|Quantitative Stellar Spectral Classification. II. Early Type Stars|
The method developed by Stock & Stock (1999) for stars of spectraltypes A to K to derive absolute magnitudes and intrinsic colors from theequivalent widths of absorption lines in stellar spectra is extended toB-type stars. Spectra of this type of stars for which the Hipparcoscatalogue gives parallaxes with an error of less than 20% were observedwith the CIDA one-meter reflector equipped with a Richardsonspectrograph with a Thompson 576×384 CCD detector. The dispersionis 1.753 Å/pixel using a 600 lines/mm grating in the first order.In order to cover the spectral range 3850 Å to 5750 Å thegrating had to be used in two different positions, with an overlap inthe region from 4800 Å to 4900 Å . A total of 116 stars wasobserved, but not all with both grating positions. A total of 12measurable absorption lines were identified in the spectra and theirequivalent widths were measured. These were related to the absolutemagnitudes derived from the Hipparcos catalogue and to the intrinsiccolors (deduced from the MK spectral types) using linear and secondorder polynomials and two or three lines as independent variables. Thebest solutions were obtained with polynomials of three lines,reproducing the absolute magnitudes with an average residual of about0.40 magnitudes and the intrinsic colors with an average residual of0.016 magnitudes.
|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.
|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 (126.96.36.199) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
|On the origin of the O and B-type stars with high velocities. II. Runaway stars and pulsars ejected from the nearby young stellar groups|
We use milli-arcsecond accuracy astrometry (proper motions andparallaxes) from Hipparcos and from radio observations to retrace theorbits of 56 runaway stars and nine compact objects with distances lessthan 700 pc, to identify the parent stellar group. It is possible todeduce the specific formation scenario with near certainty for twocases. (i) We find that the runaway star zeta Ophiuchi and the pulsarPSR J1932+1059 originated about 1 Myr ago in a supernova explosion in abinary in the Upper Scorpius subgroup of the Sco OB2 association. Thepulsar received a kick velocity of ~ 350 km s-1 in thisevent, which dissociated the binary, and gave zeta Oph its large spacevelocity. (ii) Blaauw & Morgan and Gies & Bolton alreadypostulated a common origin for the runaway-pair AE Aur and mu Col,possibly involving the massive highly-eccentric binary iota Ori, basedon their equal and opposite velocities. We demonstrate that these threeobjects indeed occupied a very small volume ~ 2.5 Myr ago, and show thatthey were ejected from the nascent Trapezium cluster. We identify theparent group for two more pulsars: both likely originate in the ~ 50 Myrold association Per OB3, which contains the open cluster alpha Persei.At least 21 of the 56 runaway stars in our sample can be linked to thenearby associations and young open clusters. These include the classicalrunaways 53 Arietis (Ori OB1), xi Persei (Per OB2), and lambda Cephei(Cep OB3), and fifteen new identifications, amongst which a pair ofstars running away in opposite directions from the region containing thelambda Ori cluster. Other currently nearby runaways and pulsarsoriginated beyond 700 pc, where our knowledge of the parent groups isvery incomplete.
|Abundances and Physical Conditions in the Warm Neutral Medium toward μ Columbae|
We present ultraviolet interstellar absorption-line measurements for thesightline toward the O9.5 V star μ Columbae (l=237.3d, b=-27.1d d~400pc, z~180 pc; ~0.06 cm-3) obtained withthe Goddard High Resolution Spectrograph (GHRS) on board the HubbleSpace Telescope. These archival data represent the most complete GHRSinterstellar absorption-line measurements for any line of sight towardan early-type star. The 3.5 km s-1 resolution of theinstrument allows us to accurately derive the gas-phase column densitiesof many important ionic species in the diffuse warm neutral medium,including accounting for saturation effects in the data and forcontamination from ionized gas along this sightline. For thelow-velocity material (-20<~vLSR<~+15 kms-1), we use the apparent column density method to derivecolumn densities. For the individual absorbing components atvLSR~-28.8, +20.1, +31.0, and +41.2 km s-1, weapply component fitting techniques to derive column densities andb-values. We have also used observations of interstellar Lyαabsorption taken with the GHRS intermediate resolution gratings toaccurately derive the H I column density along this sightline. Theresulting interstellar column density, logN(H I)=19.86+/-0.015, is inagreement with other determinations but is significantly more precise.The low-velocity material shows gas-phase abundance patterns similar tothe warm cloud (cloud A) toward the disk star ζ Ophiuchi, while thecomponent at vLSR~+20.1 km s-1 shows gas-phaseabundances similar to those found in warm halo clouds. We find that thevelocity-integrated gas-phase abundances of Zn, P, and S relative to Halong this sightline are indistinguishable from solar system abundances.We discuss the implications of our gas-phase abundance measurements forthe