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Starspots
Starspots are created by local magnetic fields on the surfaces of stars,just as sunspots. Their fields are strong enough to suppress theoverturning convective motion and thus block or redirect the flow ofenergy from the stellar interior outwards to the surface andconsequently appear as locally cool and therefore dark regions againstan otherwise bright photosphere (Biermann in Astronomische Nachrichten264:361, 1938; Z Astrophysik 25:135, 1948). As such, starspots areobservable tracers of the yet unknown internal dynamo activity and allowa glimpse into the complex internal stellar magnetic field structure.Starspots also enable the precise measurement of stellar rotation whichis among the key ingredients for the expected internal magnetictopology. But whether starspots are just blown-up sunspot analogs, we donot know yet. This article is an attempt to review our current knowledgeof starspots. A comparison of a white-light image of the Sun (G2V, 5Gyr) with a Doppler image of a young solar-like star (EK Draconis;G1.5V, age 100 Myr, rotation 10 × ? Sun) and witha mean-field dynamo simulation suggests that starspots can be ofsignificantly different appearance and cannot be explained with ascaling of the solar model, even for a star of same mass and effectivetemperature. Starspots, their surface location and migration pattern,and their link with the stellar dynamo and its internal energytransport, may have far reaching impact also for our understanding oflow-mass stellar evolution and formation. Emphasis is given in thisreview to their importance as activity tracers in particular in thelight of more and more precise exoplanet detections around solar-like,and therefore likely spotted, host stars.
| An Orbital Period Investigation of the Solar-Type Overcontact Binary V700 Cygni
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| Photometry of three chromospherically active stars: V340 Gem, SAO 62042 and FI Cnc
We present a photometric study of three chromospherically active starswith long periods (V340 Gem, SAO 62042 and FI Cnc). The observationswere made at the ÇOMU Observatory in 2006 and 2007. We have madeinitial photometric analyses of V340 Gem and SAO 62042, which are newlydiscovered RS CVn type SB1 binaries, and established the photometricvariations of FI Cnc, which is a single G8III active star. Photometricrotation periods of these stars were obtained by analyzing their lightvariations. The light variations, observed over three or moreconsecutive orbital cycles, were investigated by using spot models withthe program SPOT. We also discussed the surface differential rotationcoefficient for the primary component of the SB1 binary star SAO 62042in this study, using our own photometric period together with an orbitalperiod taken from the literature.
| New absolute magnitude calibrations for W Ursa Majoris type binaries
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed.31 W UMa stars, which have the most accurate parallaxes(σπ/π<0.15) which are neither associated with aphotometric tertiary nor with evidence of a visual companion, wereselected for re-calibrating the Period-Luminosity-Color (PLC) relationof W UMa stars. Using the Lutz-Kelker (LK) bias corrected (mostprobable) parallaxes, periods ({0.26< P< 0.87}, P in days), andcolors ({0.04<(B-V)0<1.28}) of the 31 selected W UMa,the PLC relation have been revised and re-calibrated. The differencebetween the old (revised but not bias corrected) and the new (LK biascorrected) relations are almost negligible in predicting the distancesof W UMa stars up to about 100 pc. But, it increases and may becomeintolerable as distances of stars increase. Additionally, using(J-H)0 and (H-K_s)0 colors from 2MASS (Two MicronAll Sky Survey) data, a PLC relation working with infrared data wasderived. It can be used with infrared colors in the range-0.01<(J-H)0<0.58, and{-0.10<(H-K_s)0<0.18}. Despite of the fact that the2MASS data refer to single epoch observations which are not guaranteedto be taken at maximum brightness of the W UMa stars, the establishedrelation has been found surprisingly consistent and reliable inpredicting LK corrected distances of W UMa stars.
| Angular momentum and mass evolution of contact binaries
Various scenarios of contact binary evolution have been proposed in thepast, giving hints of (sometimes contradictory) evolutionary sequencesconnecting A- and W-type systems. As the components of close detachedbinaries approach each other and contact binaries are formed, followingevolutionary paths transforms them into systems of two categories:A-type and W-type. The systems evolve in a similar way but underslightly different circumstances. The mass/energy transfer rate isdifferent, leading to quite different evolutionary results. Analternative scenario of evolution in contact is presented and discussed,based on the observational data of over one hundred low-temperaturecontact binaries. It results from the observed correlations amongcontact binary physical and orbital parameters. Theoretical tracks arecomputed assuming angular momentum loss from a system via stellar wind,accompanied by mass transfer from an advanced evolutionary secondary tothe main-sequence primary. A good agreement is seen between the tracksand the observed graphs. Independently of details of the evolution incontact and a relation between A- and W-type systems, the ultimate fateof contact binaries involves the coalescence of both components into asingle fast rotating star.
