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Contribution to the study of composite spectra - IX. Spectroscopic orbital elements of 10 systems*
We present the results of a radial-velocity study of 10 spectroscopicbinaries with composite spectra that were observed at Observatoire deHaute-Provence with the CORAVEL instrument. Those systems, including acool, evolved, primary and a hot secondary of type B or A, were found tobe spectroscopic binaries. We computed their orbital elements for thefirst time. For three systems, the large mass function implies i~90°, with the possibility of eclipses. Mean angular separations arevery small (a<= 0.010 arcsec), which makes those systems resolvableonly with multi-pupil large interferometers.
| Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components.
A sample of 135 stars with composite spectra has been observed in thenear-UV spectral region with the Aurélie spectrograph at theObservatoire de Haute-Provence. Using the spectral classifications ofthe cool components previously determined with near infrared spectra, weobtained reliable spectral types of the hot components of the samplesystems. The hot components were isolated by the subtraction methodusing MK standards as surrogates of the cool components. We also derivedthe visual magnitude differences between the components usingWillstrop's normalized stellar flux ratios. We propose a photometricmodel for each of these systems on the basis of our spectroscopic dataand the Hipparcos data. We bring to light a discrepancy for the Gsupergiant primaries between the visual absolute magnitudes deduced fromHipparcos parallaxes and those tabulated by Schmidt-Kaler for the GIbstars: we propose a scale of Mv-values for these stars incomposite systems. By way of statistics, about 75% of the hot componentsare dwarf or subgiant stars, and 25% should be giants. The distributionin spectral types is as follows: 41% of B-type components, 57% of typeA, and 2% of type F; 68% of the hot components have a spectral type inthe range B7 to A2. The distribution of the ΔMv-valuesshows a maximum near 0.75 mag.
| Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The Entire IUE Sample
We have obtained or retrieved IUE spectra for over 100 middle- andlate-type giant and supergiant stars whose spectra indicate the presenceof a hot component earlier than type F2. The hot companions areclassified accurately by temperature class from their far-UV spectra.The interstellar extinction of each system and the relative luminositiesof the components are derived from analysis of the UV and opticalfluxes, using a grid of UV intrinsic colors for hot dwarfs. We find thatthere is fair agreement in general between current UV spectralclassification and ground-based hot component types, in spite of thedifficulties of assigning the latter. There are a few cases in which thecool component optical classifications disagree considerably with thetemperature classes inferred from our analysis of UV and opticalphotometry. The extinction parameter agrees moderately well with otherdeterminations of B-V color excess. Many systems are worthy of furtherstudy especially to establish their spectroscopic orbits. Further workis planned to estimate luminosities of the cool components from the dataherein; in many cases, these luminosities' accuracies should becomparable to or exceed those of the Hipparcos parallaxes.
| Spectral classifications in the near infrared of stars with composite spectra. II. Study of a sample of 180 stars
A sample of 180 supposedly composite-spectrum stars has been studied onthe basis of spectra obtained in the near infrared (8370-8780 Angstroms)at a dispersion of 33 Anstroms/mm. The objective was to study the coolercomponents of the systems. Of our sample, 120 are true compositespectra, 35 are hot spectra of types B, F and 25 are Am stars. We find astrong concentration of the cooler components of the composite spectraaround G8III. In view of the difficulty of classifying compositespectra, because of the super position of an early type dwarf and a latetype giant or supergiant spectrum, we have made several tests to controlthe classification based upon the infrared region. Since all tests gavepositive results, we conclude that our classifications can be consideredas being both reliable and homogeneous. Table \ref{tab1} is alsoavailable electronically at the CDS via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstracts.html} Based upon observationscarried out at Observatoire de Haute-Provence (CNRS).
| Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. IV - Further IUE detections
We have obtained IUE spectra for 31 middle and late-type giant andsupergiant stars whose TD-1 fluxes or ground-based spectra indicate thepresence of a hot component, or whose radial velocities indicate anunseen component. Stellar components earlier than type F1 were detectedin 22 cases. While 20 of the hot secondaries are seen weakly in opticalspectra, two are UV discoveries: HD 58134 and HD 183864. The hotcompanions are classified accurately by temperature class from theirfar-UV spectra. The interstellar extinction of each system and therelative luminosities of the components are derived from the UV andoptical fluxes, using a new grid of UV intrinsic colors for hot dwarfs.We find that many giant stars apparently have companions which are toohot and hence too luminous for consistency with the primary's spectralclassification.
| Further IUE Detections of Hot Companions to Cool Stars
Many late-type giants and supergiants have companion stars still on theupper main sequence, but barely detectable in ground-based observations.In 1989-90 we continued our surveys of suspected hot companions with theIUE satellite. Of 32 spectrum binaries or SB1 systems observed, 25reveal clear signatures in the UV of a B or A type component. The far-UVspectra are easily classified by temperature class with respect to IUEstandard stars. Some of the more significant new results: ground UVspectrosc. HD no. V spectral type type binary? Note---------------------------------------------------------- 25555 5.47 G0III + A4 dB8+ var 32835/6 7.65 F5 V + A dB8.5 a 37269AB 5.40 G5 III: +A3 d:A0 var 49126 7.28 F8 IV-V + B9.5 dB8.5 a 52690 6.55 M1 Ib + A-BgB8- 58134 7.64: G5 Ib g:A1- p 63208 6.18 G2 III + A4 gB9.5 var? 1675168.46 G5 III + A -- b 183864 7.32 G2 Ib d:A0 296.0d 218600 8.39 F2 Ib + A-- b In two systems the ground-based luminosity classifications of theirprimaries are seriously inconsistent with their upper main sequencecompanions (note a). Two spectrum binaries with supposedly A-typesecondaries show no evidence of such in the UV (note b). Several othercases demonstrate a trend in our surveys: although some classificationsare confirmed, we frequently find that the IUE spectral class is hotterthan the ground estimate by 2 or more subclasses. This work is supportedunder NASA contract NAS 5-28749. SBP is a staff member of the SpaceTelescope Science Institute. TBA is a member of the GHRS Science Team.
| Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. II - BVRI observations
Johnson system BVRI measurements are presented for 117 stars, most ofthem with no previous R and I photometry and many with no previous B andV. The prime objects for measurement are unresolved or nearly unresolvedbinaries containing a late-type giant or supergiant and an early-typecompanion. Other objects on the program include suspected binaries andother F-G giants and supergiants lacking at least R and I magnitudes.The variable F and G supergiants 1 Mon, 89 Her, HR 7308, HR 8157, HR8752, and rho-Cas and the eclipsing systems W Ser and ST Aqr wereobserved; HR 8752 showed significant dimming and cooling over 125 days.Several of Halliwell's (1979) candidates for nearby stars were measured.
| Composite spectrum stars susceptible to lunar occultation
The use of lunar occultations to detect close double stars has becomeroutine practice. Since a number of composite spectrum stars havealready been noted as double by occultation observers, an additionallist, complementary to those of Herr, of potential occultation doublesshould be useful. To this end, the paper examines the stars from fivegeneral studies of composites for their susceptibility to lunaroccultation. An identification list of 68 composite spectrum starssusceptible to lunar occultation is presented. Predicted times offavorable occultation events are given for several of the faintercandidates.
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| Csillagkép: | Bika |
| Rektaszcenzió: | 05h07m05.15s |
| Deklináció: | +26°59'45.3" |
| Vizuális fényesség: | 7.713 |
| Távolság: | 228.311 parszek |
| RA sajátmozgás: | 3.5 |
| Dec sajátmozgás: | -6.6 |
| B-T magnitude: | 8.758 |
| V-T magnitude: | 7.8 |
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