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Integrated optics for astronomical interferometry. VI. Coupling the light of the VLTI in K band
Aims. Our objective is to prove that integrated optics (IO) is not onlya good concept for astronomical interferometry but also a workingtechnique with high performance. Methods: . We used thecommissioning data obtained with the dedicated K-band integrated opticstwo-telescope beam combiner that now replaces the fiber coupler MONA inthe VLTI/VINCI instrument. We characterize the behavior of this IOdevice and compare its properties to other single mode beam combinerlike the previously used MONA fiber coupler. Results: . The IOcombiner provides a high optical throughput, a contrast of 89% with anight-to-night stability of a few percent. Even if a dispersive phase ispresent, we show that it does not bias the measured Fourier visibilityestimate. An upper limit of 5×10-3 for the cross-talkbetween linear polarization states has been measured. We take advantageof the intrinsic contrast stability to test a new astronomical procedurefor calibrating diameters of simple stars by simultaneously fitting theinstrumental contrast and the apparent stellar diameters. This methodreaches an accuracy with diameter errors on the order of previous onesbut without the need of an already known calibrator. Conclusions:. These results are an important step for IO, since they prove itsmaturity in an astronomical band where the technology has been speciallydeveloped for astronomical convenience. It paves the way to incomingimaging interferometer projects.
| Structure and dynamics of the Shapley Supercluster. Velocity catalogue, general morphology and mass
We present results of our wide-field redshift survey of galaxies in a285 square degree region of the Shapley Supercluster (SSC), based on aset of 10 529 velocity measurements (including 1201 new ones) on 8632galaxies obtained from various telescopes and from the literature. Ourdata reveal that the main plane of the SSC (v≈ 14 500 kms-1) extends further than previous estimates, filling thewhole extent of our survey region of 12 degrees by 30 degrees on the sky(30× 75 h-1 Mpc). There is also a connecting structureassociated with the slightly nearer Abell 3571 cluster complex (v≈ 12000 km s-1). These galaxies seem to link two previouslyidentified sheets of galaxies and establish a connection with a thirdone at overline v= 15 000 km s-1 near RA= 13^h. They alsotend to fill the gap of galaxies between the foreground Hydra-Centaurusregion and the more distant SSC. In the velocity range of the ShapleySupercluster (9000 km s-1< cz < 18 000 kms-1), we found redshift-space overdensities with b_j<17.5of ≃5.4 over the 225 square degree central region and ≃3.8in a 192 square degree region excluding rich clusters. Over the largeregion of our survey, we find that the intercluster galaxies make up 48per cent of the observed galaxies in the SSC region and, accounting forthe different completeness, may contribute nearly twice as much mass asthe cluster galaxies. In this paper, we discuss the completeness of thevelocity catalogue, the morphology of the supercluster, the globaloverdensity, and some properties of the individual galaxy clusters inthe Supercluster.
| The epoch of the constellations on the Farnese Atlas and their origin in Hipparchus's lost catalogue
Not Available
| Thermal infrared observations of the Hayabusa spacecraft target asteroid 25143 Itokawa
We obtained N- and Q-band observations of the Apollo-type asteroid25143 Itokawa during its close Earth approach in July2004 with TIMMI2 at the ESO 3.6 m telescope. Our photometricmeasurement, in combination with already published data, allowed us toderive a radiometric effective diameter of 0.32 ± 0.03 km and analbedo of 0.19+0.11-0.03 through a thermophysicalmodel. This effective diameter corresponds to a slightly asymmetricaland flattened ellipsoid of the approximate size of 520(±50)× 270(±30) × 230(±20) m, based on theKaasalainen et al. (2005, Proceedings of the 1st Hayabusa Symposium, ASPConf. Ser., submitted) shape model. Our studies show that the thermalobservations lead to size estimates which are about 15% smaller than theradar results (Ostro et al. 2005, Met. Plan. Sci., submitted), slightlyoutside the stated radar uncertainties of ±10%. We determined arather high thermal inertia of 750 J m-2 s-0.5K-1. This is an indication for a bare rock dominated surface,a thick dust regolith can be excluded as well as a metallic surface.From our data we constructed a 10.0 μm thermal lightcurve which isnicely matched in amplitude and phase by the shape and spin vectorsolution in combination with our TPM description. The assumed S-typebulk density in combination with radiometric size lead to a total massestimate of 4.5+2.0-1.8 × 1010kg.
