High-precision effective temperatures of 161 FGK supergiants from line-depth ratios
Precise effective temperatures (Teff) are determined for 161FGK supergiants using method of line-depth ratios. We obtain a set of131 relations for temperatures of supergiants as a function of linedepths. These relations have been calibrated against previouslypublished accurate temperature estimates. The application range of themethod is 3600-7800 K (F0I-K5I). The internal error of a singlecalibration is less than 110 K, while combination of all calibrationsreduces uncertainty to only 5-30 K (standard error). The error in thezero-point is estimated to be less than 100-200 K. A significantadvantage of the line ratio method is its independence of theinterstellar reddening, and only modest sensitivity to abundance,macroturbulence, rotation and other factors.
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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Observability of Scattered-Light Echoes around Variable Stars and Cataclysmic Events
Scattered-light echoes from variable and cataclysmic stars offer one ofthe most effective means to probe the structure and composition ofcircumstellar and interstellar media. I build a simple model oflight-echo surface brightness by considering the source spectrum and thedust density, geometry, and scattering efficiency. I use this model toinvestigate whether echoes should be observable around short andlong-period giants, cataclysmic variables, and supernovae. Onlysupernovae are expected to illuminate material on both circumstellar andinterstellar scales. Giant and post-AGB stars (e.g., Cepheids and Miras)with high mass-loss rates can produce observable echoes within theircircumstellar envelopes. Echoes from novae and dwarf novae are probablydetectable only from nearby material, and only in unusually dense gas. Ipresent characteristic exposure times to image such echoes over a widerange of wavelengths for ground-based and Hubble Space Telescopeobservations. I apply these results to analyze the dust properties ofthe recently reported echoes around SN 1993J, finding the dust in M81 tohave a grain-size distribution and chemical composition consistent withGalactic dust. Optimal observing strategies for echo detection are alsodiscussed.
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A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars
Rotational velocity vsin i and mean radial velocity are presented for asample of 231 Ib supergiant stars covering the spectral region F, G andK. This work is the second part of the large survey carried out with theCORAVEL spectrometer to establish the behavior of the rotation for starsevolving off the main sequence (De Medeiros & Mayor 1999). Thesedata will add constraints to the study of the rotational behavior inevolved stars, as well as solid information concerning tidalinteractions in binary systems and on the link between rotation,chemical abundance and activity in stars of intermediate masses. Basedon observations collected at the Haute-Provence Observatory,Saint-Michel, France and at the European Southern Observatory, La Silla,Chile Table 1 is 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/395/97
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Spectroscopic survey of field stars : A search for metal-poor stars
We have undertaken a spectroscopic survey of field stars to finemetal-poor objects among them. Though the main objective of the surveyis to find new metal-poor stars, stellar parameterization is carried outfor all the sample stars so that the other categories of interestingobjects like composite stars, weak or strong CN, CH stars etc. can alsobe identified. Observations are carried out using OMR spectrographattached to VBT, Kavalur. The sample of candidate stars are chosen fromprismatic survey of Beers and his collaborators covering a large part ofthe Galaxy. At the first phase of this project, the analysis ofcompleted for a set of 19 relatively hot stars (Teff in 6000 to 8000Krage). The metallicities of the program stars are derived bysynthesizing the spectrum in the wavelength range 4900 to 5400 Åfor different metallicities and matching them with the observed spectra.This spectral region contains strong feature of Fe I at 5269 Å andone moderately strong Fe I blend at 5228 Å. These features weregenerally relied upon for Fe/H determination. More than half of thecandidate stars were found to show (Fe/H) in -0.7 to -1.2 range. Twomost metal-poor stars have (Fe/H) values of -1.3 and -1.8. It appearsthat metal-poor candidates suggested by Beers et al. from theirprismatic survey has a very significant fraction of metal-poor stars.The significantly metal-poor stars found so far would be studied indetail using high resolution spectra to understand nucleosynthesisprocesses that might have occurred in early Galaxy.
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Library of Medium-Resolution Fiber Optic Echelle Spectra of F, G, K, and M Field Dwarfs to Giant Stars
We present a library of Penn State Fiber Optic Echelle (FOE)observations of a sample of field stars with spectral types F to M andluminosity classes V to I. The spectral coverage is from 3800 to 10000Å with a nominal resolving power of 12,000. These spectra includemany of the spectral lines most widely used as optical and near-infraredindicators of chromospheric activity such as the Balmer lines (Hαto Hepsilon), Ca II H & K, the Mg I b triplet, Na I D_1, D_2, He ID_3, and Ca II IRT lines. There are also a large number of photosphericlines, which can also be affected by chromospheric activity, andtemperature-sensitive photospheric features such as TiO bands. Thespectra have been compiled with the goal of providing a set of standardsobserved at medium resolution. We have extensively used such data forthe study of active chromosphere stars by applying a spectralsubtraction technique. However, the data set presented here can also beutilized in a wide variety of ways ranging from radial velocitytemplates to study of variable stars and stellar population synthesis.This library can also be used for spectral classification purposes anddetermination of atmospheric parameters (T_eff, logg, [Fe/H]). A digitalversion of all the fully reduced spectra is available via ftp and theWorld Wide Web (WWW) in FITS format.
