An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey .
In a small area of sky ( 190 square degrees ) , observed much like the full survey will be , 269 white dwarfs and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and 5 hot subdwarfs were known previously .
Most are ordinary DA ( hydrogen atmosphere ) and DB ( helium ) types .
In addition , in the full survey to date , a number of WDs have been found with uncommon spectral types .
Among these are blue DQ stars displaying lines of atomic carbon ; red DQ stars showing molecular bands of C _ { 2 } with a wide variety of strengths ; DZ stars where Ca and occasionally Mg , Na , and/or Fe lines are detected ; and magnetic WDs with a wide range of magnetic field strengths in DA , DB , DQ , and ( probably ) DZ spectral types .
Photometry alone allows identification of stars hotter than 12000 K , and the density of these stars for 15 < g < 20 is found to be \sim 2.2 deg ^ { -2 } at Galactic latitudes 29–62 ^ { \circ } .
Spectra are obtained for roughly half of these hot stars .
The spectra show that , for 15 < g < 17 , 40 % of hot stars are WDs and the fraction of WDs rises to \sim 90 % at g = 20 .
The remainder are hot sdB and sdO stars .