目录
图像
上传图像
DSS Images Other Images
相关文章
New insights on the complex planetary nebula Hen 2-113
We report on infrared observations of the planetary nebula Hen 2-113obtained with VLT/NACO, VLTI/MIDI, VLT/ISAAC and TIMMI at the ESO 3.6 m.Hen 2-113 exhibits a clear ring-like structure superimposed to a morediffuse environment visible in the L' (3.8 μm), M' (4.78 μm) and8.7 μm bands. No clear core at 8.7 μm and no fringes through the Nband could be detected for this object with MIDI. A qualitativeinterpretation of the object structure is proposed using a diabolo-likegeometrical model. The PAH content of the nebula was also studied withISAAC and TIMMI observations. This indicates that the PAHs are mostlyconcentrated towards the lobes of the diabolo and the bipolar lobes ofthe nebula. In L' band, a void 0.3 arcsec in diameter was discoveredwith NACO around the central source. The L' and M' fluxes from thecentral source were derived from NACO data indicating an importantinfrared excess with respect to the expected stellar emission based onstellar models and short wavelength data. The observed flux from thissource in the L' and M' is about 300 and 800 times respectively thanthose expected from a model including only the central star. Moreover,the central object appears resolved in L' band with measured FWHM of 155mas. This infrared excess can be explained by emission from a cocoon ofhot dust (T1000 K) with a total mass~10-9~Mȯ.
| A 10 μm spectroscopic survey of Herbig Ae star disks: Grain growth and crystallization
We present spectroscopic observations of a large sample of Herbig Aestars in the 10 μm spectral region. We perform compositional fits ofthe spectra based on properties of homogeneous as well as inhomogeneousspherical particles, and derive the mineralogy and typical grain sizesof the dust responsible for the 10 μm emission. Several trends arereported that can constrain theoretical models of dust processing inthese systems: i) none of the sources consists of fully pristine dustcomparable to that found in the interstellar medium; ii) all sourceswith a high fraction of crystalline silicates are dominated by largegrains; iii) the disks around more massive stars (M 2.5{M}ȯ, L 60 {L}ȯ) have a higherfraction of crystalline silicates than those around lower mass stars,iv) in the subset of lower mass stars (M 2.5 {M}ȯ)there is no correlation between stellar parameters and the derivedcrystallinity of the dust. The correlation between the shape andstrength of the 10 micron silicate feature reported by van Boekel et al.(2003) is reconfirmed with this larger sample. The evidence presented inthis paper is combined with that of other studies to present a likelyscenario of dust processing in Herbig Ae systems. We conclude that thepresent data favour a scenario in which the crystalline silicates areproduced in the innermost regions of the disk, close to the star, andtransported outward to the regions where they can be detected by meansof 10 micron spectroscopy. Additionally, we conclude that the finalcrystallinity of these disks is reached very soon after active accretionhas stopped.
| First VLTI/MIDI observations of a Be star: Alpha Arae
We present the first VLTI/MIDI observations of the Be star alpha Ara (HD158 427), showing a nearly unresolved circumstellar disk in the N band.The interferometric measurements made use of the UT1 and UT3 telescopes.The projected baselines were 102 and 74 meters with position angles of 7° and 55°, respectively. These measurements put an upper limiton the envelope size in the N band under the uniform disk approximationof φmax= 4±1.5 mas, corresponding to 14R*, assuming R*=4.8 Rȯ and theHipparcos distance of 74 pc. On the other hand the disk density must belarge enough to produce the observed strong Balmer line emission. Inorder to estimate the possible circumstellar and stellar parameters wehave used the SIMECA code developed by Stee et al. (1995, A&A, 300,219) and Stee & Bittar (2001, A&A, 367, 532). Optical spectrataken with the échelle instrument Heros and the ESO-50 cmtelescope, as well as infrared ones from the 1.6m Brazilian telescopewere used together with the MIDI spectra and visibilities. Theseobservations place complementary constraints on the density and geometryof the alpha Ara circumstellar disk. We discuss the potential truncationof the disk by a companion and we present spectroscopic indications of aperiodic perturbation of some Balmer lines.
