The fast, luminous ultraviolet transient AT2018cow: extreme supernova, or disruption of a star by an intermediate-mass black hole?
Date Issued
2019
Author(s)
Perley, Daniel A.
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Mazzali, Paolo A.
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Yan, Lin
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Cenko, S. Bradley
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Gezari, Suvi
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Taggart, Kirsty
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Blagorodnova, Nadia
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Fremling, Christoffer
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Mockler, Brenna
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Singh, Avinash
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Tominaga, Nozomu
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Tanaka, Masaomi
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Watson, Alan M.
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Ahumada, Tomás
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Anupama, G. C.
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Ashall, Chris
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Becerra, Rosa L.
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Bersier, David
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Bhalerao, Varun
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Bloom, Joshua S.
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Butler, Nathaniel R.
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Copperwheat, Chris
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Coughlin, Michael W.
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De, Kishalay
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Drake, Andrew J.
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Duev, Dmitry A.
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Frederick, Sara
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González, J. Jesús
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Goobar, Ariel
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Heida, Marianne
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Ho, Anna Y. Q.
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Horst, John
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Hung, Tiara
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Itoh, Ryosuke
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Jencson, Jacob E.
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Kasliwal, Mansi M.
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Kawai, Nobuyuki
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Khanam, Tanazza
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Kulkarni, Shrinivas R.
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Kumar, Brajesh
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Kumar, Harsh
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Kutyrev, Alexander S.
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Lee, William H.
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Maeda, Keiichi
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Mahabal, Ashish
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Murata, Katsuhiro L.
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Neill, James D.
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Ngeow, Chow-Choong
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Penprase, Bryan
•
•
Quimby, Robert
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Ramirez-Ruiz, Enrico
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Richer, Michael G.
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Román-Zúñiga, Carlos G.
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Sahu, D. K.
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Srivastav, Shubham
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Socia, Quentin
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Sollerman, Jesper
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Tachibana, Yutaro
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Taddia, Francesco
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Tinyanont, Samaporn
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Troja, Eleonora
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Ward, Charlotte
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Wee, Jerrick
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Yu, Po-Chieh
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 low redshift. Our first spectra (<2 days after discovery) are entirely featureless. A very broad absorption feature suggestive of near-relativistic 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 this would 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.
Volume
484
Issue
1
Start page
1031
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.484.1031P
Rights
open.access
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