| 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 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.
| Infrared portrait of the nearby massive star-forming region IRAS 09002-4732
We present high-resolution near-infrared and mid-infrared imaging,mid-infrared spectroscopy and millimetre-wavelength continuumobservations of the nearby massive star-forming complex IRAS 09002-4732.A rich cluster of young stars displaying near-infrared excess emissionis detected. We identify the ionising source of the ultracompact H IIregion G268.42-0.85 and show that this star is the dominant heating andilluminating source of the region. Spectral type estimates based ondifferent methods are consistent with a star of spectral type O9. Thecombination of the new observations with literature data allows us toset up the first structural model for the region. We argue that theultracompact H II region is embedded in the rear side of the southern CSclump. Additionally, we detect several interesting objects. Among theseobjects are a network of dark dust filaments, an elongated, externallyheated object with strong infrared excess inside the H II region andobjects seen as silhouettes in the foreground of the large southernreflection nebulosity. The filamentary structures may play an importantrole in the star formation process.
| The K-band intensity profile of R Leonis probed by VLTI/VINCI
We present near-infrared K-band interferometric measurements of the Mirastar R Leonis obtained in April 2001 and January 2002 with the VLTI, thecommissioning instrument VINCI, and the two test siderostats. Theseepochs correspond to near-maximum stellar variability phases ~0.08 and~1.02 (one cycle later), respectively. The April 2001 data cover a rangeof spatial frequencies (31 35 cycles/arcsecond) within the first lobe ofthe visibility function. These measurements indicate a center-to-limbintensity variation (CLV) that is clearly different from a uniform disk(UD) intensity profile. We show that these measured visibility valuesare consistent with predictions from recent self-excited dynamic Miramodel atmospheres that include molecular shells close tocontinuum-forming layers. We derive high-precision Rosseland diametersof 28.5 ± 0.4 mas and 26.2 ± 0.8 mas for the April 2001and January 2002 data, respectively. Together with literature estimatesof the distance and the bolometric flux, these values correspond tolinear radii of 350+50-40 R_ȯ and320+50-40 R_ȯ, and to effective temperaturesof 2930 ± 270 K and 3080 ± 310 K, respectively.Based on public commissioning data released from the ESO VLTI(www.eso.org/projects/vlti/instru/vinci/ vinci_data_sets.html)
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| High spatial resolution mid-infrared spectroscopy of NGC 5253: The stellar content of the embedded super-star cluster
We present the N-band (8-13 μm) spectrum of the hidden compact radiosuper-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6m telescope. The spectrum is characterised by a rising continuum due towarm dust, a silicate absorption and a strong [S IV] line at 10.5 μm.Weaker lines of [Ar II]I at 9.0 μm and [Ne II] at 12.8 μm are alsopresent. The continuum can be modelled by an optically thick emissionfrom hot (Td=253 ± 1 K) dust emission extinguished bya cold foreground dust screen and a silicate absorption feature withAsil = 0.73 ± 0.05 mag. We show how the spatial scaleof the observations greatly determine the mid-IR appearance of NGC 5253and the important implications that this has on the interpretation ofline fluxes in terms of the properties (age, IMF, etc.) of the embeddedcluster. We have modelled the observed line fluxes towards C2 usingphotoionisation models with the most recent spectral energydistributions available to describe the integrated properties of thestellar cluster. The detailed dependence of the mid-IR lines onparameters such as the cluster age, upper mass cutoff and power lawindex of the IMF, as well as the local abundance, the presence ofinternal dust and the density structure is largely discussed. Strongconstraints on the geometry based on high spatial resolutionobservations at different wavelengths - near-IR (HST and Keck), mid-IR(TIMMI2) and radio (VLA) - allows us to restrain the ionisationparameters to values log U ≥-0.5 dex. This constraint on U leads totwo possible solutions for the age and upper mass cutoff of C2: 1) ayoung (<4 Myr) cluster with a ``non-standard'' IMF having a low uppermass cutoff Mup,< 50 Mȯ; and 2) a clusterof 5-6 Myr with a standard high upper mass cutoff(Mup, 100 Mȯ). A young age of <4 Myrwould agree with the lack of supernovae signatures in C2 and in case ofbeing confirmed, would be the first indication for a ``non-standard'',low upper mass cutoff of the IMF for an individual massive cluster. Anolder age of 5-6 Myr would imply that it is possible to ``contain''and hide such a compact cluster for a longer time that what it isgenerally thought. Arguments in favour and against these two scenariosare presented. The origin of the [O IV] 25.9 μm emission measured byISO and the possible presence of an intermediate mass black hole insideC2 are also addressed.Based on observations obtained at the European Southern Observatory, LaSilla, Chile (ID 70.B-0583).
