Journal article

ASASSN-18am/SN 2018gk: an overluminous Type IIb supernova from a massive progenitor

Subhash Bose, Subo Dong, CS Kochanek, MD Stritzinger, Chris Ashall, Stefano Benetti, E Falco, Alexei Filippenko, Andrea Pastorello, Jose L Prieto, Auni Somero, Tuguldur Sukhbold, Junbo Zhang, Katie Auchettl, Thomas G Brink, JS Brown, Ping Chen, A Fiore, Dirk Grupe, TWS Holoien Show all

Monthly Notices of the Royal Astronomical Society | OXFORD UNIV PRESS | Published : 2021


ABSTRACT ASASSN-18am/SN 2018gk is a newly discovered member of the rare group of luminous, hydrogen-rich supernovae (SNe) with a peak absolute magnitude of MV ≈ −20 mag that is in between normal core-collapse SNe and superluminous SNe. These SNe show no prominent spectroscopic signatures of ejecta interacting with circumstellar material (CSM), and their powering mechanism is debated. ASASSN-18am declines extremely rapidly for a Type II SN, with a photospheric-phase decline rate of ∼6.0 mag (100 d)−1. Owing to the weakening of H i and the appearance of He i in its later phases, ASASSN-18am is spectroscopically a Type IIb SN with a partially stripped envelope. However, its photo..

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University of Melbourne Researchers


Awarded by NSF

Awarded by Independent Research Fund Denmark (IRFD)


Awarded by FONDECYT

Awarded by Ministry of Economy, Development, and Tourism's Millennium Science Initiative

Awarded by NASA

Awarded by Danish National Research Foundation

Awarded by Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)

Awarded by National Natural Science Foundation of China

Awarded by Gordon and Betty Moore Foundation

Funding Acknowledgements

An anonymous referee provided helpful suggestions for improving this paper. We thank Boaz Katz and Amir Sharon for their assistance, and Dan Perley for reducing the Keck/LRIS +8.3 d spectrum. KZS and CSK are supported by NSF grants AST-1515927, AST-1814440, and AST-1908570. MS is supported by a project grant (802100170B) from the Independent Research Fund Denmark (IRFD) and by generous grants (13261 and 28021) from VILLUM FONDEN. BJS is supported by NSF grants AST-1907570, AST-1908952, AST1920392, and AST-1911074. Support for JLP is provided in part by FONDECYT through grant 1191038 and by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. TAT is supported in part by NASA grant 80NSSC20K0531. KAA is supported by the Danish National Research Foundation (DNRF132). Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. JZ is supported by the National Natural Science Foundation of China (grants 11803049 and 41727803). AVF's supernova group is grateful for financial assistance from the Christopher R. Redlich Fund, the TABASGO Foundation, and the Miller Institute for Basic Research in Science (U.C. Berkeley). ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, and by NSF grants AST-1515927 and AST-1908570. Development of ASAS-SN was supported by NSF grant AST-0908816, theMt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics, at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), the Villum Foundation, and George Skestos. Some of the 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 NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank the staffs at Lick and Keck Observatories for their assistance. Research at Lick Observatory is partially supported by a generous gift from Google. We acknowledge the support of the staff of the Xinglong 2.16m telescope. This work was partially supported by the Open Project Program of the CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences. We acknowledge the Telescope Access Program (TAP) funded by NAOC, CAS, and the Special Fund for Astronomy from the Ministry of Finance. This work is partly based on NUTS2 observations made with the NOT, operated by the NOT Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of IAC. ALFOSC is provided by IAA under a joint agreement with the University of Copenhagen and NOTSA. NUTS2 is funded in part by the Instrument Center for Danish Astrophysics (IDA). This work is partly based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof ' isica de Canarias, on the island of La Palma. The LBT is an international collaboration among institutions in the United States, Italy, and Germany.LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.