| AD Cancri: A Shallow Contact Solar-Type Eclipsing Binary and Evidence for a Dwarf Third Component and a 16 Year Magnetic Cycle
CCD photometric observations of AD Cancri obtained from 2000 March 7 to2004 December 20 are presented. Variations of the light levels at theprimary minimum and both maxima are found. Uniform solutions of foursets of photometric data were derived by using the Wilson-Devinneymethod. The solutions suggest that AD Cancri is a shallow W-type contactbinary (f=8.3%+/-1.3%) with a high mass ratio of 1/q=0.770+/-0.002. Thelong-term variation of the light curve is explained by variabledark-spot models of the more massive component star with a possible 17yr cycle. Our 13 times of light minimum over 5 years, including otherscollected from the literature, have been used for the period study. Thecomplex period changes can be sorted into a long-term period increase atrate of dP/dt=+(4.94+/-0.16)×10-7 days yr-1,a 16.2 yr periodic component (A3=0.0155 days), and a verysmall amplitude period oscillation (A4=0.0051 days,P4=6.6 yr). The existence of third light may indicate thatthere is a tertiary component in the binary system. Solving thefour-band light curves of Samec & Bookmyer, it is found that thecontribution of the tertiary component to the total light of the triplesystem increases with wavelength, which suggests that it is very cooland may be a very red main-sequence star. The small-amplitude periodoscillation may be caused by the light-time effect of the cool tertiarycomponent (M3~0.41 Msolar). The 16.2 yr periodiccomponent in the orbital period and the 17 yr cyclic activity of thedark spot on the more massive component both may reveal that the moremassive component displays solar-type magnetic activity with a cyclelength of about 16 yr.
| Contact Binaries with Additional Components. III. A Search Using Adaptive Optics
We present results of the Canada-France-Hawaii Telescope adaptive optics(AO) search for companions of a homogeneous group of contact binarystars, as a contribution to our attempts to prove the hypothesis thatthese binaries require a third star to become as close as observed. Inaddition to directly discovering companions at separations of>=1″, we introduced a new method of AO image analysis utilizingdistortions of the AO diffraction ring pattern at separations of0.07″-1″. Very close companions, with separations in thelatter range, were discovered in the systems HV Aqr, OO Aql, CK Boo, XYLeo, BE Scl, and RZ Tau. More distant companions were detected in V402Aur, AO Cam, and V2082 Cyg. Our results provide a contribution to themounting evidence that the presence of close companions is a very commonphenomenon for very close binaries with orbital periods <1 day.Based on observations obtained at the Canada-France-Hawaii Telescope,which is operated by the National Research Council of Canada, theInstitut National des Sciences de l'Univers of the Centre National de laRecherche Scientifique of France, and the University of Hawaii.
| Evolution of Magnetic Flux Tubes in Convective Envelopes of Close Binary Stars
Observations of cool stars with very high activity levels show atendency of magnetic regions to be concentrated near the poles. In closebinaries a preference of low latitude regions to appear at fixedlongitudes has also been suggested.We modeled a 3D process of emergence of a thin magnetic tube through aconvective envelope of a solar type component of a close binary. In nocase the emerging tube approached a pole by more than 20 arcdeg,compared to its initial latitude. Assuming that dynamo operates mainlyat low and moderate latitudes, the polar magnetic regions cannot beformed unless an additional poleward transport of magnetic fields existsin rapidly rotating stars.Preferred longitudes in active close binaries result in our model froman azimuthal variation of effective gravity, hence buoyancy, throughoutthe convection zone of each component. The variation is strong enough ina contact binary with orbital period of 0.3days to force parts of thetube emerging in the regions of enhanced buoyancy to approach stellarsurface substantially sooner than the rest of the tube, thus forming twopreferred longitudes 180 arcdeg apart.The precise positions of thepreferred longitudes depend on binary parameters. The gravity variationis, however, too weak in a close binary with a period of 2 days toinfluence significantly the emergence rate of different tube parts. Amagnetic region can form at any longitude, depending mostly on aninitial perturbation, provided the original tube is placed on anequipotential surface. Such a location of the tube seems to be a correctinitial condition. The tube originally placed on a spherical surface hasparts lying closer to the unstable zone, where the tube instabilitypreferentially develops. This results in magnetic flux emergence atpreferred longitudes.
