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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
| Decoupled line driven outflow around B and Be stars.
The semi-analytic model of Bjorkman & Cassinelli for the equatorial`discs' around Be stars is re-examined and shown to be capable ofproducing higher equator-to-pole density contrasts when the effects ofthe dynamical decoupling of the stellar radiation field from theoutflowing gas are incorporated. The enhancement, as measured by thenormal component of the momentum fed into the disc, is in the region ofa factor of 2. Inclusion of the effect also lowers the threshold stellarrotation rate for the formation of a wind-compressed disc fromv_rot_/v_crit_=~0.4 to 0.25. Two physical mechanisms that may give riseto this decoupling, which are most effective in B star winds, arepresented and their relative merits compared. This comparison isperformed with reference to available UV and X-ray observations.Ion-stripping (Springmann & Pauldrach 1992) could be the cause ofthe low observed maximum outflow velocities, but it cannotsimultaneously explain the ubiquitous high-temperature (>10^6^K)X-ray emission. Shock disruption of the wind ionization balance (Castor1987) may also terminate the outward radiative acceleration in the windsof B stars. This effect suggests a simple method for setting an upperlimit to the X-ray emission from weak shock-disrupted winds whichcompares reasonably favourably with X-ray luminosities derived fromROSAT data.
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| Takýmyýldýz: | Irmak |
| Sað Açýklýk: | 04h33m06.32s |
| Yükselim: | -12°32'36.2" |
| Görünürdeki Parlaklýk: | 6.673 |
| Uzaklýk: | 119.332 parsek |
| özdevim Sað Açýklýk: | -28 |
| özdevim Yükselim: | -37.3 |
| B-T magnitude: | 8.065 |
| V-T magnitude: | 6.788 |
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