/ftp/cats/i/270



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I/270      Catalog of Positions of IR Stellar Sources (CPIRSS)  (Hindsley+ 1994)
The following files can be converted to FITS (extension .fit .fgz or .fiZ)
	cpirss01.dat
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Query from: http://vizier.cds.unistra.fr/cgi-bin/VizieR?-source=I/270
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Beginning of ReadMe : I/270 Catalog of Positions of IR Stellar Sources (CPIRSS) (Hindsley+ 1994) ================================================================================ The U.S. Naval Observatory Catalog of Positions of Infrared Stellar Sources (Upgraded in 1996 and 2001) Hindsley R., Harrington R., Urban S. <Astron. J. 107, 280 (1994)> =1994AJ....107..280H ================================================================================ ADC_Keywords: Infrared sources ; Positional data ; Proper motions ; Surveys ; Photometry Description: The U.S. Naval Observatory Catalog of Positions of Infrared Stellar Sources (CPIRSS) was originally compiled in 1994 to provide astrometry at the sub-arcsecond level for many of the point sources in the 1987 version of the IRAS Point Source Catalog (NASA RP-1190). This was accomplished by the identification of IRAS sources with bright optical stars, checked by requiring the color V-[12] (with [12] being a magnitude derived from the IRAS flux) to be consistent with the optical colors or spectral type. Additionally, the K magnitude (2.2 microns) has been estimated. This version, completed in 2001, contains 37,700 stars and includes the Hipparcos and Tycho-2 astrometry and photometry which was unavailable at the time of the original compilation. Introduction: The Infrared Astronomical Satellite (IRAS) carried out an all-sky survey at 12, 25, 60 and 100 microns. Approximately 250 000 point sources were identified. However, by the standards of optical astrometry, the positions of these sources are poorly determined, with errors of tens of arc-seconds. Optical astrometric catalogs such as Hipparcos (ESA 1997) and Tycho-2 (Hoeg et al. 2000) have errors in position under 0.1 arc-seconds, some two to three orders of magnitude less than the IRAS positions. Many of the sources in the IRAS Point Source Catalog (1987, hereafter referred to as PSC) have been identified as stars. Thus it is possible to construct a higher quality astrometric catalog of infrared sources by combining these positions with the IRAS identifications. However, because the IRAS positions have such large errors, the identifications provided in the PSC are suspect. The V-[12] color, with [12] being a magnitude determined from the 12 micron flux, is very sensitive to temperature. If the optical identification of an IRAS source is correct, the V-[12] color should be consistent with optical colors or spectral type. Once a cross-correlation is established, an estimation of the Johnson system K magnitudes is made. Hindsley and Harrington (1994) describe the details on the confirmation identification based on color and the K magnitude determination. The CPIRSS has had two upgrades following the 1994 release; one in 1996 and one in 2001. In 1996, 4022 new sources were added, bringing the total to 37,700. As with the 33,678 stars in the original CPIRSS, the positional matches were checked by using the optical colors and visual magnitudes to estimate the 12 micron magnitudes, which were compared to the actual IRAS 12 micron measurement. Stars with an estimate that do not match the observations are included in the catalog but flagged so that the user is aware of the questionable identification. Also in 1996, the record number in the IRAS Point Source Catalog was added to each record. The 1996 version also had various errata corrected. In 2001, better astrometry was substituted. Of the 37,700 stars, all but 105 were found in either the Hipparcos or Tycho-2 catalogs (Cat. I/246, I/259). Since these surpass the accuracies found in the astrometric catalogs used in earlier versions, their values were added. Given the availability of both for a star, the Hipparcos data take precedence. Both Hipparcos and Tycho-2 numbers are provided, along with several flags that can give users warning of possible multiplicity or non-linear proper motions. At the same time, the V magnitudes from Hipparcos or Tycho-2 were substituted for the poorer values found in the previously used astrometric catalogs. Since much of the original work was performed using those older values, differences between them and the current values are provided for the user. Earlier versions of this work were not put into the Astronomical Data Centers, but were made available through the U.S. Naval Observatory.