SN 2019tsf: Evidence for Extended Hydrogen-poor CSM in the Three-peaked Light Curve of Stripped Envelope of a Type Ib Supernova

Zenati, Y; Wang, Q; Bobrick, A; DeMarchi, L; Glanz, H; Rozner, M; Jencson, JE; Rest, A; Metzger, BD; Margutti, R; Gomez, S; Smith, N; Toonen, S; Bright, JS; Norman, C; Foley, RJ; Gagliano, A; Krolik, JH; Smartt, SJ; Villar, AV; Narayan, G; Fox, O; Auchettl, K; Brethauer, D

Journal article

SN 2019tsf: Evidence for Extended Hydrogen-poor CSM in the Three-peaked Light Curve of Stripped Envelope of a Type Ib Supernova

Abstract:: We present multiband ATLAS and ZTF photometry for SN 2019tsf, a Type Ib stripped-envelope supernova (SESN). The slow spectral evolution could be associated with an uncommon explosion mechanism specific to this SN. Possible explanations include fallback accretion onto a compact remnant or a long-lived central engine, both of which could provide extended energy injection responsible for the late-time rebrightening and unusual spectral features. The rebrightening observations represent the latest photometric measurements of a multipeaked Type Ib SN. As late-time photometry and spectroscopy suggest no hydrogen, the potential circumstellar material (CSM) must be H-poor. The absence of a nebular phase and the lack of narrow emission lines in the late-time spectra (>142 days) of the SNe suggest that any CSM interaction is likely asymmetric and enveloped by the SN ejecta. However, an extended CSM structure is evident through a follow-up radio campaign with the Karl G. Jansky Very Large Array (VLA), indicating a source of bright optically thick radio emission at late times, which is highly unusual among H-poor SESNe. We attribute this phenomenology to an interaction of the supernova ejecta with asymmetric CSM, potentially disk-like, and we present several models that may explain the origin of this rare Type Ib supernova. We propose a warped disk model in which a tertiary companion—commonly present around massive stars—perturbs the progenitor’s CSM, producing density enhancements that may explain the observed multipeaked SN 2019tsf light curve. This SN 2019tsf is a unique SN Type Ib among the recently discovered class of SNe that undergo mass transfer at the moment of explosion.

Publication status:: Published

Peer review status:: Peer reviewed

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APA Style

Zenati, Y., Wang, Q., Bobrick, A., DeMarchi, L., Glanz, H., Rozner, M., Jencson, J. E., Rest, A., Metzger, B. D., Margutti, R., Gomez, S., Smith, N., Toonen, S., Bright, J. S., Norman, C., Foley, R. J., Gagliano, A., Krolik, J. H., Smartt, S. J., … Brethauer, D. (2025). SN 2019tsf: Evidence for Extended Hydrogen-poor CSM in the Three-peaked Light Curve of Stripped Envelope of a Type Ib Supernova. The Astrophysical Journal, 992(1).

MLA Style

Zenati, Y., et al. “SN 2019tsf: Evidence for Extended Hydrogen-Poor CSM in the Three-Peaked Light Curve of Stripped Envelope of a Type Ib Supernova.” The Astrophysical Journal, vol. 992, no. 1, American Astronomical Society, 2025.

Chicago Style

Zenati, Y, Q Wang, A Bobrick, L DeMarchi, H Glanz, M Rozner, JE Jencson, et al. 2025. “SN 2019tsf: Evidence for Extended Hydrogen-Poor CSM in the Three-Peaked Light Curve of Stripped Envelope of a Type Ib Supernova.” The Astrophysical Journal 992 (1).
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