| A near-infrared stellar spectral library: I. H-band spectra.
This paper presents the H band near-infrared (NIR) spectral library of135 solar type stars covering spectral types O5-M3 and luminosityclasses I-V as per MK classification. The observations were carried outwith 1.2 meter Gurushikhar Infrared Telescope (GIRT), at Mt. Abu, Indiausing a NICMOS3 HgCdTe 256 x 256 NIR array based spectrometer. Thespectra have a moderate resolution of 1000 (about 16 A) at the H bandand have been continuum shape corrected to their respective effectivetemperatures. This library and the remaining ones in J and K bands oncereleased will serve as an important database for stellar populationsynthesis and other applications in conjunction with the newly formedlarge optical coude feed stellar spectral library of Valdes et al.(2004). The complete H-Band library is available online at: http://vo.iucaa.ernet.in/~voi/NIR_Header.html
| The hot core-ultracompact H II connection in G10.47+0.03
We present infrared imaging and spectroscopic data of the complexmassive star-forming region G10.47+0.03. The detection of sevenmid-infrared (MIR) sources in our field combined with a sensitiveKs/ISAAC image allows to establish a very accurate astrometry, at thelevel of 0.3 arcsec. Two MIR sources are found to be coincident with twoultracompact H II regions (UCH II s) within our astrometric accuracy.Another MIR source lies very close to three other UCH II regions and tothe hot molecular core (HMC) in G10.47+0.03. Spectroscopy of two of themost interesting MIR sources allows to identify the location andspectral type of the ionizing sources. We discuss in detail therelationship between the HMC, the UCH II regions and the nearby MIRsource. The nature of the other MIR sources is also investigated.Based on observations collected at the European Southern Observatory, LaSilla, Chile. Prop.ID:67.C-0359(A) and Prop.ID:69.C-0189(A).
| Data reduction methods for single-mode optical interferometry. Application to the VLTI two-telescopes beam combiner VINCI
The interferometric data processing methods that we describe in thispaper use a number of innovative techniques. In particular, theimplementation of the wavelet transform allows us to obtain a goodimmunity of the fringe processing to false detections and largeamplitude perturbations by the atmospheric piston effect, through acareful, automated selection of the interferograms. To demonstrate thedata reduction procedure, we describe the processing and calibration ofa sample of stellar data from the VINCI beam combiner. Starting from theraw data, we derive the angular diameter of the dwarf star α CenA. Although these methods have been developed specifically for VINCI,they are easily applicable to other single-mode beam combiners, and tospectrally dispersed fringes.Appendices A, B and C are only available in electronic form athttp://www.edpsciences.org
| Mid-infrared emission of galactic nuclei. TIMMI2 versus ISO observations and models
We investigate the mid-infrared radiation of galaxies that are poweredby a starburst or by an AGN. For this end, we compare the spectraobtained at different spatial scales in a sample of infrared brightgalaxies. ISO observations which include emission of the nucleus as wellas most of the host galaxy are compared with TIMMI2 spectra of thenuclear region. We find that ISO spectra are generally dominated bystrong PAH bands. However, this is no longer true when inspecting themid-infrared emission of the pure nucleus. Here PAH emission is detectedin starbursts whereas it is significantly reduced or completely absentin AGNs. A physical explanation of these new observational results ispresented by examining the temperature fluctuation of a PAH afterinteraction with a photon. It turns out that the hardness of theradiation field is a key parameter for quantifying the photo-destructionof small grains. Our theoretical study predicts PAH evaporation in softX-ray environments. Radiative transfer calculations of clumpy starburstsand AGN corroborate the observational fact that PAH emission isconnected to starburst activity whereas PAHs are destroyed near an AGN.The radiative transfer models predict for starbursts a much largermid-infrared size than for AGN. This is confirmed by our TIMMI2acquisition images: We find that the mid-infrared emission of Seyfertsis dominated by a compact core while most of the starbursts arespatially resolved.Based on ESO: 68.B-0066(A) and observations with ISO, an ESA projectwith instruments funded by ESA Member States (especially the PIcountries: France, Germany, The Netherlands and the UK) with theparticipation of ISAS and NASA.}