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Red supergiants in the LMC - III: luminous F and G stars
New BVRI observations for 40 and spectrophotometric measurements for 23F to G LMC supergiant candidates (and 3 galactic F to G supergiants) arepresented. The errors of the BVRI data are 0.01 to 0.03 mag in mostcases. The wavelength range of the spectra is 3400 to 6400 Angstroms,their resolution 10 Angstroms. The mean error of the fluxes is 0.03 mag.Spectral indices measuring the strengths of the Hβ , Hγ ,Hdelta , NaD and CaII H+K lines, the CHα_ {0} and CNbeta_ {0}bands, of the Balmer jump and the slope of the continuum redwards arediscussed as measures of effective temperature and luminosity on thebasis of galactic stars with accurate MK types and parallaxes. TheHγ line and the continuum gradient are very good temperaturecriteria, the CHα_ {0} band and especially the Balmer jump forluminosity. The luminosity classification given for F to G supergiantcandidates in the LMC in the literature is often doubtful. 5 of the 23stars observed spectrophotometrically turn out to be probably galacticforeground dwarfs on the basis both of the Balmer jump and thecomparison of their flux distributions with synthetic ones based on theKurucz model atmospheres. Surface gravities derived purely on the basisof flux distributions and such ones given by models of stellar evolutionagree with each other for dwarfs and giants only. For supergiants theformer are about 1.0 dex higher than the latter. As a consequenceeffective temperatures and metallicities given by these two methodsdeviate from each other for such stars, too. The intrinsic colours andtemperatures of galactic and LMC supergiants do not differ. Withabsolute magnitudes up to -9.6 mag the upper luminosity limit in the LMCdoes not exceed that in the Galaxy, where Ia-0 supergiants haveMV of up to -9.5 mag. The metallicities of the supergiantsshow a rather large scatter. Nevertheless the mean metallicities of 0.02+/- 0.09 dex for the Galaxy and -0.26 +/- 0.10 dex for the LMC agreewell with other observations.
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UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
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Colour excesses of F-G supergiants and Cepheids from Geneva photometry.
A reddening scale for F-G supergiants and Cepheids is presented.Supergiants with low reddenings or in clusters form the basis of thecalibration. In this sense, it is entirely empirical. The data have beenobtained in the Geneva photometric system. Comparisons with otherreddening scales show no disagreement. The only problem is with Fernie'sscale for Cepheids (1990), where a systematic trend exists. Its originis not clear. It is suggested to extend the number of supergiants withindependently obtained colour excesses in order to test the existence ofa possible luminosity dependence of the calibration. A period-colourrelation for Cepheids is deduced, on the basis of the present reddeningcorrections. It gives strong support for V473 Lyr being a secondovertone pulsator.
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Photometric Parameters for Short-Period Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1313E&db_key=AST
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Optical spectroscopy of Z Canis Majoris, V1057 Cygni, and FU Orionis - Accretion disks and signatures of disk winds
High resolution, high SNR optical spectra have been used to investigatethe hypothesis that in outburst, FU Ori objects are self-luminousaccretion disks whose light dominates at optical and near-IRwavelengths. Strong evidence has been found for linewidth versuswavelength correlation in good agreement with model predictions for ZCMa and V1057 Cyg, but not for FU Ori itself. Linewidth variescontinuously with wavelength at optical wavelengths in the former twoobjects, In the case of FU Ori, it is argued that a combination ofstrong wind components to spectral lines, and surface gravity possiblybeing lower than that of supergiants, conceals the underlying linewidthversus wavelength relationship. A marginal correlation is found betweenlinewidth and lower excitation potential in all three objects. Syntheticdisk spectra are subtracted from observed spectral, and remarkably goodfits are found for all three objects for wavelengths longer than about5000 A.
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Photometry of F-K type bright giants and supergiants. I - Intermediate band and H-Beta observations
Over 1500 observations of 560 bright giants and supergiants of types F-Kare presented and compared to the observations by Gray and Olsen (1991).The present results include intermediate-band which is slightlydifferent from the Stromgren data by Gray and Olsen due to a differentwidth for the v filter. A systematic difference in m(1) - M(1) withdecreasing temperature is noted in the two H-Beta data sets, and thecorrelations are defined.
