|Binary Star Observations in Selected Instants of Good Seeing|
Video recordings of images of binary stars at the focus of a 0.36mtelescope have been used to select images recorded in instants of goodseeing. The selected images have been analysed to give separations andposition angles for the binary systems which are in good agreement withvalues predicted from previous observations. In these exploratoryobservations it has been shown that separations of 0.9 arcseconds can bemeasured with an accuracy of ~2% and position angles to ~1-2 degreeswhen the average seeing was ~1.3 arcseconds. These observationsdemonstrated that the diffraction limit of the telescope could bereached when the seeing was a factor of 2-3 greater than it. A binarywith three magnitudes difference in the brightness of its components hasbeen measured with comparable accuracy although difficulties areanticipated for binaries with components closer than ~2 arcseconds withthis magnitude difference. The limiting magnitude is determined by theneed to limit exposure times of individual frames to be comparable withor less than the atmospheric coherence time.
|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
|A near IR adaptive optics search for faint companions to early-type multiple stars|
We report on a high dynamical range (>10(m) ) and high angularresolution (down to 0.2arcsec ) search for low-mass components ofearly-type primaries in 7 intermediate-age (5 Myr) multiple systems withthe ESO 3.6 m telescope and the adaptive optics system ADONIS. Theimages were obtained in the J and SK bands with and without acoronographic mask of 2arcsec diameter. The census is nearly complete inthe angular separation range 1arcsec - 6arcsec , corresponding to linearseparations of 200-1200 AU, which have remained unstudied so far due tothe intrinsic brightness of the massive primaries. The best detectionlimits are around K=15(m) at 1arcsec and K=19(m) at 5arcsec separationfrom the primary. In 13 fields of 12.5arcsec x 12.5arcsec 6 new faintstars were detected. Their magnitudes and colours indicate that 2 ofthem can be physical low-mass components. The bright (K=11.2, J-K=1.2)companion to HD 108250 C at 2.17arcsec has an IR excess and deservesfurther study. Several fields were explored without a mask; somewhatsurprisingly, no new components at sub-arcsecond separations down to0.2arcsec were detected. The first order stability analysis indicatesthat the studied multiple systems are hierarchical at spatial scales of40-1000 AU. The data are briefly discussed in the light of the formationand evolution of multiple systems with massive primaries. Based onobservations collected at the ESO La Silla Observatory (program58.D-0455).
|High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2.|
We investigate the rotational velocities of early-type stars in the ScoOB2 association. We measure v.sin(i) for 156 established and probablemembers of the association. The measurements are performed with threedifferent techniques, which are in increasing order of expectedv.sin(i): 1) converting the widths of spectral lines directly tov.sin(i), 2) comparing artificially broadened spectra of low v.sin(i)stars to the target spectrum, 3) comparing the HeI λ4026 lineprofile to theoretical models. The sample is extended with literaturedata for 47 established members of Sco OB2. Analysis of the v.sin(i)distributions shows that there are no significant differences betweenthe subgroups of Sco OB2. We find that members of the binary populationof Sco OB2 on the whole rotate more slowly than the single stars. Inaddition, we find that the B7-B9 single star members rotatesignificantly faster than their B0-B6 counterparts. We test varioushypotheses for the distribution of v.sin(i) in the association. Theresults show that we cannot clearly exclude any form of randomdistribution of the direction and/or magnitude of the intrinsicrotational velocity vector. We also investigate the effects of rotationon colours in the Walraven photometric system. We show that positions ofB7-B9 single dwarfs above the main sequence are a consequence ofrotation. This establishes the influence of rotation on the Walravencolours, due primarily to surface gravity effects.
|The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM|
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
|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.
|Some revisions to the Bright Star Catalogue and its supplement|
|The Einstein Slew Survey|
A catalog of 819 sources detected in the Einstein IPC Slew Survey of theX-ray sky is presented; 313 of the sources were not previously known asX-ray sources. Typical count rates are 0.1 IPC count/s, roughlyequivalent to a flux of 3 x 10 exp -12 ergs/sq cm s. The sources havepositional uncertainties of 1.2 arcmin (90 percent confidence) radius,based on a subset of 452 sources identified with previously knownpointlike X-ray sources (i.e., extent less than 3 arcmin).Identifications based on a number of existing catalogs of X-ray andoptical objects are proposed for 637 of the sources, 78 percent of thesurvey (within a 3-arcmin error radius) including 133 identifications ofnew X-ray sources. A public identification data base for the Slew Surveysources will be maintained at CfA, and contributions to this data baseare invited.
