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Multi-periodic oscillations of HD 32887 and HD 81797.
In this paper we present two evolved stars, HD 32887 and HD 81797, whichshow multi-periodic oscillations. We observed the oscillations by meansof the precise radial velocity technique with the simultaneouscalibration method. The high-resolution spectra of each star have beenobtained with FEROS at the 2.2 m-MPG/ESO telescope in La SillaObservatory, Chile. We found variation in the stellar radial velocitiesand spectral line profiles. The periods of the oscillations are fromseveral hours up to few days. The sources of the short-term oscillationsof HD 32887 and HD 81797 are obviously due to stellar pulsations, whichare similar to solar-like oscillations. In particular, in HD 81797 wefound a clear correlation between the variation in the asymmetry of thespectral line profile, measured in the bisector velocity spans, and theradial velocity. Both stars have bisector velocity spans which also showoscillations. The periods of the bisector oscillations are similar tothose of the radial velocity variation. The detection of themulti-periodic oscillations in HD 32887 and HD 81797 makes these star tobe amenable targets for asteroseismology, in particular, of stars in thered giant branch.
| The epoch of the constellations on the Farnese Atlas and their origin in Hipparchus's lost catalogue
Not Available
| Discovery of a Candidate Protoplanetary Disk around the Embedded Source IRc9 in Orion
We report the detection of spatially extended mid-infrared emissionaround the luminous embedded star IRc9 in OMC-1, as seen in 8.8, 11.7,and 18.3 μm images obtained with the Thermal-Region Camera andSpectrograph on Gemini South. The extended emission is asymmetric, andthe morphology is reminiscent of warm dust disks around other youngstars. The putative disk has a radius of roughly 1.5" (700 AU) and alikely dust mass of almost 10 M⊕. The infrared spectralenergy distribution of IRc9 indicates a total luminosity of ~100Lsolar, implying that it will become an early A-type starwhen it reaches the main sequence. Thus, the candidate disk around IRc9may be a young analog of the planetary debris disks around Vega-likestars and the disks of Herbig Ae stars, and may provide a laboratory inwhich to study the earliest phases of planet formation. A disk aroundIRc9 may also add weight to the hypothesis that an enhanced T Tauri-likewind from this star has influenced the molecular outflow from the OMC-1core.Based on observations obtained at the Gemini Observatory, which isoperated by the Association of Universities for Research in Astronomy,Inc., under a cooperative agreement with the NSF on behalf of the Geminipartnership: the National Science Foundation (US), the Particle Physicsand Astronomy Research Council (UK), the National Research Council(Canada), CONICYT (Chile), the Australian Research Council (Australia),CNPq (Brazil), and CONICET (Argentina).
| Joint VLBA/VLTI Observations of the Mira Variable S Orionis
We present the first coordinated Very Long Baseline Array (VLBA) / VeryLarge Telescope Interferometer (VLTI) measurements of the stellardiameter and circumstellar atmosphere of a Mira variable star.Observations of the v=1, J=1-0 (43.1 GHz) and v=2, J=1-0 (42.8 GHz) SiOmaser emission toward the Mira variable S Ori were conducted using theVLBA. Coordinated near-infrared K-band measurements of the stellardiameter were performed using VLTI-VINCI closely spaced in time to theVLBA observations. Analysis of the SiO maser data recorded at a visualvariability phase 0.73 shows the average distance of the masers from thecenter of the distribution to be 9.4 mas for the v=1 masers and 8.8 masfor the v=2 masers. The velocity structure of the SiO masers appears tobe random, with no significant indication of global expansion/infall orrotation. The determined near-infrared, K-band, uniform disk (UD)diameters decreased from ~10.5 mas at phase 0.80 to ~10.2 mas at phase0.95. For the epoch of our VLBA measurements, an extrapolated UDdiameter of ΘKUD=10.8+/-0.3 mas wasobtained, corresponding to a linear radius ofRKUD=2.3+/-0.5 AU orRKUD=490+/-115 Rsolar. Our coordinatedVLBA/VLTI measurements show that the masers lie relatively close to thestellar photosphere at a distance of ~2 photospheric radii, consistentwith model estimates. This result is virtually free of the usualuncertainty inherent in comparing observations of variable stars widelyseparated in time and stellar phase.
| 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.
