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Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 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/397/997
| 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.
| Long-Term VRI Photometry of Small-Amplitude Red Variables. I. Light Curves and Periods
We report up to 5000 days of VRI photometry, from a robotic photometrictelescope, of 34 pulsating red giants, namely, TV Psc, EG And, Z Psc, RZAnd, 4 Ori, RX Lep, UW Lyn, η Gem, μ Gem, ψ1 Aur,V523 Mon, V614 Mon, HD 52690, Y Lyn, BC CMi, X Cnc, UX Lyn, RS Cnc, VYUMa, ST UMa, TU CVn, FS Com, SW Vir, 30 Her, α1 Her,V642 Her, R Lyr, V450 Aql, V1293 Aql, δ Sge, EU Del, V1070 Cyg, WCyg, and μ Cep, as well as a few variable comparison stars. V, R, andI variations are generally in phase. The length and density of the dataenable us to look for variations on timescales ranging from days toyears. We use both power-spectrum (Fourier) analysis and autocorrelationanalysis, as well as light-curve analysis; these three approaches arecomplementary. The variations range from regular to irregular, but inmost of the stars, we find a period in the range of 20-200 days, whichis probably due to low-order radial pulsation. In many of the stars, wealso find a period which is an order of magnitude longer. It may be dueto rotation, or it may be due to a new kind of convectively inducedoscillatory thermal mode, recently proposed by P. Wood.
| Long-Term VRI Photometry of Pulsating Red Giants
We report up to 5000 days of VRI photometry, from a robotic photometrictelescope, of 37 pulsating red giants, namely: TV Psc, EG And, Z Psc, RZAnd, 4 Ori, RX Lep, η Gem, μ Gem, UW Lyn, ψ 1 Aur,V523 Mon, V614 Mon, HD 52690, Y Lyn, BC CMi, X Cnc, UX Lyn, RS Cnc, VYUMa, ST UMa, TU CVn, FS Com, 35 Com, SW Vir, 30 Her, α1 Her, V642 Her, R Lyr, HD 174621, V450 Aql, V1293 Aql,δ Sge, EU Del, V1070 Cyg, W Cyg, μ Cep, and ν Cep. V, R, andI variations are generally in phase. The length and density of the dataenable us to look for variations on time scales ranging from days toyears. We use both power-spectrum (Fourier) analysis, andautocorrelation analysis, as well as light-curve analysis; these threeapproaches are complementary. The variations range from regular toirregular but, in most of the stars, we find a period in the range of 20to 200 days which is probably due to low-order radial pulsation. In manyof the stars, we also find a period which is an order of magnitudelonger. It may be due to rotation, or it may be due to a new kind ofconvectively-induced oscillatory thermal mode, recently proposed byPeter Wood. Supported by NASA, NSF, and NSERC Canada.
| 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.
| Mass-losing M supergiants in the solar neighborhood
A list of the 21 mass-losing red supergiants (20 M type, one G type; Lgreater than 100,000 solar luminosities) within 2.5 kpc of the sun iscompiled. These supergiants are highly evolved descendants ofmain-sequence stars with initial masses larger than 20 solar masses. Thesurface density is between about 1 and 2/sq kpc. As found previously,these stars are much less concentrated toward the Galactic center thanW-R stars, which are also highly evolved massive stars. Although withconsiderable uncertainty, it is estimated that the mass return by the Msupergiants is somewhere between 0.00001 and 0.00003 solar mass/sq kpcyr. In the hemisphere facing the Galactic center there is much less massloss from M supergiants than from W-R stars, but, in the anticenterdirection, the M supergiants return more mass than do the W-R stars. Theduration of the M supergiant phase appears to be between 200,000 and400,000 yr. During this phase, a star of initially at least 20 solarmasses returns perhaps 3-10 solar masses into the interstellar medium.
| New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
| A Search for Carbon Stars in the AFGL Catalogue
A comparison between the General Catalogue of Cool Carbon Stars (CCS)and the AFGL Catalogue has been performed. Eighty-five stars have beenfound in common between the two lists. Eighty-four stars which werepresent in Baumert's comparison between CCS and the 2 ~ Sky Survey haveno counterpart in the AFGL. Four new tentative identifications aregiven. The analysis of the two colours diagrams K-[4.2 p~ vs. I-K andI-[4.2 ~ vs. [4.2 ~]-[11 ~t] led to the conclusion that all the infraredemission from the sources seems to come from a single circumstellarshell
| Rotational velocities and spectral types for a sample of binary systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&AS...19...91L&db_key=AST
| Spectral Classification of Stars Noted on Case Objective Prism Plates. II
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Osservazione e dati astrometrici
| Costellazione: | Unicorno |
| Ascensione retta: | 07h02m06.73s |
| Declinazione: | -03°45'17.4" |
| Magnitudine apparente: | 6.618 |
| Distanza: | 675.676 parsec |
| Moto proprio RA: | -3.9 |
| Moto proprio Dec: | -0.3 |
| B-T magnitude: | 8.732 |
| V-T magnitude: | 6.793 |
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