New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
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Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere
Within the scope of a Key Programme determining fundamental parametersof stars observed by HIPPARCOS, spectra of 525 B8 to F2-type starsbrighter than V=8 have been collected at ESO. Fourier transforms ofseveral line profiles in the range 4200-4500 Å are used to derivev sin i from the frequency of the first zero. Statistical analysis ofthe sample indicates that measurement error is a function of v sin i andthis relative error of the rotational velocity is found to be about 6%on average. The results obtained are compared with data from theliterature. There is a systematic shift from standard values from\citet{Slk_75}, which are 10 to 12% lower than our findings. Comparisonswith other independent v sin i values tend to prove that those fromSlettebak et al. are underestimated. This effect is attributed to thepresence of binaries in the standard sample of Slettebak et al., and tothe model atmosphere they used. Based on observations made at theEuropean Southern Observatory (ESO), La Silla, Chile, in the frameworkof the Key Programme 5-004-43K. Table 4 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/105
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Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars
A selection criterion based on the relative strength of the largestpeaks in the amplitude spectra, and an information criterion are used incombination to search for multiperiodicities in Hipparcos epochphotometry. The method is applied to all stars which have beenclassified as variable in the Hipparcos catalogue: periodic, unsolvedand microvariables. Results are assessed critically: although there aremany problems arising from aliasing, there are also a number ofinteresting frequency combinations which deserve further investigation.One such result is the possible occurrence of multiple periods of theorder of a day in a few early A-type stars. The Hipparcos catalogue alsocontains a number of these stars with single periodicities: such starswith no obvious variability classifications are listed, and informationabout their properties (e.g., radial velocity variations) discussed.These stars may constitute a new class of pulsators.
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Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable 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/qcar?J/A+A/367/521
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Understanding A-type supergiants. I. Ultraviolet and visible spectral atlas
This paper is the first of a series whose aim is to perform a systematicstudy of A-type supergiant atmospheres and winds. Here we present aspectral atlas of 41 A-supergiants observed by us in high and mediumresolution in the visible and ultraviolet. The atlas consists ofprofiles of the Hα , Hβ , Hγ , Hdelta , Hepsilon , CaII (H and K), Na I (D1 and D2), Mg II4481, Mg II [uv1] and FeII [uv1, uv2, uv3, uv62, uv63, uv161] lines for 41 stars with spectraltypes ranging from B9 to A9 and luminosity classes Ia, Iab and Ib, andprovides the basic data for a thoughtful study of these stars. Theoverall characteristics of the sample as well as the data reductionprocedures are described. We also present some examples of spectralvariability. Figures 1-3 are only available in electronic form at thehttp://www.edpsciences.com} of A-type supergiants\fnmsep\thanks{Based onobservations made with the INT and JKT telescopes operated on the islandof La Palma by the RGO in the Spanish Observatorio del Roque de LosMuchachos of the Instituto de Astrofisica de Canarias, with the 2.2~mtelescope at Calar Alto Observatory, Spain, with the Bernard Lyot 2~mtelescope at Pic Du Midi Observatory, France and observations collectedat the European Southern Observatory at La Silla, Chile.
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Radial velocities of HIPPARCOS southern B8-F2 type stars
Radial velocities have been determined for a sample of B8-F2 type starsobserved by the Hipparcos satellite. Observations were obtained withinthe framework of an ESO key-program. Radial velocities have beenmeasured using a cross-correlation method, the templates being a grid ofsynthetic spectra. The obtained precision depends on effectivetemperature and projected rotational velocity of the star as well as ona possible asymmetry of the correlation peak generally due to secondarycomponents. New spectroscopic binaries have been detected from theseasymmetries and the variability of the measured radial velocity.Simulations of binary and triple systems have been performed. Forbinaries our results have been compared with Hipparcos binary data.Adding the variable radial velocities, the minimum binary fraction hasbeen found 60% for physical systems. Radial velocities have beendetermined for 581 B8-F2 stars, 159 being new. Taking into accountpublished radial velocities, 39% south A-type stars with V magnitudelower than 7.5 have a radial velocity. Based on observations obtained atthe European Southern Observatory (ESO, La Silla, Chile) and on datafrom the ESA Hipparcos astrometry satellite.}\fnmsep \thanks{Tables 7, 8and 9 are only available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Understanding A-type supergiants. II. Atmospheric parameters and rotational velocities of Galactic A-type supergiants
We present the second paper of a series whose aim is to perform a globalstudy of Galactic A-supergiants. Very little work has been carried outto determine the stellar parameters of these stars. This is illustratedwith a brief review of some previous works. In this paper we analyze thedetermination of absolute magnitudes, spectral types and atmosphericparameters using the most recent Kurucz LTE blanketed model atmospheresand we discuss the applicability of the calibrations, such as theSchmidt-Kaler's (\cite{Sch-K}) calibration. Rotation is also animportant parameter in A-supergiants but their rotational velocities arepoorly known. We have calculated projected rotational velocities fromthe Fourier analysis of the observed Mg II (4481 Ä) line. Based onobservations made with the INT and JKT telescopes operated on the islandof La Palma by the RGO in the Spanish Observatorio del Roque de LosMuchachos of the Instituto de Astrofisica de Canarias, with the 2.2mtelescope at Calar Alto Observatory, Spain, with the Bernard Lyot 2mtelescope at Pic Du Midi Observatory, France and observations collectedat the European Southern Observatory at La Silla, Chile
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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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On the Variability of Early A-Type Supergiants
An examination of the Hipparcos photometry of 26 bright early A-typesupergiants shows that they are all variable.