|An optical search for Beta Pictoris-like disks around nearby stars|
A coronagraphic survey of more than one hundred stars has been carriedout in a search at optical wavelengths for circumstellar materialsimilar to that found in the Beta Pictoris disk. The survey stars wereprimarily dwarfs in the spectral range A to K and most were closer than100 pc. No evidence of circumstellar material was found around any ofthe stars, suggesting that Beta Pictoris is an abnormal object,surrounded by an unusually large amount of optically scatteringmaterial.
|Catalogue of i and w/w crit values for rotating early type stars|
|Absolute fluxes for supernova 1987A. II - Days 51 to 157|
The 0.61-m Bochum telescope was used to obtain opticalspectrophotometric fluxes for SN 1987A from day 53 to day 157 after theexplosion. The evolution of the line spectrum is found to becharacterized by remarkable constancy in time, with the exception ofsome lines, including the Balmer lines. The disappearance of H-beta andH-gamma are interpreted as being related to the H-alpha Bochum event andto be due to the pervasion of radioactively heated hydrogen throughoutthe photosphere. Results are presented for absorption through equivalentwidths for H-alpha, Ca II, and Na I-D, as well as for integral linefluxes for the P Cyg emissions of Ca II and H-alpha and for theforbidden Ca II emission line at 7300 A.
|On the Origin of the Ptolemaic Star Catalogue - Part Two|
|Local intersteller medium|
Radio, IR, optical, UV, and X-ray observations of the local interstellarmedium (LISM) are reviewed, confirming the previous suggestion that thesun is located near an edge of a giant cavern with a radius of about 180pc whose center coincides with the Sco-Cen associated center. It issuggested that the bright spots of soft X-rays observed near thegalactic poles are produced by an interaction of stellar winds with theouter edge of the local cloud near the ends of Tinbergen's (1982) 'patchof polarization'. Results indicate that the main source of ionization ofextended H II regions of low density in the LISM is the Lyman continuumradiation from Sco-Cen stars.
|Photometric Data for the Bright Stars|
|The ionization of the very local interstellar gas|
The possible sources of the radiation responsible for the high degree ofionization observed in the interstellar H gas within about 10 micropc ofthe sun are investigated on the basis of published observational data.The photon fluxes of nearby B stars and hot white dwarfs are found to beinsufficient to account for the apparent ionization rate of about 10 tothe -13th/s H-atom, even when cosmic rays and the diffuse X-raybackground are taken into account. It is shown that a diffuse13.6-24.6-eV EUV flux of 10,000-100,000/sq cm s, probably from nearbygas at 100,000 K, or a transient event some 200-500 kyr ago would besufficient.
|Oscillator strengths for transitions in N I and the interstellar abundance of nitrogen|
Oscillator strengths based on configuration interaction wavefunctionsare presented for both optically allowed and forbidden transitions in NI. Particular attention is given to the multiplets at 951 A (2P3 4S-2p23d2 D), 952 A (2p3 4S-2p2 3d4 D) and 1160 A (2p3 4S-2p2 3s2 P) whichhave been extensively observed by the COPERNICUS satellite. For thesetransitions, the radiative rates are estimated to have an accuracy of 20percent or better. A reanalysis of the COPERNICUS observational dataindicates there is no depletion of nitrogen towards reddened stars.Possible causes of a small depletion towards several nearby unreddenedstars are discussed.
|Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.|
|Close visual binaries. I - MK classifications|
Each component of 170 close visual binaries has been classified with newprocedures for controlling contamination problems. These classificationsare presented and are shown to be on the MK system. Two sources of areascanner UBV photometry were compared in order to establish homogeneousphotometric as well as spectroscopic data. From a consideration ofsystematic errors in the V magnitude difference (Delta V) betweencomponents the photometry of Hurly and Warner (1983) is to be preferred.Absolute magnitudes for each binary are derived from Delta V via atested MK - M(v) map.
|Interstellar magnesium abundances|
An improved evaluation of the Mg II 1240 A doublet oscillator strengthis used in conjunction with recently published Copernicus observationsto derive accurate Mg II column densities toward 74 stars. These implyan average of 40 percent of interstellar magnesium is in the gaseousphase. Magnesium depletion is examined as a function of variousinterstellar extinction and density parameters, and the results arebriefly discussed in terms of current depletion theories.
