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Absolute dimensions of eclipsing binaries. XXV. U Ophiuchi and the evolution and composition of 5 Mȯ stars
Context: Precise stellar masses and radii provide unique information onstellar evolution. In a Galactic context, they may also provideinformation on the evolution of the Solar neighbourhood. Aims: Weaim to determine absolute dimensions for the mid B-type eclipsing binaryU Ophiuchi and compare the inferred ages and chemical compositions tothose of other binary stars with masses near 5 {M}ȯ. Methods: We determine masses, radii, log g, log T_eff, andluminosities for the stars in U Oph from new radial velocities and uvbylight curves. By improving the Wilson-Devinney code, we also deriveprecise apsidal-motion and light-time orbits of this triple system,using 353 times of minimum over 120 years. Finally, we compare the datafor U Oph and three similar systems with the predictions of stellarmodels. Results: The stars in U Oph have masses of 5.27 ±0.09 {M}ȯ and 4.74 ± 0.07 {M}ȯ,radii of 3.48 ± 0.02 {R}ȯ and 3.11 ± 0.03{R}ȯ; we argue that systematic errors are negligible.The apsidal motion period is exceptionally short, U ˜21 yr, whilethe light-time orbit has P3 ˜ 38.4 yr. The precise logg values for DI Her, U Oph,V760 Sco, and MU Cas, all within10% of 5 {M}ȯ, place them successively from the ZAMS tothe TAMS, at ages of 5-100×106 yr. Current stellarevolution models fit both stars in each system very well if the(otherwise unconstrained) metal abundance Z is adjusted in each case. Conclusions: More accurate data and/or binary systems with largermass ratios are needed to actually test stellar models near 5{M}ȯ. The different Z values found for these young,nearby systems suggest that disk stars form with a range of metalabundances even today, but more data are needed to confirm this result.Based on observations collected at the European Southern Observatory, LaSilla, Chile. Table [see full textsee full textsee full text] is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/469/285
| Hubble Space Telescope Measurements of Vacuum Ultraviolet Lines of Interstellar CH
Three interstellar absorption lines near 1370 Å seen toward ζOph have been assigned by Watson to Rydberg transitions in the G-X (or3d-X) band of CH. Our survey of a dozen diffuse interstellar lines ofsight shows that the three absorption lines are consistent with theknown column densities of CH, by deriving the following oscillatorstrengths: f(1368.74)=0.019+/-0.003, f(1369.13)=0.030+/-0.005, andf(1370.87)=0.009+/-0.001. We also determined intrinsic line widths thatcorrespond to decay rates of (1.5+/-0.6)×1011,(3.8+/-0.7)×1011, and (1.1+/-0.6)×1010s-1 for λλ1368, 1369, and 1370, respectively.These rates are significantly higher than those associated withradiative decays and, thus, are readily attributable to predissociationof the Rydberg state. A fourth interstellar line near 1271 Å hasbeen conjectured by Watson to be the strongest transition in the 4d-XRydberg band of CH. We detected this line along four sight lines and ourspectrum syntheses show that with f(1271.02)=0.007+/-0.002, it is alsoconsistent with the known column densities of CH. In addition, weconducted a search for the F-X band of CH near 1549 Å, andsuccessfully discovered two of its absorption features along four sightlines. The astronomical oscillator strengths derived for these featuresare f(1549.05)=0.021+/-0.006 and f(1549.62)=0.013+/-0.003. Finally, theX Per sight line provided us with an astronomical detection of anotherCH band via two D-X features near 1694 Å. Comparisons with resultsof available theoretical calculations for the four CH bands arepresented.
| Apsidal motion in eccentric eclipsing binaries: CW Cephei, V478 Cygni, AG Persei, and IQ Persei
Aims.About thirty new times of minimum light recorded with photoelectricor CCD photometers were obtained for four early-type eccentric-orbiteclipsing binaries CW Cep (P=2.73d, e=0.029), V478 Cyg ( 2.88d, 0.016),AG Per ( 2.03d, 0.071), and IQ Per ( 1.74d, 0.076). Methods:.Their O-C diagrams were analysed using all reliable timings found inthe literature, and elements of apsidal motion were improved.Results: .We confirm relatively short periods of apsidal motion of about46, 27, 76, and 124 years for CW Cep, V478 Cyg, AG Per, and IQ Per,respectively. The corresponding internal structure constants, log k_2,are then found to be -2.12, -2.25, -2.15, and -2.36, under theassumption that the component stars rotate pseudosynchronously. Therelativistic effects are negligible, being up to 8% of the total apsidalmotion rate in all systems. Using the light-time effect solution, wehave predicted a faint third component orbiting with a period of about39 years for CW Cep.
