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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.
| 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.
| Microvariability in the optical polarization of 3C 279
We present results of a microvariability polarization study in theviolently variable quasar 3C279. We have resolved the polarizationcurves in the V band for this object down to timescales of minutes. Wefound two main components in the evolution of the degree of linearpolarization, one consisting of a flicker with timescales of severaltens of minutes and other component with far more significant variationson timescales of a few days. The linear polarization descended from ~17% down to ~ 8% in three nights. The polarization angle underwent asudden change of more that 10 degrees in a few hours, perhaps indicatingthe injection of a new shock in the jet. The amplitude of the intranightflickering in the degree of polarization is at the level of ~ 1%. Theseare probably the best sampled polarization data ever obtained for thisobject. We also performed IR observations and we provide a follow-up ofthe evolution of this source at such energies after the mainpolarization outburst.Based on observations made at the Complejo Astronómico ElLeoncito, which is operated under agreement between CONICET and theNational Universities of La Plata, Córdoba, and San Juan, as wellas at the Laboratório Nacional de Astrofísica, LNA-CNPq,Brazil.}\fnmsep\thanks{Table 2 is only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via \http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/857
| A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| 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
| Spectropolarimetry of the Luminous Narrow-Line Seyfert Galaxies IRAS 20181-2244 and IRAS 13224-3809
We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS13224-3809 with a new spectropolarimeter on the Ritchey-Chrétienspectrograph at the CTIO 4 m telescope. Previously it had been suggestedthat IRAS 20181-2244 was a type 2 QSO and thus might contain an obscuredbroad-line region that could be detected by the presence of broad Balmerlines in the polarized flux. We found the object to be polarized atabout 2% and constant with wavelength (unlike most narrow-line Seyfert 1galaxies), but with no evidence of broad Balmer lines in polarized flux.The spectropolarimetry indicates that the scattering material is insidethe broad-line region. IRAS 13224-3809, notable for its high variabilityin X-ray and UV wavelengths, has a low polarization consistent with aGalactic interstellar origin.
| Observations of BN and AN stars: New Be stars
From a survey of spectra of Bn/An stars, we have detected seven new Bestars: HR 1056 (A0Vn), 1544 (A1Vn), 2191 (A0Vnn), 2300 (B8Vn), 3134(B9.5 Vn), 3878 (B0.5 IIIn) and 4552 (B9IIIpSi). H_alpha profiles ofthese stars are presented. Measured values of equivalent widths, fullwidths at half intensity maximum, and the peak-separations of theH_alpha emission profiles are also tabulated in this paper. We have alsocomputed the radii of emission disks of the newly detected Be stars.
| The Chamaeleon Infrared Nebula: A Polarization Study with High Angular Resolution
We performed high-angular resolution imaging polarimetry of theChamaeleon Infrared Nebula (Cha IRN) in the J and H bands. In thisLetter, we present a polarization map in the H band. These newmeasurements, together with previous polarization data, are interpretedusing a Monte Carlo model for radiative transfer. As a result of thesecalculations, we derive properties of the circumstellar dustconfiguration of Cha IRN.
| 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.
| UBV photometry of HD stars in the fields of selected cataclysmic variables.
Not Available
| 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
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kentaur |
| Rektaszcenzió: | 11h17m11.80s |
| Deklináció: | -38°00'52.0" |
| Vizuális fényesség: | 6.27 |
| Távolság: | 71.633 parszek |
| RA sajátmozgás: | -72.3 |
| Dec sajátmozgás: | 10 |
| B-T magnitude: | 6.368 |
| V-T magnitude: | 6.249 |
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INHABITED SKY
