November 1985 • 1985MNRAS.217..327B
Abstract • This paper presents a model-independent overview of the origin of the near infrared (1-2 micron) light of a sample of 28 cataclysmic binary stars, largely dwarf novae in quiescence. The infrared light comes from the red dwarf that supplies matter to the white dwarf companion and the accretion disc around the white dwarf. The complex nature of the disc prevents near-infrared photometry from being a good probe of the red dwarfs, even in those systems where they are seen in the visual. All that can be found reliably is an upper limit to the proportion of light that the red dwarfs supply, and consequently lower limits to the distances to the systems. The infrared light of the discs comes from opaque material and from the optically thin gas that gives rise to the visual and UV emission lines. The proportion of light supplied by each differs widely from system to system. 10-micron observations of five systems of cataclysmic binary stars show that they contain less than 10 to the -7th solar masses of dust at 300 K, and less than 7 x 10 to the -10th solar masses at 1000 K. Such grains as are present most likely form in the plane of the orbit, from material carried away from the red star by flares.