paper

The two most recent thermonuclear supernovae in the Local Group: radio constraints on their progenitors and evolution

arXiv:1709.05346 · doi:10.3847/1538-4357/ab027f

Abstract

Young supernova remnants (SNRs) provide a unique perspective on supernova (SN) progenitors and connect the late evolution of SNe with the onset of the SNR phase. Here we study SN 1885A and G1.9+0.3, the most recent thermonuclear SNe in the Local Group (with ages years) with radio data, which provides a sensitive probe of the SN environment and energetics. We reduce and co-add 4-8 GHz observations from Karl G. Jansky Very Large Array (VLA) to produce the deepest radio image of the M31 central region (RMS noise of 1.3 Jy/beam at 6.2 GHz). We detect some diffuse emission near SN 1885A at 2.6 , but the association with SN 1885A is uncertain because diffuse radio emission pervades the M31 central region. The VLA upper limit and HST measurements yield an ambient density, cm ( 0.03 cm due to systematics) for SN 1885A, and kinetic energies, ergs for ejecta masses of M. For the same ejecta mass range, VLA observations of G1.9+0.3 yield cm, and ergs. We argue that a sub-Chandrasekhar explosion model may be likely for SN 1885A, in agreement with X-ray studies, but in tension with models for the HST absorption spectra. The analysis of G1.9+0.3 is consistent with both Chandrasekhar and sub-Chandrasekhar SN Ia models, but rules out Type Iax explosions.

Submitted to ApJ. 15 pages, 9 figures

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