| 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
| VINCI-VLTI measurements of HR 4049: The physical size of the circumbinary envelope
We present the first detection of the envelope which surrounds thepost-AGB binary source HR 4049. VINCI-VLTI K-band interferometricobservations of this source imply the existence of a large structurewith a Gaussian angular FWHM 22.4 ± 1.4 mas or uniform diskdiameter of 34.9 ± 1.9 mas. With the Hipparcos parallax of 1.50± 0.64 mas these values correspond to a physical size of14.9+11.1-4.4 AU and23.3+17.3-7.0 AU, respectively. Our measurements,covering an azimuth range of 60 ° for the sky-projectedbaseline, provide information on the geometry of the emitting region andshow that there is only a slight variation of the measured angularvalues along the different directions sampled. Thus, our results areconsistent with a spherical geometry of the envelope. However, we cannotcompletely rule out the existence of an asymmetric envelope (like thecircumbinary disk envisaged by some recent models) because of thelimited spatial frequency and azimuth range covered by the observations.Based on public shared risk science program data released from the ESOVLTI: http://www.eso.org/projects/vlti/instru/vinci/vinci_data_sets.html
| Ca II K Emission-Line Asymmetries Among Red Giants
Measurements of the asymmetry of the K2 emission line of CaII have been made for a sample of bright field giants with B-V>1.15observed with the Cassegrain echelle spectrometer on the McDonaldObservatory 2.1 m telescope. The asymmetry of the Ca II K2line is quantified through measurement of a parameter V/R, which isdefined as the ratio between the maximum counts recorded in the violetand red components of the double-peaked emission profile. Red-maximumasymmetry (V/R<1.0) is found in our sample of 35 giants only amongstars with B-V>1.35, a trend that is still maintained (with oneexception) with the inclusion of an additional sample of giantspreviously observed by us with the same spectrograph. Althoughexceptional stars can be found in the literature, the data support anearlier finding by R. Stencel that among luminosity class III fieldgiants the occurrence of V/R<1.0 is generally restricted to effectivetemperatures cooler than 4320 K. This limit may coincide with the onsetof pulsation.
| The European Large Area ISO Survey - VIII. 90-μm final analysis and source counts
We present a re-analysis of the European Large Area Infrared SpaceObservatory (ISO) Survey (ELAIS) 90-μm observations carried out withISOPHOT, an instrument on board the ISO of the European Space Agency.With more than 12 deg2, the ELAIS survey is the largest areacovered by ISO in a single programme and is about one order of magnitudedeeper than the IRAS 100-μm survey. The data analysis is presentedand was mainly performed with the PHOT interactive analysis software butusing the pairwise method of Stickel et al. for signal processing fromedited raw data to signal per chopper plateau. The ELAIS 90-μmcatalogue contains 237 reliable sources with fluxes larger than 70 mJyand is available in the electronic version of this article. Numbercounts are presented and show an excess above the no-evolution modelprediction. This confirms the strong evolution detected at shorter (15μm) and longer (170 μm) wavelengths in other ISO surveys. TheELAIS counts are in agreement with previous works at 90 μm and inparticular with the deeper counts extracted from the Lockman holeobservations. Comparison with recent evolutionary models show that themodels of Franceschini et al. and Guiderdoni et al. (which includes aheavily extinguished population of galaxies) give the best fit to thedata. Deeper observations are nevertheless required to discriminatebetter between the model predictions in the far-infrared, and arescheduled with the Spitzer Space Telescope, which has already startedoperating, and will also be performed by ASTRO-F.
| Classification of Spectra from the Infrared Space Observatory PHT-S Database
We have classified over 1500 infrared spectra obtained with the PHT-Sspectrometer aboard the Infrared Space Observatory according to thesystem developed for the Short Wavelength Spectrometer (SWS) spectra byKraemer et al. The majority of these spectra contribute to subclassesthat are either underrepresented in the SWS spectral database or containsources that are too faint, such as M dwarfs, to have been observed byeither the SWS or the Infrared Astronomical Satellite Low ResolutionSpectrometer. There is strong overall agreement about the chemistry ofobjects observed with both instruments. Discrepancies can usually betraced to the different wavelength ranges and sensitivities of theinstruments. Finally, a large subset of the observations (~=250 spectra)exhibit a featureless, red continuum that is consistent with emissionfrom zodiacal dust and suggest directions for further analysis of thisserendipitous measurement of the zodiacal background.Based on observations with the Infrared Space Observatory (ISO), aEuropean Space Agency (ESA) project with instruments funded by ESAMember States (especially the Principle Investigator countries: France,Germany, Netherlands, and United Kingdom) and with the participation ofthe Institute of Space and Astronautical Science (ISAS) and the NationalAeronautics and Space Administration (NASA).