composition of interstellar dust grains. We find a dust-phaseabundance [(Fe+Mg)/Si]d =2.7-3.3 in the low-velocity gas;therefore the dust cannot be composed solely of common silicate grains,but must also include oxides or pure iron grains. The low-velocitymaterial along this sightline is characterized by T~6000-7000 K withne~0.3 cm-3, derived from the ionizationequilibrium of Mg and Ca. The relative ionic column density ratios ofthe intermediate-velocity components at vLSR=+31.0 and +41.2km s-1 show the imprint both of elemental incorporation intograins and (photo)ionization. These clouds have low total hydrogencolumn densities [logN(H)~17.4-17.7], and our component fitting b-valuesconstrain the temperature in the highest velocity component to beT=4000+/-700 K. The electron density of this cloud is ne~0.6cm-3, derived from the 2P1/2 to2P3/2 fine structure excitation of C II. Thecomponents at vLSR~-30 and -48 km s-1 along thissightline likely trace shocked gas with very low hydrogen columndensities. The vLSR~-30 km s-1 component isdetected in a few strong low-ionization lines, while both are easilydetected in Si III. The relative column densities of the -30 kms-1 suggest that the gas is collisionally ionized at moderatetemperatures (T~25,000 K). This is consistent with the measured b-valuesof this component, though nonthermal motions likely contributesignificantly to the observed breadths.
|A Search for Pulsar Companions to OB Runaway Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..357S&db_key=AST
|DO OB Runaway Stars Have Pulsar Companions?|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1220P&db_key=AST
|The ROSAT all-sky survey catalogue of optically bright OB-type stars.|
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
|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.
|SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).|
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
|The position corrections of 1400 stars observed with PA II in San Juan.|
|Second astrolabe catalogue of Santiago.|
Positions for 350 FK5 and 164 FK5 Extension stars as determined with theDanjon astrolabe of Santiago and differences astrolabe-catalogue aregiven for Equinox J2000.0 and for the mean observation epoch of eachstar. The average mean error in alpha is +/-0.005s and +/-0.07" indelta. The mean epoch of observation of the catalogue is J1979.96.
|Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension|
|An Einstein Observatory SAO-based catalog of B-type stars|
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
|Narrow band multicolor photometry of reddened and unreddened early-type stars|
Photometric measurements and interstellar extinction curves of reddenedand unreddened early-type Southern Hemisphere stars are presented. It isshown that a number of shallow features exist in the extinction curvesrelative to a straight-line approximation.
|Early type high-velocity stars in the solar neighborhood. IV - Four-color and H-beta photometry|
Results are presented from photometric obaservations in the Stromgrenuvby four-color and H-beta systems of early-type high-velocity stars inthe solar neighborhood. Several types of photometrically peculiar starsare selected on the basis of their Stromgren indices and areprovisionally identified as peculiar A stars, field horizontal-branchstars, metal-poor stars near the Population II and old-disk turnoffs,metal-poor blue stragglers, or metallic-line A stars. Numerousphotometrically normal stars were also found.
|Micrometric measurements of visual binaries (5th list)|
The data resulting from 596 micrometric measurements of 152 binaries areset forth which represent observations taken on the GPO astrograph(described by Scardia, 1990). The traditional declination method is usedto track star position, and some of the measurements are related toprevious work by the author (1990). The data given include O-Cmeasurements corresponding to the Worley and Heintz catalogue (1984) andother relevant data.
|Catalogue of i and w/w crit values for rotating early type stars|
|Empirical temperature calibrations for early-type stars|
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
|Determination of omega and IOTA values for rotating BO-B3 stars. I.|
|Interstellar polarization from observations of A and F stars in high and intermediate galactic latitudes, and from stars in the Mathewson and Ford polarization catalogue|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...64..487K&db_key=AST
|A catalog of ultraviolet interstellar extinction excesses for 1415 stars|
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
|A search for X-rays from runaway stars|
Enhanced X-ray emission from an early-type runaway star would be directevidence for the presence of a collapsed companion, and thus for itsorigin as the result of a supernova explosion in a massive binary. Totest this idea, measurements of X-ray fluxes in the 0.5-3 keV energyrange from nine O and B type runaway stars were made with the EinsteinObservatory. In each case, the X-ray luminosity observed does not exceedthat expected from a normal OB star. Therefore we conclude that, if therunaway stars have collapsed companions, the separations of thecomponents must be much greater than those in normal OB binaries.