| Computed Hβ indices from ATLAS9 model atmospheres
Aims.Grids of Hβ indices based on updated (new-ODF) ATLAS9 modelatmospheres were computed for solar and scaled solar metallicities[+0.5], [+0.2], [0.0], [ -0.5] , [ -1.0] , [ -1.5] , [ -2.0] , [ -2.5]and for α enhanced compositions [+0.5a], [0.0a], [ -0.5a] , [-1.0a] , [ -1.5a] , [ -2.0a] , [ -2.5a] , and [ -4.0a] . Methods:.Indices for T_eff > 5000 K were computed with the same methods asdescribed by Lester et al. (1986, LGK86) except for a differentnormalization of the computed natural system to the standard system.LGK86 used special ODFs to compute the fluxes. For T_eff ≤ 5000 K wecomputed the fluxes using the synthetic spectrum method. In order toassess the accuracy of the computed indices comparisons were made withthe indices computed by Smalley & Dworetsky (1995, A&A, 293,446, MD95) and with the empirical relations T_eff-Hβ given byAlonso et al. (1996, A&A, 313, 873) for several metallicities.Furthermore, for cool stars, temperatures inferred from the computedindices were compared with those of the fundamental stars listed byMD95. The same kind of comparison was made between gravities for B-typestars. Results: .The temperatures from the computed indices are ingood agreement, within the error limits, with the literature values for4750 K ≤ T_eff ≤ 8000 K, while the gravities agree for T_eff> 9000 K. The computed Hβ indices for the Sun and for Procyonare very close to the observed values. The comparison between theobserved and computed Hβ indices as function of the observedHβ has shown a very small trend which almost completely disappearswhen only stars hotter than 10 000 K are considered. The trend due tothe cool stars is probably related with the low accuracy of thefundamental T_eff which are affected by large errors for most of thestars.
| Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
| 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.
| Binarity as a tool for determining the physical properties and evolutionary aspects of A-stars
Double-lined-eclipsing binaries are the essential systems for themeasurement of stellar masses and radii. About 50-60 systems havecomponents (mostly A-stars) for which these values are known with anuncertainty less than 1-2%. Therefore, these systems are very suitableto improve our understanding of stellar structure and evolution. In thispaper, special attention is given to the assessment of the role ofinternal rotation of the early-type stars in selected double-linedbinaries (i.e., EK Cep, PV Cas, and θ2 Tau): it isshown that adoption of rapidly rotating cores for such stars permits themodels to be in very good agreement with the observational resultsincluding the apsidal advance rates.
| Apsidal Motion in Binaries: Rotation of the Components
A sample of 51 separated binary systems with measured apsidal periodsand rotational velocities of the components is examined. The ranges ofthe angles of inclination of the equatorial planes of the components tothe orbital plane are estimated for these systems. The observed apsidalvelocities can be explained by assuming that the axes of rotation of thestars are nonorthogonal to the orbital plane in roughly 47% of thesystems (24 of the 51) and the rotation of the components is notsynchronized with the orbital motion in roughly 59% of the systems (30of 51). Nonorthogonality and nonsynchrony are defined as deviations from90° and a synchronized angular velocity, respectively, at levels of1 or more.
| Ultra-high-resolution observations of CH in Southern Molecular Cloud envelopes
We present a mini-survey of ultrahigh-resolution spectroscopy (UHRS) ofCH towards three southern molecular cloud envelopes. The sightlines areselected to probe physically similar gas in different Galacticenvironments. With a velocity resolution of ~0.5kms-1(R=575000) these observations resolve most kinematic components of theabsorption lines. We do, however, detect one line component in the Lupusregion, which is not resolved and for which an upper limit ofb<0.3kms-1 is found. We find a correlation betweendistance of the absorbing gas from the Galactic mid-plane and thefractional abundance of CH. We show that this correlation can beexplained as being a result of a fall-off in the ultraviolet radiationfield intensity and propose that CH observations in carefully selectedsightlines might allow a mapping of the variations in the interstellarradiation field.
