Fifty hours of new high-speed photometric observations of the rapidly oscillating Ap star HD 137949 obtained mostly in 1987 with the 1.0- and 1.9-m telescopes of the SAAO are presented. These new observations have less noise than the previous observations made in 1981 with a 0.5-m telescope. The principal frequency in HD 137949 in the 1987 data is |v₁ = 2014.781 ± 0.001 \,μ\,Hz| in the 1981 data it is |v₁ = 2014.821 ± 0.003 \,| This indicates that |d \,ln\, v/dt = (-9.9 ± 0.7) × 10⁻¹⁴ s⁻¹ [dP/dt = (+4.9 ± 0.3) × 10⁻¹¹\, s\, \,s⁻¹]|, which is about two orders of magnitude larger than expected theoretically from evolution. There is however, possibly a second frequency at, or near, |v₂ = 1975 \,μ Hz|, the reality of which needs confirmation. This secondary frequency, and possibly other unresolved secondary frequencies, could perturb the measurement of v1 and hence distort the measurement of d ln v/dt so that it is unreliable. If v2 is real, the separation |v₁-v₂ ≈ 40 \,μ Hz| gives an estimate of the luminosity of HD 137949. The first harmonic of |v₁ \,at\, 2v₁ = 4029.559 ± 0.009 \,μ Hz| is clearly present in the data. This brings to five the number of rapidly oscillating Ap stars which have non-linear light variations.
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D. W. Kurtz (1991) studied this question.