Gamma-Ray emission from SN2014J near maximum optical light

TL;DR

This study analyzes gamma-ray data from SN2014J near optical maximum, revealing a high-velocity 56Ni plume not predicted by existing models, providing new insights into supernova explosion asymmetries.

Contribution

It presents the first detection of a high-velocity 56Ni plume in SN2014J through gamma-ray observations, challenging current supernova explosion models.

Findings

Detection of 158 keV gamma-ray line at ~5 sigma significance.

Identification of a 56Ni-rich plume moving at high velocity.

Implication that SN2014J's explosion geometry is more complex than models predict.

Abstract

The optical light curve of Type Ia supernovae (SNIa) is powered by thermalized gamma-rays produced by the decay of 56Ni and 56Co, the main radioactive isotopes synthesized by the thermonuclear explosion of a C/O white dwarf. Gamma-rays escaping the ejecta can be used as a diagnostic tool for studying the characteristics of the explosion. In particular, it is expected that the analysis of the early gamma emission, near the maximum of the optical light curve, could provide information about the distribution of the radioactive elements in the debris. In this paper, the gamma data obtained from SN2014J in M82 by the instruments on board of INTEGRAL are analyzed taking special care of the impact that the detailed spectral response has on the measurements of the intensity of the lines. The 158 keV emission of 56Ni has been detected in SN2014J at ~5 sigma at low energy with both ISGRI and SPI around the maximum of the optical light curve. After correcting the spectral response of the detector, the fluxes in the lines suggest that, in addition to the bulk of radioactive elements buried in the central layers of the debris, there is a plume of 56Ni, with a significance of ~3 sigma, moving at high velocity and receding from the observer. The mass of the plume is in the range of ~ 0.03-0.08 solar masses. No SNIa explosion model had predicted the mass and geometrical distribution of 56Ni suggested here. According to its optical properties, SN2014J looks as a normal SNIa. So it is extremely important to discern if it is also representative in the gamma-ray band.