J-band spectroscopy of cataclysmic variables

Abstract

We present time resolved J-band (1.025 - 1.340 micron) infrared spectra of the short-period dwarf novae (DNe) WZ Sge, VY Aqr and single spectra of the short-period DN EF Peg and the novalike variable PX And. There is some evidence in the spectra of VY Aqr and EF Peg that we have detected the secondary star, both in the continuum slope and also through the possible presence of spectral features. The spectra of WZ Sge and PX And, on the other hand, show no evidence for the secondary star, with upper limits for its contribution to the J-band light of 10% and 20% respectively. The spectral type of the secondary in WZ Sge is constrained to be later than M7.5V. Using skew mapping we have been able to derive a value for the radial velocity semi-amplitude of the secondary star in VY Aqr of Kr = (320 +/- 70) km/s, which in conjunction with Kw from Thorstensen & Taylor (1997) gives a mass ratio of q = 0.15 +/- 0.04.