Discovery of jets launched by classical nova eruptions

Thesis

Classical novae are stellar explosions that occur on the surface of white dwarfs in close binary systems. This thesis presents time-domain spec- troscopy of four recent eruptions in the Milky Way, carried out by the Global Jet Watch telescopes. Careful analysis of these observations re- veals the presence of a circumbinary disc around classical nova V906 Car following its cataclysmic event in March 2018. Its existence may provide an answer to the long-standing problem of explaining the white dwarf mass distribution. This thesis also presents the discovery of line-emitting jets and an accre- tion disc in classical nova YZ Reticuli, using sustained follow-up spec- troscopy commencing soon after the eruption in July 2020 and lasting several months. A qualitatively similar spectral signature is also observed for classical nova V6568 Sgr, hinting that jets may be a feature of classical novae more generally than previously thought. The same jets and accretion disc model is subsequently applied to the remaining two classical novae in the Global Jet Watch archive, V5668 Sgr and V906 Car, which exhibit the same behaviour. In the case of V5668 Sgr, the jets are found to persist for at least 2000 days after the eruption in March 2015. This thesis then suggests future imaging measurements that could be obtained using current instrumentation for spatially-resolved spectroscopy, which would elucidate further properties of nova jets like those discovered in all four classical novae observed by the Global Jet Watch. This thesis also uses Global Jet Watch time-lapse spectroscopy on classical novae V906 Car and V5668 Sgr to tightly constrain (to within hundreds of seconds) the duration of certain phases and their transitions that take place in the immediate aftermath of these recent eruptions.

Authors: McLoughlin, D

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: transient; classical nova; astrophysics
• Subjects: Physics