| First results from the ESO VLTI calibrators program
The ESO Very Large Telescope Interferometer (VLTI) is one of the leadinginterferometric facilities. It is equipped with several 8.2 and 1.8 mtelescopes, a large number of baselines up to 200 m, and with severalsubsystems designed to enable high quality measurements and to improvesignificantly the limits of sensitivities currently available tolong-baseline interferometry. The full scientific potential of the VLTIcan be exploited only if a consistent set of good quality calibrators isavailable. For this, a large number of observations of potentialcalibrators have been obtained during the commissioning phase of theVLTI. These data are publicly available. We briefly describe theinterferometer, the VINCI instrument used for the observations, the dataflow from acquisition to processed results, and we present and commenton the volume of observations gathered and scrutinized. The result is alist of 191 calibrator candidates, for which a total of 12 066observations can be deemed of satisfactory quality. We present a generalstatistical analysis of this sample, using as a starting point theangular diameters previously available in the literature. We derive thegeneral characteristics of the VLTI transfer function, and its trendwith time in the period 2001 through mid-2004. A second paper will bedevoted to a detailed investigation of a selected sample, aimed atestablishing a VLTI-based homogeneous system of calibrators.
| Mid-infrared interferometry of the Mira variable RR Sco with the VLTI MIDI instrument
We present the results of the first mid-infrared interferometricobservations of the Mira variable RR Sco with the MID-infraredInterferometer (MIDI) coupled to the European Southern Observatory's(ESO) Very Large Telescope Interferometer (VLTI), together with K-bandobservations using VLTI VINCI. The observations were carried out in June2003, when the variability phase of the object was 0.6, using two unittelescopes (UT1 and UT3), as part of the Science Demonstration Time(SDT) program of the instrument. Projected baseline lengths ranged from73 to 102 m, and a spectral resolution of 30 was employed in theobservations, which enabled us to obtain the wavelength dependence ofthe visibility in the region between 8 and 13 μm. The uniform-diskdiameter was found to be 18 mas between 8 and 10 μm, while itgradually increases at wavelengths longer than 10 μm to reach 24 masat 13 μm. The uniform-disk diameter between 8 and 13 μm issignificantly larger than the K-band uniform-disk diameter of 10.2± 0.5 mas measured using VLTI VINCI with projected baselinelengths of 15-16 m, three weeks after the MIDI observations. Our modelcalculations show that optically thick emission from a warm molecularenvelope consisting of H2O and SiO can cause the apparent mid-infrared diameter to be much larger than the continuum diameter. Wefind that the warm molecular envelope model extending to 2.3R\star with a temperature of 1400 K and column densitiesof H2O and SiO of 3 × 1021 cm-2and 1 × 1020 cm-2, respectively, canreproduce the observed uniform-disk diameters between 8 and 10 μm.The observed increase of the uniform-disk diameter longward of 10 μmcan be explained by an optically thin dust shell consisting of silicateand corundum grains. The inner radius of the optically thin dust shellis derived to be 7-8 R\star with a temperature of 700 K,and the optical depth at 10 μm is found to be 0.025.Based on observations made with the Very Large Telescope Interferometerof the European Southern Observatory.
| Mid-infrared sizes of circumstellar disks around Herbig Ae/Be stars measured with MIDI on the VLTI
We present the first long baseline mid-infrared interferometricobservations of the circumstellar disks surrounding Herbig Ae/Be stars.The observations were obtained using the mid-infrared interferometricinstrument MIDI at the European Southern Observatory (ESO) Very LargeTelescope Interferometer VLTI on Cerro Paranal. The 102 m baseline givenby the telescopes UT1 and UT3 was employed, which provides a maximumfull spatial resolution of 20 milli-arcsec (mas) at a wavelength of 10μm. The interferometric signal was spectrally dispersed at aresolution of 30, giving spectrally resolved visibility information from8 μm to 13.5 μm. We observed seven nearby Herbig Ae/Be stars andresolved all objects. The warm dust disk of HD 100546 could even beresolved in single-telescope imaging. Characteristic dimensions of theemitting regions at 10 μm are found to be from 1 AU to 10 AU. The 10μm sizes of our sample stars correlate with the slope of the 10-25μm infrared spectrum in the sense that the reddest objects are thelargest ones. Such a correlation would be consistent with a differentgeometry in terms of flaring or flat (self-shadowed) disks for sourceswith strong or moderate mid-infrared excess, respectively. We comparethe observed spectrally resolved visibilities with predictions based onexisting models of passive centrally irradiated hydrostatic disks madeto fit the SEDs of the observed stars. We find broad qualitativeagreement of the spectral shape of visibilities corresponding to thesemodels with our observations. Quantitatively, there are discrepanciesthat show the need for a next step in modelling of circumstellar disks,satisfying both the spatial constraints such as are now available fromthe MIDI observations and the flux constraints from the SEDs in aconsistent way.Based on observations made with the Very Large Telescope Interferometerat Paranal Observatory.
| The latitude and epoch for the formation of the southern Greek constellations
Not Available
| 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
| Dating Ptolemy's star catalogue through proper motions : the Hipparchan epoch.
