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Three-micron spectra of AGB stars and supergiants in nearby galaxies
The dependence of stellar molecular bands on the metallicity is studiedusing infrared L-band spectra of AGB stars (both carbon-rich andoxygen-rich) and M-type supergiants in the Large and Small MagellanicClouds (LMC and SMC) and in the Sagittarius Dwarf Spheroidal Galaxy. Thespectra cover SiO bands for oxygen-rich stars, and acetylene (C2H2), CHand HCN bands for carbon-rich AGB stars. The equivalent width ofacetylene is found to be high even at low metallicity. The high C2H2abundance can be explained with a high carbon-to-oxygen (C/O) ratio forlower metallicity carbon stars. In contrast, the HCN equivalent width islow: fewer than half of the extra-galactic carbon stars show the 3.5μm HCN band, and only a few LMC stars show high HCN equivalent width.HCN abundances are limited by both nitrogen and carbon elementalabundances. The amount of synthesized nitrogen depends on the initialmass, and stars with high luminosity (i.e. high initial mass) could havea high HCN abundance. CH bands are found in both the extra-galactic andGalactic carbon stars. One SMC post-AGB star, SMC-S2, shows the 3.3μm PAH band. This first detection of a PAH band from an SMC post-AGBstar confirms PAHs can form in these low-metallicity stars. None of theoxygen-rich LMC stars show SiO bands, except one possible detection in alow quality spectrum. The limits on the equivalent widths of the SiObands are below the expectation of up to 30 Å for LMC metallicity.Several possible explanations are discussed, mostly based on the effectof pulsation and circumstellar dust. The observations imply that LMC andSMC carbon stars could reach mass-loss rates as high as their Galacticcounterparts, because there are more carbon atoms available and morecarbonaceous dust can be formed. On the other hand, the lack of SiOsuggests less dust and lower mass-loss rates in low-metallicityoxygen-rich stars. The effect on the ISM dust enrichment is discussed.
| MSX, 2MASS, and the LARGE MAGELLANIC CLOUD: A Combined Near- and Mid-Infrared View
The Large Magellanic Cloud (LMC) has been observed by the MidcourseSpace Experiment (MSX) in the mid-infrared and the Two Micron All SkySurvey (2MASS) in the near-infrared. We have performed across-correlation of the 1806 MSX catalog sources and nearly 1.4 million2MASS cataloged point and extended sources and find 1664 matches. Usingthe available color information, we identify a number of stellarpopulations and nebulae, including main-sequence stars, giant stars, redsupergiants, carbon- and oxygen-rich asymptotic giant branch (AGB)stars, planetary nebulae, H II regions, and other dusty objects likelyassociated with early-type stars. A total of 731 of these sources haveno previous identification. We compile a listing of all objects, whichincludes photometry and astrometry. The 8.3 μm MSX sensitivity is thelimiting factor for object detection: only the brighter red objects,specifically the red supergiants, AGB stars, planetary nebulae, and H IIregions, are detected in the LMC. The remaining objects are likely inthe Galactic foreground. The spatial distribution of the infrared LMCsources may contribute to understanding stellar formation and evolutionand the overall galactic evolution. We demonstrate that a combined mid-and near-infrared photometric baseline provides a powerful means ofidentifying new objects in the LMC for future ground-based andspace-based follow-up observations.
