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

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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 - Mar 21 2019
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the GROWTH project funded by the National Science Foundation under Grant No 1545949. GROWTH is a collaborative project between California Institute of Technology, Pomona College, San Diego State University, Los Alamos National Laboratory, University of Maryland College Park, University of Wisconsin Milwaukee (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), and Liverpool John Moores University (UK). This paper used the GROWTH marshal to filter alerts and co-ordinate follow-up.

Funding Information:
FT and JS gratefully acknowledge support from the Knut and Alice Wallenberg Foundation. JS acknowledges the support of Vetenskapsrådet through VR grants 2012-2265 and 2017-03699.

Funding Information:
AYQH was supported by a National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469. MC was supported by the David and Ellen Lee Postdoctoral Fellowship at the California Institute of Technology. JSB was supported by a Data-Driven Discovery grant from the Moore Foundation.

Funding Information:
C-C Ngeow and P-C Yu thank the Ministry of Science and Technology (MoST, Taiwan) for funding under grant 104-2923-M-008-004-MY5 and 106-2112-M-008-007. This publication has made use of data collected at Lulin Observatory, partly supported by MoST grant 105-2112-M-008-024-MY3.

Funding Information:
RI is supported by JSPS and NSF under the JSPS-NSF Partnerships for International Research and Education (PIRE), YT and NK supported by JSPS KAKENHI Grant Numbers JP16J05742 and JP17H06362. YT is also financially supported by Academy for Global Leadership (AGL) of Tokyo Institute of Technology. MITSuME Akeno 50cm telescope is also supported by the joint research program of the Institute for Cosmic Ray Research (ICRR), the University of Tokyo, and Optical and Near-Infrared Astronomy Inter-University Cooperation Program in Japan (KLM).

Funding Information:
GCA and VB acknowledge the support of the Science and Engineering Research Board, Department of Science and Technology, India and the Indo-US Science and Technology Forum for the GROWTH-India project. BK acknowledges the Science and Engineering Research Board under the Department of Science & Technology, Govt. of India, for financial assistance in the form of National Post-Doctoral Fellowship (PDF/2016/001563) and BRICS grant DST/IMRCD/BRICS/PilotCall1/MuMeSTU/2017(G).

Funding Information:
The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. We acknowledge helpful support from the entire LT staff, including Robert Smith, Jon Marchant, and Iain Steele, and to the LT review panel for approving our requests for Reactive time (JQ18A01).

Funding Information:
These results made use of the Discovery Channel Telescope at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale. We thank Debra Fischer for graciously assisting with our Target of Opportunity request at the DCT.

Funding Information:
This work is partly based on observations made with the Kitt Peak EMCCD Demonstrator (KPED) camera on the Kitt Peak 84 inch telescope. The KPED team thanks the National Science Foundation, discretionary funds of SRK, and donors to SRK for support in the building and operation of KPED. In addition, they thank the Chimera project for use of the EMCCD.

Funding Information:
Some of the data used in this paper were acquired with the COATLI telescope and interim instrument, and with the RATIR instrument on the 1.5-meter Harold L. Johnson telescope; both at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, México. COATLI is funded by CONACyT (LN 232649, 260369, and 271117) and the Universidad Na-cional Autónoma de México (CIC and DGAPA/PAPIIT IT102715, IG100414, and IN109408). RATIR is funded by the University of California and NASA Goddard Space Flight Center. COATLI and the Johnson 1.5-m telescope are operated and maintained by the Observatorio Astronómico Nacional and the Instituto de Astronomía of the Universidad Nacional Autónoma de México. We acknowledge the contribution of Leonid Georgiev and Neil Gehrels to the development of RATIR.

Funding Information:
Based partially on data from the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovac¸ão (Brazil). Data were taken under program GN-2018A-Q-902 and acquired through the Gemini Observatory Archive.

Funding Information:
Some data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

Funding Information:
Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions.

Funding Information:
The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation.

Keywords

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

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