A Systematic Study of Ia-CSM Supernovae from the ZTF Bright Transient Survey

Yashvi Sharma, Jesper Sollerman, Christoffer Fremling, Shrinivas R. Kulkarni, Kishalay De, Ido Irani, Steve Schulze, Nora Linn Strotjohann, Avishay Gal-Yam, Kate Maguire, Daniel A. Perley, Eric C. Bellm, Erik C. Kool, Thomas G. Brink, Rachel Bruch, Maxime Deckers, Richard Dekany, Alison Dugas, Alexei V. Filippenko, Samantha GoldwasserMatthew J. Graham, Melissa L. Graham, Steven L. Groom, Matt Hankins, Jacob Jencson, Joel P. Johansson, Viraj Karambelkar, Mansi M. Kasliwal, Frank J. Masci, Michael S. Medford, James D. Neill, Guy Nir, Reed L. Riddle, Mickael Rigault, Tassilo Schweyer, Jacco H. Terwel, Lin Yan, Yi Yang, Yuhan Yao

Research output: Contribution to journalArticlepeer-review


Among the supernovae (SNe) that show strong interaction with a circumstellar medium (CSM), there is a rare subclass of Type Ia supernovae, SNe Ia-CSM, which show strong narrow hydrogen emission lines much like SNe IIn but on top of a diluted Type Ia spectrum. The only previous systematic study of this class identified 16 SNe Ia-CSM, eight historic and eight from the Palomar Transient Factory (PTF). Now using the successor survey to PTF, the Zwicky Transient Facility (ZTF), we have classified 12 additional SNe Ia-CSM through the systematic Bright Transient Survey (BTS). Consistent with previous studies, we find these SNe to have slowly evolving optical light curves with peak absolute magnitudes between −19.1 and −21, spectra having weak Hβ and large Balmer decrements of ∼7. Out of the 10 SNe from our sample observed by NEOWISE, nine have 3σ detections, with some SNe showing a reduction in the red wing of Hα, indicative of newly formed dust. We do not find our SN Ia-CSM sample to have a significantly different distribution of equivalent widths of He i λ5876 than SNe IIn as observed in Silverman et al. The hosts tend to be late-type galaxies with recent star formation. We derive a rate estimate of 29 − 21 + 27 Gpc−3 yr−1 for SNe Ia-CSM, which is ∼0.02%-0.2% of the SN Ia rate. We also identify six ambiguous SNe IIn/Ia-CSM in the BTS sample and including them gives an upper limit rate of 0.07%-0.8%. This work nearly doubles the sample of well-studied Ia-CSM objects in Silverman et al., increasing the total number to 28.

Original languageEnglish
Article number52
Number of pages21
JournalAstrophysical Journal
Issue number1
StatePublished - 1 May 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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