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The infrared void in the Lupus dark clouds revisited: a polarimetric approach
The results of B-band CCD imaging linear polarimetry obtained for starsfrom the Hipparcos catalogue are used to re-examine the distribution ofthe local interstellar medium towards the IRAS 100-μm emission voidin the Lupus dark clouds. The analysis of the obtainedparallax-polarization diagram assigns to the dark cloud Lupus1 adistance between 130 and 150pc and assures the existence of a low columndensity region coincident with the observed infrared void. Moreover,there are clear indications of the existence of absorbing material atdistances closer than 60-100pc, which may be associated with theinterface boundary between the Local Bubble and its neighbourhood LoopIsuperbubble.
| The Fine Guidance Sensor Orbit of the G4 Bright Giant HD 173764
TRANS and POS mode observations of the G4 IIa star β Scuti (HD173764) have been made with a Hubble Space Telescope (HST) Fine GuidanceSensor (FGS3). This spectroscopic binary with a period of 833 days andan eccentricity of 0.36 offered hope of resolving the secondary stellarcomponent and inferring the orbital inclination, distance, and masses,thus contributing to comparisons with theory for rapidpost-main-sequence evolution. From analysis of IUE observations and thetotal UV-optical energy distribution, the secondary has a spectral classof B9 and a difference in visual luminosity of ~3 mag. Isochrone fittingusing this ΔV and temperatures from the spectral types yields ~26mas for the anticipated projected separation at apastron. The TRANS modedata demonstrate duplicity in the signal but fail to provide reliableseparations and position angles even near apastron. This separation isinstead no more than 22 mas. However, the parallax is probably smaller,by a similar factor, than that expected from initial isochrone fitting,and β Sct is more luminous than originally estimated. Analysis ofPOS mode data reveals the orbital inclination and the orientation on thesky for a semimajor axis of only 5.7+/-0.4 mas for the primary's orbitaround the center of mass. The parallax from POS mode observations isquite small, only consistent with isochrones at the 2 σ level.From all of the evidence, the system lies at 210+/-23 pc and the evolvedG-type primary has Mv~=-2.9.
| Southern stars that can be used as unpolarized standards
Results are presented from a programme of linear polarimetry to findunpolarized stars in the solar vicinity that could be used as standardstars and are within reach of telescopes in the southern hemisphere. Wefind up to 10 suitable candidates. On the other hand, among the observedstars, HD 112164, HD 114613, HD 130307 and HD 160691 are objects within27 pc of the Sun but showed a relatively high polarization in the ~0.1per cent level, which must be of intrinsic origin.
| The 2MASS Wide-Field T Dwarf Search. II. Discovery of Three T Dwarfs in the Southern Hemisphere
We present the discovery of three new southern hemisphere T dwarfsidentified in the Two Micron All Sky Survey. These objects, 2MASS0348-6022, 2MASS 0516-0445, and 2MASS 2228-4310, have classificationsT7, T5.5, and T6.5, respectively. Using linear absolutemagnitude/spectral type relations derived from T dwarfs with measuredparallaxes, we estimate spectrophotometric distances for thesediscoveries; the closest, 2MASS 0348-6022, is likely within 10 pc of theSun. Proper motions and estimated tangential velocities are consistentwith membership in the Galactic disk population. We also list southernhemisphere T dwarf candidates that were either not found in subsequentnear-infrared imaging observations and are most likely uncataloged minorplanets, or have near-infrared spectra consistent with background stars.
| VLT-spectropolarimetry of the high-polarization Seyfert 1 galaxy Fairall 51
We present high-precision optical spectropolarimetry of the Seyfert 1galaxy Fairall 51 (F51) taken with FORS1 at the VLT.The observed spectrum shows unpolarized and linearly polarizedcomponents. The AGN continuum and the broad lines show (after correctionfor the Galactic interstellar polarization and the light contribution ofthe F51 host galaxy) a practically identical amountof intrinsic polarization ranging from 5% in the red to 13% in the UV.The narrow lines are unpolarized or show only little intrinsicpolarization. The observed AGN continuum and the broad line radiationcan be explained by a combination of reddened (and attenuated) directlight and scattered light reflected from an optically thin dust region.Hence, within the framework of the unification scheme of AGN, theSeyfert 1 galaxy F51 appears to be an example of aborderline Seyfert 1/Seyfert 2 case where the nucleus is partiallyobscured like for other type 1 AGN with high intrinsic scatteringpolarization. It is found that the scattering region inF51 is located far from the BLR and the continuumsource. Thanks to this special scattering configuration, we were able tostudy the kinematics (line profiles) of the broad line region from twodifferent viewing angles, one along the line of sight (in total light)and one via the scattering region (in polarized light). The lineprofiles in polarized and total light are found to be indistinguishableto a very high accuracy, strongly indicating that the velocity field ofthe F51 BLR is essentially spherically symmetric.Based on observations obtained at the ESO VLT UT1 (Antu) at CerroParanal, Chile (ESO program 63.P-0074).
