Polarimetry and Spectroscopy of the `Oxygen Flaring' DQ Herculis-like nova: V5668 Sagittarii (2015)

Abstract

Classical novae are eruptions on the surface of a white dwarf in a binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust around the system. The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky. In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii. To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light-curve's dust-dip. High-cadence optical polarimetry and spectroscopy observations of a nova are presented. The ejecta is modelled in terms of morpho-kinematics and photoionisation structure. Initially observational results are presented, including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption. Variability over these observations provides clues towards the evolving structure of the nova shell. The position angle of the shell is derived from polarimetry, which is attributed to scattering from small dust grains. Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics. Changes in density and temperature as the super soft source phase of the nova began are discussed. Gas densities are found to be of the order of 10${}^9$ cm${}^{-3}$ for the nova in its auroral phase. The blackbody temperature of the central stellar system is estimated to be around $2.2\times 10^5$ K at times coincident with the super soft source turn-on. It was found that the blend around 4640 $\mathring{\mathrm{A}}$ commonly called `nitrogen flaring' is more naturally explained as flaring of the O~{\sc ii} multiplet (V1) from 4638 - 4696 $\mathring{\mathrm{A}}$, i.e. `oxygen flaring'.

arXiv comment17 pages, 13 figures, 3 tables, Accepted A&A 22 Nov 2017

References in corpus (15)

• An Extended Grid of Nova Models: II. The Parameter Space of Nova Outbursts
• Catalog of 93 Nova Light Curves: Classification and Properties
• Shocks in nova outflows. I. Thermal emission
• On the Progenitors of Galactic Novae
• Fermi LAT Gamma-ray Detections of Classical Novae V1369 Centauri 2013 and V5668 Sagittarii 2015
• INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables
• A fully automated data reduction pipeline for the FRODOSpec integral field spectrograph
• Radiative shocks create environments for dust formation in novae
• A remarkable recurrent nova in M31 - The X-ray observations
• A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray Luminous Classical Nova to Date
• Recombination coefficients for O II lines in nebular conditions
• High-precision optical polarimetry of the accreting black hole V404 Cyg during the June 2015 outburst
• V4743 Sgr, a magnetic nova?
• Rapid Dust Formation in Novae: The Speed Class - Formation Timescale Correlation Explained
• A WISE view of novae. I. The data

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