| J - K DENIS photometry of a VLTI-selected sample of bright southern stars
We present a photometric survey of bright southern stars carried outusing the DENIS instrument equipped with attenuating filters. Theobservations were carried out not using the survey mode of DENIS, butwith individual target pointings. This project was stimulated by theneed to obtain near-infrared photometry of stars to be used in earlycommissioning observations of the ESO Very Large TelescopeInterferometer, and in particular to establish a network of brightcalibrator sources.We stress that near-infrared photometry is peculiarly lacking for manybright stars. These stars are saturated in 2MASS as well as in regularDENIS observations. The only other observations available for brightinfrared stars are those of the Two Micron Sky Survey dating from overthirty years ago. These were restricted to declinations above≈-30°, and thus cover only about half of the sky accessible fromthe VLTI site.We note that the final 2MASS data release includes photometry of brightstars, obtained by means of point-spread function fitting. However, thismethod only achieves about 30% accuracy, which is not sufficient formost applications.In this work, we present photometry for over 600 stars, each with atleast one and up to eight measurements, in the J and K filters. Typicalaccuracy is at the level of 0\fm05 and 0\fm04 in the J and K_s bands,respectively.Based on observations collected at the European Southern Observatory, LaSilla.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/413/1037
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| The interferometric diameter and internal structure of Sirius A
The interferometric observations of dwarf stars in the solarneighbourhood, combined with HIPPARCOS parallaxes provide very precisevalues of their linear diameters. In this paper, we report the directmeasurement of the angular diameter of the bright star Sirius A with theVINCI/VLTI instrument. We obtain a uniform disk angular diameter oftheta_UD = 5.936 +/- 0.016 mas in the K band and a limb darkened valueof theta_LD = 6.039 +/- 0.019 mas. In combination with the HIPPARCOSparallax of 379.22 +/- 1.58 mas, this translates into a linear diameterof 1.711 +/- 0.013 Dsun. Using the VINCI/VLTI interferometricdiameter and the published properties of Sirius A, we derive internalstructure models corresponding to ages between 200 and 250 +/- 12 Myr.This range is defined mainly by the hypothesis on the mass of the star,the overshoot and the metallicity.
| The diameters of alpha Centauri A and B. A comparison of the asteroseismic and VINCI/VLTI views
We compare the first direct angular diameter measurements obtained onour closest stellar neighbour, alpha Centauri, to recent modeldiameters constrained by asteroseismic observations. Using the VINCIinstrument installed at ESO's VLT Interferometer (VLTI), the angulardiameters of the two main components of the system, alpha Cen A and B,were measured with a relative precision of 0.2% and 0.6% respectively.Particular care has been taken in the calibration of these measurements,considering that VINCI is estimating the fringe visibility using abroadband K filter. We obtain uniform disk angular diameters for alphaCen A and B of thetaUD [A] = 8.314 +/- 0.016 mas andthetaUD [B] = 5.856 +/- 0.027 mas, and limb darkened angulardiameters of thetaLD [A] = 8.511 +/- 0.020 mas andthetaLD [B] = 6.001 +/- 0.034 mas. Combining these valueswith the parallax from Söderhjelm (\cite{soderhjelm}), we derivelinear diameters of D[A] = 1.224 +/- 0.003 Dsun and D[B] =0.863 +/- 0.005 Dsun. These values are compatible with themasses published by Thévenin et al. (\cite{thevenin02}) for bothstars.
| Dating the Almagest star catalogue using proper motions : a reconsideration.
