White Dwarfs in Wide Binaries - Part Two - Double Degenerates and Composite Spectra

Abstract

view Abstract Citations (48) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS White dwarfs in wide binaries. II. Double degenerates and composite spectra. Greenstein, J. L. Abstract Spectrophotometry of six northern visual pairs containing two degenerate stars shows that the components are quite similar in luminosity and temperature. Presumably the two progenitors were similar and had nuclear lifetimes short compared to the subsequent cooling ages of the white dwarfs. The white dwarfs are near twins, with dispersion in radii below 14%. The mean cooling age of the pairs is 4 × l09 yr, their luminosity Mv = + 14.5 mag. One pair is relatively young, with components less similar. Study of pairs containing a white dwarf and a main-sequence star shows that a large fraction of such pairs are undiscovered. Those containing a hot white dwarf and a red main-sequence companion, discovered from the composite spectra, are quite blue and have an infrared excess. When the fluxes in pairs observed as resolved are added, the composite so synthesized is yellow or red, with a large violet or ultraviolet excess. Methods of discovery of white dwarfs leave regions of the color-color diagrams untouched. A possible technique of searching for violet excess suggested involves magnitudes in the infrared, visual, and blue. Analysis of old novae, spectroscopic binaries containing a white dwarf, and a dM star with a faint white dwarf companion displays composite spectra. Whether the large number of missing white dwarfs in noninteracting binaries exist, or whether the progenitor binaries have been dissolved, remains undecided. Publication: The Astronomical Journal Pub Date: October 1986 DOI: 10.1086/114220 Bibcode: 1986AJ.....92..867G full text sources ADS | data products SIMBAD (57) Related Materials (1) Part 1: 1986AJ.....92..859G