| Determination of the Ages of Close Binary Stars on the Main Sequence from Evolutionary Model Stars of Claret and Gimenez
A grid of isochrones, covering a wide range of stellar ages from thezero-age main sequence to 10 billion years, is calculated in the presentwork on the basis of the model stars of Claret and Gimenez withallowance for convective overshoot and mass loss by the components. Theages of 88 eclipsing variables on the main sequence from Andersen'scatalog and 100 chromospherically active stars from Strassmeier'scatalog are calculated with a description of the method of optimuminterpolation. Comparisons with age determinations by other authors aregiven and good agreement is established.
| Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations
A list of 62 detached binaries having reliable data on the rotation ofthe line of apsides is considered. Theoretical estimates of the rate ofapsidal motion are obtained. These estimates are compared withobservational data. It is shown that cases in which the theoreticalestimate exceeds the observed value are several times more frequent thancases in which the theoretical value is lower than the observed one.This discrepancy increases when systems with more reliable observationaldata are considered.
| New results on the apsidal-motion test to stellar structure and evolution including the effects of dynamic tides
We revised the current status of the apsidal-motion test to stellarstructure and evolution. The observational sample was increased by about50% in comparison to previous studies. Classical and relativisticsystems were analyzed simultaneously and only systems with accurateabsolute dimensions were considered. New interior models incorporatingrecent opacity tables, stellar rotation, mass loss, and moderate coreovershooting were used as theoretical tools to compare the predictedwith the observed shifts of the position of the periastron. The stellarmodels were computed for the precise observed masses and the adoptedchemical compositions are consistent with the corresponding tables ofopacities to avoid the inherent problems of interpolation in mass and in(X, Z). The derived chemical composition for each individual system wasused to infer the primordial helium content as well as a law ofenrichment. The values found are in good agreement with those obtainedfrom various independent sources. For the first time, the effects ofdynamic tides are taken into account systematically to determine thecontribution of the tidal distortion to the predicted apsidal-motionrate. The deviations between the apsidal-motion rates resulting from theclassical formula and those determined by taking into account theeffects of dynamic tides are presented as a function of the level ofsynchronism. For systems close to synchronisation, dynamic tides causedeviations with respect to the classical apsidal-motion formula due tothe effects of the compressibility of the stellar fluid. For systemswith higher rotational angular velocities, additional deviations due toresonances arise when the forcing frequencies of the dynamic tides comeinto the range of the free oscillation modes of the component stars. Theresulting comparison shows a good agreement between the observed andtheoretical apsidal-motion rates. No systematic effects in the sensethat models are less mass concentrated than real stars and nocorrelations with the evolutionary status of the systems were detected.
| Studies of Intermediate-Mass Stellar Models Using Eclipsing Binaries
Evolutionary computations for intermediate-mass stars are analyzed usingobserved parameters for eclipsing SB2 binaries and theoreticalparameters based on evolutionary tracks. Modern observations cannot beused to distinguish between models with and without convectiveovershooting for stars in the vicinity of the main sequence.Statistically significant discrepancies between the observed andcomputed stellar parameters are associated with systematic errors inphotometric effective temperatures. After taking into account systematiceffects, the theoretical computations fit the observational datauniformly well throughout the entire mass interval studied. Empiricaland semiempirical (i.e., reduced to the ZAMS and with solar elementalabundances) formulas for the mass-luminosity, mass-effectivetemperature, and mass-radius relations are proposed.
| Age and Metallicity Estimates for Moderate-Mass Stars in Eclipsing Binaries
We estimate the ages and metallicities for the components of 43 binarysystems using a compilation of accurate observational data on eclipsingbinaries for which lines of both components are visible in theirspectra, together with two independent modern sets of stellar evolutionmodels computed for a wide range of masses and chemical abundances. Theuncertainties of the resulting values are computed, and their stabilityis demonstrated. The ages and metallicity are compared with thosederived in other studies using different methods, as well as withindependent estimates from photometric observations and observations ofclusters. These comparisons con firm the reliability of our ageestimates. The resulting metallicities depend significantly on thechoice of theoretical model. Comparison with independent estimatesfavors the estimates based on the evolutionary tracks of the Genevagroup.
| 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.
| On the Variability of Late B III-V Stars
We investigate the Hipparcos Satellite photometry of luminosity classIII-V B6-B9 stars. Most are relatively non-variable. Candidates forwhich further study is desirable are identified.
