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The Fast, Luminous Ultraviolet Transient AT2018cow: Extreme Supernova, or Disruption of a Star by an Intermediate-Mass Black Hole?

Perley, DA, Mazzali, PA, Yan, L, Cenko, SB, Gezari, S, Taggart, K, Blagorodnova, N, Fremling, C, Mockler, B, Singh, A, Tominaga, N, Tanaka, M, Watson, AM, Ahumada, T, Anupama, GC, Ashall, C, Becerra, RL, Bersier, D, Bhalerao, V, Bloom, JS , Butler, NR, Copperwheat, CM, Coughlin, MW, De, K, Drake, AJ, Duev, DA, Frederick, S, González, JJ, Goobar, A, Heida, M, Ho, AYQ, Horst, J, Hung, T, Itoh, R, Jencson, JE, Kasliwal, MM, Kawai, N, Kulkarni, SR, Kumar, B, Kumar, H, Kutyrev, AS, Khanam, T, Lee, WH, Maeda, K, Mahabal, A, Murata, KL, Neill, JD, Ngeow, C-C, Penprase, B, Pian, E, Quimby, R, Ramirez-Ruiz, E, Richer, M, Román-Zúñiga, CG, Srivastava, S, Socia, Q, Sollerman, J, Tachibana, Y, Taddia, F, Tinyanont, K, Troja, E, Ward, C and Wee, J (2018) 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). pp. 1031-1049. ISSN 0035-8711

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Abstract

Wide-field optical surveys have begun to uncover large samples of fast (t_rise < 5d), luminous (M_peak < -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 a detailed investigation of their properties until now. We present photometry and spectroscopy from a comprehensive worldwide campaign to observe AT2018cow (ATLAS18qqn), 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 3-8 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<10^14 cm after 1 month). This behavior 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.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Authros. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: astro-ph.HE; astro-ph.HE
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 18 Dec 2018 11:21
Last Modified: 25 Mar 2019 17:38
URI: http://researchonline.ljmu.ac.uk/id/eprint/9097

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