| Ternarity, Activity, and Evolutionary State of the W UMa-Type Binary UX Eridani
Charge-coupled device photometric observations of the W UMa-type binarystar UX Eridani are presented. Comparing the B light curve with thatobtained by Binnendijk in 1964-1965, the variation of the light curvearound the primary minimum was found. Photometric solutions ofBinnendijk's and our light curves were derived by using the new versionof the Wilson-Devinney program. Our solutions confirmed that UX Eri is amarginal W-type overcontact binary system with a very low degree ofovercontact, f < 15%. The change of the light curve around theprimary minimum was explained as the disappearance of a dark spot on themore massive component star. This suggests that UX Eri shows strongmagnetic activity, which is in agreement with its having the highestX-ray flux among 57 W UMa-type binary stars studied by Stepien et al.The high level of magnetic activity was interpreted as the result of ashallow common convective envelope. Orbital period changes were analyzedusing several newly determined CCD times of light minimum together withothers collected from the literature. A cyclic period change (T = 45.3yr) was found to be superimposed on a long-term increase (dP/dt = +7.7× 10-8 days yr-1). The period oscillationand the existence of third light both confirm that UX Eri contains atertiary component. Since no spectroscopic companion was found, it isestimated that the mass of the third body is M3 < 0.56Modot. The tertiary component star is moving in an eccentricorbit (e' = 0.72) with an orbital inclination of i' > 44.5°. Thetertiary component may have played an important role in the formation ofthe progenitor of UX Eri by transferring angular momentum during theKozai oscillation. In that way, the detached progenitor could evolveinto overcontact configuration via magnetic braking. It was found thatthe timescale of the period increase is close to the thermal timescaleof the less massive component, which suggests that UX Eri is in anevolutionary state of thermally conservative mass transfer from the lessmassive component to the more massive one.
| B.R.N.O. Contributions #34
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| New Times of Minima of Some Eclipsing Binary Stars
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| Radial Velocity Studies of Southern Close Binary Stars. II. Spring/Summer Systems
Radial velocity measurements and sine-curve fits to the orbital velocityvariations are presented for 14 close binary stars, S Ant, TT Cet, TWCet, AA Cet, RW Dor, UX Eri, YY Eri, BV Eri, CT Eri, SZ Hor, AD Phe, TYPup, HI Pup, and TZ Pyx. All are double-lined binaries, and all exceptthe last one are contact binaries. The orbital data must be consideredpreliminary because of the relatively small number of observations(6-12), a circumstance that is partly compensated by the good definitionof the broadening functions used for the radial velocity determinations.Based on data obtained at the European Southern Observatory.
| 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.
| Orbital period investigations of two short-period early-type overcontact binaries BH Cen and V701 Sco in two extremely young galactic clusters IC 2944 and NGC 6383
Both V701 Sco and BH Cen are two early-type short-period overcontactsystems (P = 0.d762 and P = 0.d792, respectively).V701 Sco is a member of the young galactic cluster NGC 6383, while BHCen is a component of a younger galactic cluster IC 2944 where starformation is in process. They provide good opportunity to understand theformation and evolution of binary stars. In the present paper, orbitalperiod changes of the two binaries are investigated. It is discoveredthat the orbital period of BH Cen shows a long-term increase with a rateof dP/dt = +1.70(±0.39) × 10‑7 days/yearwhile it undergoes a cyclic oscillation with a period of 44.6 years andan amplitude of A3 = 0.d0216. For V701 Sco, itsO-C curve reveals a periodic change with a period of 41.2 years andamplitude of A3 = 0.d0158. The mass ratio of BHCen is 0.84, but V701 Sco contains twin B1-1.5V type stars with a massratio of unit. The continuous period increase of BH Cen is caused by themass transfer from the less massive component to the more massive one ata rate of dM2/dt = 3.5 × 10‑6days/year. The cyclic period changes of both systems can be plausiblyexplained as the results of light-travel time effects suggesting thatthey are triple systems. The astrophysical parameters of the unseentertiary components in the two systems have been determined. We thinkthat the invisible tertiary components in both binaries played animportant role in the formations and evolutions of the overcontactconfigurations by bringing angular momentum out from the centralsystems. For BH Cen, this process created the initial short period andwill support its evolution into an overcontact configuration via a CaseA mass transfer within the life time of the extremely young cluster IC2944. For V701 Sco, two identical zero-age main-sequence components inan overcontact configuration suggest that it may have been formed byfission, possibly by the fission of the third body. The fact that nolong-term continuous period variations were found for V701 Sco maysuggest that an overcontact binary with the mass ratio of unity can bein an equilibrium revealing that the original configuration of thebinary was overcontact as is its present state. It has been reportedthat faint stars in the two extremely young clusters are relativelyscare. From the present study, it is shown that faint stars in youngclusters are usually formed as companions of OB stars (includingbinaries). It is very difficult to detect them because of their lowluminosity when compared with the more luminous OB stars.