| Apsidal motion in southern eccentric eclipsing binaries: YY Sgr, V523 Sgr, V1647 Sgr, V2283 Sgr and V760 Sco
Several new times of minimum light recorded with photoelectric meanshave been gathered for the early-type eccentric eclipsing binaries YYSgr (P = 2fd 63, e = 0.16), V523 Sgr (2fd 32, 0.16), V1647 Sgr (3fd 28,0.41), V2283 Sgr (3fd 47, 0.49) and V760 Sco (1fd 73, 0.03). The O - Cdiagrams are analyzed using all reliable timings found in the literatureand improved values for the elements of the apsidal motion are computed.We find more precise periods of apsidal motion of about 290, 202, 531,528 and 38.5 years for YY Sgr, V523 Sgr V1647 Sgr, V2283 Sgr and V760Sco, respectively. The corresponding internal structure constants logk_2 are derived and compared to their theoretical values. Based onobservations collected at the South Africa Astronomical Observatory,Sutherland, South Africa
| Chemical composition of eclipsing binaries: a new approach to the helium-to-metal enrichment ratio
The chemical enrichment law Y(Z) is studied by using detacheddouble-lined eclipsing binaries with accurate absolute dimensions andeffective temperatures. A sample of 50 suitable systems was collectedfrom the literature, and their effective temperatures were carefullyre-determined. The chemical composition of each of the systems wasobtained by comparison with stellar evolutionary models, under theassumption that they should fit an isochrone to the observed propertiesof the components. Evolutionary models covering a wide grid in Z and Ywere adopted for our study. An algorithm was developed for searching thebest-fitting chemical composition (and the age) for the systems, basedon the minimization of a χ2 function. The errors (andbiases) of these parameters were estimated by means of Monte Carlosimulations, with special care put on the correlations existing betweenthe errors of both components. In order to check the physicalconsistency of the results, we compared our metallicity values withempirical determinations, obtaining excellent coherence. Theindependently derived Z and Y values yielded a determination of thechemical enrichment law via weighted linear least-squares fit. Our valueof the slope, ΔY/ΔZ=2.2+/-0.8, is in good agreement withrecent results, but it has a smaller formal error and it is free ofsystematic effects. Linear extrapolation of the enrichment law to zerometals leads to an estimation of the primordial helium abundance ofYp=0.225+/-0.013, possibly affected by systematics in theeffective temperature determination.
| Estimating the ages of eclipsing variable DM-stars on the basis of the evolutionary star models by Maeder and Meynet
A set of isochrones covering a wide range of star ages from5\cdot106 to 1010 yr was built on the basis of thestellar models by A. Maeder and G. Meynet with overshooting and massloss for Population I stars with abundances (X, Y, Z) = 0.70, 0.28,0.02. The isochrones were used to compute the ages of 88 eclipsingvariable stars from the catalog by Andersen which lie on the mainsequence. The influence of initial data errors on the rezultes wasinvestigated. The ages derived are in good agreement with the results ofother authors.
| Apsidal Motion in Double Stars. I. Catalog
A catalog of 128 double stars with measured periods of apsidal motion iscompiled. Besides the apsidal periods, the orbital elements of binariesand physical parameters of components (masses, radii, effectivetemperatures, surface gravities) are given. The agreement of the apsidalperiods found by various authors is discussed.
| Further discussion of binary star radio survey data
Statistical information on 8280 individual radio observations of binarystars, predominantly at 8.4 GHz using the Parkes 64 m antenna, ispresented. Three main groups are distinguished: (i) RS CVn stars, (ii)classical Algol binaries (EA2s) and (iii) detached pairs of generallyearly type (ETBs). The RS CVn stars more frequently gave rise todetectable fluxes, while the ETBs, in this data, are a small and ratherheterogeneous class. The Algols' emission appears to increase nearconjunction phases, though we cannot clearly distinguish any specialproperty of the Algols' phase-dependent behaviour which is not alsoshared by the RS CVn binaries. Both these categories' data show abimodal, phase-dependent pattern to the distribution of detections,suggesting both binary types share similar underlying physicalproperties, though there could also be other factors at play. The samplesizes of the Algols and particularly the ETB detections are too smallfor effective, discriminatory statistics, however.
| Photometric versus empirical surface gravities of eclipsing binaries.
