The UV/optical spectra of the Type Ia supernova SN 2010jn: a bright supernova with outer layers rich in iron-group elements

TL;DR

This study analyzes UV and optical spectra of the Type Ia supernova SN 2010jn to reveal detailed iron-group element distribution in its outer layers, supporting delayed-detonation explosion models.

Contribution

It provides the most precise iron-group abundance measurements in SN Ia outer layers using UV spectra and Abundance Tomography, highlighting the presence of burned material at high velocities.

Findings

SN 2010jn has outer layers rich in iron-group elements.

The supernova's properties support delayed-detonation models.

Early UV spectra are effective diagnostics of ejecta composition.

Abstract

Radiative transfer studies of Type Ia supernovae (SNe Ia) hold the promise of constraining both the time-dependent density profile of the SN ejecta and its stratification by element abundance which, in turn, may discriminate between different explosion mechanisms and progenitor classes. Here we present a detailed analysis of Hubble Space Telescope ultraviolet (UV) and ground-based optical spectra and light curves of the SN Ia SN 2010jn (PTF10ygu). SN 2010jn was discovered by the Palomar Transient Factory (PTF) 15 days before maximum light, allowing us to secure a time-series of four UV spectra at epochs from -11 to +5 days relative to B-band maximum. The photospheric UV spectra are excellent diagnostics of the iron-group abundances in the outer layers of the ejecta, particularly those at very early times. Using the method of 'Abundance Tomography' we have derived iron-group abundances in SN 2010jn with a precision better than in any previously studied SN Ia. Optimum fits to the data can be obtained if burned material is present even at high velocities, including significant mass fractions of iron-group elements. This is consistent with the slow decline rate (or high 'stretch') of the light curve of SN 2010jn, and consistent with the results of delayed-detonation models. Early-phase UV spectra and detailed time-dependent series of further SNe Ia offer a promising probe of the nature of the SN Ia mechanism.