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A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&db_key=AST
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OB Stellar Associations in Crux. I. Observations With the Glazar Space Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111..299T&db_key=AST
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A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
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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.
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Stromgren and H-Beta Photometry of Associations and Open Clusters - Part Three - CENTAURUS-OB1 and CRUX-OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.269..289K&db_key=AST
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The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
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A survey of Balmer-line profiles and IRAS fluxes in forty yellow supergiants
Results of a survey of yellow supergiants (predominantly F and G) thatwas undertaken to search for distorted Balmer lines are presented. Acomparison between the photometrically variable and nonvariablesupergiants is made with respect to the distorted and undistortedBalmer-line profiles. To complement the analysis, IRAS data are used todetect excess infrared emission, to infer circumstellar dust, and tosuggest a possible prior M supergiant evolutionary phase. Plans forfuture work are briefly discussed.
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The extension of the MK spectral classification system to the intermediate population II F type stars
A grid of metal-weak spectral-classification standards is used tosystematically extend the MK spectral-classification system to F-typestars of the intermediate population II. The present method allowsmetal-weak program stars to be compared with standards of similarmetallicity and effective temperature. The results demonstrate that theintermediate population II is very homogeneous. Excellent agreement isobtained between the classifications of the present extended system anduvby-beta photometric results.
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UBV Photoelectric Photometry Catalogue (1986). III Errors and Problems on DM and HD Stars
Not Available
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Small Magellanic Cloud: H-gamma-line equivalent widths and luminosity classes of the brightest blue star members
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..421A&db_key=AST
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Some crucial X-ray observations - One or two SNR(s) in crux?
A new Exosat (LE/CMA) observation of the region in Crux (R.A. ofapproximately 11 h 45 m, Dec. of approximately -62 deg) where Markert etal. (1981) reported the existence of two X-ray SNR's is presented. After'cleaning' the CMA field from the point source component due to the UVemission of the numerous stars in the field, the smoothed X-ray contoursare compared to the 408 MHz radio map of Caswell et al. (1983). Theexistence of two well-separate X-ray emission regions is confirmed byExosat, and the current X-ray/radio picture is not sufficient todistinguish clearly between the assumption of one or two (possiblyinteracting) SNR's in the region.
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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.
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UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
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Variability and mass loss in IA O-B-A supergiants
Recently completed catalogs of MK spectral types and UBV photometry of1227 OB stars in the southern Milky Way have been analyzed toinvestigate brightness and color variability among the Ia supergiants.It is found that brightness variability is common among the O9-B1supergiants with typical amplitudes about 0.1 and time scales longerthan a week and shorter than 1000 days. Among the A supergiantsfluctuations in U-B color are found on similar time scales and withamplitude about 0.1. For many early Ia supergaints there is a poorcorrelation between Balmer jump and spectral type, as had been knownpreviously. An attempt to correlate the Balmer jump deficiency with massloss rate yielded uncertain results.
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Standard Stars for Hα Photometry
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&AS...44..337S&db_key=AST
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Correlations between the lambda 2200 feature, the diffuse lambda 4430 band, and E/B-V/
The 2200 A extinction feature has been measured from ANS observations of30 stars. For each star, the depth of the 2200 A feature is compared toE(B-V) and the equivalent width of the diffuse band 4430 A. A goodcorrelation appears out to E(B-V) = 1.13. The various mechanisms forproducing the diffuse and 2200 A features are discussed and adiscriminatory test is put forward based on observations of theMagellanic Clouds.
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Uvby-Beta Photometry of Equatorial and Southern Bright Stars - Part Two
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...42..311H&db_key=AST
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Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
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Observations in linearly polarized light of the intensity of the diffuse lam 6180 absorption band in 56 southern O, B and A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....70..195G&db_key=AST
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A new optical supernova remnant in Crux
Spectral data are presented which confirm a supernova-remnantclassification for a weak filamentary emission nebula that was found tobe coincident with the radio remnant G296.1-0.7. The structures of theradio and optical remnants are described, spatially resolved opticalspectra of three filaments are examined, and an average heliocentricradial velocity of -26 (+ or - 3) km/s is measured for these filaments.Line ratios and electron densities are evaluated for the filaments, theBalmer decrement in G296.1-0.7 is estimated, and a distance of 4 kpc isadopted. A diameter of 17 pc is calculated for the optical remnant.Identification of the optical nebulosity as a supernova remnant is shownto be confirmed by the good correlation between the radio source and thenebula, the ringlike structure and the spectral index of the radiosource, the filamentary nature of the nebulosity, its collisionallyexcited spectrum, the high density of the brightest filament, and thelarge velocity broadening of spectral lines.
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NEWS@SKY (Science&Space News)
