We have obtained high‐ and intermediate‐resolution optical spectra of the black hole candidate Nova Scorpii 1994 in 1998 May/June, when the source was in complete (X‐ray) quiescence. We measure the radial velocity curve of the secondary star and obtain a semi‐amplitude of K2=215.5 ± 2.4 km s‐1, which is 6 per cent lower than the only previously determined value. This new value for K2 thus reduces the binary mass function to f(M) = 2.73 ± 0.09 M⊙. Using only the high‐resolution spectra, we constrain the rotational broadening of the secondary star, v sin i, to lie in the range 82.9–94.9 km s‐1 (95 per cent confidence) and thus constrain the binary mass ratio to lie in the range 0.337–0.436 (95 per cent confidence). We can also combine our results with published limits for the binary inclination to constrain the mass of the compact object and secondary star to the ranges 5.5–7.9 and 1.7–3.3 M⊙ respectively (95 per cent confidence). Finally, we report on the detection of the lithium resonance line at 6707.8 Å, with an equivalent width of 55 ± 8 m Å.

The dwarf nova GW Librae (GW Lib) is the first cataclysmic variable (CV) discovered to have a primary in a white dwarf instability strip, making it the first multimode, non‐radially pulsating star known to be accreting. The primaries of CVs, embedded in hot, bright accretion discs, are difficult to study directly. Applying the techniques of asteroseismology to GW Lib could therefore give us an unprecedented look at a white dwarf that has undergone ∼109 yr of accretion. However, an accreting white dwarf may have characteristics sufficiently different from those of single pulsating white dwarfs to render the standard models of white dwarf pulsations invalid for its study. This paper presents amplitude spectra of GW Lib from a series of observing campaigns conducted during 1997, 1998 and 2001. We find that the dominant pulsation modes cluster at periods near 650, 370 and 230 s, which also appear in linear combinations with each other. The pulsation spectrum of GW Lib is highly unstable on time‐scales of months, and exhibits clusters of signals very closely spaced in frequency, with separations on the order of 1 μHz.

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