Type IIn supernova light-curve properties measured from an untargeted survey sample^{⋆,⋆⋆,⋆⋆⋆}

¹ Department of Astronomy and the Oskar Klein Centre, Stockholm University, AlbaNova 10691 Stockholm, Sweden
e-mail: anders.nyholm@astro.su.se
² Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
³ Department of Astrophysics/IMAPP, Radboud University, Houtlaan 4, 6525 XZ Nijmegen, The Netherlands
⁴ Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
⁵ Miller Senior Fellow, Miller Institute for Basic Research in Science, University of California, Berkeley, CA 94720, USA
⁶ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, 234 Herzl St., Rehovot 76100, Israel
⁷ Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
⁸ Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
⁹ IPAC, California Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
¹⁰ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
¹¹ Department of Physics and the Oskar Klein Centre, Stockholm University, AlbaNova 10691, Stockholm, Sweden
¹² National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹³ Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot, Israel
¹⁴ Department of Astronomy/Mount Laguna Observatory, San Diego State University, 5500 Campanile Drive, San Diego, CA 92812-1221, USA
¹⁵ Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
¹⁶ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA

Received: 13 June 2019
Accepted: 30 September 2019

Abstract

The evolution of a Type IIn supernova (SN IIn) is governed by the interaction between the SN ejecta and a hydrogen-rich circumstellar medium. The SNe IIn thus allow us to probe the late-time mass-loss history of their progenitor stars. We present a sample of SNe IIn from the untargeted, magnitude-limited surveys of the Palomar Transient Factory (PTF) and its successor, the intermediate PTF (iPTF). To date, statistics on SN IIn optical light-curve properties have generally been based on small (≲10 SNe) samples from targeted SN surveys. The SNe IIn found and followed by the PTF/iPTF were used to select a sample of 42 events with useful constraints on the rise times as well as with available post-peak photometry. The sample SNe were discovered in 2009−2016 and have at least one low-resolution classification spectrum, as well as photometry from the P48 and P60 telescopes at Palomar Observatory. We study the light-curve properties of these SNe IIn using spline fits (for the peak and the declining portion) and template matching (for the rising portion). We study the peak-magnitude distribution, rise times, decline rates, colour evolution, host galaxies, and K-corrections of the SNe in our sample. We find that the typical rise times are divided into fast and slow risers at 20 ± 6 d and 50 ± 11 d, respectively. The decline rates are possibly divided into two clusters (with slopes 0.013 ± 0.006 mag d⁻¹ and 0.040 ± 0.010 mag d⁻¹), but this division has weak statistical significance. We find no significant correlation between the peak luminosity of SNe IIn and their rise times, but the more luminous SNe IIn are generally found to be more long-lasting. Slowly rising SNe IIn are generally found to decline slowly. The SNe in our sample were hosted by galaxies of absolute magnitude −22 ≲ M_g ≲ −13 mag. The K-corrections at light-curve peak of the SNe IIn in our sample are found to be within 0.2 mag for the observer’s frame r-band, for SNe at redshifts z <  0.25. By applying K-corrections and also including ostensibly “superluminous” SNe IIn, we find that the peak magnitudes are M_peak^r = −19.18 ± 1.32 mag. We conclude that the occurrence of conspicuous light-curve bumps in SNe IIn, such as in iPTF13z, are limited to 1.4^+14.6_−1.0 % of the SNe IIn. We also investigate a possible sub-type of SNe IIn with a fast rise to a ≳50 d plateau followed by a slow, linear decline.