Multi-wavelength Spectroscopic Study of Shock Phenomena Driven by Explosive Outbursts in Symbiotic-like Recurrent Novae.
Dipartimento
FISICA
Corso di studi
FISICA
Relatori
relatore Shore, Steven Neil
Parole chiave
optical
outburst
recurrent novae
shock
spectroscopy
symbiotics
ultraviolet
Data inizio appello
22/07/2021
Consultabilità
Completa
Riassunto
Symbiotic-like Recurrent Novae are interacting binary systems in which a compact, degenerate and hot White Dwarf (WD) accretes mass from a Red Giant companion, whose stellar wind creates a dense circumbinary environment. Mass accretion by the WD occurs through stellar wind capture unlike a compact Classical Nova (CN) or cataclysmic variable and, when sufficient material has accreted on the WD envelope, a thermonuclear runaway is triggered and the system explosively ejects much of the accumulated gas. This periodically occurs, more frequently than usual CN because here the WD is at the extreme end of the stable mass range. The explosion and material ejection from the WD produce shock waves that propagate in the surrounding medium and strongly interact with the wind from the companion. A wide variety of radiative and dynamical signatures of the propagation distinguish the analysis from that of freely expanding ejecta. This also, for example, informs the study of SNIa circumstellar interactions. In this thesis, shock phenomena during outbursts of the five known Galactic Symbiotic-like Recurrent Novae (RS Ophiuchi, V745 Scorpii, V3890 Sagittarii, T Coronae Borealis, V407 Cygni) are analysed through a spectroscopic study at wavelengths in the optical and vacuum UV. Spectroscopy provides a fundamental tool to investigate the dynamics of the environment through line profiles and intensity analysis. RS Oph is the system for which the most information is available, with the most recent outbursts in 1985 and 2006. The 1985 event was extensively observed in the UV while the optical data are heterogeneous and sparse, whereas the next outburst was extensively observed in the optical and IR, but not in the UV until the present work. Previously unexamined archival UV data from the Swift satellite have been used for the study and compared with optical and UV spectral sequences acquired by several other instruments during recorded outbursts and quiescent phases of the other Novae. The comparison between these systems, whose separations range over an order of magnitude in distance and significant differences in the properties of the giants, highlights how the shock breakout, precursor and reverse shock phenomena, asphericities require careful attention to specific dynamical and plasma diagnostics. Unlike CN, these systems present the extreme case of mass accumulation following ejection. A comparison with hydrodynamic and radiative transfer simulations is also presented.