The fast, luminous ultraviolet transient AT2018cow: Extreme supernova, or disruption of a star by an intermediate-mass black hole?

Daniel A. Perley, Paolo A. Mazzali, Lin Yan, S. Bradley Cenko, Suvi Gezari, Kirsty Taggart, Nadia Blagorodnova, Christoffer Fremling, Brenna Mockler, Avinash Singh, Nozomu Tominaga, Masaomi Tanaka, Alan M. Watson, Tomás Ahumada, G. C. Anupama, Chris Ashall, Rosa L. Becerra, David Bersier, Varun Bhalerao, Joshua S. BloomNathaniel R. Butler, Chris Copperwheat, Michael W. Coughlin, Kishalay De, Andrew J. Drake, Dmitry A. Duev, Sara Frederick, J. Jesús González, Ariel Goobar, Marianne Heida, Anna Y.Q. Ho, John Horst, Tiara Hung, Ryosuke Itoh, Jacob E. Jencson, Mansi M. Kasliwal, Nobuyuki Kawai, Tanazza Khanam, Shrinivas R. Kulkarni, Brajesh Kumar, Harsh Kumar, Alexander S. Kutyrev, William H. Lee, Keiichi Maeda, Ashish Mahabal, Katsuhiro L. Murata, James D. Neill, Chow Choong Ngeow, Bryan Penprase, Elena Pian, Robert Quimby, Enrico Ramirez-Ruiz, Michael G. Richer, Carlos G. Romań-Zúñiga, D. K. Sahu, Shubham Srivastav, Quentin Socia, Jesper Sollerman, Yutaro Tachibana, Francesco Taddia, Samaporn Tinyanont, Eleonora Troja, Charlotte Ward, Jerrick Wee, Po Chieh Yu

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < -18), blue transients. While commonly attributed to the breakout of a supernova shock into a dense wind, the great distances to the transients of this class found so far have hampered detailed investigation of their properties. We present photometry and spectroscopy from a comprehensive worldwide campaign to observe AT 2018cow (ATLAS 18qqn), the first fast-luminous optical transient to be found in real time at lowredshift. Our first spectra (<2 days after discovery) are entirely featureless. A very broad absorption feature suggestive of nearrelativistic velocities develops between 3 and 8 days, then disappears. Broad emission features of H and He develop after >10 days. The spectrum remains extremely hot throughout its evolution, and the photospheric radius contracts with time (receding below R < 1014 cm after 1 month). This behaviour does not match that of any known supernova, although a relativistic jet within a fallback supernova could explain some of the observed features. Alternatively, the transient could originate from the disruption of a star by an intermediate-mass black hole, although thiswould require long-lasting emission of highly super-Eddington thermal radiation. In either case, AT 2018cow suggests that the population of fast luminous transients represents a new class of astrophysical event. Intensive follow-up of this event in its late phases, and of any future events found at comparable distance, will be essential to better constrain their origins.

Original languageEnglish (US)
Pages (from-to)1031-1049
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume484
Issue number1
DOIs
StatePublished - 2019

Keywords

  • Black hole
  • Stars
  • Supernova: individual: AT2018cow
  • Supernovae: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Perley, D. A., Mazzali, P. A., Yan, L., Cenko, S. B., Gezari, S., Taggart, K., Blagorodnova, N., Fremling, C., Mockler, B., Singh, A., Tominaga, N., Tanaka, M., Watson, A. M., Ahumada, T., Anupama, G. C., Ashall, C., Becerra, R. L., Bersier, D., Bhalerao, V., ... Yu, P. C. (2019). The fast, luminous ultraviolet transient AT2018cow: Extreme supernova, or disruption of a star by an intermediate-mass black hole? Monthly Notices of the Royal Astronomical Society, 484(1), 1031-1049. https://doi.org/10.1093/mnras/sty3420