| Thermal-Infrared Detection of Optical Outflow Sources in OMC-1 South
We present the first thermal-infrared imaging photometry for severalembedded sources in the OMC-1 South cloud core in the Orion Nebula, andwe propose that some of these drive the optical Herbig-Haro jetsemerging from the region. Thermal-infrared images at 8.8 and 11.7 μmobtained at Gemini South show a handful of sources in OMC-1 South withno visual-wavelength counterparts, although a few can be seen in recentnear-infrared data. For the three brightest mid-infrared sources, wealso present 18.75 μm photometry obtained with the Keck telescope.The most prominent blueshifted outflows in the Orion Nebula at visualwavelengths, such as HH 202, HH 203/204, HH 529, and HH 269, alloriginate from OMC-1S. The brightest infrared source in OMC-1S at 11.7μm is located at the base of the prominent jet that powers HH 202 andis likely to be the sought-after driver of this outflow. The secondbrightest infrared source is located at the base of the HH 529 jet. Weconsider the possibility that HH 203/204 and HH 269 trace parts of asingle bent outflow from the third brightest infrared source. Whilethere may be some lingering ambiguity about which infrared stars drivespecific jets, there is now a sufficient number of embedded sources toplausibly account for the multiple outflows from OMC-1S.Based on observations obtained at the Gemini Observatory, which isoperated by the Association of Universities for Research in Astronomy,Inc., under a cooperative agreement with the NSF on behalf of the Geminipartnership: the National Science Foundation (US), the Particle Physicsand Astronomy Research Council (UK), the National Research Council(Canada), CONICYT (Chile), the Australian Research Council (Australia),CNPq (Brazil), and CONICET (Argentina).
| Precise radial velocity measurements of G and K giants. Multiple systems and variability trend along the Red Giant Branch
We present the results of our radial velocity (RV) measurements of G andK giants, concentrating on the presence of multiple systems in oursample. Eighty-three giants have been observed for 2.5 years with thefiber-fed echelle spectrograph FEROS at the 1.52 m ESO telescope in LaSilla, Chile. Seventy-seven stars (93%) of the targets have beenanalyzed for RV variability using simultaneous Th-Ar calibration and across-correlation technique. We estimate the long-term precision of ourmeasurement as better than 25 m s-1. Projected rotationalvelocities have been measured for most stars of the sample. Within ourtime-base only 21 stars (or 27%) show variability below 2\sigma, whilethe others show RV variability with amplitudes up to several kms-1. The large amplitude (several km s-1) andshape (high eccentricity) of the RV variations for 11 of the programstars are consistent with stellar companions, and possibly brown dwarfcompanions for two of the program stars. In those systems for which afull orbit could be derived, the companions have minimum masses from0.6 M\sun down to 0.1 M\sun. To thesemultiple systems we add the two candidates of giant planets alreadydiscovered in the sample. This analysis shows that multiple systemscontribute substantially to the long-term RV variability of giant stars,with about 20% of the sample being composed of multiple systems despitescreening our sample for known binary stars. After removing binaries,the range of RV variability in the whole sample clearly decreases, butthe remaining stars retain a statistical trend of RV variability withluminosity: luminous cool giants with B-V≥1.2 show RV variationswith \sigma_{/lineRV} > 60 m s-1, while giants with B-V< 1.2 including those in the clump region exhibit less variability orthey are constant within our accuracy. The same trend is observed withrespect to absolute visual magnitudes: brighter stars show a largerdegree of variability and, when plotted in the RV variability vs.magnitude diagram a trend of increasing RV scatter with luminosity isseen. The amplitude of RV variability does not increase dramatically, aspredicted, for instance, by simple scaling laws. At least two luminousand cooler stars of the sample show a correlation between RV andchromospheric activity and bisector asymmetry, indicating that in thesetwo objects RV variability is likely induced by the presence of(chromospheric) surface structures.Based on observations collected at the 1.52 m-ESO telescope at the LaSilla Observatory from Oct 1999 to Feb. 2002 under ESO programs and theESO-Observatório Nacional, Brazil, agreement and in part onobservations collected on the Alfred Jensch 2 m telescope of theThüringer Landessternwarte Tautenburg.