| 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 Hubble Space Telescope's High-Speed Photometer
We present an overview of the performance of the High Speed Photometer(HSP), one of the five original instruments on the Hubble SpaceTelescope (HST). As its name implies, the HSP was designed for precisehigh time resolution photometry from visual to ultraviolet wavelengths;sample times as short as 10.7 mus were possible. Three image dissectorsalong with 23 different broad- and narrowband filters spanning thespectral range from 1200 to 7500 Å were used for photometry ofstars and galaxies. A fourth image dissector with associatedpolarization analyzers allowed the measurement of broadband linearpolarization at near-ultraviolet wavelengths. Simultaneous observationsin the blue and red could be made using one of the dissectors and aphotomultiplier. Except for an instability in the sensitivity of one ofthe image dissectors and a reduced throughput in a specializedobservational mode, the instrument met or exceeded operationalspecifications until it was removed from HST in 1993 December. Theability of HSP to carry out its primary program, however, was nearlytotally compromised by the poor performance of the telescope, i.e., thespherical aberration of the primary mirror that greatly amplified theeffects of large spacecraft pointing jitter and telescope ``breathing.''As a consequence, the real possibility of HST/HSP opening a new era ofastronomical photometry was lost. HSP data affected by various telescopeproblems, as well as data in which these complications were relativelysmall, are shown. The excellent condition of the HSP after its return toEarth is described briefly.
| Polarimetry of the ultraviolet continua of southern radio galaxies
This paper reports new B-band polarimetry measurements for fourintermediate-redshift (0.3<z<0.7) southernradio galaxies. Deep optical spectra show that three of these objectsare broad-line radio galaxies, while the fourth is a narrow-line radiogalaxy. Despite the fact that the measurements were made in therest-frame ultraviolet (UV) in each object, and that emission-linecontamination is small, we find that the majority of objects display lowintrinsic continuum polarization. In two of the broad-line objects (PKS1602+01 and PKS 2135-20), this may result from our viewing thebroad-line region directly. The significant polarization measure, andcorresponding polarization orientation, in the narrow-line object PKS2250-41 is most consistent with scattering of light from the activenucleus. We therefore identify a diversity of UV polarization propertiesin powerful radio galaxies at intermediate redshifts. Not all radiogalaxies possess large intrinsic polarizations. Therefore the UVexcesses observed in these objects are unlikely to result solely fromscattered light.
| 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.
| An IRAS survey of main sequence B, A, and F stars
Results are presented of an IRAS survey of main-sequence B, A, and Fstars, based on three primary sources as a data base: theBernacca-Perinotto Catalog of Stellar Rotational Velocities, theMichigan Spectral Catalog, and the Bright Star Catalog. The stars in thedata base are divided into four categories: (1) main-sequence singlestars, (2) main-sequence close binary stars, (3) spectrally peculiarstars such as Am, Ap, Fm, and Fp stars, and (4) subgiants. It is foundthat about 20 percent of main-sequence single stars show an IR colorexcess in at least one of the 12, 25, or 60 micron IRAS bands, while theother three groups do not show any statistically significant percentageof IR color excess stars. It is also found that stars with large (v sini) values are more likely to show color excesses at IRAS wavelengthsthan stars with small (v sin i) values.
| An atlas of Hubble Space Telescope photometric, spectrophotometric, and polarimetric calibration objects
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99.1243T&db_key=AST
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Four-colour and H BET photometry of some bright southern stars- II.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972MNRAS.160..155S&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Corona Australe |
| Ascensione retta: | 19h02m08.70s |
| Declinazione: | -41°54'36.0" |
| Magnitudine apparente: | 6.23 |
| Distanza: | 108.108 parsec |
| Moto proprio RA: | 30.4 |
| Moto proprio Dec: | -9.8 |
| B-T magnitude: | 6.202 |
| V-T magnitude: | 6.207 |
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INHABITED SKY
