SPECTROPHOTOMETRY OF WHITE-DWARFS AS OBSERVED AT HIGH SIGNAL-TO-NOISE RATIO .2.

We analyze in detail CCD spectrophotometry, at high signal-to-noise ratio, of 140 white dwarfs, for which we give energy distributions measured at 14 100 Å bandpasses from 3571 to 8300 Å. The equivalent widths of lines of H, He I, metals, and atomic and molecular carbon are given as a function of color for DB, DQ, DZ, and DA stars, grouped by color classes (roughly, temperatures). We study in detail the new transitions and trace elements seen in the complex spectra. New forbidden He I transitions at 6068 Å (2 3P°-3 3P0) and 6632 Å (2 1P°-3 1P0) are present in at least the two hottest DB stars; other possible detections are noted. Traces of hydrogen appear in several of the hotter helium-rich stars. The spectrum of the hot DQAB star G227-5 (1728 + 550) is discussed in detail. The He-rich objects of color class 5 (near 10,000 K) show spectra with various combinations of weak helium and trace hydrogen, metallic, and carbon features. New metallic features are found in cooler DZ stars, and the presence of Ca I in vMa 2 (0046 + 051) is confirmed. The apparent, pressure shifted carbon bands seen in 0038-226 (LHS 1126) are discussed in detail. Comparison of the optical energy distribution with published infrared fluxes shows that the 1-2 μm wavelength region is strongly depressed, suffering extensive blanketing. Blackbody fits to the optical and infrared fluxes give much different temperatures. Similar fits to the energy distributions of cool stars with known trigonometric parallaxes are used to estimate the radii and bolometric corrections, which prove to be small. There is evidence for unresolved features blanketing the infrared or the optical wavelengths in different red degenerates. Equivalent widths, central depths, and width parameters are presented for Ha in 73 DA stars in the sample; their dependences on color are studied. Several DA's deviate from these correlations and have quite discrepant line profiles. Three, with shallow and weak lines, may each be unresolved, composite DA + DC white dwarfs.