|Observations of the stellar radiation field at 975 A|
Stellar observations in the extreme-ultraviolet (EUV) portion of thespectrum have been conducted by means of sounding rocket experiments.The first photometric measurements below 1000 A were carried out from arocket by Troy et al. (1975), who used channel electron multipliers withindium bandpass filters as detectors. The present investigation isconcerned with results obtained with a simple wide-field photometersimilar to that employed by Troy et al. However, in this case thephotometer was carried by a satellite and most of the celestial spherecould be observed. Only a few stars were spatially isolated enough forindividual flux determinations to be made. However, the measurementswere well suited for the determination of the total stellar radiationfield between 911 A and 1050 A. The STP 72-1 satellite, which carriedthe experiment, was launched into a circular 750 km altitude earth orbitin October 1972.
|On the distribution of interstellar matter around the sun|
Available data on interstellar line or EUV continuum absorptionattributable to the local (r equal to or less than 100 pc) interstellarmedium are presented and analyzed as a whole for clues leading to adeeper understanding of the spatial distribution and physical propertiesof this material. By using these data in conjunction with upper limitsprovided by polarization and color excess surveys and relatingeverything to the neutral-hydrogen column density, it is shown that thedata are consistent with a simple model that assumes the relativelypervasive presence of a tenuous (nH = 0.07 per cu cm), possibly warm (T= 1,000-10,000 K) gas extending uniformly out to considerable distancesfrom the sun in most directions. The only region manifestly clear ofthis material lies in the 200 deg to 270 deg galactic longitude range inboth high and low latitudes. Strong density discontinuities are clearlyobservable at r approximately 100-150 pc in the general directions ofthe Sco-Cen and Per associations and a weaker discontinuity much closerto the sun running along a ridge oriented parallel to the lineconnecting their centers. Beyond these fronts, the space density ofinterstellar matter must fall to very low values that extend out toseveral hundred parsecs or so from the sun. These results are notincompatible with H I, 21-cm, and soft X-ray all-sky surveys. Theimplication of these findings for the theory of the interstellar mediumand EUV visibility is briefly discussed.
|Area Scanner Observations of Close Visual Double Stars - Part Two - Results for 153 Southern Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983MNRAS.202..761H&db_key=AST
|Non-LTE analysis of carbon lines in the spectra of hot stars|
|Space distribution of stars in the southern Milky Way. III - A region in Centaurus-Crux|
Objective prism and photometric data on about 8000 stars of commonphotometric type and 158 OB stars are used to derive the space density,at various distances, of stars in several spectral-type groupings. At adistance of about 350 parsecs, a pronounced maximum is noted in thenumbers of B8-A1 stars and G-K giants. Indications are also found of amaximum in the OB star distribution at a distance of the order of 2500kpc. There is a sharp decrease in the numbers of later-type dwarfs withincreasing distance from the sun, although the data in question are onlyreliable for a few hundred parsecs.
|Photographic observations of visual double stars|
The results of photographic observations of 199 visual double stars,obtained at the Bosscha Observatory at Lembang, Indonesia, in the years1958-1975 (with one 1953 plate) are presented. The material comprises708 plates with an average of 37 images measured per plate. A shortdescription of the program is given (cf. van Albada-van Dien, 1958).
|Current NASA studies for a Far Ultraviolent Spectrographic Explorer (FUSE)|
The NASA plans for FUSE, a satellite which obtains spectra withresolutions between 100,000 and 100 in the spectral regions from 912 to1216A and 100 to 912A, are outlined. Scientific problems which can betackled by FUSE, but not by IUE or the Space Telescope, are discussed. Agrazing incidence echelle and a hybrid echelle design are presented.They have high throughput, large simultaneous spectral range, and lowbackground photon counting statistics. The satellite operationalorganization is similar to that of IUE.
|An Investigation of the Ancient Star Catalog|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982PASP...94..359R&db_key=AST
|Near-infrared observations of trapezium-type multiple systems Catalogue of observations and a new determination of the reddening law|
Results are presented from a large scale near-infrared survey of smallsky areas of the Milky Way containing trapezium-type multiple starsystems located within young galactic clusters, H II regions or darknebulosities. Photometric maps at wavelength 2.2 microns complemented bybroadband JHKL photometry of the majority of the sources detected and ofthe star members of the systems were obtained. A number of randomlychosen comparison regions along the galactic plane were also mapped andthe results were also used, with recent semi-empirical models, todetermine the number of field stars expected for the program surveys.Analyses of the infrared two-color diagrams provide determinations ofthe values of the color excess ratios E(J-H)/E(H-K), E(H-K)/E(K-L) andE(J-K)/E(K-L). The resulting reddening law is found to differsignificantly from that in the direction of the Ophiuchus and Taurusdark clouds and possibly towards the Galactic Center.