Not Available
| Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog
We present refined coordinates and proper-motion data for the highproper-motion (HPM) stars in the Luyten Half-Second (LHS) catalog. Thepositional uncertainty in the original Luyten catalog is typicallygreater than 10" and is often greater than 30". We have used the digitalscans of the POSS I and POSS II plates to derive more accurate positionsand proper motions of the objects. Out of the 4470 candidates in the LHScatalog, 4323 objects were manually reidentified in the POSS I and POSSII scans. A small fraction of the stars were not found because of thelack of finder charts and digitized POSS II scans. The uncertainties inthe revised positions are typically ~2" but can be as high as ~8" in afew cases, which is a large improvement over the original data.Cross-correlation with the Tycho-2 and Hipparcos catalogs yielded 819candidates (with mR<~12). For these brighter sources, theposition and proper-motion data were replaced with the more accurateTycho-2/Hipparcos data. In total, we have revised proper-motionmeasurements and coordinates for 4040 stars and revised coordinates for4330 stars. The electronic version of the paper5 contains the updated information on all 4470stars in the LHS catalog.
| Infrared spectral classification of normal stars.
Moderate resolution (~400) 2.38-45.2 mu m infrared spectra of starswithout dust features were obtained with the Short WavelengthSpectrometer (SWS) on board the Infrared Space Observatory (ISO). Theobservations are part of a larger program with the objective to extendand refine the current infrared classification schemes. In particular,our data provide the basis for a more detailed classification of the1.N-1.NO sources (ordinary and oxygen rich naked stars) as defined byKraemer et al. (\cite{kraemer}) in a comprehensive classification of theISO-SWS spectra. For our analysis, the continuum was determined byfitting Engelke's function (Engelke \cite{engelke}) to the SWS data. Thestellar angular diameters derived from these estimates of the continuumare in good agreement with values obtained by other methods. Analysis ofthe equivalent widths of the CO fundamental and first overtone molecularbands, the SiO fundamental and first overtone, as well as theH2O bending mode band as a function of MK class, reveals thatthere is sufficient information in the SWS spectra to distinguishbetween hot (B, A, F) and cool stars. Furthermore, it is possible todetermine the spectral type for the G, K and M giants, and subtyperanges in a sequence of K and M giants. The equivalent widths of the COand SiO bands are found to be well correlated in K and M stars, suchthat the equivalent widths of the CO fundamental, the SiO first overtoneand the SiO fundamental can be reasonably well extrapolated from thedepth of the CO first overtone. We have identified two stars,HR 365 and V Nor, whosemid-infrared spectrum does not correspond to their respective opticalclassification. HR 365 may have a late M companion,which dominates the observed infrared spectrum while VNor is a late type giant that was included because itsspectrum was classified as featureless under the IRAS LRS scheme.According to Kraemer et al. (\cite{kraemer}), V Norhas a thin dust shell, which distorts the analysis of its mid-infraredabsorption bands. Based on observations with ISO, an ESA project withinstruments funded by ESA Member States (especially the PI countries:France, Germany, The Netherlands and the UK) and with the participationof ISAS and NASA.