Not Available
| 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).
| Late-type giants with infrared excess. I. Lithium abundances
de la Reza et al. (1997) suggested that all K giants become Li-rich fora short time. During this period the giants are associated with anexpanding thin circumstellar shell supposedly triggered by an abruptinternal mixing mechanism resulting in the surface Li enrichment. Inorder to test this hypothesis twenty nine late-type giants withfar-infrared excess from the list of Zuckerman et al. (1995) wereobserved in the Li-region to study the connection between thecircumstellar shells and Li abundance. Eight giants have been found tohave log epsilon (Li) > 1.0. In the remaining giants the Li abundanceis found to be much lower. HD 219025 is found to be a rapidly rotating(projected rotational velocity of 23 +/-3 km s(-1) ), dusty and Li-rich(log epsilon (Li) = 3.0+/-0.2) K giant. Absolute magnitude derived fromthe Hipparcos parallax reveals that it is a giant and not apre-main-sequence star. The evolutionary status of HD 219025 seems to besimilar to that of HDE 233517 which is also a rapidly rotating, dustyand Li-rich K giant. The Hipparcos parallaxes of all the well studiedLi-rich K giants show that most of them are brighter than the ``clump"giants. Their position in the H-R diagram indicates that they have gonethrough mixing and the initial abundance of Li is not preserved. Thereseems to be no correlations between Li abundances, rotational velocitiesand carbon isotope ratios. The only satisfactory explanation for theoverabundance of lithium in these giants is the creation of Li by theextra deep mixing and the associated ``cool bottom processing". Based onobservations obtained at the European Southern Observatory, La Silla,Chile, and at the Observatoire de Haute Provence, France.
| Comparison of the ACRS and PPM Catalogs with the FK5 in the Southern Hemisphere
A comparison of the Astrographical Catalog of Reference Stars (ACRS) andthe Positions and Proper Motions Catalog (PPM) with the FK5 in thesouthern hemisphere, is presented. To this aim, the positions of FK5stars uniformly spread over the celestial sphere were astrographicallytaken. These positions were reduced in the ACRS and PPM systems and thencompared with those from the FK5 for the epoch of observation. The (FK5- ACRS) and (FK5 - PPM) systematic differences thus obtained, in thedeclination range from -30o down to the South Pole, for themean epoch of 1994.50, are shown.
| 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.
| 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
| 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%.
| ROSAT X-ray observations of a complete, volume-limited sample of late-type giants.
We have investigated a complete sample of the nearest 39 late typegiants (d<=25pc) for which we have probed the X-ray luminosityfunction with unprecedented sensitivity by deep (3...18ksec) ROSATPSPC-observations in the pointed mode, together with ROSAT All-Skysurvey (RASS) data. We confirm the X-ray dividing line for luminosityclass III giants as proposed by Haisch et al. (1991, 1992) and we findevidence, that essentially all luminosity class III giants withB-V<1.2 or spectral type
| Luminosity Class III Stars with Excess Far-Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...446L..79Z&db_key=AST
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| The position corrections of 1400 stars observed with PA II in San Juan.
Not Available
| A Spectrophotometric Catalogue of 60 Selected Southern Stars
Not Available
| 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.
| Optical Polarization of 1000 Stars Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..551L&db_key=AST
| A Polarimetric Investigation on Interstellar Dust Within 50-PARSECS from the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..203L&db_key=AST
| Corrections to the right ascension to be applied to the apparent places of 1217 stars given in "The Chinese Astronomical Almanach" for the year 1984 to 1992.
Not Available
| Spectroscopic investigation of cool giants and the authenticity of their reported microwave emission
Surface velocities and metal abundances for 19 red giant stars in thespectral range G5 to M3 are derived on the basis of AAT echellespectroscopy data. Attention is given to the question of whether thestars reported to emit radio bursts had different physical properties(rotation rate, macroturbulence, microturbulence, and metal abundance)from those without the radio bursts, which might explain why they wereradio emitters. The various velocities had values consistent with thosepreviously found for other similar stars. There was an observed increasein both macroturbulent and, less definitely, microturbulent velocitieswith lateness of spectral type at K3 and later. A weak correlationbetween surface velocities and 8.4-GHz radio surface fluxes was found.No connection between iron abundances and radio surface fluxes wasdetected. It is concluded that few, if any, of the cool giants are radioemitters.
| Second Rio Grande catalogue (RG2).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990RMxAA..21..286H&db_key=AST
| Physical data of the fundamental stars.
Not Available
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
