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|Statistical Constraints for Astrometric Binaries with Nonlinear Motion|
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
|Classification and Identification of IRAS Sources with Low-Resolution Spectra|
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
|Giants with infrared excess.|
We have correlated optical and infrared catalogs in order to extract alarge sample of luminosity class III stars with known infrared fluxdensities. For a non-negligible fraction of G and K giants, afar-infrared excess emission was found, starting beyond 25μm. Anexplanation in terms of present-day mass loss thus becomes unlikely,since the dust should then be warmer and the excess emission less far inthe infrared. We believe that the far-infrared excesses of theseobjects, most likely first-ascent giants, are related to the Vegaphenomenon. The dusty disks around these stars, gradually cooled downduring their main-sequence phase, could be reheated once the star leavesthe main sequence and enters the luminous post-main-sequence phase. Thefairly large sample we constructed enables us to derive an estimationfor the occurrence of excesses. This fraction of G or K giants withfar-infrared excess appears to be distinctly smaller than amongmain-sequence stars. Since the higher radiation field of giants couldlead to a larger evaporation rate of the circumstellar debris, this factdoes not conflict with our hypothesis.
|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%.
|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 position corrections of 1400 stars observed with PA II in San Juan.|
|Planetary system evolution and the VEGA stars: The potential for ESA's Infrared Space Observatory|
ESA's Infrared Space Observatory (ISO), scheduled for launch within thenext 2-3 years, will place a complement of powerful infrared imagers andspectrometers into high orbit, with an operational life anticipated tobe about 18 months. During this time, numerous scientific investigationsof every conceivable astrophysical target will be made. The purpose ofthis paper is to consider the instrumental complement in terms ofspecific observations of Vega-like systems with cold, infrared excesses,in order to investigate problems relating to the evolution of planetarysystems, and to optimize the scientific results possible with ISO onsuch topics.
|Evolved GK stars near the Sun. 2: The young disk population|
From a sample of nearly 2000 GK giants a group of young disk stars withwell determined space motions has been selected. The zero point of theluminosity calibrations, both from the ultraviolet flux (modifiedStroemgren system) and that in the region of 4200 to 4900 A (DDOsystem), show a discontinuity of about a half magnitude at the border ofthe young disk and old disk domains. The population separation is basedon the space velocity components, which are also an age discriminant,with the population interface near 2 x 109 yr, based onmodels with convective overshoot at the core. This age corresponds togiant masses near 1.7 solar mass, near the critical mass separating theyoung stars that do not burn helium in degenerate cores from older starsthat do. Ten percent of both populations show CN anomalies in that thederived value of P(Fe/H) from CN (Cm) and fromFe(M1) differ by more than 0.1 dex and the weak and strong CNstars occur equally in the old disk but the weak CN stars predominate inthe young disk. Peculiar stars, where flux distortions affect theluminosity calibrations, are of the CH+(Ba II) and CH-(weak G band)variety and represent less than 1% of the stars in both populations. Theyoung disk giants are restricted to ages greater than about109 yr, because younger stars are bright giants orsupergiants (luminosity class 2 or 1), and younger than about 2 x109 yr, because the old disk-young disk boundary occurs near1.7 solar mass. The distribution of heavy element abundances, P(Fe/H),for young disk giants is both more limited in range (+/- 0.4 dex) and isskewed toward higher abundances, compared with the nearly normaldistribution for old disk giants. The distribution of (U,V) velocityvectors gives (U,V,W) and their dispersions = (+17.6 +/- 18.4, -14.8 +/-8.4, -6.9 +/- 13.0) and (+3.6 +/- 38.4, -20.7 +/- 27.5, -6.7 +/-17.3)km/s for young and old disk giants, respectively.
|Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension|
|The absence of circumstellar dust debris around G giants|
The IRAS data base has been searched for evidence for circumstellar dustaround luminosity class III G giants, stars whose progenitors are mostlymain-sequence A stars. While 20 percent of all main-sequence A dwarfshave dust which absorbs at least 5 x 10 to the -6th of the light fromthe star, less than 3 percent of all G giants have such clouds. Onepossible explanation for the absence of detectable dust debris aroundthe G giants is that the Poynting-Robertson effect leads to the decay ofthe dust around the main-sequence A stars, and that the supply of thesegrains is not renewed indefinitely. In this case, the derived upperlimit to the grain radius of about 0.2 cm for the bulk of the grainsemitting the far-infrared emission is consistent with data derived fromground-based submillimeter observations. Another possible explanationfor the lack of grains around at least some G giants is that the dustaround the original A dwarf is mainly composed of relatively volatilematerial like water ice which thermally evaporates in a relatively shorttime during the giant phase of higher luminosity.
|Stellar integrated fluxes in the wavelength range 380 NM - 900 NM derived from Johnson 13-colour photometry|
Petford et al. (1988) have reported measured integrated fluxes for 216stars with a wide spread of spectral type and luminosity, and mentionedthat a cubic-spline integration over the relevant Johnson 13-colormagnitudes, converted to fluxes using Johnson's calibration, is inexcellent agreement with those measurements. In this paper a list of thefluxes derived in this way, corrected for a small dependence on B-V, isgiven for all the 1215 stars in Johnson's 1975 catalog with completeentries.
