SN 2017ati: A luminous type IIb explosion from a massive progenitor
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arXiv
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| author | Peng, Z. -H. Benetti, S. Cai, Y. -Z. Pastorello, A. Zhao, J. -W. Reguitti, A. Wang, Z. -Y. Cappellaro, E. Elias-Rosa, N. Fang, Q. -L. Fraser, M. Kangas, T. Kankare, E. Kostrzewa-Rutkowska, Z. Lundqvist, P. Mattila, S. Reynolds, T. M. Stritzinger, M. D. Somero, A. Tomasella, L. Pei, S. -P. Yang, Y. -J. Zhang, J. -J. Pan, Y. |
| author_facet | Peng, Z. -H. Benetti, S. Cai, Y. -Z. Pastorello, A. Zhao, J. -W. Reguitti, A. Wang, Z. -Y. Cappellaro, E. Elias-Rosa, N. Fang, Q. -L. Fraser, M. Kangas, T. Kankare, E. Kostrzewa-Rutkowska, Z. Lundqvist, P. Mattila, S. Reynolds, T. M. Stritzinger, M. D. Somero, A. Tomasella, L. Pei, S. -P. Yang, Y. -J. Zhang, J. -J. Pan, Y. |
| contents | We present optical photometric and spectroscopic observations of the Type~IIb supernova (SN)~2017ati. It reached the maximum light at about 27~d after the explosion and the light curve shows a broad, luminous peak with an absolute $r$-band magnitude of $M_{r} = -18.48 \pm 0.16$~mag. At about 50~d after maximum light, SN~2017ati exhibits a decline rate close to that expected from the $^{56}$Co $\rightarrow$ $^{56}$Fe radioactive decay, at 0.98 mag per 100 days, as usually observed in SNe IIb. However, it remains systematically brighter at late times by about 1--2~mag, exceeding the usual upper luminosity range of this class. As a result, modelling the light curve of SN~2017ati with a standard $^{56}$Ni decay scenario requires a large nickel mass of up to $\sim0.37\,M_{\odot}$ and still fails to reproduce the early-time light curve adequately. In contrast, incorporating additional energy input from a magnetar yields a significantly improved fit to the light curve of SN~2017ati, which would reduce the nickel mass to $\sim0.21\,M_{\odot}$, still close to the upper end of the range typically inferred for SNe~IIb. Comparing the fitted results of SN~2017ati with the known sample of SNe~IIb indicates that its luminosity evolution is best explained by a combination of neutron star spin-down energy and radioactive nickel deposition. From late-time nebular spectra of SN~2017ati, the luminosity of the [\Oi]~$λ\lambda6300,6364$ doublet implies an oxygen mass of $\sim1.82-3.34\,M_{\odot}$, and the combination of a [\Caii]/[\Oi] flux ratio of $\sim0.5$ with nebular spectral model comparisons favours a progenitor zero-age main-sequence mass of $\geq17\,M_{\odot}$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_04474 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | SN 2017ati: A luminous type IIb explosion from a massive progenitor Peng, Z. -H. Benetti, S. Cai, Y. -Z. Pastorello, A. Zhao, J. -W. Reguitti, A. Wang, Z. -Y. Cappellaro, E. Elias-Rosa, N. Fang, Q. -L. Fraser, M. Kangas, T. Kankare, E. Kostrzewa-Rutkowska, Z. Lundqvist, P. Mattila, S. Reynolds, T. M. Stritzinger, M. D. Somero, A. Tomasella, L. Pei, S. -P. Yang, Y. -J. Zhang, J. -J. Pan, Y. Solar and Stellar Astrophysics Astrophysics of Galaxies High Energy Astrophysical Phenomena We present optical photometric and spectroscopic observations of the Type~IIb supernova (SN)~2017ati. It reached the maximum light at about 27~d after the explosion and the light curve shows a broad, luminous peak with an absolute $r$-band magnitude of $M_{r} = -18.48 \pm 0.16$~mag. At about 50~d after maximum light, SN~2017ati exhibits a decline rate close to that expected from the $^{56}$Co $\rightarrow$ $^{56}$Fe radioactive decay, at 0.98 mag per 100 days, as usually observed in SNe IIb. However, it remains systematically brighter at late times by about 1--2~mag, exceeding the usual upper luminosity range of this class. As a result, modelling the light curve of SN~2017ati with a standard $^{56}$Ni decay scenario requires a large nickel mass of up to $\sim0.37\,M_{\odot}$ and still fails to reproduce the early-time light curve adequately. In contrast, incorporating additional energy input from a magnetar yields a significantly improved fit to the light curve of SN~2017ati, which would reduce the nickel mass to $\sim0.21\,M_{\odot}$, still close to the upper end of the range typically inferred for SNe~IIb. Comparing the fitted results of SN~2017ati with the known sample of SNe~IIb indicates that its luminosity evolution is best explained by a combination of neutron star spin-down energy and radioactive nickel deposition. From late-time nebular spectra of SN~2017ati, the luminosity of the [\Oi]~$λ\lambda6300,6364$ doublet implies an oxygen mass of $\sim1.82-3.34\,M_{\odot}$, and the combination of a [\Caii]/[\Oi] flux ratio of $\sim0.5$ with nebular spectral model comparisons favours a progenitor zero-age main-sequence mass of $\geq17\,M_{\odot}$. |
| title | SN 2017ati: A luminous type IIb explosion from a massive progenitor |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2602.04474 |