Early evolution of the extraordinary Nova Delphini 2013 (V339 Del)

Abstract

Aims. We determine the temporal evolution of the luminosity (L WD ), radius (R WD ) and effective temperature (T eff ) of the white dwarf (WD) pseudophotosphere of V339 Del from its discovery to around day 40. Another main objective was studying the ionization structure of the ejecta. Methods. These aims were achieved by modelling the optical/near-IR spectral energy distribution (SED) using low-resolution spectroscopy (3500-9200 Å), UBVR C I C and JHKLM photometry. Important insights in the physical conditions of the ejecta were gained from an analysis of the evolution of the Hα and Raman-scattered 6825 Å O vi line using medium-resolution spectroscopy (R ∼ 10 000). Results. During the fireball stage (Aug. 14. 8-19.9, 2013), T eff was in the range of 6000-12 000 K, R WD was expanding non-uniformly in time from ∼66 to ∼300 (d/3 kpc) R , and L WD was super-Eddington, but not constant. Its maximum of ∼9 × 10 38 (d/3 kpc) 2 erg s −1 occurred around Aug. 16.0, at the maximum of T eff , half a day before the visual maximum. After the fireball stage, a large emission measure of 1.0−2.0×10 62 (d/3 kpc) 2 cm −3 constrained the lower limit of L WD to be well above the super-Eddington value. The mass of the ionized region was a few ×10 −4 M , and the mass-loss rate was decreasing from ∼5.7 (Aug. 22) to ∼0.71× 10 −4 M yr −1 (Sept. 20).The evolution of the Hα line and mainly the transient emergence of the Raman-scattered O vi 1032 Å line suggested a biconical ionization structure of the ejecta with a disk-like H i region persisting around the WD until its total ionization, around day 40. On Sept. 20 (day 35), the model SED indicated a dust emission component in the spectrum. The dust was located beyond the H i zone, where it was shielded from the hard, > ∼ 10 5 K, radiation of the burning WD at that time. Conclusions. Our extensive spectroscopic observations of the classical nova V339 Del allowed us to map its evolution from the very early phase after its explosion. It is evident that the nova was not evolving according to the current theoretical prediction. The unusual non-spherically symmetric ejecta of nova V339 Del and its extreme physical conditions and evolution during and after the fireball stage represent interesting new challenges for the theoretical modelling of the nova phenomenon.

Rise and fall of the dust shell of the classical nova V339 Delphini

“…These were no longer present by day 14.76. In the optical, Skopal et al (2014) found that the Hα line displayed a P Cygni profile, with terminal velocity −1600 km s −1 at t 0.95 d, decreasing to −730 km s −1 at t 6 d. Despite the lower resolution of our IR data at this time, the IR terminal velocity seems consistent with that in the optical.…”

“…Extensive optical spectroscopy during the early phase was described by Skopal et al (2014). They determined that the effective temperature of the stellar remnant was in the range of 6000-12000 K, and that the stellar remnant was super-Eddington.…”

“…Gehrz et al estimated the amount of dust to be ∼1.3 × 10 −9 M 78.66 d after outburst and ∼1.2 [ ± 0.4] × 10 −7 M 102 d after outburst. Skopal et al (2014) determined that the dust was located beyond the neutral hydrogen zone, where it was shielded from the hard radiation field of the stellar remnant (see e.g. Evans & Rawlings 1994;Williams et al 2013).…”

COLLIMATION AND ASYMMETRY OF THE HOT BLAST WAVE FROM THE RECURRENT NOVA V745 Sco

“…In addition to the radio and HST images of RS Oph (Hjellming et al 1986;Taylor et al 1989;O'Brien et al 2006;Bode et al 2007;Rupen et al 2008;Sokoloski et al 2008)-the most studied nova blast wave to dateobservations of other novae have shown similar characteristics. Examples include infrared interferometry of V1663 Aql revealing asymmetry (Lane et al 2007), both radio and optical HST observations of light echoes revealing an asymmetric remnant of T Pyx outbursts (Sokoloski et al 2013) together with optical spectroscopy suggesting bipolarity in its 2011 outburst (Shore et al 2013;Tofflemire et al 2013), radio observations of V959 Mon Linford et al 2015) revealing bipolar structure, optical, radio, and X-ray imaging observations of asymmetry in the GK Per nova remnant (Bode et al 2004;Takei et al 2015), and UV spectroscopic and IR interferometric evidence of a bipolar ejection in V339 Del (Schaefer et al 2014;Skopal et al 2014).…”

On the Raman O VI and related lines in classical novae

“…In a recent paper, Skopal et al (2014) have identified a line in the optical spectrum of V339 Del (Nova Del 2013) and other classical novae as the O VI Raman feature at around 6830 Å. Raman scattering is an established radiative process in symbiotic stars. It was first proposed by Nussbaumer et al (1989) to explain the enigmatic 6825, 7083 Å emission line doublet.…”