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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.
| The First Multi-Color Photometric Study of the Near-Contact Binary as Serpentis
The first complete multi-color CCD photometric light curves of theeclipsing binary AS Ser were obtained over three nights in 2005. Usingthe latest Wilson-Devinney (WD) code, we computed the photometricelements of this system. It turns out that AS Ser is a near-contactbinary system with both components filling more than 99% of their Rochelobes. It belongs to a marginal contact binary system within theparameter uncertainties. The marginal characteristic of AS Ser revealsthat this target may be in a rare phase predicted by the thermalrelaxation oscillation (TRO) theory. The asymmetry of the light curvescan be explained by a dark spot on the secondary component, which isconsistent with its late-type nature. Combining all available times oflight minimum, we derived a new orbital period of AS Ser and found aperiodic oscillation varying within an amplitude of 0.0049 days and aperiod of 11.8 years. This period change may be the result of thelight-time effect due to a presumed tertiary component (M 3> 0.28M sun) or might result from magnetic activity cyclesof the two components.
| 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.
| Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79
The secondary photometric standard star number 79 for the FS Aur field(Henden & Honeycutt 1997), designated as [HH97] FS Aur-79 (GSC1874-399), is a short-period (0.2508 days) eclipsing binary whose lightcurve is a combination of the β Lyr and BY Dra type variables. Highsignal-to-noise ratio multicolor photometry was obtained using the USNaval Observatory 1 m telescope. These light curves show asymmetry atquadrature phases (the O'Connell effect), which can be modeled with thepresence of starspots. A low-resolution spectrum obtained with the 3.5 mWisconsin-Indiana-Yale-NOAO telescope at orbital phase 0.76 isconsistent with a spectral type of dK7e and dM3e. A radial velocitycurve for the primary star was constructed using 24 high-resolutionspectra from the 9.2 m Hobby-Eberly Telescope. Spectra show Hα andHβ in emission confirming chromospheric activity and possibly thepresence of circumstellar material. Binary star models thatsimultaneously fit the U, B, V, R, and radial velocity curves are thosewith a primary star of mass 0.59+/-0.02 Msolar, temperature4100+/-25 K, and mean radius 0.67 Rsolar, just filling itsRoche lobe, and a secondary star of mass 0.31+/-0.09 Msolar,temperature 3425+/-25 K, and mean radius 0.48 Rsolar, justwithin its Roche lobe. An inclination angle of83deg+/-2deg with a center-of-mass separation of1.62 Rsolar is also derived. Starspots, expected for arotation period of less than 1 day, had to be included in the modelingto fit the O'Connell effect.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
| 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.
| Search for associations containing young stars (SACY). I. Sample and searching method
We report results from a high-resolution optical spectroscopic surveyaimed to search for nearby young associations and young stars amongoptical counterparts of ROSAT All-Sky Survey X-ray sources in theSouthern Hemisphere. We selected 1953 late-type (B-V~≥~0.6),potentially young, optical counterparts out of a total of 9574 1RXSsources for follow-up observations. At least one high-resolutionspectrum was obtained for each of 1511 targets. This paper is the firstin a series presenting the results of the SACY survey. Here we describeour sample and our observations. We describe a convergence method in the(UVW) velocity space to find associations. As an example, we discuss thevalidity of this method in the framework of the β Pic Association.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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).
| 165. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
Not Available
| 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.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| 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.
| Possible connection between period change and magnetic activity of the very short-period binary VZ Piscium
New times of light minimum of the short-period (P=0d.26)close binary system, VZ Psc, are presented. A period investigation ofthe binary star, by combining the three new eclipse times with theothers collected from the literatures, shows that the variation of theperiod might be in an alternate way. Under the hypothesis that thevariation of the orbital period is cyclic, a period of 25 years and anamplitude of 0.d0030 for the cyclic change are determined. Ifthis periodic variation is caused by the presence of a third body, themass of the third body (m3) should be no less than 0.081Mȯ. Since both components of VZ Psc are strongchromospherically active and the level of activity of the secondarycomponent is higher than that of the primary one, the period may be moreplausibly explained by cyclic magnetic activity of the less massivecomponent.
| 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
| Period and light variations for the cool, overcontact binary BX Pegasi
New charge-coupled device photometric observations of the W UMa-typebinary BX Pegasi (BX Peg) were collected on four nights from 1999October to 2000 September. The light curve was covered completely ineach season. Seven new times of minimum light were determined. It wasfound that the orbital period of the system has varied recently in asinusoidal way, superimposed on a downward parabolic variation. Thelong-term period decrease rate is deduced as dP/dt=-8.62 or 9.59 ×10-8 d yr-1, which can be interpreted as eithermass transfer from the more massive cool star to the less massive hotcomponent, or as the combination of mass transfer and angular momentumloss due to a magnetic stellar wind. The period and amplitude of thesinusoidal period variation were calculated to be about 35.3 yr and0.015 d, respectively. The light curves of BX Peg are asymmetric andshow year-to-year light variability. A spot model has been applied toanalyse these light curves. After using the light curves of 1999 asreference ones, we solve those of 2000 by adjusting only the spotparameters. One cool-spot model on the cool secondary satisfies theobserved light curves of both 1999 and 2000 quite well and shows a goodrepresentation of the BX Peg system for both the photospheric and spotdescriptions. The brightness variations of BX Peg are not coincidentwith the period variations and so do not conform to a prediction of theApplegate mechanism. We think the most likely cause of the cyclicalvariation is the light-time effect due to a third body, although nothird light was detected in the light-curve analysis. If it exists, thehypothetical object could be a very red main-sequence star or a whitedwarf. We have solved anew the historical published light curve for onlythe spot parameters and these closely resemble our spot parameters. Wespeculate that this result is associated with the small coronalsaturation of the cool star of the system.
