Dust and the type II-Plateau supernova 2004dj

TL;DR

This study presents mid-infrared observations of supernova SN 2004dj, revealing dust formation in the ejecta and its evolution, with implications for understanding dust production in supernovae.

Contribution

First detailed MIR spectroscopy of SN 2004dj showing dust formation, distribution, and evolution, providing insights into supernova dust contribution.

Findings

Dust formed in the ejecta, reaching 0.5 x 10^{-4} Msun by 996 days.

Dust was distributed as a shrinking disk, likely due to reverse shock heating.

The dust mass is consistent with previous supernova studies, suggesting limited contribution to cosmic dust.

Abstract

We present mid-infrared (MIR) spectroscopy of a Type II-plateau supernova, SN 2004dj, obtained with the Spitzer Space Telescope, spanning 106--1393 d after explosion. MIR photometry plus optical/near-IR observations are also reported. An early-time MIR excess is attributed to emission from non-silicate dust formed within a cool dense shell (CDS). Most of the CDS dust condensed between 50 d and 165 d, reaching a mass of 0.3 x 10^{-5} Msun. Throughout the observations much of the longer wavelength (>10 microns) part of the continuum is explained as an IR echo from interstellar dust. The MIR excess strengthened at later times. We show that this was due to thermal emission from warm, non-silicate dust formed in the ejecta. Using optical/near-IR line-profiles and the MIR continua, we show that the dust was distributed as a disk whose radius appeared to be slowly shrinking. The disk radius may correspond to a grain destruction zone caused by a reverse shock which also heated the dust. The dust-disk lay nearly face-on, had high opacities in the optical/near-IR regions, but remained optically thin in the MIR over much of the period studied. Assuming a uniform dust density, the ejecta dust mass by 996 d was 0.5 +/- 0.1) x 10^{-4} Msun, and exceeded 10^{-4}Msun by 1393 d. For a dust density rising toward the center the limit is higher. Nevertheless, this study suggests that the amount of freshly-synthesized dust in the SN 2004dj ejecta is consistent with that found from previous studies, and adds further weight to the claim that such events could not have been major contributors to the cosmic dust budget.