| Deep, Low Mass Ratio Overcontact Binary Systems. VI. AH Cancri in the Old Open Cluster M67
CCD photometric light curves in the B and V bands obtained in 2001 andin the V band obtained in 2002 of AH Cnc in the old open cluster M67 arepresented. It is shown that AH Cnc is a total-eclipsing binary and itslight curves correspond to a typical A type according to Binnendijk'sclassification. The variations of the light curve around the primaryminimum and second maximum were found. Our nine epochs of light minimummonitored from 2001 to 2005, including others collected from theliterature, were used to create the first study of the period changes ofthe binary system. A cyclic oscillation with a period of 36.5 yr and anamplitude of 0.0237 days was discovered to be superposed on a continuousperiod increase (dP/dt=3.99×10-7 days yr-1).Weak evidence indicates that there exists another small-amplitude periodoscillation (A4=0.0035 days, P4=7.75 yr). Thesymmetric light curves in the B and V bands obtained in 2001 wereanalyzed with the 2003 version of the Wilson-Devinney code. It isconfirmed that AH Cnc is a deep overcontact binary system with a highdegree of overcontact f=58.5%+/-4.5% and a low mass ratio ofq=0.1682+/-0.0012. The existence of the third light and the cyclicperiod oscillation both may suggest that AH Cnc is a triple systemcontaining an unseen third body. The tertiary component may have playedan important role in the origin of the overcontact binary star byremoving angular momentum from the central system, which would cause itto have a short initial orbital period and thus evolve into anovercontact configuration by angular momentum loss. The long-term periodincrease can be interpreted as a mass transfer from the less massivecomponent to the more massive one. As the orbital period increases, thedecrease of the mass ratio will cause it finally to evolve into a singlerapid-rotating star when the system meets the more familiar criterionthat the orbital angular momentum be less than 3 times the total spinangular momentum. Therefore, AH Cnc may be a progenitor of the bluestraggler stars in M67.
| 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.
| W Ursae Majoris Contact Binary Variables as X-Ray Sources
We present cross-identification of archived ROSAT X-ray point sourceswith W UMa variable stars found in the All-Sky Automated Survey. A totalof 34 W UMa stars have been found associated with X-ray emission. Wecompute the distances of these W UMa systems and hence their X-rayluminosities. Our data support the ``supersaturation'' phenomenon seenin these fast rotators, namely that the faster a W UMa star rotates, theweaker its X-ray luminosity.
| 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.
| Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
| 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.
| GU Bootis: A New 0.6 Msolar Detached Eclipsing Binary
We have found a new low-mass, double-lined, detached eclipsing binary,GU Boo, among a sample of new variables from the ROTSE-I database. Thebinary has an orbital period of 0.488728+/-0.000002 days and estimatedapparent magnitudes Vrotse~=13.7 and I~=11.8. Our analysis ofthe light and radial velocity curves of the system yields individualmasses and radii of M1=0.610+/-0.007 Msolar,M2=0.599+/-0.006 Msolar,R1=0.623+/-0.016 Rsolar, andR2=0.620+/-0.020 Rsolar. The stars in GU Boo aretherefore very similar to the components of the eclipsing binary YY Gem.For this study we have adopted a mean effective temperature for thebinary of Teff=3870+/-130 K. Based on its space velocities wesuggest that GU Boo is a main-sequence binary, possibly with an age ofseveral Gyr. The metallicity of the binary is not well constrained atthis point, but we speculate that it should not be very different fromsolar. We have compared the physical parameters of GU Boo with currentlow-mass stellar models, accounting for uncertainties in age andmetallicity by considering a wide range of values for those parameters.Our comparisons reveal that all the models underestimate the radii ofthe components of GU Boo by at least 10%-15%. This result is inagreement with the recent studies of YY Gem and CU Cnc.
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 70 minima times of 35 eclipsing binaries.
| CCD Observations of Times of Minima of Eclipsing Binaries
120 minima timings are reported for 39 E. B. systems observed from 2002to 2005 with the Rigel telescope at Winer Observatory. The timings weredetermined using a folded light curve analysis of light curves derivedfrom CCD images. Typical timing uncertainties were 30-60 sec.
| 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.
| CCD Minima for Selected Eclipsing Binaries in 2004
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| CCD Times of Minima of Selected Eclipsing Binaries
682 CCD minima observations of 259 eclipsing binaries made mainly byauthor are presented. The observed stars were chosen mainly fromcatalogue BRKA of observing programme of BRNO-Variable Star Section ofCAS.
| 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
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
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Observation and Astrometry data
| Constellation: | Ηριδανός |
| Right ascension: | 04h12m08.85s |
| Declination: | -10°28'10.0" |
| Apparent magnitude: | 8.414 |
| Distance: | 55.679 parsecs |
| Proper motion RA: | -111.2 |
| Proper motion Dec: | -117.2 |
| B-T magnitude: | 9.239 |
| V-T magnitude: | 8.483 |
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INHABITED SKY
