Bumpy declining light curves are common in hydrogen-poor superluminous supernovae

Griffin Hosseinzadeh*, Edo Berger, Brian D. Metzger, Sebastian Gomez, Matt Nicholl, Peter Blanchard

*Corresponding author for this work

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Abstract

Recent work has revealed that the light curves of hydrogen-poor (Type I) superluminous supernovae (SLSNe), thought to be powered by magnetar central engines, do not always follow the smooth decline predicted by a simple magnetar spin-down model. Here we present the first systematic study of the prevalence and properties of "bumps"in the post-peak light curves of 34 SLSNe. We find that the majority (44%-76%) of events cannot be explained by a smooth magnetar model alone. We do not find any difference in supernova properties between events with and without bumps. By fitting a simple Gaussian model to the light-curve residuals, we characterize each bump with an amplitude, temperature, phase, and duration. We find that most bumps correspond with an increase in the photospheric temperature of the ejecta, although we do not see drastic changes in spectroscopic features during the bump. We also find a moderate correlation (ρ ≈ 0.5; p ≈ 0.01) between the phase of the bumps and the rise time, implying that such bumps tend to happen at a certain "evolutionary phase," (3.7 ± 1.4)trise. Most bumps are consistent with having diffused from a central source of variable luminosity, although sources further out in the ejecta are not excluded. With this evidence, we explore whether the cause of these bumps is intrinsic to the supernova (e.g., a variable central engine) or extrinsic (e.g., circumstellar interaction). Both cases are plausible, requiring low-level variability in the magnetar input luminosity, small decreases in the ejecta opacity, or a thin circumstellar shell or disk.

Original languageEnglish
Article number14
Number of pages15
JournalAstrophysical Journal
Volume933
Issue number1
Early online date28 Jun 2022
DOIs
Publication statusPublished - 1 Jul 2022

Bibliographical note

Funding Information:
We thank Manos Chatzopoulos for helpful discussions regarding models of magnetar-powered SNe and circumstellar interaction. The Berger Time-domain Group at Harvard is supported in part by the NSF under grant AST-1714498 and by NASA under grant NNX15AE50G. G.H. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant #1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. B.D.M. acknowledges support from the NSF (grant no. AST-2002577). M.N. is supported by a Royal Astronomical Society Research Fellowship and by the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 948381). Las Cumbres Observatory observations were taken as part of the Global Supernova Project. Based on observations obtained at the international Gemini Observatory, a program of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The computations in this paper were run on the FASRC Cannon cluster supported by the FAS Division of Science Research Computing Group at Harvard University.

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

Keywords

  • Circumstellar matter
  • Circumstellar shells
  • Magnetars
  • Supernovae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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