Systematic differences in photometric stellar surface gravitydetermination are studied by means of the comparison with empiricalvalues derived from detached double-lined eclipsing binaries.Photometric gravities were computed using Moon & Dworetsky(1985MNRAS.217..305M) grids based on Kurucz (1979ApJS...40....1K)atmosphere models, and empirical gravities were taken from Andersen(1991A&ARv...3...91A). Individual Stroemgren colours and βindices of each component of the binary system have to be taken intoaccount to correctly analyze the observed differences. A compilation ofdata on a sample containing 30 detached double-lined eclipsing binarieswith accurate (=~1-2%) determination of mass and radius and availableuvbyHbeta_ photometric data is also presented. Correction ofthe differences in terms of T_eff_ and logg for the range11000K
| Further critical tests of stellar evolution by means of double-lined eclipsing binaries
The most accurately measured stellar masses and radii come fromdetached, double-lined eclipsing binaries, as compiled by Andersen. Wepresent a detailed quantitative comparison of these fundamental datawith evolution models for single stars computed with our evolution code,both with and without the effects of enhanced mixing or overshootingbeyond the convective cores. We use the same prescription forovershooting that Schroder, Pols & Eggleton found to reproduce theproperties of zeta Aurigae binaries. For about 80 per cent of the 49binary systems in the sample, both sets of models provide a good fit toboth stars at a single age and metallicity within the observationaluncertainties. We discuss possible causes for the discrepancies in theother systems. For only one system, AI Hya, do the enhanced-mixingmodels provide a significantly better fit to the data. For two others(WX Cep and TZ For) the fit to the enhanced-mixing models is alsobetter. None of the other systems can individually distinguish betweenthe models with and without enhanced mixing. However, the number ofsystems in a post-main-sequence phase is in much better agreement withthe enhanced-mixing models. This test provides supportive evidence forextended mixing in main-sequence stars in the range 2-3Msolar.
| Eclipsing binaries as IRAS sources.
In a systematic search we looked for coincidences in the positions ofeclipsing binaries and IRAS point sources as evidence of a physicalassociation. In a detailed discussion of the available optical andinfrared data combined with model calculations, we show that 50-75% ofthe coincidences between eclipsing binaries and IRAS sources are real.We discuss a subsample of 44 stars in some detail and surveyed thevicinity of them on POSS and SRC/ESO atlases for possible opticalcounterparts and present identification maps. In the cases of BS Sco andV 718 Sco the infrared radiation may come from an accretion disk.
| Far-Ultraviolet Stellar Photometry: Fields Centered on rho Ophiuchi and the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..104..101S&db_key=AST
| Improved Elements for Vv-Orionis
Not Available
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Far-ultraviolet stellar photometry: Fields in Sagittarius and Scorpius
Far-ultraviolet photometry for 741 objects in a field in Sagittariuscentered near M8 and 541 objects in a field centered near sigma Scorpiiis presented. These data were extracted from electographic imagesobtained with two cameras during a shuttle flight in 1991 April/May. Thecameras provided band passes with lambdaeff = 1375 A andlambdaeff = 1781 A. Synthetic colors show that these bandsare sensitive to effective temperature for hot stars. Our measurementswere placed on a quantitative far-ultraviolet magnitude scale byconvolving the spectra of stars observed by IUE with our cameras'spectral response functions. Fifty-eight percent of the ultravioletobjects were identified with visible stars using the SIMBAD databasewhile another 40% of the objects are blends of early type stars tooclose together to separate with our resolution. Our photometry iscompared with that from the TD-1, OAO 2, and ANS satellites and the S201(Apollo 16) far-ultraviolet camera and found to agree at the level of afew tenths of a magnitude. Unlike previous studies, almost half of theidentified visual counterparts to the ultraviolet objects are early Bstars. A plot of distance modulus against ultraviolet color excessreveals a significant population of stars with strong ultravioletexcess.
| On the absolute brightnesses and masses of early-type stars
A new empirical brightness calibration of early-type stars is presented,entirely based on accurate binary data. This calibration agreesremarkably well with the predictions of the most recent stellar models,but disagrees completely with all other currently used calibrations forearly-type stars. The binaries used to derive the new calibration covera range of masses from about 1.3 solar mass to 25 solar mass,corresponding to a temperature range from 6,700 K to 38,000 K. Over thewhole mass range, no systematic differences between the observed andevolutionary masses were found. The application to the alpha Per clustergives a distance modulus which agrees perfectly with that derived bycomparing its lower main-seqeunce to stars with known parallaxes.
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Observation and Astrometry data
| Constellation: | Skorpion |
| Right ascension: | 16h24m43.72s |
| Declination: | -34°53'37.5" |
| Apparent magnitude: | 7.067 |
| Distance: | 591.716 parsecs |
| Proper motion RA: | -4.1 |
| Proper motion Dec: | -18.4 |
| B-T magnitude: | 7.217 |
| V-T magnitude: | 7.08 |
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