Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
C II Abundances in Early-Type Stars: Solution to a Notorious Non-LTE Problem
We address a long-standing discrepancy between non-LTE analyses of theprominent C II 4267 and 6578/82 Å multiplets in early-type stars.A comprehensive non-LTE model atom of C II is constructed based oncritically selected atomic data. This model atom is used for anabundance study of six apparently slow-rotating main-sequence and giantearly B-type stars. High-resolution and high S/N spectra allow us toderive highly consistent abundances not only from the classical featuresbut also from up to 18 additional C II lines in the visual-including twoso far unreported emission features equally well reproduced in non-LTE.These results require the stellar atmospheric parameters to bedetermined with care. A homogeneous (slightly) subsolar present-daycarbon abundance from young stars in the solar vicinity (in associationsand in the field) of log(C/H)+12=8.29+/-0.03 is indicated.
| A high-resolution spectroscopy survey of β Cephei pulsations in bright stars
We present a study of absorption line-profile variations in early-B typenear-main-sequence stars without emission lines. We have surveyed atotal of 171 bright stars using the Nordic Optical Telescope (NOTSA),William Herschel Telescope (ING) and Coudé Auxiliary Telescope(ESO). Our sample contains 75% of all O9.5-B2.5 III-V non-emission-linestars brighter than 5.5 mag. We obtained high signal-to-noise,high-resolution spectra of the SiIII λ4560 triplet - for 125stars of our sample we obtained more than one spectrum - and examinedthese for pulsational-like line-profile variations and/or structure. Weconclude that about half of our sample stars show evidence forline-profile variations (LPV). We find evidence for LPV in about 65% ofour sample stars brighter than V=5.5. For stars with rotationalbroadening V sin i 100 km s-1, we find evidence for LPVin about 75% of the cases. We argue that it is likely that these LPV areof pulsational origin, and that hence more than half of thesolar-neighbourhood O9.5-B2.5 III-V stars is pulsating in modes that canbe detected with high-resolution spectroscopy. We detected LPV in 64stars previously unknown to be pulsators, and label these stars as newβ Cep candidates. We conclude that there is no obvious differencein incidence of (pulsational) LPV for early-B type near-main-sequencestars in binaries or in OB associations, with respect to single fieldstars.
| Catalog of Galactic β Cephei Stars
We present an extensive and up-to-date catalog of Galactic β Cepheistars. This catalog is intended to give a comprehensive overview ofobservational characteristics of all known β Cephei stars, coveringinformation until 2004 June. Ninety-three stars could be confirmed to beβ Cephei stars. We use data from more than 250 papers publishedover the last nearly 100 years, and we provide over 45 notes onindividual stars. For some stars we reanalyzed published data orconducted our own analyses. Sixty-one stars were rejected from the finalβ Cephei list, and 77 stars are suspected to be β Cepheistars. A list of critically selected pulsation frequencies for confirmedβ Cephei stars is also presented.We analyze the β Cephei stars as a group, such as the distributionsof their spectral types, projected rotational velocities, radialvelocities, pulsation periods, and Galactic coordinates. We confirm thatthe majority of the β Cephei stars are multiperiodic pulsators. Weshow that, besides two exceptions, the β Cephei stars with highpulsation amplitudes are slow rotators. Those higher amplitude starshave angular rotational velocities in the same range as thehigh-amplitude δ Scuti stars (Prot>~3 days).We construct a theoretical HR diagram that suggests that almost all 93β Cephei stars are main-sequence objects. We discuss theobservational boundaries of β Cephei pulsation and the physicalparameters of the stars. We corroborate that the excited pulsation modesare near to the radial fundamental mode in frequency and we show thatthe mass distribution of the stars peaks at 12 Msolar. Wepoint out that the theoretical instability strip of the β Cepheistars is filled neither at the cool nor at the hot end and attempt toexplain this observation.
| Video observation of meteors at Yunnan Observatory
In the last 20 years, with the development of the CCD and imageintensifiers, the use of small flexible video meteor observation systemshas gradually increased, with the prospect that one day videoobservation will replace the visual observation and ordinaryphotographic observations. In this paper we report on the research anddevelopment of the No.1 meteor-comet video camera system of YunnanObservatory and some preliminary observed results. The system consistsof 5 changeable modules; it has a 36° large-field camera dedicatedto the observation of meteors, with which a magnitude 6 star can berecorded on a single frame with an accuracy of about 0.2 mag. We alsopresent a comparison of the video camera system with the traditionalphotographic system, and outline the merits, possible improvements andfuture development of the video system.
