THE PECULIAR COOL WHITE-DWARF LHS-1126 REVISITED

We present a detailed analysis of new photometric and spectroscopic data, both in the optical and in the infrared, of the cool white dwarf LHS 1126. We show that the peculiar energy distribution of this object, and especially the large infrared flux deficiency, is the result of the collision-induced absorption by molecular hydrogen due to collisions with helium. The effective temperature and the helium abundance are determined from a fit to the energy distribution while the surface gravity is constrained by the trigonometric parallax measurement. We obtain T(eff) = 5400 +/- 200 K, log g = 7.85 +/- 0.17, and log N(He)/N(H) = 0.8 +/- 0.2. The nature of the spectroscopic features observed previously in the infrared and in the optical are rediscussed within the context of both these new observations and our model atmosphere fit.