Image of SN 2020nlb in its environment. Credit: arXiv (2024). DOI: 10.48550/arxiv.2401.08759
Using various ground-based telescopes, astronomers conducted photometric and spectroscopic observations of a nearby Type Ia supernova known as SN 2020nlb. Results of the observation campaign, presented on January 16 on the pre-print server arXivprovide important information on the evolution of this stellar explosion.
Type Ia supernovae (SN Ia) are found in binary systems in which one of the stars is a white dwarf. Stellar explosions of this type are important to the scientific community because they offer essential clues about the evolution of stars and galaxies.
SN 2020nlb was detected on June 25, 2020 by the Asteroid Land Impact Warning System (ATLAS), shortly after its explosion in the lenticular galaxy Messier 85 (or M85 for short), located some 60 million years away -light. Spectroscopic observations of SN 2020nlb, begun shortly after its detection, confirmed that it is a Type Ia supernova.
A team of astronomers led by Steven Williams of the University of Turku, Finland, began monitoring SN 2020nlb 16 hours after its discovery. Observations, carried out mainly with the Liverpool Telescope (LT) and the Nordic Optical Telescope (NOT), have provided a wealth of data on the properties of this supernova.
“Here we present observations that include one of the first high-quality spectra and some of the first multicolor photometries of an SN Ia to date,” the researchers wrote.
The photometric and spectroscopic observations conducted by Williams’ team lasted nearly 600 days after the explosion of SN 2020nlb. The supernova is estimated to have been discovered just two days after its first light.
Observations revealed that SN 2020nlb lost 1.28 mag in the B band during the first 15 days after its peak brightness. Therefore, it decayed faster than an average normal Type Ia supernova, suggesting that it has a lower luminosity than the typical SNe of this class.
The spectrum of SN 2020nlb, taken almost three days after first light, shows strong features from mono-ionized metals. In addition, a nebular spectrum taken 594 days after the light maximum shows that the strong iron emission line had disappeared, with the ionization budget of the ejecta decreasing.
The first spectra of SN 2020nlb resembled the peak light spectra of SN 1991bg and similar supernovae. Subsequently, the spectrum of SN 2020nlb evolved to become warmer and more similar to that of SN 2011fe as it brightened toward its peak.
According to the authors of the paper, the nebular spectra of SN 2020nlb, compared to other nebular spectra of SNe Ia, indicate a possible trend whereby SNe that were brighter at the peak tended to have higher ionization in the nebular phase. This may indicate that there is something fundamentally different between SN 2020nlb and SNe similar to most of the normal SN Ia population.
More information:
SC Williams et al, Observations of the Type Ia supernova SN 2020nlb up to 600 days after the explosion, and the distance to M85, arXiv (2024). DOI: 10.48550/arxiv.2401.08759
Journal information:
arXiv
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