| A 3-5 μ m VLT spectroscopic survey of embedded young low mass stars I. Structure of the CO ice
Medium resolution (lambda /Delta lambda = 5000-10 000) VLT-ISAACM-band spectra are presented of 39 young stellar objects in nearbylow-mass star forming clouds showing the 4.67 μm stretching vibrationmode of solid CO. By taking advantage of the unprecedentedly largesample, high S/N ratio and high spectral resolution, similarities in theice profiles from source to source are identified. It is found thatexcellent fits to all the spectra can be obtained using aphenomenological decomposition of the CO stretching vibration profile at4.67 μm into 3 components, centered on 2143.7 cm-1, 2139.9cm-1 and 2136.5 cm-1 with fixed widths of 3.0, 3.5and 10.6 cm-1, respectively. All observed interstellar COprofiles can thus be uniquely described by a model depending on only 3linear fit parameters, indicating that a maximum of 3 specific molecularenvironments of solid CO exist under astrophysical conditions. A simplephysical model of the CO ice is presented, which shows that the 2139.9cm-1 component is indistinguishable from pure CO ice. It isconcluded, that in the majority of the observed lines of sight, 60-90%of the CO is in a nearly pure form. In the same model the 2143.7cm-1 component can possibly be explained by the longitudinaloptical (LO) component of the vibrational transition in pure crystallineCO ice which appears when the background source is linearly polarised.The model therefore predicts the polarisation fraction at 4.67 μm,which can be confirmed by imaging polarimetry. The 2152 cm-1feature characteristic of CO on or in an unprocessed water matrix is notdetected toward any source and stringent upper limits are given. Whenthis is taken into account, the 2136.5 cm-1 component is notconsistent with the available water-rich laboratory mixtures and wesuggest that the carrier is not yet fully understood. A shallowabsorption band centered between 2165 cm-1 and 2180cm-1 is detected towards 30 sources. For low-mass stars, thisband is correlated with the CO component at 2136.5 cm-1,suggesting the presence of a carrier different from XCN at 2175cm-1. Furthermore the absorption band from solid13CO at 2092 cm-1 is detected towards IRS 51 inthe rho Ophiuchi cloud complex and an isotopic ratio of12CO/13CO=68+/-10 is derived. It is shown that allthe observed solid 12CO profiles, along with the solid13CO profile, are consistent with grains with an irregularlyshaped CO ice mantle simulated by a Continuous Distribution ofEllipsoids (CDE), but inconsistent with the commonly used models ofspherical grains in the Rayleigh limit.Based on observations obtained at the European Southern Observatory,Paranal, Chile, within the observing programs 164.I-0605 and 69.C-0441.ISO is an ESA project with instruments funded by ESA Member States(especially the PI countries: France, Germany, The Netherlands and theUK) and with the participation of ISAS and NASA.Table \ref{SourceList} and Appendices A and B are only available inelectronic form at http://www.edpsciences.org
| Revisiting the solid HDO/H2O abundances
We revisit the reported detection and upper limits on HDO in ice mantlespresent in the molecular cloud environments of the massive youngprotostars Gl 2136 and W33 A, using independent VLT-ISAAC and UKIRT-CGS4spectroscopic observations. We also present VLT and UKIRT spectra ofRAFGL 7009 near the HDO absorption wavelength and reanalyze the ISO-SWSspectral data for NGC 7538 IRS9, Orion-BN and S140. We demonstrate thatthe previously reported detections of HDO in W33 A and NGC 7538 IRS9 areincorrect. We present an in-depth analysis that shows that, besides thesensitivity limits, detection of low levels of HDO is difficult inamorphous ice mantles when features from solid methanol, a common grainmantle constituent, are present. We discuss the specific problemsarising in the ISO data in this wavelength range for NGC 7538 IRS9.Using VLT-ISAAC observations, we also investigate the HDO/H2Oratio toward the intermediate mass stars IRAS 05329-0728 and IRAS08448-4343. Our derived upper limits for the D/H ratio in water icerange from HDO/H2O < 1% to 0.2% in the different sources,and we discuss these limits in comparison with values derived in otherenvironments.Based on observations collected at the European Southern Observatory,Paranal, Chile (ESO Programme 164.I-0605(A)), UKIRT, Mauna Kea, Hawaii,and ISO satellite. The United Kingdom Infrared Telescope is operated bythe Joint Astronomy Centre on behalf of the UK Particle Physics andAstronomy Research Council. TRG's research is supported by the GeminiObservatory, which is operated by the Association of Universities forResearch in Astronomy, Inc., on behalf of the international Geminipartnership of Argentina, Australia, Brazil, Canada, Chile, the UK, andthe USA.