| 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/.
| CCD Minima for Selected Eclipsing Binaries in 2003
Not Available
| 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.
| Are overcontact binaries undergoing thermal relaxation oscillation with variable angular momentum loss?
Orbital period variations of five W-type overcontact binaries, GW Cep,VY Cet, V700 Cyg, EM Lac and AW Vir, are presented based on the analysisof all available times of light minimum. It is discovered that theperiod of GW Cep is decreasing at a rate of dP/dt=-6.62×10-8 d yr-1. For VY Cet and V700 Cyg, acyclic oscillation is found superimposed on a secular period increase,which can be explained either by the light-time effect of an assumedthird body or by magnetic activity cycles. For the other two, EM Lac andAW Vir, the periods show a secular increase. GW Cep is a low mass ratiosystem with q= 0.37, while the others are high mass ratio systems (q=0.67, 0.65, 0.63 and 0.76, respectively). The period changes of the fivesample stars are in good agreement with Qian's conclusion that low massratio overcontact binaries usually show a decreasing period, while theperiods of high mass ratio systems are increasing.Based on the period variations of 59 overcontact binaries, a statisticalinvestigation of period change is given. It is confirmed that the periodchange of a W UMa-type binary star is correlated with the mass ratio (q)and with the mass of the primary component (M1). Meanwhile,some statistical relations (M1-P,Js-M1, Js-M2 andJs-P) for overcontact binaries are presented using theabsolute parameters of 78 systems. From these relations, the followingresults may be drawn: (i) free mass transfer in both directions existsbetween the components, which is assumed by thermal relaxationoscillation (TRO) theory; (ii) angular momentum loss (AML) can make a WUMa-type star maintain shallow overcontact and not evolve fromovercontact to semidetached configurations as proposed by Rahunen; (iii)the evolution of the W UMa-type systems may be oscillation around acritical mass ratio, while the critical mass ratio varies with the massof the primary component. These results can be plausibly explained bythe combination of the TRO and the variable AML via a change of depth ofthe overcontact, which is consistent with the X-ray and IUEobservations.
| Photometric study of the over-contact binary star GSC 3822-1056
Here we present the first Johnson-Cousins VRC light curves ofthe over-contact binary star GSC 3822-1056. A periodstudy and the light curve solution are also given. An extremely highrate of period increase (+11.6 s/century) was found. The origin of thisperiod change can be: (i) partly covered light-time effect due to theorbital motion around the mass center of a possible third body; (ii)mass transfer between the components.The light curve was solved using the 1998 Wilson-Devinney Code. Weexamined the light curve with and without third light. Both solutionsyielded a contact configuration with high temperature difference betweenthe components. Despite the high degree of the contact (f=0.57), thetemperature difference between the components DeltaT=Tprimary-Tsecondary=1045 K.The high mass ratio of the system and its other unusual propertiessuggest that GSC 3822-1056 may be a recently formedcontact binary.Observations were made by the 80 cm ``IAC80'' telescope at Observatoriodel Teide in Tenerife, Spain, operated by Instituto de Astrofisica deCanarias.Tables 2a-c are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/403/637
| Times of Minima for Neglected Eclipsing Binaries in 2002
We present several CCD minima observations of 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.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| ROSAT all-sky survey of W Ursae Majoris stars and the problem of supersaturation
From ROSAT all-sky survey (RASS) data we obtained X-ray fluxes for 57 WUMa type contact systems. In our sample we detected three stars whichare the shortest period main sequence binaries ever found as X-raysources. For stars with (B-V)_0 < 0.6 the normalized X-ray fluxdecreases with a decreasing color index but for (B-V)_0 > 0.6 aplateau is reached, similar to the saturation level observed for single,rapidly rotating stars. The X-ray flux of W UMa stars is about 4-5 timesweaker than that of the fastest rotating single stars. Because earlytype, low activity variables have longer periods, an apparentperiod-activity relation is seen among our stars, while cool stars with(B-V)_0 > 0.6 and rotation periods between 0.23 and 0.45 days do notshow any such relation. The lower X-ray emission of the single, ultrafast rotators (UFRs) and W UMa stars is interpreted as the result of adecreased coronal filling factor. The physical mechanisms responsiblefor the decreased surface coverage differs for UFRs and W UMa systems.For UFRs we propose strong polar updrafts within a convection zone,driven by nonuniform heating from below. The updrafts should beaccompanied by large scale poleward flows near the bottom of theconvective layer and equatorward flows in the surface layers. The flowsdrag dynamo generated fields toward the poles and create a field-freeequatorial region with a width depending on the stellar rotation rate.For W UMa stars we propose that a large scale horizontal flow embracingboth stars will prevent the magnetic field from producing long-livedstructures filled with hot X-ray emitting plasma. The decreased activityof the fastest rotating UFRs increases the angular momentum loss timescale of stars in a supersaturated state. Thus the existence of a periodcutoff and a limiting mass of W UMa stars can be naturally explained.
