A long life of excess: The interacting transient SN 2017hcc

¹ Department of Physics and Astronomy, University of Turku, Vesilinnantie 5 20500, Finland
e-mail: semoke@utu.fi
² School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
³ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁴ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, 20014 Turku, Finland
⁵ School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
⁶ Cosmic Dawn Center, DTU Space, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
⁷ Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 København N, Denmark
⁸ European Southern Observatory, Alonso de Córdova, 3107 Casilla 19, Santiago, Chile
⁹ George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, Texas A. & M. University, Department of Physics and Astronomy, 4242 TAMU, College Station, TX 77843, USA
¹⁰ INAF – Osservatorio astronomico di Brera, Via Bianchi 46, 23807 Merate (LC), Italy
¹¹ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
¹² The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden
¹³ INAF – Capodimonte Astronomical Observatory, Salita Moiariello 16, 80131 Napoli, Italy
¹⁴ INFN – Napoli, Strada Comunale Cinthia, 80126 Napoli, Italy
¹⁵ ICRANet, Piazza della Repubblica 10, 65122 Pescara, Italy
¹⁶ Institut d’Astrophysique de Paris (IAP), CNRS & Sorbonne Université, 75014 Paris, France
¹⁷ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Barcelona, Spain
¹⁸ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
¹⁹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, 44001 Teruel, Spain
²⁰ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
²¹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138-1516, USA
²² Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
²³ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
²⁴ School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK
²⁵ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
²⁶ Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
²⁷ Instituto de Astrofísica, Departamento de Ciencias Físicas – Universidad Andres Bello, Avda. República 252, 8320000 Santiago, Chile
²⁸ Millennium Institute of Astrophysics, Nuncio Monsenor Sótero Sanz 100, Providencia, 8320000 Santiago, Chile
²⁹ Department of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USA
³⁰ Astrophysics Research Centre, School of Maths and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK

Received: 21 July 2022
Accepted: 22 October 2022

Abstract

In this study we present the results of a five-year follow-up campaign of the long-lived type IIn supernova SN 2017hcc, found in a spiral dwarf host of near-solar metallicity. The long rise time (57 ± 2 days, ATLAS o band) and high luminosity (peaking at −20.78 ± 0.01 mag in the ATLAS o band) point towards an interaction of massive ejecta with massive and dense circumstellar material (CSM). The evolution of SN 2017hcc is slow, both spectroscopically and photometrically, reminiscent of the long-lived type IIn, SN 2010jl. An infrared (IR) excess was apparent soon after the peak, and blueshifts were noticeable in the Balmer lines starting from a few hundred days, but appeared to be fading by around +1200 d. We posit that an IR light echo from pre-existing dust dominates at early times, with some possible condensation of new dust grains occurring at epochs ≳+800 d.