Master Thesis Defense by Maja Skafsgaard

Title: 2020hgw: Properties of an Unusually Bright Type II Supernova

Abstract: In this thesis I present photometric and spectroscopic analysis of the atypical Type II Supernova, 2020hgw, and compare its properties to a sample population of Type II SNe. 2020hgw appears remarkably bright and seems to exhibit a very short plateau in its r-band light curve. I find the peak absolute r-band magnitude to be −18.69 ± 0.065 and through analysis of the light curve I find the plateau duration to be P d = 31.70 ± 0.64 days and the duration of the optically thick phase to be OP T d = 59.79 ± 0.44 days. I also measure the decline rate from the peak to the beginning of the plateau, s1 = 0.024 ± 0.006, and the decline rate of the plateau, s2 = 0.011 ± 0.005. I statistically and visually inspect whether the light curve is best fitted with or without a plateau, and find the best fit for the r-band to include a plateau. From fitting the Hα P-Cygni profiles at four different epochs, I find the expansion velocities from the absorption and emission lines and the ratio of absorption to emission, a/e. At a comparable epoch to the comparison sample, I measure the Hα absorption velocity to be Hαvelocity = 4314.11 ± 12.03km s−1 and the ratio to be a/e = 0.4321 ± 0.0003. I measure the total radiated energy to be 1.559 ± 0.004 × 1044erg s−1. I find that for most of the parameters, 2020hgw lies within the general scatter of the whole Type II SN sample, however, it is atypical for a bright Type II SN with much lower s1, s2 and Hαvelocity and relatively higher a/e, but comparable P d and OP T d. I discuss some of the implications of these results. Whether 2020hgw is a typical example of a ‘short plateau SN’ or an exceptional case is unclear.


  • Christa Gall & Charlotte Angus, University of Copenhagen, Niels Bohr Institute


  • Hans Kjeldsen, Aarhus University

Post Defense Reception to be held at: øv - NBB 01.2.I.158, Jagtvej 155

Zoom Meeting

Meeting ID: 663 4257 2727
Passcode: 163553