2017MNRAS.470.4061T

The very fast classical nova V5589 Sgr was observed serendipitously at a continuous cadence of 40 min during both the rise phase, and the first 17 d of the decline phase, by the inner Heliospheric Imager (HI-1) telescope aboard the STEREO-B spacecraft. A previous analysis of these data presented evidence for two pre-maximum halts during the rise phase, and considerable variability during the decline phase, which is normally associated with much slower novae. This work is a reanalysis of the same data, but with a different approach to removing the local background around the nova image. The resulting light curve is much smoother than that found in the previous work. This smoothness must be intrinsic to the nova, since nothing in the measurements or data analysis would artificially impose smoothness. Hence, this work completely refutes the conclusions from the previous analysis of V5589 Sgr. No evidence was found for any pre-maximum halts, nor any unusual short-term variations in the nova brightness during the early decline phase. The peak brightness was found to be 8.23 ± 0.03 mag in the HI-1 bandpass, with the time of peak brightness being within 80 min of JD 245 6039.3224. The time to decline by two magnitudes is t₂ = 5.0 ± 0.6 d, and the time to decline by three magnitudes is t₃ = 10.9 ± 0.7 d.