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Photometry of F-K type bright giant and supergiants. II - Calibration on indices in terms of luminosity reddening and abundance of F-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991AJ....102.1826E&db_key=AST
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Supergiants and the Galactic metallicity gradient. II - Spectroscopic abundances for 64 distant F- to M-type supergiants
The metallicity gradient in the Galactic disk from in situ stars withvisual magnitude ranging from 6 to 10 is analyzed. Atmosphericparameters and detailed chemical abundances for 64 Population Isupergiants of spectral types F through M and luminosity classes Iathrough II have been determined. The derived Fe/H ratios ranging from-0.5 to + 0.7 show a mean value of +0.13 with an estimated uncertaintyof + or - 0.2. A subset of 25 supergiants fainter than 7th magnitudelying in the direction of the Galactic center shows a Fe/H mean of +0.18+ or - 0.04, while a similar sample of 15 faint supergiants lying in thedirection of the Galactic anticenter shows a lower Fe/H mean of +0.07 +or - 0.06. For a sample of bright supergiants analyzed by Luck andLambert (1985), the mean abundance pattern for all 64 stars showed thefollowing: deficient C and O along with enhancement of N, indicatingmixing of CNO-cycled material to the stellar surfaces; an apparent Srenhancement attributed to departures from LTE; and an essentially solarpattern of other chemical elements.
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Pre-main-sequence disk accretion in Z Canis Majoris
It is suggested that the pre-main-sequence object Z CMa is a luminousaccretion disk, similar in many respects to the FU Orionis variables. ZCMa shows the broad, doubled optical absorption lines expected from arapidly rotating accretion disk. The first overtone CO absorptiondetected in Z CMa is blue-shifted, suggesting line formation in a diskwind. Accretion at rates about 0.001 solar mass/yr over 100 yr isrequired to explain the luminosity of Z CMa. The large amount ofmaterial accreted (0.1 solar mass/yr) indicates that Z CMa is in a veryearly stage of stellar evolution, possibly in an initial phase ofmassive disk accretion.
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Accretion disk models for FU Orionis and V1057 Cygni - Detailed comparisons between observations and theory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988ApJ...325..231K&db_key=AST
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A library of stellar spectra
Spectra for 161 stars having spectral classes O-M and luminosity classesV, III, and I have been incorporated into a library available onmagnetic tape. The spectra extend from 3510 to 7427 A at a resolution ofabout 4.5 A. The typical photometric uncertainty of each resolutionelement in the spectra is on the order of 1 percent while broad-bandvariations are smaller than 3 percent. Potential uses for the libraryinclude population synthesis of galaxies and clusters, tests of stellaratmosphere models, spectral classification, and the generation of colorindices having arbitrary wavelength and bandpass.
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Nineteen new spectroscopic binaries and the rate of binary stars among F-M supergiants
Nineteen spectroscopic binaries (SBs) have been discovered in radialvelocity measurements made with the CORAVEL spectrophotometer on 181northern F-M supergiants. The rate of detected SBs among northern F-Msupergiants is 21 percent, without any dependence on spectral orluminosity class. The study of the binary F-M supergiants with knownorbital elements indicates that all the systems with a period smallerthan the critical value P(circ) have a nearly circular orbit. The valueof P(circ) depends on the luminosity class, being 400-600 d for class Iband 2000-7000 d for class Ia. This circularization of the orbits may bedue to the transfer of angular momentum during the phase of binary massexchange.
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Spectral classification of middle-type supergiants in the photographic infrared
A semiquantitative spectral classification scheme for middle-typesupergiant stars is presented which is wholly dependent on data in thenear infrared. The method involves the measurement of central depths asindicators of the strengths of the Paschen hydrogen lines 12 through 16,the Ca II infrared triplet and the 7774-A blend of O I, and was testedon slit spectrograms of previously classified stars of spectral types B8through G2. Results for the 142 stars considered are found to agree wellwith the MK spectral types determined previously, particularly inspectral types A5 through G0 and luminosity classes Ia through II.
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Photoelectric Equivalent Widths of the OIλ7774 Line and M_{υ}'s of Selected F Supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86...33B&db_key=AST
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Photometric data for 139 supergiants.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..150F&db_key=AST
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Color Excesses for Supergiants and Classical Cepheids.VI. on the Intrinsic Colors and the Hess Diagram of Late-Type Supergiants.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...134..850K&db_key=AST
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Color Excesses from Six-Color Photometry of Supergiant Stars
Not Available
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Spectral Classification of Stars Noted on Case Objective-Prism Plates. I
Not Available
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A Finding List of F Stars of High Luminosity.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...115..475N&db_key=AST
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INHABITED SKY
