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Published November 1, 2020 | Published + Submitted
Journal Article Open

A Model for the Fast Blue Optical Transient AT2018cow: Circumstellar Interaction of a Pulsational Pair-instability Supernova

Abstract

The fast blue optical transient (FBOT) ATLAS18qqn (AT2018cow) has a light curve as bright as that of superluminous supernovae (SLSNe) but rises and falls much faster. We model this light curve by circumstellar interaction of a pulsational pair-instability (PPI) supernova (SN) model based on our PPISN models studied in previous work. We focus on the 42 M_⊙ He star (core of a 80 M_⊙ star) which has circumstellar matter (CSM) of mass 0.50 M_⊙. With the parameterized mass cut and the kinetic energy of explosion E, we perform hydrodynamical calculations of nucleosynthesis and optical light curves of PPISN models. The optical light curve of the first ~20 days of AT2018cow is well reproduced by the shock heating of CSM for the 42 M_⊙ He star with E = 5 × 10⁵¹ erg. After day 20, the light curve is reproduced by the radioactive decay of 0.6 M_⊙⁵⁶Co, which is a decay product of ⁵⁶Ni in the explosion. We also examine how the light-curve shape depends on the various model parameters, such as CSM structure and composition. We also discuss (1) other possible energy sources and their constraints, (2) the origin of the observed high-energy radiation, and (3) how our result depends on the radiative transfer codes. Based on our successful model for AT2018cow and the model for SLSN with CSM mass as large as 20 M⊙, we propose the working hypothesis that PPISN produces SLSNe if the CSM is massive enough and FBOTs if CSM is less than ~1 M_⊙.

Additional Information

© 2020. The American Astronomical Society. Received 2020 February 7; revised 2020 September 17; accepted 2020 September 18; published 2020 November 3. This work was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and JSPS KAKENHI grant Nos. JP17K05382 and JP20K04024. K.N. would like to thank Brian Metzger and Raffaella Margutti for useful discussion at the UCSB/KITP program "The New Era of Gravitational-Wave Physics and Astrophysics" in 2019. S.C.L. thanks the MESA development community for making the code open source and V. Morozova and her collaborators in providing the snec code open source. S.C.L. acknowledges support by funding HST-AR-15021.001-A and 80NSSC18K1017. S.B. is sponsored by grant RSF 19-12-00229 in his work on supernova simulations with the stella code. P.B.'s work on understanding the effect on light curves of different approaches in the SNEC and stella codes is supported by the grant RSF 18-12-00522. E.S. is supported by the grant RFBR 19-52-50014 in her work on developing codes modeling the radiative transfer in supernovae. Software: MESA (v8118; Paxton et al. 2011, 2013, 2015, 2017), SNEC (Morozova et al. 2015), stella (Blinnikov et al. 2006; Baklanov et al. 2015).

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Published - Leung_2020_ApJ_903_66.pdf

Submitted - 2008.11404.pdf

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August 22, 2023
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October 20, 2023