| An Ultraviolet Study of the Short-Period Binary OO Aquilae
OO Aql is a rare W UMa-type eclipsing binary in which the two solar-typestars may have only recently evolved into contact. The binary has anunusually high mass ratio (0.84) and a relatively long orbital period(0.506 days) for its spectral type (mid-G). Twelve ultraviolet spectraof OO Aql were obtained in 1988 with the International UltravioletExplorer satellite, including a series of consecutive observations thatcover nearly a complete orbital cycle. Chromospheric activity is studiedby means of the Mg II h and k emission at 2800 Å. The Mg IIemission is found to vary, even when the emission is normalized to theadjacent continuum flux. This variation may be correlated with orbitalphase in the 1988 observations. It also appears that the normalized MgII emission varies with time, as seen in spectra obtained at twodifferent epochs in 1988 and when compared with two spectra obtainedseveral years earlier. The level of chromospheric activity in OO Aql isless than that of other W UMa-type binaries of similar colors, but thisis attributed to its early stage of contact binary evolution.Ultraviolet light curves were composed from measurements of theultraviolet continuum in the spectra. These were analyzed, along withvisible light curves of OO Aql, to determine the system parameters. Thelarge wavelength range in the light curves enabled a well-constrainedfit to a cool spot in the system.
| Radial Velocity Studies of Close Binary Stars. III
Radial velocity measurements and simple sine-curve fits to the orbitalvelocity variations are presented for the third set of 10 close binarysystems: CN And, HV Aqr, AO Cam, YY CrB, FU Dra, RZ Dra, UX Eri, RT LMi,V753 Mon, and OU Ser. All systems except two (CN And and RZ Dra) arecontact, double-line spectroscopic binaries, with four of them (YY CrB,FU Dra, V753 Mon, and OU Ser) being the recent discoveries of theHipparcos satellite project. The most interesting object is V753 Monwith the mass ratio closest to unity among all contact systems(q=0.970+/-0.003) and large total mass[(M1+M2)sin3i=2.93+/-0.06]. Several ofthe studied systems are prime candidates for combined light and radialvelocity synthesis solutions. Based on data obtained at the David DunlapObservatory, University of Toronto.
| The Second Extreme Ultraviolet Explorer Right Angle Program Catalog
We present the detection of 235 extreme ultraviolet sources, of which169 are new detections, using the Extreme Ultraviolet Explorer's (EUVE)Right Angle Program (RAP) data. This catalog includes observations sincethe first EUVE RAP catalog (1994 January) and covers 17% of the sky. TheEUVE RAP uses the all-sky survey telescopes (also known as``scanners''), mounted at right angles to the Deep Survey andspectrometer instruments, to obtain photometric data in four wavelengthbands centered at ~100 Å (Lexan/B), ~200 Å (Al/Ti/C), ~400Å (Ti/Sb/Al), and ~550 Å (Sn/SiO). This allows the RAP toaccumulate data serendipitously during pointed spectroscopicobservations. The long exposure times possible with RAP observationsprovide much greater sensitivity than the all-sky survey. We presentEUVE source count rates and probable source identifications from theavailable catalogs and literature. The source distribution is similar toprevious extreme ultraviolet (EUV) catalogs with 2% early-type stars,45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no firmclassification, and 15% with no optical identification. We also present36 detections of early-type stars that are probably the result ofnon-EUV radiation. We have detected stellar flares from approximately 12sources, including: EUVE J0008+208, M4 star G32-6 (EUVE J0016+198), anew source EUVE J0202+105, EUVE J0213+368, RS CVn V711 Tau (EUVEJ0336+005), BY Draconis type variable V837 Tau (EUVE J0336+259), the newK5 binary EUVE J0725-004, EUVE J1147+050, EUVE J1148-374, EUVE J1334-083(EQ Vir), EUVE J1438-432 (WT 486/487), EUVE J1808+297, and the M5.5estar G208-45 (EUVE J1953+444). We present sample light curves for thebrighter sources.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | דגים |
| התרוממות ימנית: | 23h27m48.38s |
| סירוב: | +04°51'24.0" |
| גודל גלוי: | 10.184 |
| תנועה נכונה: | 436.3 |
| תנועה נכונה: | 180.4 |
| B-T magnitude: | 11.658 |
| V-T magnitude: | 10.306 |
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