| A catalogue of calibrator stars for long baseline stellar interferometry
Long baseline stellar interferometry shares with other techniques theneed for calibrator stars in order to correct for instrumental andatmospheric effects. We present a catalogue of 374 stars carefullyselected to be used for that purpose in the near infrared. Owing toseveral convergent criteria with the work of Cohen et al.(\cite{cohen99}), this catalogue is in essence a subset of theirself-consistent all-sky network of spectro-photometric calibrator stars.For every star, we provide the angular limb-darkened diameter, uniformdisc angular diameters in the J, H and K bands, the Johnson photometryand other useful parameters. Most stars are type III giants withspectral types K or M0, magnitudes V=3-7 and K=0-3. Their angularlimb-darkened diameters range from 1 to 3 mas with a median uncertaintyas low as 1.2%. The median distance from a given point on the sky to theclosest reference is 5.2degr , whereas this distance never exceeds16.4degr for any celestial location. The catalogue is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/183
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| On the Wilson-Bappu relationship in the Mg II k line
An investigation is carried out on the Wilson-Bappu effect in the Mg Iik line at 2796.34 Å. The work is based on a selection of 230 starsobserved by both the IUE and HIPPARCOS satellites, covering a wide rangeof spectral types (F to M) and absolute visual magnitudes (-5.4<=MV <=9.0). A semi-automatic procedure is used to measurethe line widths, which applies also in the presence of strong centralabsorption reversal. The Wilson-Bappu relationship here provided isconsidered to represent an improvement over previous recent results forthe considerably larger data sample used, as well as for a properconsideration of the measurement errors. No evidence has been found fora possible dependence of the WB effect on stellar metallicity andeffective temperature.
| 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
| Dark-speckle coronagraphic detection of binary stars in the near-IR
In this paper, we present the first attempt to obtain images of binarystars in the near IR using the dark-speckle method on the 3.6 mtelescope at La Silla. Promising results are presented, despite theeffect of the detector high read-out noise affecting the efficiency ofspeckle observations. We give some comparisons with the long exposuremethod. We derive in these data a reliable limit of detection for binarystar companions, around mK<4 stars, which is about<~ mK~ 6-7 for angular separations ranging from 0.5'' to0.9''. Based on observations collected at the European SouthernObservatory, La Silla, Chile.
| Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/297
| 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
| Ultraviolet Emission Lines in BA and Non-BA Giants
With the Hubble Space Telescope (HST) and the Goddard High ResolutionSpectrograph we have observed four barium and three weak barium stars inthe ultraviolet spectral region, together with two nonpeculiar giantstandard stars. An additional suspected Ba star was observed with HSTand the Space Telescope Imaging Spectrograph. In the H-R diagram, threeof the observed Ba stars lie on the same evolutionary tracks as theHyades giants. Using International Ultraviolet Explorer (IUE) spectra ofpreviously studied giants together with our HST spectra, we investigatewhether the chromospheric and transition layer emission-line spectra ofthe Ba stars are different from those of nonpeculiar giants and fromthose of giants with peculiar carbon and/or nitrogen abundances. Exceptfor the Ba star HD 46407 and the suspected Ba star HD 65699, the Ba starand mild Ba star emission-line fluxes are, for a given effectivetemperature and for a given luminosity, lower than those for thenonpeculiar giants observed with IUE. In comparison with theHST-observed standard stars, the C IV λ1550-to-C II λ1335line flux ratios are smaller, but not necessarily so in comparison withall IUE-observed nonpeculiar giants. However, the C IV-to-C II line fluxratios for the Ba stars decrease with increasing carbon abundances. Thisshows that the energy balance in the lower transition layer isinfluenced by the carbon abundance. The temperature gradient appears tobe smaller in the C II line-emitting region. There does not seem to be adifference in chromospheric electron densities for the Ba and non-Bastars, though this result is rather uncertain. Based on observationswith the NASA/ESA Hubble Space Telescope obtained at the Space TelescopeScience Institute, which is operated by the Association of Universitiesfor Research in Astronomy, Inc., under NASA contract NAS 5-26555.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קנטאור |
| התרוממות ימנית: | 14h06m41.00s |
| סירוב: | -36°22'12.0" |
| גודל גלוי: | 2.06 |
| מרחק: | 18.685 פארסק |
| תנועה נכונה: | -519.7 |
| תנועה נכונה: | -519.2 |
| B-T magnitude: | 3.359 |
| V-T magnitude: | 2.158 |
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