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A nearby super-luminous supernova with a long pre-maximum plateau and strong C (II) features
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Number of Authors: 662018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 620, article id A67Article in journal (Refereed) Published
Abstract [en]

Context. Super-luminous supernovae (SLSNe) are rare events defined as being significantly more luminous than normal terminal stellar explosions. The source of the additional power needed to achieve such luminosities is still unclear. Discoveries in the local Universe (i.e. z < 0.1) are scarce, but afford dense multi-wavelength observations. Additional low-redshift objects are therefore extremely valuable.

Aims. We present early-time observations of the type I SLSN ASASSN-18km/SN 2018bsz. These data are used to characterise the event and compare to literature SLSNe and spectral models. Host galaxy properties are also analysed.

Methods. Optical and near-IR photometry and spectroscopy were analysed. Early-time ATLAS photometry was used to constrain the rising light curve. We identified a number of spectral features in optical-wavelength spectra and track their time evolution. Finally, we used archival host galaxy photometry together with H( II )region spectra to constrain the host environment.

Results. ASASSN-18km/SN 2018bsz is found to be a type I SLSN in a galaxy at a redshift of 0.0267 (111 Mpc), making it the lowest-redshift event discovered to date. Strong C- II lines are identified in the spectra. Spectral models produced by exploding a Wolf-Rayet progenitor and injecting a magnetar power source are shown to be qualitatively similar to ASASSN-18km/SN 2018bsz, contrary to most SLSNe-I that display weak or non-existent C (II) lines. ASASSN-18km/SN 2018bsz displays along, slowly rising, red plateau of >26 days, before a steeper, faster rise to maximum. The host has an absolute magnitude of -19.8 mag (r), a mass of M-* = 1.5(-0.33)(+0.08) x 10(9) M-circle dot, and a star formation rate of =0.50(-0.19)(+2.22) M-circle dot yr(-1). A nearby H (II) region has an oxygen abundance (O3N2) of 8.31 +/- 0.01 dex.

Place, publisher, year, edition, pages
2018. Vol. 620, article id A67
Keywords [en]
supernovae, general - supernovae, individual, SN 2018bsz-supernovae, individual, ASASSN-18km
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-163607DOI: 10.1051/0004-6361/201833725ISI: 000452389000001OAI: oai:DiVA.org:su-163607DiVA, id: diva2:1277145
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved

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Bulla, Mattia
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)
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