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Keck Interferometer Nuller Data Reduction and On-Sky Performance
We describe the Keck Interferometer nuller theory of operation, datareduction, and on-sky performance, particularly as it applies to thenuller exozodiacal dust key science program that was carried out between2008 February and 2009 January. We review the nuller implementation,including the detailed phasor processing involved in implementing thenull-peak mode used for science data and the sequencing used for scienceobserving. We then describe the Level 1 reduction to convert theinstrument telemetry streams to raw null leakages, and the Level 2reduction to provide calibrated null leakages. The Level 1 reductionuses conservative, primarily linear processing, implemented consistentlyfor science and calibrator stars. The Level 2 processing is moreflexible, and uses diameters for the calibrator stars measuredcontemporaneously with the interferometer's K-band cophasing system inorder to provide the requisite accuracy. Using the key science data setof 462 total scans, we assess the instrument performance for sensitivityand systematic error. At 2.0 Jy we achieve a photometrically-limitednull leakage uncertainty of 0.25% rms per 10 minutes of integration timein our broadband channel. From analysis of the Level 2 reductions, weestimate a systematic noise floor for bright stars of rms null leakageuncertainty per observing cluster in the broadband channel. A similaranalysis is performed for the narrowband channels. We also provideadditional information needed for science reduction, including detailson the instrument beam pattern and the basic astrophysical response ofthe system, and references to the data reduction and modeling tools.
| 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
| Observations of occultations of stars by the moon
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..395H&db_key=AST
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Virgo |
| Ascensió Recta: | 13h54m21.37s |
| Declinació: | -17°10'48.4" |
| Magnitud Aparent: | 6.597 |
| Distancia: | 206.612 parsecs |
| Moviment propi RA: | -28.5 |
| Moviment propi Dec: | -6.1 |
| B-T magnitude: | 8.413 |
| V-T magnitude: | 6.747 |
Catàlegs i designacions:
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