A refined radial velocity curve for the L dwarf donor of WZ Sagittae

Abstract

We have obtained a radial velocity curve for the L dwarf donor in WZ Sagittae using phase-resolved J-band spectra obtained with GNIRS on Gemini-north. We find a radial velocity semi-amplitude of K2 = 525 ± 11 km s−1. This result reduces the error bar by a factor of three over previous attempts. A relatively strong, unidentified emission line centered near 1.177 μm, corrupts the blue K I doublet in these data. While an H I emission feature near 1.2527 μm distorts the depth of the red K I doublet. In addition, a weak H I emission line at 1.1969 μm falls in the middle of the strongest FeH feature in these spectra. The combination of these contaminants prevents us from precisely constraining the spectral type of the donor. The strength of the absorption features remains consistent with an early L spectral type.