Hydrodynamic simulations of the recurrent nova T Coronae Borealis: Nucleosynthesis predictions

¹ Departament de Física, EEBE, Universitat Politècnica de Catalunya (UPC), c/Eduard Maristany 16, E-08019 Barcelona, Spain
² Institut d’Estudis Espacials de Catalunya (IEEC), c/Esteve Terradas 1, E-08860 Castelldefels, Spain
³ Institut de Ciències de l’Espai (ICE-CSIC), Campus UAB, Camí de Can Magrans s/n, E-08193 Bellaterra, Spain

^⋆ Corresponding author: jordi.jose@upc.edu

Received: 15 January 2025
Accepted: 25 April 2025

Abstract

Context. Recurrent novae are, by definition, novae observed in outburst more than once or identified by the presence of vast super-shells, ejected in previous eruptions, surrounding the system. These systems are characterized by remarkably short recurrence times between outbursts, typically ranging from 1 to about 100 yr. Such short recurrence times require very high mass-accretion rates, white dwarf masses approaching the Chandrasekhar limit, and very high initial white dwarf luminosities.

Aims. T Coronae Borealis (T CrB) is one of the eleven known recurrent novae in our Galaxy. It was observed in outburst in 1866 and 1946, with additional likely eruptions recorded in 1217 and 1787. Given its predicted recurrence period of approximately 80 yr, the next outburst is anticipated to occur imminently, thus motivating a thorough examination of the main characteristics of this system.

Methods. We present 11 new hydrodynamic models of the explosion of T CrB for different combinations of parameters (i.e., the mass, composition, and initial luminosity of the white dwarf, the metallicity of the accreted matter, and the mass-transfer rate). We also report on 8 additional hydrodynamic models that include mixing at the interface between the accreted envelope and the outermost layers of the underlying white dwarf, and 3 models for 1.20 M_⊙ white dwarfs.

Results. We show that mass-accretion rates of Ṁ_acc ∼ 10⁻⁸−10⁻⁷  M_⊙ yr⁻¹ are required to trigger an outburst after 80 yr of accretion of solar-composition material onto white dwarfs with masses M_WD∼1.30−1.38 M_⊙ and initial luminosities L_WD∼0.01−1 L_⊙. For lower white dwarf luminosities, less massive white dwarfs, or reduced metallicity in the accreted material, higher mass-accretion rates are required to drive an explosion within this timescale. A decrease in metallicity or initial white dwarf luminosity leads to higher accumulated masses and ignition pressures, resulting in more violent outbursts. These outbursts exhibit higher peak temperatures, higher ejected masses, and greater kinetic energies. Models computed for different white dwarf masses but identical initial luminosities reveal significant differences in the elemental abundances of a wide range of species, including Ne, Na, Mg, Al, Si, P, S, Ar, K, Ca, and Sc. These compositional differences offer a potential diagnostic tool for constraining the parameter space and discriminating between the various T CrB models reported in this study.