ALMA Polarimetry of AT2018cow

Kuiyun Huang, Jiro Shimoda, Yuji Urata, Kenji Toma, Kazutaka Yamaoka, Keiichi Asada, Hiroshi Nagai, Satoko Takahashi, Glen Petitpas, Makoto Tashiro

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


We present the first radio polarimetric observations of a fast-rising blue optical transient, AT2018cow. Two epochs of polarimetry with additional coincident photometry were performed with the Atacama Large Millimeter/submillimeter Array. The overall photometric results based on simultaneous observations in the 100 and 230 GHz bands are consistent with the nonthermal radiation model reported by Ho et al. and indicate that the spectral peaks (∼110 GHz at the first epoch and ∼67 GHz at the second epoch) represent the synchrotron self-absorption frequency. The non-detection of linear polarization with <0.15% in the 230 GHz band at the phase when the effect of synchrotron self-absorption was quite small in the band may be explained by internal Faraday depolarization with high circumburst density and strong magnetic field. This result supports the stellar explosion scenario rather than the tidal disruption model. The maximum energy of accelerating particles at the shocks of AT2018cow-like objects is also discussed.

Original languageEnglish
Article numberL25
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 2019 Jun 10


  • polarization
  • relativistic processes
  • submillimeter: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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