| 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.}
| Tests of stellar model atmospheres by optical interferometry. VLTI/VINCI limb-darkening measurements of the M4 giant ψ Phe
We present K-band interferometric measurements of the limb-darkened (LD)intensity profile of the M 4 giant star ψ Phoenicis obtained withthe Very Large Telescope Interferometer (VLTI) and its commissioninginstrument VINCI. High-precision squared visibility amplitudes in thesecond lobe of the visibility function were obtained employing two 8.2 mUnit Telescopes (UTs). This took place one month after light from UTswas first combined for interferometric fringes. In addition, we sampledthe visibility function at small spatial frequencies using the 40 cmtest siderostats. Our measurement constrains the diameter of the star aswell as its center-to-limb intensity variation (CLV). We construct aspherical hydrostatic PHOENIX model atmosphere based onspectrophotometric data from the literature and compare its CLVprediction with our interferometric measurement. We compare as well CLVpredictions by plane-parallel hydrostatic PHOENIX, ATLAS 9, and ATLAS 12models. We find that the Rosseland angular diameter as predicted bycomparison of the spherical PHOENIX model with spectrophotometry is ingood agreement with our interferometric diameter measurement. The shapeof our measured visibility function in the second lobe is consistentwith all considered PHOENIX and ATLAS model predictions, and issignificantly different to uniform disk (UD) and fully darkened disk(FDD) models. We derive high-precision fundamental parameters for ψPhe, namely a Rosseland angular diameter of 8.13 ± 0.2 mas, withthe Hipparcos parallax corresponding to a Rosseland linear radius R of86 ± 3 Rȯ, and an effective temperature of 3550± 50 K, with R corresponding to a luminosity of \logL/Lȯ=3.02 ± 0.06. Together with evolutionarymodels, these values are consistent with a mass of 1.3 ± 0.2Mȯ, and a surface gravity of \log g = 0.68 ±0.11.Based on public data released from the European Southern ObservatoryVLTI obtained from the ESO/ST-ECF Science Archive Facility. The VLTI wasoperated with the commissioning instrument VINCI and the MONA beamcombiner.
| A far-infrared view of the Lockman Hole from ISO 95-μm observations - I. A new data reduction method
We report results from a new analysis of a deep 95-μm imaging surveywith the photopolarimeter ISOPHOT on-board the Infrared SpaceObservatory, over a 40 × 40 arcmin2 area within theLockman Hole. To this end we exploit a newly developed parametricalgorithm able to identify and clean spurious signals induced by cosmicrays impacts and by transient effects and non-linearities in thedetectors. These results provide us with the currently deepest - to ourknowledge - far-infrared (far-IR) image of the extragalactic sky. Withinthe survey area, we detect 36 sources with signal-to-noise ratio S/N> 3 (corresponding to a flux of 16 mJy), making up a completeflux-limited sample for S95μm>= 100 mJy. Reliablesources are detected, with decreasing but well-controlled completeness,down to S95μm~= 20 mJy. The source extraction process andthe completeness, the photometric and astrometric accuracies of thiscatalogue have been tested by us with extensive simulations accountingfor all the details of the procedure. We estimate source counts down toa flux of ~30 mJy, at which limit we evaluate that 10-20 per cent of thecosmic IR background (CIRB) has been resolved into sources (contributingto the CIRB intensity ~=2.0 × 10-9 W m-2sr-1).The 95-μm galaxy counts reveal a steep slope atS95μm<= 100 mJy (α~= 1.6), in excess of thatexpected for a non-evolving source population. The shape of these countsagrees with those determined by ISO at 15 and 175 μm, and startssetting strong constraints on the evolution models for the far-IR galaxypopulations.
| Discovery of a dust cloud next to sigma Orionis
We report on the discovery of a mid-infrared source at a projecteddistance of only 1200 AU from the O9.5 V star sigma Orionis. Thespatially resolved, fan-shaped morphology and the presence of anionization front, as well as evidence in the spectrum for processed dustgrains, all suggest that it is a proto-planetary disk being dispersed bythe intense ultraviolet radiation from sigma Orionis. We compute themass budget and the photo-evaporation timescale, and discuss thepossible nature of this remarkable object.
