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A near-infrared interferometric survey of debris disk stars. I. Probing the hot dust content around ? Eridani and ? Ceti with CHARA/FLUOR
Context: The quest for hot dust in the central region of debris disksrequires high resolution and high dynamic range imaging. Near-infraredinterferometry is a powerful means to directly detect faint emissionfrom hot grains. Aims: We probed the first 3 AU around ?Ceti and ? Eridani with the CHARA array (Mt Wilson, USA) inorder to gauge the 2 ?m excess flux emanating from possible hot dustgrains in the debris disks and to also resolve the stellar photospheres.Methods: High precision visibility amplitude measurements wereperformed with the FLUOR single mode fiber instrument and telescopepairs on baselines ranging from 22 to 241 m of projected length. Theshort baseline observations allow us to disentangle the contribution ofan extended structure from the photospheric emission, while the longbaselines constrain the stellar diameter. Results: We havedetected a resolved emission around ? Cet, corresponding to aspatially integrated, fractional excess flux of 0.98±0.21 ×10-2 with respect to the photospheric flux in the K'-band.Around ? Eri, our measurements can exclude a fractional excessof greater than 0.6× 10-2 (3?). We interpret thephotometric excess around ? Cet as a possible signature of hotgrains in the inner debris disk and demonstrate that a faint, physicalor background, companion can be safely excluded. In addition, wemeasured both stellar angular diameters with an unprecedented accuracy:?_LD(? Cet)= 2.015 ± 0.011 mas and ?_LD(?Eri)=2.126 ± 0.014 mas.
| A catalog of bright calibrator stars for 200-m baseline near-infrared stellar interferometry
We present in this paper a catalog of reference stars suitable forcalibrating infrared interferometric observations. In the K band,visibilities can be calibrated with a precision of 1% on baselines up to200 meters for the whole sky, and up to 300 meters for some part of thesky. This work, extending to longer baselines a previous catalogcompiled by Bordé et al. (2002, A&A, 393, 183), isparticularl y well adapted to hectometric-class interferometers such asthe Very Large Telescope Interferometer (VLTI, Glindemann et al. 2003,Proc. SPIE, 4838, 89) or the CHARA array (ten Brummelaar et al. 2003,Proc. SPIE, 4838, 69) when one is observing well-resolved, high-surfacebrightness objects (K 8). We use the absolute spectro-photometriccalibration method introduced by Cohen et al. (1999, AJ, 117, 1864) toderive the angular diameters of our new set of 948 G8-M0 calibratorstars extracted from the IRAS, 2MASS and MSX catalogs. Angular stellardiameters range from 0.6 mas to 1.8 mas (median is 1.1 mas) with amedian precision of 1.35%. For both the northern and southernhemispheres, the closest calibrator star is always less than 10°away.
| 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
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable 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/qcat?J/A+A/397/997
| Accurate Positions Of Suspected Variable Stars Near The South Galactic Pole
Not Available
| UBVRI Photometry of FKSZ Stars - Part One
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...70..369C&db_key=AST
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| Takýmyýldýz: | Balina |
| Sað Açýklýk: | 02h03m53.88s |
| Yükselim: | -17°30'49.1" |
| Görünürdeki Parlaklýk: | 7.046 |
| Uzaklýk: | 338.983 parsek |
| özdevim Sað Açýklýk: | -3.1 |
| özdevim Yükselim: | -11 |
| B-T magnitude: | 9.131 |
| V-T magnitude: | 7.219 |
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