| The latitude and epoch for the formation of the southern Greek constellations
Not Available
| Boron Abundances in Early B Stars: Results from the B III Resonance Line in IUE Data
We have used archival International Ultraviolet Explorer high-dispersionSWP spectra to study the B III resonance line at 2065.8 Å in 44early B stars. We find a median boron abundance about half that of solarsystem meteoritic material, consistent with the values found fromprevious studies of boron in early B stars. About one-third of the starsstudied appear to have boron abundances that are a factor of 4 or morelower than this median. Many of these are stars with enhanced nitrogenabundances, confirming the belief that deep envelope mixing can occur inmain-sequence B stars. A few stars with low boron abundances have normalN/C ratios. It is unclear whether all of these can be explained as starswhere mixing depleted the boron but did not go deep enough to bringCN-processed material to the surface or if some stars were actuallyformed with an unusually low boron abundance.
| Observations of OB-stars at the former Leiden Southern Station
About 700 stars, mostly OB-stars, were observed by the author at theformer Leiden Southern Station at Hartebeespoortdam, South Africa, inthe observing seasons 1965, 1968, 1969, 1974, 1977, 1978. Observationswere made in the five channels of the Walraven photometric system. Dueto weathering of the telescope mirror the W channel gave no reliableresults for the faintest stars (m = 11 mag); in these cases the U-Wcolour index is not given. The change in sensitivity in the V channel,supposedly having occurred in 1968, was not recognised. Table~5 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/369/527
| 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
| The proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
| Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over more than twocenturies and summarized in the FK5. Part I of the FK6 (abbreviatedFK6(I)) contains 878 basic fundamental stars with direct solutions. Suchdirect solutions are appropriate for single stars or for objects whichcan be treated like single stars. From the 878 stars in Part I, we haveselected 340 objects as "astrometrically excellent stars", since theirinstantaneous proper motions and mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,199 of the stars in Part I are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives in addition to the SI mode the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(I) proper motion in the single-star mode is 0.35 mas/year. This isabout a factor of two better than the typical HIPPARCOS errors for thesestars of 0.67 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(I) proper motions have atypical mean error of 0.50 mas/year, which is by a factor of more than 4better than the corresponding error for the HIPPARCOS values of 2.21mas/year (cosmic errors included).
| A Second Catalog of Orbiting Astronomical Observatory 2 Filter Photometry: Ultraviolet Photometry of 614 Stars
Ultraviolet photometry from the Wisconsin Experiment Package on theOrbiting Astronomical Observatory 2 (OAO 2) is presented for 614 stars.Previously unpublished magnitudes from 12 filter bandpasses withwavelengths ranging from 1330 to 4250 Å have been placed on thewhite dwarf model atmosphere absolute flux scale. The fluxes wereconverted to magnitudes using V=0 for F(V)=3.46x10^-9 ergs cm^-2 s^-1Å^-1, or m_lambda=-2.5logF_lambda-21.15. This second catalogeffectively doubles the amount of OAO 2 photometry available in theliterature and includes many objects too bright to be observed withmodern space observatories.
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| Mapping the contours of the Local bubble: preliminary results
We present preliminary results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,taking advantage of Hipparcos stellar distances. Equivalent widths ofthe NaI D-line doublet at 5890 Å are presented for thelines-of-sight towards some 143 new target stars lying within 300 pc ofthe Sun. Using these data which were obtained at the Observatoire deHaute Provence, together with previously published NaI absorptionmeasurements towards a further 313 nearby targets, we present absorptionmaps of the distribution of neutral gas in the local interstellar mediumas viewed from 3 different galactic projections. In particular, thesemaps reveal the Local Bubble region as a low neutral densityinterstellar cavity in the galactic plane with radii between 65-250 pcthat is surrounded by a (dense) neutral gas boundary (or ``wall''). Wehave compared our iso-column contours with the contours derived bySnowden et al. (\cite{snowden98}) using ROSAT soft X-ray emission data.Consistency in the global dimensions derived for both sets of contoursis found for the case of a million degree hot LB plasma of emissivity0.0023 cm(-6) pc with an electron density of 0.005 cm(-2) . We havedetected only one relatively dense accumulation of cold, neutral gaswithin 60 pc of the Sun that surrounds the star delta Cyg, and note thatthe nearest molecular cloud complex of MBM 12 probably resides at thevery edge of the Local Bubble at a distance of ~ 90 pc. Our observationsmay also explain the very different physical properties of the columnsof interstellar gas in the line-of-sight to the two hot stars epsilonCMa and beta CMa as being due to their locations with respect to theBubble contours. Finally, in the meridian plane the LB cavity is foundto be elongated perpendicularly to the Gould's Belt plane, possiblybeing ``squeezed'' by the expanding shells of the Sco-Cen andPerseus-Taurus OB associations. Tables 1 and 2 are also available inelectronic form at the CDS (Strasbourg) via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| A Minisurvey of Interstellar Titanium from the Southern Hemisphere
