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Description
The Palomar-Green Catalog of UV-Excess Stellar Objects provides positions (the original_ra and original_dec parameters) accurate to about 8 arcsec in each coordinate, photographic B-magnitudes accurate to 0.29 mag, spectral types, some cross-references, and photoelectric broad-band, multichannel, and Stroemgren colors when available. Of the 1874 objects in the catalog as published in 1986 (1878 in this version), 1715 comprise a statistically complete sample covering 10714 square degrees from 266 fields taken on the Palomar 18-inch Schmidt telescope. Limiting magnitudes vary from field to field, ranging from 15.49 to 16.67. The overall completeness is estimated to be 84%, but that figure and the relative contributions of magnitude, color, and accidental errors vary depending on the magnitude and color distribution of the spectroscopic subsample. The dominant population in this catalog is that of the hot, hydrogen-atmosphere subdwarfs, the sdB stars, which comprise nearly 40 per cent of the sample. The hot white dwarfs of spectral types DA, DB, and DO account for 21, 2.8, and 1.0 per cent of the sample, respectively, while cooler DC or DZ white dwarfs add another 1.2 per cent. Cataclysmic variables and composite-spectrum binaries account for 5 per cent, although many other spectra dominated by a hot star showed evidence for a cool companion at red wavelengths. Planetary nebulae central stars account for another 0.5 per cent. Extragalactic objects comprise about 9 per cent of the complete sample, with QSOs representing 5.4 per cent. Only 0.3 per cent (6 objects) remain with totally unsatisfactory or unknown spectral classes. (Notice that all of these percentage estimates are based on the published version of this catalog, and that the values in the current online version may be slightly different, as the latter includes a small number of updates and additions). In 2009, an additional data resource was added to this catalog by CDS, namely a file containing more accurate (sub-arcsecond) positions and V magnitudes (the skiff_vmag parameter), and also additional comments (the skiff_comments parameter). This new material has now been included in the HEASARC version of the PG Catalog. A full discussion of this addition can be found at <a href="http://cdsarc.u-strasbg.fr/ftp/cats/II/207A/pg_2009.txt">http://cdsarc.u-strasbg.fr/ftp/cats/II/207A/pg_2009.txt</a>. This database was initially made available at the HEASARC in June 1998 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/207A">CDS catalog II/207A</a> file catalog.dat which had been last updated on Oct 17 1997. In 2017, the HEASARC re-ingested this CDS catalog as it had been updated several times in the interim, notably in 2009 when an additional file (pg_pos.dat) with precise coordinates and comments provided by Brian Skiff was added. This is a service provided by NASA HEASARC .
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