| Obscured AGB stars in the Magellanic Clouds. I. IRAS candidates
We have selected 198 IRAS sources in the Large Magellanic Cloud, and 11in the Small Magellanic Cloud, which are the best candidates to bemass--loosing AGB stars (or possibly post--AGB stars). We used thecatalogues of \cite[Schwering \& Israel (1990)]{ref42} and\cite[Reid et al. (1990)]{ref36}. They are based on the IRAS pointedobservations and have lower detection limits than the Point SourceCatalogue. We also made cross-identifications between IRAS sources andoptical catalogues. Our resulting catalogue is divided in 7 tables.Table \ref{tab1} lists optically known red supergiants and AGB stars forwhich we found an IRAS counterpart (7 and 52 stars in the SMC and LMC,respectively). Table \ref{tab2} lists ``obscured'' (or ``cocoon'') AGBstars or late-type supergiants which have been identified as such inprevious works through their IRAS counterpart and JHKLM photometry (2SMC and 34 LMC sources; no optical counterparts). Table \ref{tab3} listsknown planetary nebulae with an IRAS counterpart (4 SMC and 19 LMC PNe).Table \ref{tab4} lists unidentified IRAS sources that we believe to begood AGB or post--AGB or PNe candidates (11 SMC and 198 LMC sources).Table~\ref{tab5} lists unidentified IRAS sources which could be any typeof object (23 SMC and 121 LMC sources). Table \ref{tab6} lists IRASsources associated with foreground stars (29 SMC and 135 LMC stars).Table \ref{tab7} lists ruled out IRAS sources associated with HIIregions, hot stars, etc... We show that the sample of IRAS AGB stars inthe Magellanic Clouds is very incomplete. Only AGB stars more luminousthan typically 10^4 L_\odot and with a mass-loss rate larger thantypically 5 10^{-6} M_\odot/yr could be detected by the IRAS satellite.As a consequence, one expects to find very few carbon stars in the IRASsample. We also expect that most AGB stars with intermediate mass--lossrates have not been discovered yet, neither in optical surveys, nor inthe IRAS survey. Tables 1 to 8 are also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Supernova 1987A - Photometry of the discovery and pre-discovery plates
An analysis of the discovery and prediscovery plates for SN 1987A ispresented. The second earliest reliable photometric measurements for theSN have found to have a B magnitude of 5.00 (+/- 0.15) on Feb.24.12 UT1987, while for Sanduleak -69 deg 202 was found to have a B magnitude of12.12 (+/- 0.15) on Feb 23.08 UT 1987. These discovery and pre-discoveryplates represent, respectively, the second earliest reliable photometricmeasure for the SN and the last known observation of its precursor. TheB magnitude reported here for SN 1987A is about 0.2 mag fainter thanfound by Shelton and Lapasset (1993) five hours later, indicating thatthe supernova was still rising to 'first maximum light' in the Bbandpass 19 hours after the IMB/Kamiokande-II neutrino detection. Dataobtained subsequent to this observation through to the third dayindicates a nearly constant B magnitude.
| 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.
| Intensive photometry of southern Be variables. II - Summer objects
Results are presented of photometric campaign on some bright southern Bestars to search for periodic light variations. In order to obtain goodphase coverage, many observations were conducted from two sites withdifferent longitudes: ESO and SAAO. A large fraction of early-Be starsare found to be variable with periods close to or equal to theirrotational periods. Particular attention is devoted to the late-Bestars. Unlike the hotter members of this class, the late-Be stars do notseem to have detectable periodic light variations except for one or twostars of very small amplitude.
| Earliest photometry of SN 1987A
Seven wide-field photographic exposures, obtained of the LMC field on1987 Feb. 22 - 24 in Australia, and including the earliest recordedimages of SN 1987A, have been scanned and photometrically calibrated bymeans of bright field stars. Accurate V-magnitudes of SN 1987A arederived by means of fixed-diaphragm, color adjusted, integrated fluxes;on Feb. 23 it is found to be 0.2 - 0.8 mag brighter than indicated byearlier estimates, based on image diameters alone. The measurements nowagree rather better with the theoretical light curves, e.g. those byWoosley (1988).
| Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
| The spectral energy distribution of early-type stars. II - The extinction law towards O-type stars
Photometric measurements through different pass-bands are used todetermine the color-excess E(B-V) for O-type stars in the UV and IRspectral regions. The results are used to examine the extinctioncharacter of the stars. It is found that, in the UV, each O-type starhas its own extinction character. In general, the visual and NIRextinction in the direction of O-type stars are normal.
