A1 Refereed original research article in a scientific journal
SN 2016gsd: an unusually luminous and linear Type II supernova with high velocities
Authors: Reynolds TM, Fraser M, Mattila S, Ergon M, Lundqvist P, Dessart L, Dong SB, Elias-Rosa N, Galbany L, Gutierrez CP, Kangas T, Kankare E, Kotak R, Kuncarayakti H, Pastorello A, Rodriguez O, Smartt SJ, Stritzinger M, Tomasella L, Chen P, Harmanen J, Hozzeinzadeh G, Howell DA, Inserra C, Nicholl M, Nielsen M, Smith K, Somero A, Tronsgaard R, Young DR
Publisher: OXFORD UNIV PRESS
Publication year: 2020
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 493
Issue: 2
First page : 1761
Last page: 1781
Number of pages: 21
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/staa365
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/46993182
We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = -19.95 +/- 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in( )H alpha are also unusually high with the blue edge tracing the fastest moving gas initially at 20 000 km s(-1), and then declining approximately linearly to 15000 km s(-1) over similar to 100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H alpha absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.
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