Early Dust Formation and a Massive Progenitor for SN 2011ja?

TL;DR

SN 2011ja exhibited early dust formation and spectral features indicating a massive progenitor, with evidence of circumstellar interaction and dust creation in the cool dense shell, suggesting a complex explosion environment.

Contribution

This study provides detailed observations and modeling of dust formation and circumstellar interaction in SN 2011ja, indicating a massive progenitor star and early dust production.

Findings

Detection of early dust formation in SN 2011ja.

Evidence of circumstellar disc-like medium interaction.

Indications of a massive (>25 Msun) progenitor star.

Abstract

SN 2011ja was a bright (I = -18.3) Type II supernova occurring in the nearby edge on spiral galaxy NGC 4945. Flat-topped and multi-peaked H-alpha and H-beta spectral emission lines appear between 64 - 84 days post-explosion, indicating interaction with a disc-like circumstellar medium inclined 30-45 degrees from edge-on. After day 84 an increase in the H- and K-band flux along with heavy attenuation of the red wing of the emission lines are strong indications of early dust formation, likely located in the cool dense shell created between the forward shock of the SN ejecta and the reverse shock created as the ejecta plows into the existing CSM. Radiative transfer modeling reveals both ~1.5 x 10^-4 Msun of pre-existing dust located ~ 10^16.7 cm away and ~ 5 x 10^-5 Msun of newly formed dust. Spectral observations after 1.5 years reveal the possibility that the fading SN is located within a young (3-6 Myr) massive stellar cluster, which when combined with tentative 56Ni mass estimates of 0.2 Msun may indicate a massive (> 25 Msun) progenitor for SN 2011ja.