SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf

Owen R. McBrien, Stephen J. Smartt, Ting Wan Chen, Cosimo Inserra, James H. Gillanders, Stuart A. Sim, Anders Jerkstrand, Armin Rest, Stefano Valenti, Rupak Roy, Mariusz Gromadzki, Stefan Taubenberger, Andreas Flörs, Mark E. Huber, Ken C. Chambers, Avishay Gal-Yam, David R. Young, Matt Nicholl, Erkki Kankare, Ken W. SmithKate Maguire, Ilya Mandel, Simon Prentice, Ósmar Rodríguez, Jonathan Pineda Garcia, Claudia P. Gutiérrez, Lluís Galbany, Cristina Barbarino, Peter S.J. Clark, Jesper Sollerman, Shrinivas R. Kulkarni, Kishalay De, David A.H. Buckley, Arne Rau

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Abstract

We present SN2018kzr, the fastest declining supernova-like transient, second only to the kilonova, AT2017gfo. SN2018kzr is characterized by a peak magnitude of M r =-17.98, a peak bolometric luminosity of ∼1.4 × 1043 erg s-1, and a rapid decline rate of 0.48 0.03 mag day-1 in the r band. The bolometric luminosity evolves too quickly to be explained by pure 56Ni heating, necessitating the inclusion of an alternative powering source. Incorporating the spin-down of a magnetized neutron star adequately describes the lightcurve and we estimate a small ejecta mass of M ej = 0.10 0.05 M o. Our spectral modeling suggests the ejecta is composed of intermediate mass elements including O, Si, and Mg and trace amounts of Fe-peak elements, which disfavors a binary neutron star merger. We discuss three explosion scenarios for SN2018kzr, given the low ejecta mass, intermediate mass element composition, and high likelihood of additional powering-the core collapse of an ultra-stripped progenitor, the accretion induced collapse (AIC) of a white dwarf, and the merger of a white dwarf and neutron star. The requirement for an alternative input energy source favors either the AIC with magnetar powering or a white dwarf-neutron star merger with energy from disk wind shocks.

Original languageEnglish
Article numberL23
Number of pages9
JournalThe Astrophysical Journal Letters
Volume885
Issue number1
DOIs
Publication statusPublished - 1 Nov 2019

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