| The circumstellar envelope of the C-rich post-AGB star HD 56126
We present a detailed study of the circumstellar envelope of thepost-asymptotic giant branch ``21 mu m object'' HD 56126. We build adetailed dust radiative transfer model of the circumstellar envelope inorder to derive the dust composition and mass, and the mass-loss historyof the star. To model the emission of the dust we use amorphous carbon,hydrogenated amorphous carbon, magnesium sulfide and titanium carbide.We present a detailed parametrisation of the optical properties ofhydrogenated amorphous carbon as a function of H/C content. Themid-infrared imaging and spectroscopy is best reproduced by a singledust shell from 1.2 to 2.6'' radius around the central star. This shelloriginates from a short period during which the mass-loss rate exceeded10-4 Msun/yr. We find that the strength of the``21'' mu m feature poses a problem for the TiC identification. The lowabundance of Ti requires very high absorption cross-sections in theultraviolet and visible wavelength range to explain the strength of thefeature. Other nano-crystalline metal carbides should be considered aswell. We find that hydrogenated amorphous carbon in radiativeequilibrium with the local radiation field does not reach a high enoughtemperature to explain the strength of the 3.3-3.4 and 6-9 mu mhydrocarbon features relative to the 11-17 mu m hydrocarbon features. Wepropose that the carriers of these hydrocarbon features are not inradiative equilibrium but are transiently heated to high temperature. Wefind that 2 per cent of the dust mass is required to explain thestrength of the ``30'' mu m feature, which fits well within the measuredatmospheric abundance of Mg and S. This further strengthens the MgSidentification of the ``30'' mu m feature.Based on observations taken at the European Southern Observatory, LaSilla, Chile and observation obtained with ISO, an ESA project withinstruments funded by ESA Member states (especially the PI countries:France, Germany, The Netherlands and the UK) with the participation ofISAS and NASA.
| Infrared observations of NGC 3603. II. A 11.9 mu m and 18 mu m survey
We present results of the first sub-arcsec resolution mid infraredsurvey of the southern hemisphere giant H II region NGC 3603. We haveobserved selected fields in the vicinity of the OB cluster atwavelengths of 11.9 mu m and 18 mu m using TIMMI 2 mounted on the ESO3.6 m telescope. These fields comprise areas with dense molecular cores,embedded near infrared sources as well as several OH, H2O andCH3OH maser sources, which give indications of ongoing starformation processes. We report the detection of 36 mid infrared pointsources and additionally provide flux measurements for 42 knots ofdiffuse emission. In the area surveyed the protostar IRS 9A is foundto be the most luminous source at both 11.9 mu m and 18 mu m. Located inits immediate vicinity two more sources (IRS 9B and IRS 9C) also exhibitsignificant 11.9 mu m and 18 mu m emission, thus providing furtherindications for IRS 9 being an association of protostars in its ownright. Several other 11.9 mu m point sources are related to nearinfrared sources with strong K-band excess emission and/or to masersources, which classifies them as young sources, too. In contrast, thesecond strongest 11.9 mu m source, IRS 4, appears to be in a moreevolved stage. Towards the center of the OB cluster we observe midinfrared emission arising from the three Wolf-Rayet stars WR 43abc,providing evidence for dust production and/or the presence of plasma intheir circumstellar envelopes. Spread all over the cluster, we detect anumber of sources with mid infrared fluxes close to the sensitivitylimit ( ~ 0.01 Jy) of our 11.9 mu m data, which apparently have very redK-N colours. We suggest that these sources are circumstellar disks whichare externally heated by the nearby massive stars. Towards the southand west of the OB cluster, large amounts of diffuse emission are foundclosely correlated with ionized material. We identify at least 7 shocksand ionization fronts, reflecting the enormous impact of the faststellar winds and ionizing photons, originating from the massive clusterstars, on the adjacent gas and dust. This is impressively emphasized bythe shocked and ionized material associated with the heads of the twoprominent pillars. Both pillars are easily seen in our 11.9 mu m and 18mu m data: the western one rather prominent in emission, the eastern onemore pronounced in absorption against a strong diffuse mid infraredbackground. Among those sources, for which our data do not reveal anypoint-like mid infrared counterpart, are IRS 1 as well as the three``proplyds''. However, at least for ``proplyd'' 3 we detect extended,rim-like 11.9 mu m emission. Therefore, we consider it likely that NGC3603's ``proplyds'' simply represent scaled-down versions of theneighbouring pillars, i.e. remnant density enhancements of the pristinemolecular cloud which to date were able to resist the ionizing andphotoevaporating radiation from the nearby OB stars.Based on data sets obtained at the European Southern Observatory on LaSilla, Chile.
