The panchromatic spectroscopic evolution of the classical CO nova V339 Delphini (Nova Del 2013) until X-ray turnoff^⋆,⋆⋆

¹ Dipartimento di Fisica “Enrico Fermi”Università di Pisa, 56127 Pisa, Italy
e-mail: shore@df.unipi.it
² INFN-Sezione Pisa, largo B. Pontecorvo 3, 56127 Pisa, Italy
³ Osservatorio Astronomico (INAF) Tireste, via G.B. Tiepolo 11, 3413 Trieste, Italy
⁴ American Astronomical Society, 2000 Florida Ave., NW, Suite 400, DC 20009-1231, USA
⁵ 67 rue Jacques Daviel, 76100 Rouen, France
⁶ Castanet Tolosan Observatory, 6 place Clemence Isaure, 31320 Castanet Tolosan, France
⁷ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁸ Department of Physics & Astronomy, University of Leicester, University Road, LE1 7RH, UK
⁹ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
¹⁰ School of Earth and Space Exploration, Arizona State University, PO Box 871404, Tempe, AZ 85287-1404, USA
¹¹ Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstraße 1, 85741 Garching, Germany
¹² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹³ Department of Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455, USA

Received: 28 November 2015
Accepted: 17 February 2016

Abstract

Context. Classical novae are the product of thermonuclear runaway-initiated explosions occurring on accreting white dwarfs.

Aims. V339 Del (Nova Delphinus 2013) was one of the brightest classical novae of the last hundred years. Spectroscopy and photometry are available from γ-rays through infrared at stages that have frequently not been observed well. The complete data set is intended to provide a benchmark for comparison with modeling and for understanding more sparsely monitored historical classical and recurrent novae. This paper is the first in the series of reports on the development of the nova. We report here on the early stages of the outburst, through the X-ray active stage.

Methods. A time sequence of optical, flux calibrated high resolution spectra was obtained with the Nordic Optical Telescope (NOT) using FIES simultaneously, or contemporaneously, with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope during the early stages of the outburst. These were supplemented with Mercator/HERMES optical spectra. High resolution IUE ultraviolet spectra of OS And 1986, taken during the Fe curtain phase, served as a template for the distance determination. We used standard plasma diagnostics (e.g., [O III] and [N II] line ratios, and the Hβ line flux) to constrain electron densities and temperatures of the ejecta. Using Monte Carlo modeling of the ejecta, we derived the structure, filling factor, and mass from comparisons of the optical and ultraviolet line profiles.

Results. We derive an extinction of E(B − V) = 0.23 ± 0.05 from the spectral energy distribution, the interstellar absorption, and H I emission lines. The distance, about 4−4.5 kpc, is in agreement with the inferred distance from near infrared interferometry. The maximum velocity was about 2500 km s^-1, measured from the UV resonance and optical profiles. The ejecta showed considerable fine structure in all transitions, much of which persisted as emission knots. The line profiles were modeled using a bipolar conical structure for the ejecta within a relatively restricted range of parameters. For V339 Del, we find that an inclination to the line of sight of about 35°−55°, an opening angle of 60°−80°, and an inner radius ΔR/R(t) ≈ 0.3 based on v_rad,max matches the permitted and intercombination lines. The filling factor is f ≈ 0.1, and the derived range in the ejecta mass is (2−3) × 10^-5M_⊙.