Long-term evolution of the SN 2009ip-like transient SN 2016cvk

¹ Department of Physics and Astronomy, University of Turku, FI-20014 University of Turku, Finland
² Nordic Optical Telescope, Aarhus Universitet, Rambla José Ana Fernàndez Pérez 7, local 5, E-38711 San Antonio, Breña Baja Santa Cruz de Tenerife, Spain
³ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
⁴ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
⁶ Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica, Chile
⁷ James Cook University, Cairns, Queensland, Australia
⁸ School of Physics, University College Dublin, LMI Main Building, Beech Hill Road, Dublin 4 D04 P7W1, Ireland
⁹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
¹⁰ European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile
¹¹ Millennium Institute of Astrophysics MAS, Nuncio Monseñor Sotero Sanz 100, Off. 104, Providencia, Santiago, Chile
¹² Instituto de Astrofísica, Departamento de Física, Facultad de Ciencias Exactas, Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago RM, Chile
¹³ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Avenida Angamos 601, Antofagasta, Chile
¹⁴ Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, 32001 Jhongli, Taiwan
¹⁵ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
¹⁶ Institut d’Estudis Espacials de Catalunya (IEEC), Edifici RDIT, Campus UPC, 08860 Castelldefels (Barcelona), Spain
¹⁷ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, E-08193 Barcelona, Spain
¹⁸ Cardiff Hub for Astrophysics Research and Technology, School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
¹⁹ School of Physics, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
²⁰ Instituto de Ciencias Exactas y Naturales (ICEN), Universidad Arturo Prat, Chile
²¹ Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK
²² Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Avenida Ejercito Libertador 441, Santiago, Chile
²³ Dipartimento di Fisica “Ettore Pancini”, Università di Napoli Federico II, Via Cinthia 9, 80126 Naples, Italy
²⁴ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Naples, Italy
²⁵ Cosmic Dawn Center (DAWN)
²⁶ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 København N, Denmark

^⋆ Corresponding author: katja.matilainen@utu.fi

Received: 30 May 2025
Accepted: 29 August 2025

Abstract

Aims. The interacting transient SN 2016cvk (ASASSN-16jt) is a peculiar SN 2009ip-like event. We present our follow-up data with an aim to draw conclusions on the physical nature of the progenitor system.

Methods. Our spectrophotometric data set of SN 2016cvk covers the ultraviolet, optical, and near-infrared wavelength region extending to +1681 d from the light curve peak. In this work, we analysed the data and made comparison with other SN 2009ip-like transients. We note that archival data reveal pre-outbursts of the progenitor with the first detection at –1219 d.

Results. The light-curve evolution of SN 2016cvk consists of two consecutive luminous events A and B, with peak magnitudes of M_V < −15.6 and M_r = −18.3 mag, respectively. The spectra are dominated by Balmer emission lines that have a complex, multi-component evolution resembling that of other SN 2009ip-like targets. SN 2016cvk is among the first detected SN 2009ip-like events that show early ‘flash ionisation’ features of C III, N III, and He II, lasting for 16 ± 5 d. Our late-time +405 d spectrum shows forbidden [Ca II], [Fe II], and [O I] features, with the latter detected particularly clearly for a SN 2009ip-like event.

Conclusions. The evolution of SN 2016cvk is similar to other SN 2009ip-like transients, with some uncommon traits. The lack of a double-peaked structure in the Balmer lines is likely caused by differences in the circumstellar medium structure or viewing angle. The flash features in the early spectra propose abundances consistent with a red, yellow, or blue supergiant progenitor, rather than a luminous blue variable, for example. The detection of [O I] in the +405 d spectrum suggests some possible evidence of nucleosynthesised material generated in a SN explosion.