| Absolute fluxes for Supernova 1987 A. I - The first 50 days
Directly measured and carefully calibrated spectrophotometric fluxes forSupernova 1987 A obtained at 10 A resolution and covering the wavelengthrange from 3200 to 9000 A are presented for the period February 25 toApril 14, 1987, the first 50 days of SN 1987 A. It is demonstrated thatthe general evolution of both the flux distribution and the linespectrum takes place in two phases. In the first phase, a rapid decreaseof UV flux, slow increase of red and near-IR flux, rapid decrease ofobserved Doppler shifts of spectral lines, and rapid evolution toward arich absorption and P Cyg-type line spectrum are observed. This phaselasts until approximately March 15, after which date a second phasebegins, characterized by a gradual increase of flux at all observedwavelengths, slow decrease of Doppler shifts, and nearly constant linespectrum.
| Photometry of SN 1987A
Photometric observations of SN 1987A have been carried out at La Sillain the UBVRI, Geneva, H-beta, Stromgren and Walraven systems. Luminosityvariations on short timescales have also been investigated. The resultsfor the period from February 24 to March 22 are reported.
| The spectral energy distribution of early type stars. I - A catalogue of photometric data of 259 stars from 0.15 to 4.8 microns
For the derivation of physical parameters (e.g., effective temperatureand radius) of early-type stars from their intrinsic spectral-energydistribution, and for the study of foreground interstellar and/orcircumstellar matter, a sample of 237 O, B, and A stars was chosen fromthe ANS catalog (Wesselius et al., 1982). The ANS ultraviolet and theJohnson UBV data (mostly from Nicolet's catalog, 1978) of these starswere supplemented with visual Walraven WULBV, red VRI, and near-infraredJHKLM measurements. All these data are given in the present catalog.Data for 22 stars of spectral type later than A are also included.
| 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.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| The galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
| The S201 far-ultraviolet imaging survey. I - Two fields at high galactic latitude
Far-ultraviolet imagery was obtained of 10 20-deg diameter fields by theS201 far-ultraviolet camera during the Apollo 16 mission. The presentdiscussion is of two high galactic latitude fields, in Grus andAquarius, in which exposures of up to 30 minutes duration were obtainedin the 1250-1600 A wavelength range (effective wavelength 1400 A), andin which objects as faint as m(1400) = 11.8 are detected. The numberversus magnitude relation for the observed objects appears to peak nearm(1400) = 10, implying that relatively few such objects exist atmagnitudes fainter than our sensitivity limit. Most of the stellarcontribution to the ultraviolet radiation field is contributed by starsbrighter than m(1400) = 6, which are mainly nearby late B and early Amembers of the galactic disk population. The objects fainter thanm(1400) = 8, however, appear to be members of a second population ofhot, subluminous objects, but further ground-based observations of theseobjects are needed.
| VBLUW photometry of Cepheids in the Magellanic Clouds made in 1971-1978
Light and color curves and the periods of 21 SMC and 20 LMC Cepheidsstudied with VBLUW photometry between 1971 and 1978 are discussed.Improved periods are given and their variations are addressed. Newformulas for the epochs of maximum light are given. Almost all theCepheids show period variations in the range of less than one percent upto a few percent. Only one Cepheid shows definite light curve changes,while two others may show changes in their light curves.
| Picture gallery - A structured presentation of OAO-2 photometric data supported by OAO-2 spectrophotometric data and UBV, ANS and TD1 observations
Graphs are presented for the stellar fluxes of 531 stars in the5500-1330 A wavelength range, which have been divided into 52 categorieson the basis of spectral types. The merging of medium band interferencefilter photometry, UBV photometry, ANS photometry and TD1 fluxes, aswell as the ordering of the objects, should prove helpful in studies ofinterstellar reddening, luminosity effects, bandwidth effects, andcomparisons with model stellar atmospheres. The agreement between thevarious UV photometric systems for early-type stars is generally betterthan 0.10 mag. A list of stars whose photometric properties indicatestellar or interstellar anomalies is also provided.
| Geneva photometric boxes. II - The reddening towards the galactic poles
It is noted that photometric boxes allow a very accurate estimation ofindividual reddenings for B- and early A-type stars. A catalog of 129stars with galactic latitudes higher than 30 deg is given. A small butsignificant reddening is seen in the direction of both the northern andsouthern galactic poles: E(B-V) approximately 0.04.
