Rare supernova explosion reveals new clues about stellar death
Astronomers observed an unusual supernova with a distinctive two-peaked brightness pattern, challenging existing models of how certain stars explode. The discovery could refine forecasting tools for understanding stellar behavior and improve methods for measuring cosmic distances—critical for applications ranging from cosmology research to technology development dependent on precise astronomical calibration.
Originaltitel: SN 2024aecx: A Double-peaked Rapidly Evolving Type IIb Supernova at 11 Mpc
<p>We present the results of low-resolution spectroscopic and densely sampled multiband photometric follow-up of supernova (SN) 2024aecx. The SN was discovered in the spiral galaxy NGC 3521 (distance ∼ 11 Mpc) within a day after the explosion. The early spectra of SN 2024aecx show a weak signature of hydrogen lines, which disappeared in ∼30 days after the explosion. Light curves in all bands show a distinct feature of two peaks, and the first peak is likely due to the emission from shock cooling. The early-phase evolution of the light curve of SN 2024aecx is similar to the typical Type IIb events, but the decay rate in different bands (e.g., Δ<em>m</em><sub>15</sub> = 1.60 ± 0.05 mag, <em>g </em>band) is significantly faster in the postpeak phase. It attained the secondary maximum in ∼19 days (<em>g </em>band) with a peak absolute magnitude of <em>M</em><sub><em>g</em></sub> = –17.94 ± 0.10 mag. The colors of SN 2024aecx tend to be redder in early epochs (<8 days), then it grows bluer for a period, then redder again >20 days after explosion. The analytical model fitting to the light curves reveals an envelope mass and progenitor radius in the ranges ∼0.03–0.24 <em>M</em><sub>⊙</sub> and ∼169–200 <em>R</em><sub>⊙</sub>, respectively. Modeling of the pseudobolometric light curve suggests that synthesized <sup>56</sup>Ni in the explosion was ∼0.15 <em>M</em><sub>⊙</sub> with ejecta mass and kinetic energy of ∼0.7 <em>M</em><sub>⊙</sub> and ∼0.16 × 10<sup>51</sup> erg, respectively. The observational properties and modeling indicate that the progenitor of SN 2024aecx belongs to the category of extended progenitors.</p>