2024/09/23 by L. Tartaglia, Tartaglia, Leonardo, G. Valerin +21 · 1 citation
Physics and Astronomy · #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2409.15431
openalex publication_date 2024/09/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/02
In this paper we analyse the spectro-photometric properties of the Type II supernova 2024bch, exploded in NGC 3206 at a distance of 19.9 \rmMpc. Its early spectra are characterised by narrow high-ionisation emission lines, often interpreted as signatures of ongoing interaction between rapidly expanding ejecta and a confined dense circumstellar medium. However, we provide a model for the bolometric light curve of the transient that does not require sources of energy different than radioactive decays and H recombination. Our model can reproduce the bolometric light curve of SN 2024bch adopting an ejected mass of Mbulk≃5 \rmM\odot surrounded by an extended envelope of only 0.2 \rmM\odot with an outer radius Renv=7.0×1013 \rmcm. An accurate modelling focused on the radioactive part of the light curve, which accounts for incomplete γ-ray trapping, gives a 56\rmNi mass of 0.048 \rmM\odot. We propose narrow lines to be powered by Bowen fluorescence induced by scattering of He II Lyα photons, resulting in the emission of high-ionisation resonance lines. Simple light travel time calculations based on the maximum phase of the narrow emission lines place the inner radius of the H-rich, un-shocked shell at a radius ≃4.4×1015 \rmcm, compatible with an absence of ejecta-CSM interaction during the first weeks of evolution. Possible signatures of interaction appear only ∼69 \rmdays after explosion, although the resulting conversion of kinetic energy into radiation does not seem to contribute significantly to the total luminosity of the transient.