| LB 3459, an O-type subdwarf eclipsing binary system. III - Radial velocity curve and orbital solutions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981MNRAS.194..429K&db_key=AST
| Five-colour photometry of blue stars in the Magellanic-Cloud region
The results of photoelectric observations of about 500 stars in andbetween the Magellanic Clouds are given. The observations were made inthe Walraven VBLUW-system. Within the limits of the study, no cloudmembers are found to be associated with the neutral hydrogen between theclouds. Seventy-five stars, previously reported to be cloud members byothers, were found independently. A large number of new members of thewing system of the SMC are identified. The great eastward extension ofthe wing system is clearly illustrated by the results
| Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIV - Filter photometry of 531 stars of diverse types
Ultraviolet magnitudes for 531 stars observed with the WisconsinExperiment Package on OAO 2 are tabulated. It is noted that these dataconstitute a subset of the OAO 2 data on file at the National SpaceScience Data Center. The tabulation contains previously published dataall reduced to a uniform magnitude system. It is pointed out that theobservations were obtained with the medium band interference filterphotometers. Eleven magnitudes are given designated by their centroidwavelengths.
| Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXVIII - A second atlas of ultraviolet stellar spectra
Ultraviolet stellar spectra are presented for 132 stars in the spectralregion from 1200 to 1850 A and 34 stars in the region from 1800 to 3600A in a graphical and tabular form. The spectra represent a subset of OAO2 spectrometer data on file at the National Space Science Data Center.The monochromatic flux is given in units of ergs/sq cm s A with aspectral resolution of about 12 A in the region from 1850 to 1160 A andof about 22 A in the region from 3600 to 1800 A.
| Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
| Space velocities and ages of nearby early-type stars
Photometric distances and space velocities have been calculated for 458B0-A0 stars with apparent magnitudes not exceeding 6.5. UsingStromgren's ubvy-beta photometry the effective temperature and theposition in bolometric magnitude over the zero-age main sequence of thestars were derived. These quantities were used to obtain age and massfor 423 of the stars by interpolation in the models of stellar evolutionfor the chemical composition (X Z) = (0.7, 0.03). A relation forderiving interstellar reddening for normal stars in the intermediategroup is given.
| Spectral classification from the ultraviolet line features of S2/68 spectra. II - Late B-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...30...71C&db_key=AST
| Properties of the Walraven VBLUW photometric system
The Walraven five-channel (VBLUW) photometer has been used primarily tostudy Cepheids and RR Lyrae variables. Those properties of the VBLUWphotometric system are discussed which are important for analyzing andinterpreting data on such stars. The standard stars that define thesystem are examined, the long-term stability of these stars is examined,and the responses of the photometric passbands are analyzed. Correctionsfor atmospheric extinction and interstellar reddening are reviewed,noting that color terms in the extinction corrections are sufficientlysmall to be neglected and that nonlinear terms in reddening correctionscan also be neglected provided the reddening is not higher than about1.25 magnitudes. Application of the VBLUW system to the classificationof A, F, and G stars, Hyades main-sequence stars, bright field stars,and subdwarfs is demonstrated, and observed two-color diagrams arecompared with theoretical diagrams based on model atmospheres. It isconcluded that a three-dimensional classification based on effectivetemperature, surface gravity, and heavy-element abundance is possiblefor A, F, and G spectral types and that VBLUW photometry is more thantwice as sensitive as Stroemgren uvby photometry to differences inheavy-element abundances below 8000 K.
| Five-channel photometry of cepheids and supergiants in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24..413P&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | דג זהב |
| התרוממות ימנית: | 05h49m53.60s |
| סירוב: | -66°54'04.0" |
| גודל גלוי: | 5.11 |
| מרחק: | 156.986 פארסק |
| תנועה נכונה: | -22 |
| תנועה נכונה: | 19.1 |
| B-T magnitude: | 4.922 |
| V-T magnitude: | 5.071 |
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