| Precise radial velocity measurements of G and K giants. First results
We present the first results of our precise radial velocity (RV)measurements of G and K giants. A number of stars from our list of 80targets have been observed for 14 months using the fibre-fed echellespectrograph FEROS at the 1.52 m ESO telescope in La Silla, Chile. Thissample increases the number of giants surveyed with precise stellarradial velocity measurements at least by a factor of 10. During thisperiod we are able to estimate the long-term accuracy of our measurementas better than 11 m s-1. We use the simultaneous Th-Arcalibration and cross-correlation technique to compute the radialvelocity by applying a numerical template for K-type stars. Standarddeviation sigma of mean radial velocity variations between 3 ms-1 and 4 km s-1 with timescales between severaldays and years are measured for 21 of G and K giants which are presentedin this paper. Fifteen stars show definite variability above 3 sigma ofour measurement uncertainties. Two stars with RV variations above 800 ms-1 are tentatively identified as new binaries. Althoughdefinitive trends between RV variations and stellar evolutionary statuscannot yet be established, all the luminous cool giants of our sampleseem to have significant radial velocity variations, while those starsin the giant's clump region can be either variable or constant.Based on observations collected at the ESO 1.52 m telescope at the LaSilla Observatory under program ESO No. 64.L-0047, 65.L-0571, 66.D-0592and from Nov. 99 to Feb. 01 under the ESO-Observatório Nacional,Brazil, agreement.}
| 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.
| ISOPHOT - Photometric calibration of point sources
All observations by the aperture photometer (PHT-P) and the far-infrared(FIR) camera section (PHT-C) of ISOPHOT included reference measurementsagainst stable internal fine calibration sources (FCS) to correct fortemporal drifts in detector responsivities. The FCSs were absolutelycalibrated in-orbit against stars, asteroids and planets, coveringwavelengths from 3.2 to 240 mu m. We present the calibration concept forpoint sources within a flux-range from 60 mJy up to 4500 Jy for staringand raster observations in standard configurations and discuss therequisite measurements and the uncertainties involved. In this processwe correct for instrumental effects like nonlinearities, signaltransients, time variable dark current, misalignments and diffractioneffects. A set of formulae is developed that describes the calibrationfrom signal level to flux densities. The scatter of 10 to 20% of theindividual data points around the derived calibration relations is ameasure of the consistency and typical accuracy of the calibration. Thereproducibility over longer periods of time is better than 10%. Thecalibration tables and algorithms have been implemented in the finalversions of the software for offline processing and interactiveanalysis.
| From Amateur Astronomer to Observatory Director: The Curious Case of R. T. A. Innes
Robert Innes was one of a select band of amateur astronomers who madethe transition to professional ranks towards the end of the nineteenthcentury. Initially he had a passion for mathematical astronomy, butafter settling in Sydney he developed a taste for observationalastronomy, specialising in the search for new double stars. He quicklybecame known for his success in this field and for his publications onsolar system perturbations, and with John Tebbutt's patronage managed tosecure a clerical position at the Royal Observatory, Cape of Good Hope.Once there he continued to observe in his spare time and to publish,and, with strong support from Sir David Gill, was appointed foundingDirector of the Transvaal Observatory. By the time he died in 1933,Innes had received an honorary D.Sc. from Leiden University, and hadestablished an international reputation as a positional astronomer. Thispaper provides an interesting case study of a well-known`amateur-turned-professional', and an example of the ways in whichpatronage played a key role in nineteenth and early twentieth centuryAustralian and South African astronomy.
