SN 2019nyk: A rapidly declining Type II supernova with early interaction signatures

¹ Instituto de Astrofísica, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, RM, Chile
e-mail: rdastidr@gmail.com
² Millennium Institute of Astrophysics (MAS), Nuncio Monsenor Sòtero Sanz 100, Providencia, Santiago, RM, Chile
³ Instituto de Alta Investigación, Universidad de Tarapacá, Santiago, RM, Chile
⁴ Aryabhatta Research Institute of observational sciencES, Manora Peak, Nainital 263001, India
⁵ Department of Applied Physics, Mahatma Jyotiba Phule Rohilkhand University, Bareilly 243006, India
⁶ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138-1516, USA
⁷ The NSF AI Institute for Artificial Intelligence and Fundamental Interactions, Cambridge, USA
⁸ Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA 93117-5575, USA
⁹ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
¹⁰ Departamento de Astronomía, Universidad de Chile, Casilla 36D, Santiago, Chile
¹¹ DiRAC Institute, Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195, USA
¹² Indian Institute of Astrophysics, Koramangala 2nd Block, Bangalore 560034, India
¹³ Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Japan
¹⁴ Department of Physics, University of Warwick, Coventry CV4 7AL, UK

Received: 16 November 2023
Accepted: 19 February 2024

Abstract

We present an optical photometric and spectroscopic analysis of the fast-declining hydrogen-rich Type II supernova (SN) 2019nyk. The light curve properties of SN 2019nyk align well with those of other fast-declining Type II SNe, such as SNe 2013by and 2014G. SN 2019nyk exhibits a peak absolute magnitude of −18.09 ± 0.17 mag in the V band, followed by a rapid decline at 2.84  ±  0.03 mag (100 d)⁻¹ during the recombination phase. The early spectra of SN 2019nyk exhibit high-ionisation emission features as well as narrow H Balmer lines, persisting until 4.1 d since explosion, indicating the presence of circumstellar material (CSM) in close proximity. A comparison of these features with other Type II SNe displaying an early interaction reveals similarities between these features and those observed in SNe 2014G and 2023ixf. We also compared the early spectra to literature models, estimating a mass-loss rate of the order of 10⁻³ M_⊙ yr⁻¹. Radiation hydrodynamical modelling of the light curve also suggests the mass loss from the progenitor within a short period prior to explosion, totalling 0.16 M_⊙ of material within 2900 R_⊙ of the progenitor. Furthermore, light curve modelling infers a zero-age main sequence mass of 15 M_⊙ for the progenitor, a progenitor radius of 1031 R_⊙, and an explosion energy of 1.1 × 10⁵¹ erg.