We report type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM, combined with radioactive decay. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results. SN 2020bqj is a compelling example of a transitional SN Ibn/IIn based on not only its spectral features, but also its lightcurve, host galaxy properties and the inferred progenitor properties. The strong similarity with SN 2011hw suggests this subclass may be the result of a progenitor in a stellar evolution phase that is distinct from those of progenitors of regular SNe Ibn.
Kool, E. C., et al. "SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau." Astronomy and Astrophysics, vol. 652, Aug. 2021. https://doi.org/10.1051/0004-6361/202039137
Kool, E. C., Karamehmetoglu, E., Sollerman, J., Schulze, S., Lunnan, R., Reynolds, T. M., Barbarino, C., Bellm, E. C., De, K., Duev, D. A., Fremling, C., Golkhou, V. Z., Graham, M. L., Green, D. A., Horesh, A., Kaye, S., Kim, Y. -L., Laher, R. R., ... Yan, L. (2021). SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau. Astronomy and Astrophysics, 652. https://doi.org/10.1051/0004-6361/202039137
Kool, E. C., Karamehmetoglu, E., Sollerman, J., et al., "SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau," Astronomy and Astrophysics 652 (2021), https://doi.org/10.1051/0004-6361/202039137
@article{osti_1864173,
author = {Kool, E. C. and Karamehmetoglu, E. and Sollerman, J. and Schulze, S. and Lunnan, R. and Reynolds, T. M. and Barbarino, C. and Bellm, E. C. and De, K. and Duev, D. A. and others},
title = {SN 2020bqj: A Type Ibn supernova with a long-lasting peak plateau},
annote = {We report type Ibn supernovae (SNe Ibn) are a rare class of stripped envelope supernovae interacting with a helium-rich circumstellar medium (CSM). The majority of the SNe Ibn reported in the literature display a surprising homogeneity in their fast-evolving lightcurves and are typically found in actively starforming spiral galaxies. We present the discovery and the study of SN 2020bqj (ZTF20aalrqbu), a SN Ibn with a long-duration peak plateau lasting 40 days and hosted by a faint low-mass galaxy. We aim to explain its peculiar properties using an extensive photometric and spectroscopic data set. We compare the photometric and spectral evolution of SN 2020bqj with regular SNe Ibn from the literature, as well as with other outliers in the SN Ibn subclass. We fit the bolometric and multi-band lightcurves with powering mechanism models such as radioactive decay and CSM interaction. We also model the host galaxy of SN 2020bqj. The risetime, peak magnitude and spectral features of SN 2020bqj are consistent with those of most SNe Ibn, but the SN is a clear outlier in the subclass based on its bright, long-lasting peak plateau and the low mass of its faint host galaxy. We show through modeling that the lightcurve of SN 2020bqj can be powered predominantly by shock heating from the interaction of the SN ejecta and a dense CSM, combined with radioactive decay. The peculiar Type Ibn SN 2011hw is a close analog to SN 2020bqj in terms of lightcurve and spectral evolution, suggesting a similar progenitor and CSM scenario. In this scenario a very massive progenitor star in the transitional phase between a luminous blue variable and a compact Wolf-Rayet star undergoes core-collapse, embedded in a dense helium-rich CSM with an elevated opacity compared to normal SNe Ibn, due to the presence of residual hydrogen. This scenario is consistent with the observed properties of SN 2020bqj and the modeling results. SN 2020bqj is a compelling example of a transitional SN Ibn/IIn based on not only its spectral features, but also its lightcurve, host galaxy properties and the inferred progenitor properties. The strong similarity with SN 2011hw suggests this subclass may be the result of a progenitor in a stellar evolution phase that is distinct from those of progenitors of regular SNe Ibn.},
doi = {10.1051/0004-6361/202039137},
url = {https://www.osti.gov/biblio/1864173},
journal = {Astronomy and Astrophysics},
issn = {ISSN 0004-6361},
volume = {652},
place = {United States},
publisher = {EDP Sciences},
year = {2021},
month = {08}}
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP); Swedish Research Council; European Union; Gordon and Betty Moore Foundation; European Research Council (ERC); University of Washington; Israel Science Foundation; US-Israel Binational Science Foundation; National Science Foundation (NSF); Heising-Simons Foundation
Grant/Contract Number:
AC02-05CH11231; SC0007914
OSTI ID:
1864173
Journal Information:
Astronomy and Astrophysics, Journal Name: Astronomy and Astrophysics Vol. 652; ISSN 0004-6361