The Nature of Faint Blue Stars in the PHL and Ton Catalogues Based on Digital Sky Surveys

We determined accurate positions for 3,000 of the "faint blue stars" in the PHL (Palomar-Haro-Luyten) and Ton/Ton S catalogues. These were published from 1957 to 1962, and, aimed at finding new white dwarfs, provide approximate positions for ∼ 10,750 blue stellar objects. Some of these "stars" had become known as quasars, a type of objects unheard-of before 1963. We derived subarcsec positions from a comparison of published finding charts with images from the first-epoch Digitized Sky Survey. Numerous objects are now well known, but as of February 2015 neither their PHL or Ton numbers, nor their discoverers, are recognized in current databases. A comparison with modern radio, IR, UV and X-ray surveys leads us to suggest that the fraction of extragalactic objects in the PHL and Ton catalogues is at least 15 %. However, as we failed to locate the original PHL plates or finding charts, it may be impossible to correctly identify the remaining 7,726 PHL objects.