| First Detections of Molecular Gas Associated with the Wolf-Rayet Ring Nebula NGC 3199
This paper presents the first observations of molecular gas associatedwith the Wolf-Rayet ring nebula NGC 3199 around the WR star WR 18. Thisincludes first observations of the molecules HCN, HCO+, CN,and HNC seen in any Wolf-Rayet ring nebula. Our observations immediatelysuggest the presence of high-density molecular gas (>104cm-3) in the nebula with significant amounts of associatedmolecular gas, which is in the form of clumpy ejecta and/or interstellarmaterial. Molecular CO gas was mapped across the optically brightportion of the nebula and out into the diffuse ionized component usingthe 12CO J=1-->0 line. CO gas is not seen within theoptically bright rim of NGC 3199 but adjacent to it. The opticalemission rim therefore appears to mark regions of photodissociation.Velocity components in the CO data are consistent with those seen inhigh-resolution optical spectra of the Hα line but extend beyondthe visible emission. A prior suggestion of the formation of the nebulavia a bow shock appears unlikely since Hipparcos measurements show theproper motion of WR 18 is almost at right angles to the directionrequired for the bow shock model. Instead, line splitting toward thenorth of the nebula suggests that a possible blowout of the Wolf-Rayetwind through surrounding ejecta may be responsible for some of thevelocity features observed. Preliminary estimates of molecularabundances in the nebula seen toward the central star are significantlyhigher than for the interstellar medium and are similar to those inplanetary nebulae, although CN is distinctly underabundant in comparisonto the very high values found in many planetary nebulae. The abundancesfound are consistent with the idea that at least a portion of themolecular material is associated with ejecta from the central star.Based on observations collected at the Swedish-ESO SubmillimetreTelescope (SEST) at the European Southern Observatory, La Silla, Chile.The Swedish-ESO Submillimetre Telescope is operated jointly by theEuropean Southern Observatory (ESO) and the Swedish National Facilityfor Radio Astronomy, Onsala Space Observatory, at Chalmers University ofTechnology.
| 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
| Deep far infrared ISOPHOT survey in ``Selected Area 57". I. Observations and source counts
We present here the results of a deep survey in a 0.4 deg2blank field in Selected Area 57 conducted with the ISOPHOT instrumentaboard ESAs Infrared Space Observatory (ISO at both 60 mu m and 90 mu m.The resulting sky maps have a spatial resolution of 15 x 23arcsec2 per pixel which is much higher than the 90 x 90arcsec2 pixels of the IRAS All Sky Survey. We describe themain instrumental effects encountered in our data, outline our datareduction and analysis scheme and present astrometry and photometry ofthe detected point sources. With a formal signal to noise ratio of 6.75we have source detection limits of 90 mJy at 60 μm and 50 mJy at 90μm. To these limits we find cumulated number densities of 5+/- 3.5deg-2 at 60 μm and 14.8+/- 5.0 deg-2 at 90μm. These number densities of sources are found to be lower thanpreviously reported results from ISO but the data do not allow us todiscriminate between no-evolution scenarios and various evolutionarymodels. Based on observations with ISO, an ESA project with instrumentsfunded by ESA member states (especially the PI countries: France,Germany, the Netherlands, and the United Kingdom) and with theparticipation of ISAS and NASA.
| 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).
| Photometric modelling of starspots - I. A Barnes-Evans-like surface brightness-colour relation using (Ic-K)
In the first part of this work, the empirical correlation of stellarsurface brightness FV with (Ic-K) broad-bandcolour is investigated by using a sample of stars cooler than the Sun. Abilinear correlation is found to represent well the brightness of G, Kand M giant stars. The change in slope occurs at (Ic-K)~2.1or at about the transition from K to M spectral types. The samerelationship is also investigated for dwarf stars and found to bedistinctly different from that of the giants. The dwarf star correlationdiffers by an average of -0.4 in (Ic-K) or by a maximum inFV of ~-0.1, positioning it below that of the giants, withboth trends tending towards convergence for the hotter stars in oursample. The flux distribution derived from theFV-(Ic-K) relationship for the giant stars,together with that derived from an FV-(V-K) relationship andthe blackbody flux distribution, is then utilized to compute syntheticlight V and colour (V-R)c, (V-I)c and (V-K) curvesof cool spotted stars. We investigate the effects on the amplitudes ofthe curves by using these FV-colour relations and by assumingthe effective gravity of the spots to be lower than the gravity of theunspotted photosphere. We find that the amplitudes produced by using theFV-(Ic-K) relationship are larger than thoseproduced by the other two brightness correlations, meaning smallerand/or warmer spots.
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Osservazione e dati astrometrici
| Costellazione: | Lepre |
| Ascensione retta: | 05h05m27.70s |
| Declinazione: | -22°22'16.0" |
| Magnitudine apparente: | 3.19 |
| Distanza: | 69.493 parsec |
| Moto proprio RA: | 21.5 |
| Moto proprio Dec: | -72.8 |
| B-T magnitude: | 5.102 |
| V-T magnitude: | 3.334 |
Cataloghi e designazioni:
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