Infrared Echo and New Dust Formation in SN~2023ixf: A multi-wavelength portrait of a hydrogen-rich supernova

by Dr Avinash Singh (Department of Astronomy, Stockholm University)

Wednesday 9 Sept 2026, 13:30 → 14:30 Europe/Stockholm

FC 61 (AlbaNova Main Building)

SN 2023ixf is a nearby Type II supernova discovered within a day of explosion, providing an unusually dense multi-wavelength dataset from the earliest phases to nearly two years after explosion. I will present optical and near-infrared photometric and spectroscopic observations, combined with JWST NIRSpec-MIRI spectroscopy from two days to nearly two years after explosion The observations reveal an early infrared excess, a later near-infrared re-brightening, the emergence of molecular CO emission, and progressively asymmetric Balmer-line profiles. We interpret the earliest infrared emission as an echo from pre-existing circumstellar dust heated by the supernova radiation. 

Multi-epoch SED modelling and JWST spectroscopy show that the infrared continuum is multi-component, including a long-lived hot component consistent with radiatively heated circumstellar dust at radii beyond 1e15 cm. Its temperature remains nearly constant while the emission fades from about three months to beyond two years, indicating a declining contribution from the illuminated circumstellar dust. In contrast, cooler components strengthen at later times, supporting a growing contribution from newly formed dust associated with the cold dense shell and/or inner ejecta after ~250 days. Independently, modelling of the evolving Halpha profile from 140–420 days shows red-wing attenuation consistent with an internal obscuring dust component of the order of 1e-5 solar-mass. Together, these observations connect progenitor mass loss and circumstellar structure to molecular cooling and the onset of supernova dust formation, making SN 2023ixf a powerful laboratory for understanding how core-collapse supernovae process and produce dust.