|A photometric survey of the bright southern Be stars|
Repeated UBV photometric measurements were made of the 86 bright Bestars south of declination -20 deg, and a network of comparison starswas set up. From a statistical study of the differential photometry itwas found that short- or intermediate-term variability seems to beoccurring in about half of the Be stars, and to be more evident in thestars of earlier spectral type. It was also possible to identify 11individual short- or intermediate-term variables. Four of these (all ofearly B spectral type) appear to exhibit significant variability on atime-scale of a day or less. More intensive observations of one of thesestars, 28 Omega CMA, indicate short-term variations consistent with thepublished spectroscopic period of 1.37 day.
|IRAS catalogues and atlases - Atlas of low-resolution spectra|
Plots of all 5425 spectra in the IRAS catalogue of low-resolutionspectra are presented. The catalogue contains the average spectra ofmost IRAS poiont sources with 12 micron flux densities above 10 Jy.
|Trigonometric parallax results for southern luminosity class III stars|
New trigonometric parallaxes are reported for ten bright, southernlate-type MK giants ranging in spectral type from K0 to M3.5. The listincludes HR 794, 1247, 2245, 2773, 3518, 3803, 5287, 5603, 6832, and6913. The modern parallaxes are compared with earlier results, and theluminosity calibration for these stars is discussed. A list of giants ispresented containing the best prospects for future parallax work onlate-type MK giants.
|Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.|
|Observations of emission from certain stars at millimeter wavelengths|
The paper presents results of observations of five alpha(2) CVn-typestars, five emission-line stars, the object SS 433, and four possiblerelated objects at 13.5 and 8.15 mm. It is confirmed that stars ofalpha(2) CVn-type are not characterized by significant radio emission.Emission variations from the emission-line star MWC 349 were detectedthat could be caused by optical luminosity variations of the star.Observations of SS 433 do not exclude the presence of an extendedenvelope around this object with dimensions and mass close to those ofthe envelope around MWC 349. It is also found that 2013 + 370 could beclassified as a BL Lac object.
|A determination of the effective temperatures, accelerations of gravity, and metallicity parameters of late-type stars from data on energy distribution in their spectra|
The effective temperatures and surface gravities are determined for 297F-M stars for which detailed spectrum energy distribution curves areavailable. For some of the stars, the Fe/H ratio is estimated. Theaccuracy of the values obtained is found to be comparable to that of theestimates based on narrow-band photometry.
|Stellar chromospheres - H-alpha and CA II K profiles|
A set of medium to high-resolution observations of H-alpha and Ca II Klines in a sample of Population I stars is presented in order to examinethe systematics of H-alpha absorption profiles and to determineempirically the extent to which velocity fields observed therein arereflected in the chromospheric component of the Ca II line. Formain-sequence stars, bright Ca II K emission profiles accompany shallowH-alpha lines with sharp central cores, unlike the apparently U-shapedH-alpha cores of stars displaying relatively weak Ca II K emission. Forgiants and supergiants, the H-alpha line is generally wider than acomputed LTE photospheric profile, with significant K(3) absorptionpresent in the Ca II K(2) reversal profile. The excess widths appear tocorrelate with the strength of the K(3) absorption. Estimates of thestrength of Ca II K(3) indicate severe modifications of Ca II K(2)widths and intensities, strongly affecting the cooling role of Ca II Kin the upper chromospheres.
|First astrolabe catalogue of Rio de Janeiro|
A catalogue of right ascensions and declinations of FK4 and FK4Supplement stars, obtained from astrolabe observations at Rio deJaneiro, is presented. The quantity and accuracy of the observations,the systematic errors of the catalogue, the group corrections, and theascension and declination corrections are considered.
|Optical, infrared, and radio studies of AFCRL sources|
The southern point sources in the AFCRL infrared (4, 11, and 20 microns)sky survey have been studied at infrared, optical, and radiowavelengths. Searches were performed at 2.2 microns to locate thesources, near-infrared photometry of them was secured, andclassification spectra of those with optical counterparts were obtained.OH observations have yielded 14 new Type II OH/IR sources and suggest acorrelation between the OH flux densities and the infrared colors. Mostof the AFCRL sources are carbon or late M stars similar to the reddestobjects in the IRC but extending to even redder color indices. Inaddition, two emission nebulae are found along with two WC stars, fiveBe stars, and three sources lying in or near reflection nebulae. Theconfirmed sources lie preferentially within a few degrees of thegalactic plane, and the carbon stars show a galactic-longitudedistribution different from that of the remainder. Many of the sourcesprobably vary at infrared wavelengths.
|Luminosity and velocity distributions of high-luminosity red stars. IV. The G-type giants|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..129E&db_key=AST
|Luminosity and velocity distribution of high-luminosity stars near the sun. II. The young disk giants|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..379E&db_key=AST
|BVRI Photoelectric Photometry for 275 Stars located between -25° y -50° Fotometría Fotoeléctrica en BVRI para 275 estrellas comprendidas en su mayoría entre -25° y -50°|
BYRI photometry in Johnson's system was done for 275 stars the mayority ofwhich are comprised between -25° and -50°. Due to systematicvariations in V magnitude in R. A. of the order of 0.2 magnitude it wasdecided to use in the present work V magnitudes of the Catalogue of theRoyal Observatory, Cape of Good Hope, South Africa. The colours presentedhere, should permit to have an homogeneous R and I Systems of photometryfor both the Northern and Southern sky, complete to the fifth magnitude, anup to -50° in declination
|The radial velocities of 185 stars observed at the Cape.|
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