmomentum loss due to mass outflow from the L2 point. Theconditions in GR Vir resemble those in AW UMa. Both systems show a highdegree of overcontact, low mass ratios, and secular shrinking of theirorbits. As their orbital periods decrease, the shrinking of the innerand outer critical Roche lobes will cause the common convective envelopeto become deeper, until finally the formation of single, rapid-rotationstars is inevitable. The period oscillation may by caused either by thepresence of an unseen tertiary component (e.g., a white dwarf) or bymagnetic activity on the part of the primary component.
| 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
| Photoelectric Minima of Selected Eclipsing Binaries
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| Photoelectric Minima of Some Eclipsing Binary Stars
We present 25 minima times of 12 eclipsing binaries.
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 48 minima times of 10 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 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.
| Period and Light-Curve Changes in AP Leonis
We present a detailed study of the period and light curve of theeclipsing binary AP Leo. We have investigated the period variation ofthe system in detail using a method proposed by Kalimeris et al.(1994a,b; AAA 061.117.039, AAA 062.117.142). The orbital period of thesystem exhibits a periodic variation which contains four components withdifferent frequencies. Our result is very different from that of otherinvestigators. We compared light curves obtained by other groups, andfound that the light curve of the system has changed considerably. Basedon an analysis, we investigated the physical mechanisms which mayunderlie the variations of the period and the light curve, and obtainedsome new results. We have concluded that the rapid light variation isprobably caused by a pulsation of the common envelope, and that themechanism causing the pulsation may be mass transfer between the twocomponents, or its variation. In addition, we have found that the masstransfer and magnetic activity may simultaneously play an important rolein the variations in the orbital period and the light curve of thesystem. The paper concludes with a discussion of the evolution of thesystem.
| Period variation and spot model for the W UMa type binary TY UMa
We present the full VRI light curves and the times of minima of TY UMato provide a complete photometric solution and a long-term trend ofperiod variation. The light curves show a high degree of asymmetry (theO'Connell effect). The maxima at 0.25 phase (Max I) are 0.021, 0.015,and 0.020mag fainter than those at 0.75 phase (Max II) in V , R , and I, respectively. The period of TY UMa has varied in a sinusoidal way,superimposed on the long-term upward parabolic variation. The secularlyincreasing rate of the period is deduced as 1.83s per century (Pdot /P=5.788×10-10 dd-1 ) . The period ofsinusoidal variation is about 57.4yr. The spot model has been applied tofit the asymmetric light curves of TY UMa, to explain light variations.By changing only the spot parameters, the model light curves can fit theobserved light curves for three epochs. This indicates that thevariation of the spot location and size is the main reason for changingthe shape of light curves, including two different maxima and theinterchanging depths of occultation and transit minima.
| New Photoelectric and CCD Minima and Updated Ephemerides of Selected Eclipsing Binaries
This report presents minima times and updated ephemerides of selectedeclipsing binaries
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Das Brunner Punktesystem.
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| Period behavior of the W Ursae Majoris contact binary AH Tauri
New timing of minimum light determined from CCD observations of the WUMa type contact binary AH Tau is presented. From the present time ofminimum light and those collected from the literature, the changes inthe orbital period of the system are analyzed. The result reveals thatthe orbital period of AH Tau continuously decreased at a rate of (Deltap)/p=-1.4*E-11 from 1944 to 1976 and suddenly and sharplydecreased by about 0.33 s around 1976. After 1976 the orbital period ofthe system continually increased at a change rate of frac (Deltap)/p=1.5*E-10. A possible explanation of the changes in theorbital period of AH Tau is discussed. They may be the result ofcompound action of three mechanisms: the cyclical magnetic activity, themass loss and the radius swelling of the two components of the system.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| A CCD Photometric Study of the Contact Binary V396 Monocerotis
Complete BV light curves of the W Ursae Majoris binary V396 Mon arepresented. The present CCD photometric observations reveal that thelight curves of the system are obviously asymmetric, with the primarymaximum brighter than the secondary maximum (the ``O'Connell effect'').The light curves are analyzed by means of the latest version of theWilson-Devinney code. The results show that V396 Mon is a W-subtype WUMa contact binary with a mass ratio of 0.402. The asymmetry of thelight curves is explained by a cool spot on the secondary component. Thenature of the overluminosity of the secondary of a W UMa-type system isanalyzed. It is shown that the overluminosity of the secondary isclearly related to the mass of the primary and that, for a W UMa system,the higher the mass of the primary, the greater the overluminosity ofthe secondary. In addition, the overluminosity of the secondary is alsorelated to its own density: the lower the density of the secondary, thegreater its overluminosity.
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Observation and Astrometry data
| Constellation: | Leo |
| Right ascension: | 11h02m10.88s |
| Declination: | +09°53'42.6" |
| Apparent magnitude: | 9.34 |
| Proper motion RA: | -13.6 |
| Proper motion Dec: | -33.7 |
| B-T magnitude: | 9.965 |
| V-T magnitude: | 9.392 |
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