We describe the results of a minisurvey of interstellar Ti II and Ca IIabsorption toward 42 early-type stars observed from the southernhemisphere at a spectral resolution of 4.5 km s-1. Results are alsopresented for the Na I ultraviolet line (3302 Angstroms) detected towardnine of these targets. We examine the dependence of the integratedcolumn densities of N(Ti II), N(Ca II), and N(Na I) on distance,reddening, neutral hydrogen column density, and their Galactic elementalabundance. Our findings support the proposition that Ti II and Ca IIabsorption originates in the same regions of the pervasive, warm, andneutral intercloud gas of the interstellar medium. We have observed acorrelation of decreasing Ti and Ca abundance with increasingline-of-sight gas density. The Ti II/Ca II abundance ratio has beenfound to be essentially constant under all the interstellar densityconditions we have sampled. Thus, we conclude that the generalabsorption properties of titanium (and calcium) are similar throughoutthe entire disk of our Galaxy.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Accuracy of effective temperatures of solar chemical composition stars derived from the flux fitting method.
We discuss the uncertainties affecting the determinations of effectivetemperature and apparent angular diameters based on the flux fittingmethod. We use Kurucz model fluxes and the spectrophotometric scansgiven in Breger Catalog. In particular, we analyze and discuss theinfluence of indetermination which may affect the fixed secondaryparameters (i.e. surface gravity, overall metallicity, and interstellarreddening correction) on the estimates of the fitted parameters, T_eff_and φ. The role of different sources of data for the same star andof each of the above mentioned parameters is described in detail forfive representative stars, while 130 non-supergiant solar chemicalcomposition stars, in the spectral range G8 - B0, are used toquantitatively illustrate the statistical behaviour of uncertainties.
| 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%.
| A Spectral Atlas of Hot, Luminous Stars at 2 Microns
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..107..281H&db_key=AST
| The Stellar Content of Star Stream I
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1615E&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.
| The determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A.
A method of determination of the effective temperature of B, A and Fmain sequence stars is proposed, using the slope of the continuumbetween 3200A and 3600A. The effective temperature calibration is basedon a sample of stars with energy distributions known from UV to the red.We have determined the Balmer jump and the effective temperatures for235 main sequence stars. The temperatures found have been compared withthose derived by Underhill et al. (1979), Kontizas & Theodossiou(1980), Theodossiou (1985), Morossi & Malagnini (1985). Thecomparison showed good agreement for most of the stars in common. On theother hand, the temperatures derived from the reddening-free colourfactor QUV, from the colour index (m1965-V) and from (B-V), given inGulati et al. (1989), are systematically lower than our temperatures,however the differences are within one-sigma error.
| 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.
Not Available
| An atlas of ultraviolet P Cygni profiles
We have selected spectra of 232 stars from the International UltravioletExplorer (IUE) archives for inclusion in an atlas intended for varioususes but tailored especially for the study of stellar winds. The atlascovers the range in spectral types from O3 to F8. The full atlas coversthe reduced and normalized high resolution spectra from the IUE long-and short-wavelength spectrographs. Here we discuss the selection of thestars and the data reduction, and we present in velocity units theprofiles of lines formed in the stellar winds. The selected lines covera wide range of ionizations, allowing a comparison of the profiles fromdifferent ions in the wind of each star and a comparison of thedifferent wind lines as a function spectral type and luminosity. We alsopresent the basic data on the program stars to facilitate study of thedependence of wind features on stellar parameters such as luminosity,temperature, escape velocity, and v sin i. We provide an overview of thecharacteristic behavior of the wind lines in the H-R diagram. Thecomplete spectra are available in digital form through the NASAAstrophysics Data System (ADS). We offer a description of the electronicdatabase that is available through the ADS and guidelines for obtainingaccess to that database.
| An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
| 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.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Компас |
| Прямое восхождение: | 08h43m35.50s |
| Склонение: | -33°11'11.0" |
| Видимая звёздная величина: | 3.68 |
| Расстояние: | 259.067 парсек |
| Собственное движение RA: | -14.4 |
| Собственное движение Dec: | 10.7 |
| B-T magnitude: | 3.438 |
| V-T magnitude: | 3.631 |
Каталоги и обозначения:
|
INHABITED SKY
