A1 Refereed original research article in a scientific journal
SN 2017ckj: A linearly declining type IIb supernova with a relatively massive hydrogen envelope
Authors: Li, L. H.; Benetti, S.; Cai, Y. -Z.; Wang, B.; Pastorello, A.; Elias-Rosa, N.; Reguitti, A.; Borsato, L.; Cappellaro, E.; Fiore, A.; Fraser, M.; Gromadzki, M.; Harmanen, J.; Isern, J.; Kangas, T.; Kankare, E.; Lundqvist, P.; Mattila, S.; Ochner, P.; Peng, Z. -h.; Reynolds, T. M.; Salmaso, I.; Srivastav, S.; Stritzinger, M. D.; Tomasella, L.; Valerin, G.; Wang, Z. -y.; Zhang, J. -j.; Wu, C. -y.
Publisher: EDP Sciences
Publication year: 2025
Journal: Astronomy and Astrophysics
Article number: A233
Volume: 704
ISSN: 0004-6361
eISSN: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202556873
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://doi.org/10.1051/0004-6361/202556873
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/508262242
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
We present optical observations of the type IIb supernova (SN) 2017ckj, covering approximately 180 days after the explosion. Its early-time multi-band light curves display no clear evidence of a shock-cooling tail, resembling the behaviour of SN 2008ax. The V-band light curve exhibits a short rise time of about 5 days and reaches an absolute fitted peak magnitude of MV = -18.49 +/- 0.18 mag. The late-time multi-band light curves reveal a linear decline. We modelled the bolometric light curve of SN 2017ckj to constrain the progenitor and the explosion parameters. We estimated a total mass of Ni-56 synthesised by SN 2017ckj of M-Ni = 0.21(-0.03)(+0.05) M-circle dot, with a massive H-rich envelope of M-env = 0.4(-0.1)(+0.1) M-circle dot. Both the Ni-56 mass and the envelope mass of SN 2017ckj are higher than those of typical SNe IIb, in agreement with its peculiar light curve evolution. The early-time spectra of SN 2017ckj are dominated by a blue continuum, accompanied by narrow H alpha and He II emission lines. The earliest spectrum exhibits flash ionisation features, from which we estimated a progenitor mass-loss rate of similar to 3 x 10(-4) M-circle dot yr(-1). At later epochs, the spectra develop broad P-Cygni profiles and become increasingly similar to those of SNe IIb, especially SN 2018gk. The late-time spectrum at around 139 days does not show a distinct decline in the strength of its H alpha emission profile, also indicating a relatively massive envelope of its progenitor. Aside from the H alpha feature, the nebular spectrum exhibits prominent emission lines of O I, Ca II, [Ca II], and Mg I], which are consistent with the prototypical SN 1993J.
Downloadable publication This is an electronic reprint of the original article. |  |
Funding information in the publication:
This work is supported by the National Natural Science Foundation of China (Nos 12288102, 12225304, 12090040/12090043, 12303054, 12473032), the National Key Research and Development Program of China (Nos. 2021YFA1600404, 2024YFA1611603), the Western Light Project of CAS (No.XBZG-ZDSYS-202117), the Yunnan Revitalization Talent Support Program (Yunling Scholar Project), the Yunnan Revitalization Talent Support Program-Young Talent project, the Yunnan Fundamental Research Projects (Nos 202201BC070003, 202401AU070063, 202501AS070078, 202501AW070001, 202501AS070005), and the International Centre of Supernovae, Yunnan Key Laboratory (No. 202302AN360001). SB, EC, NER,PO, AP, AR, IS, LT and GV acknowledge financial support from the PRIN-INAF 2022 "Shedding light on the nature ofgap transients: from the observations to the models". AR alsoacknowledges financial support from the GRAWITA Large Program Grant (PI P. D'Avanzo). AF acknowledges fundingby the European Union - NextGenerationEU RFF M4C2 1.1PRIN 2022 project "2022RJLWHN URKA" and by INAF 2023Theory Grant ObFu 1.05.23.06.06 "Understanding R-process& Kilonovae Aspects (URKA)". JH acknowledges the Vilho, Yrjoe and Kalle Vaeisaelae Foundation of the Finnish Academy of Science and Letters. TK acknowledges support from the Research Council of Finland project 360274. T.M.R is part ofthe Cosmic Dawn Center (DAWN), which is funded by the Danish National Research Foundation under grant DNRF140.T.M.R acknowledges support from the Research Council of Finland project 350458. S.M. acknowledges financial supportfrom the Research Council of Finland project 350458. We thankS. Taubenberger for conducting the template observations withthe Copernico Telescope. We thank Jingxiao Luo, Xinbo Huangand Zeyi Zhao for helpful discussions and valuable suggestions.
