The precessing jets of classical nova YZ Reticuli

Abstract

The classical nova YZ Reticuli was discovered in 2020 July. Shortly after this, we commenced a sustained, highly time-sampled coverage of its subsequent rapid evolution with time-resolved spectroscopy from the Global Jet Watch observatories. Its H-alpha complex exhibited qualitatively different spectral signatures in the following weeks and months. We find that these H-alpha complexes are well described by the same five Gaussian emission components throughout the six months following eruption. These five components appear to constitute two pairs of lines, from jet outflows and an accretion disc, together with an additional central component. The correlated, symmetric patterns that these jet/accretion disc pairs exhibit suggest precession, probably in response to the large perturbation caused by the nova eruption. The jet and accretion disc signatures persist from the first 10 d after brightening-evidence that the accretion disc survived the disruption. We also compare another classical nova (V6568 Sgr) that erupted in 2020 July whose H-alpha complex can be described analogously, but with faster line-of-sight jet speeds exceeding 4000 km s-1. We suggest that classical novae with higher mass white dwarfs bridge the gap between recurrent novae and classical novae such as YZ Reticuli.