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A systematic reclassification of type IIn supernovae

Ransome, CL, Habergham-Mawson, SM, Darnley, MJ, James, PA, Filippenko, AV and Schlegel, EM (2021) A systematic reclassification of type IIn supernovae. Monthly Notices of the Royal Astronomical Society, 506 (4). pp. 4715-4734. ISSN 0035-8711

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Type IIn supernovae (SNe IIn) are a relatively infrequently observed subclass of SNe whose photometric and spectroscopic properties are varied. A common thread among SNe IIn are the complex multiple-component hydrogen Balmer lines. Owing to the heterogeneity of SNe IIn, online databases contain some outdated, erroneous, or even contradictory classifications. SN IIn classification is further complicated by SN impostors and contamination from underlying HII regions. We have compiled a catalogue of systematically classified nearby (redshift z < 0.02) SNe IIn using the Open Supernova Catalogue (OSC). We present spectral classifications for 115 objects previously classified as SNe IIn. Our classification is based upon results obtained by fitting multiple Gaussians to the H-alpha profiles. We compare classifications reported by the OSC and Transient Name Server (TNS) along with the best matched templates from SNID. We find that 28 objects have been misclassified as SNe IIn. TNS and OSC can be unreliable; they disagree on the classifications of 51 of the objects and contain a number of erroneous classifications. Furthermore, OSC and TNS hold misclassifications for 34 and twelve (respectively) of the transients we classify as SNe IIn. In total, we classify 87 SNe IIn. We highlight the importance of ensuring that online databases remain up to date when new or even contemporaneous data become available. Our work shows the great range of spectral properties and features that SNe IIn exhibit, which may be linked to multiple progenitor channels and environment diversity. We set out a classification sche me for SNe IIn based on the H-alpha profile which is not greatly affected by the inhomogeneity of SNe IIn.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: astro-ph.SR; astro-ph.SR; astro-ph.HE
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 07 Jul 2021 10:09
Last Modified: 18 Jan 2022 11:45
DOI or ID number: 10.1093/mnras/stab1938
URI: https://researchonline.ljmu.ac.uk/id/eprint/15257
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