Volume 569, September 2014
|Number of page(s)||14|
|Section||Stellar structure and evolution|
|Published online||01 October 2014|
Early evolution of the extraordinary Nova Delphini 2013 (V339 Del)⋆
Astronomical Institute, Slovak Academy of Sciences,
2 Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander-Universität Erlangen-Nürnberg, Sternwartstraße 7, 96049 Bamberg, Germany
3 Crimean Astrophysical Observatory, 298409 Nauchny, Crimea, Russia
4 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, 606-8502 Kyoto, Japan
5 Fujii Kurosaki Observatory, 4500 Kurosaki, Tamashima, Kurashiki, 713-8126 Okayama, Japan
6 67 rue Jacques Daviel, 76100 Rouen, France
7 Observatoire de la Tourbière, 38690 Chabons, France
8 Balmes 2, 08784 Piera, Barcelona, Spain
9 1833 Bobwhite Dr. Ammon, Idaho, 83401, USA
10 Castanet Tolosan Observatory, 6 place Clemence Isaure, 31320 Castanet Tolosan, France
11 Lieu-dit Durfort, 81150 Fayssac, France
12 6 rue Virgile, 42100 Saint-Étienne, France
13 Chelles Observatory, 23 avenue Hénin, 77500 Chelles, France
14 Durtal Observatory, 6 rue des Glycines, 49430 Durtal, France
15 Mirranook Observatory, Boorolong Rd Armidale, NSW, 2350, Australia
16 Société Astronomique de Bourgogne-Dijon, France
17 23746 Schoolhouse Road, Manhattan, Illinois, 60442, USA
Accepted: 25 July 2014
Aims. We determine the temporal evolution of the luminosity (LWD), radius (RWD) and effective temperature (Teff) 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), UBVRCIC 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), Teff was in the range of 6000–12 000 K, RWD was expanding non-uniformly in time from ~66 to ~300 (d/ 3 kpc) R⊙, and LWD was super-Eddington, but not constant. Its maximum of ~9 × 1038 (d/ 3 kpc)2 erg s-1 occurred around Aug. 16.0, at the maximum of Teff, half a day before the visual maximum. After the fireball stage, a large emission measure of 1.0−2.0 × 1062 (d/ 3 kpc)2 cm-3 constrained the lower limit of LWD 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, ≳105 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.
Key words: novae, cataclysmic variables / stars: fundamental parameters / stars: individual: V339 Del
© ESO, 2014
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