|Early-type high-velocity stars in the solar neighborhood. III - Radial velocities, rotation indices, and line-strength indices for southern candidates|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983AJ.....88.1349S&db_key=AST
|Equivalent widths of spectral lines in B stars|
Previously published equivalent widths of 26 strong spectral linesmeasured at various reciprocal dispersions, ranging from 1 to 75 A/mm,in 172 B stars and 14 A stars are collected and analyzed. The linesconsidered include H-alpha and H-beta; six of He I and one of He II; oneof C III; two of N II and one of N III; two of O II; one of Mg II; twoeach of Si II, Si III, and Si IV; one of Ca II; and three of Fe II. Acomparison of the measurements made at the different reciprocaldispersions reveals that the equivalent width of a given line increasessystematically with decreasing reciprocal dispersion. Only measurementsmade at a reciprocal dispersion of not more than 40 A/mm are used toplot average curves showing equivalent width as a function of spectraltype and luminosity class for all 26 lines. In all but two cases (He Iat 4121 A and Ca II at 4267 A), the behavior of the lines as a functionof temperature and gravity is found to be in accordance withmodel-atmosphere theory.
|Early-type high-velocity stars in the solar neighborhood. II Photometry for 78 candidates|
H-beta and four-color photometry are presented for 78 early-type,high-velocity star candidates consisting of: (1) 74 candidates listed ina previous paper; and (2) four candidates identified by Eggen (1970).All of the sample appears to be near the main sequence, with theexception of five of the AO-type stars that are probably on the fieldPopulation II horizontal branch. Almost one-third of the main-sequence Astars and nearly all of the F stars are seen as true high-velocityobjects, and several of the high-velocity F stars appear to have solarmetal abundances. The existence of young, metal-rich, high-velocitystars is supported by the data, and it is concluded that this populationmay contribute one A star to every thousand stars in the solarneighborhood.
|Early-type high-velocity stars in the solar neighborhood. I - List of candidates|
Suspected nearby high-velocity stars of spectral types B and A areidentified by their proper motions, which are generally too small forthe stars to have been included in previous catalogs of high-velocitystars. The same selection process is then extended to spectral type Fstars, in order to both provide a companion sample and investigatewhether the hypothetical high-velocity, metal-rich population continuesto later spectral types. Of the presented list of 371 stars withconfirmed proper motions, 168 are of A and B spectral types. Photometricand spectroscopic observations of these stars are required to eliminatethose with misclassified spectra and convert proper motions into spacevelocities. The identification of type of stars is important forunderstanding apparent exceptions to the correlation between stellarages, metal abundances, and kinematic properties.
|A search for X-ray binary stars in their quiescent phase|
Fourteen early-type stars representative of systems which may beharboring a neutron star companion and are thus potential progenitors ofmassive X-ray binaries have been examined for X-ray emission with theHEAO A-1 experiment. Limits on the 0.5-20 keV luminosity for theseobjects lie in the range 10 to the 31-33 erg/sec. In several cases, thehypothesis of a collapsed companion, in combination with the X-raylimit, places a serious constraint on the mass-loss rate of the primarystar. In one instance, an X-ray source was discovered coincident with acandidate star, although the luminosity of 5 x 10 to the 31 isconsistent with that expected from a single star of the same spectraltype. The prospects for directly observing the quiescent phase of abinary X-ray source with the Einstein Observatory are discussed in thecontext of these results.
|Absorption spectra of interstellar grains. I - Reference stars|
In order to find the proper standards for the precise extraction ofinterstellar spectral features, an analysis was made of low-resolutionUV spectra of unreddened early-type stars. Stars having a E(B-V) colorexcess below 0.05m contained in the catalog of TD-1 satelliteobservations made during the S2/68 experiment are examined.
|Spectral classification from the ultraviolet line features of S2/68 spectra. V - Supplement series|
The paper presents the ultraviolet classification of more than 450 B-Aand F spectra obtained with the sky survey telescope mounted on the TD1satellite. Concerning abnormal objects, attention is given to the Bestars, the binary stars, the helium weak stars, and the lambda Booobjects. With regard to Be stars, it is concluded that the 1930 Awavelength feature is linked to the existence of either shell structuresor Fe II emission lines in the visual spectral range. In addition, it issuggested that stellar spectra at wavelengths of 1410, 1610-20 and 2400A are equivalent to the He-weak group in the classical range.