Volume 620, December 2018
|Number of page(s)||16|
|Published online||30 November 2018|
A nearby super-luminous supernova with a long pre-maximum & “plateau” and strong C II features
European Southern Observatory, Alonso de Córdova 3107, Casilla 19 Santiago, Chile
2 Instituto de Astrofísica de La Plata (IALP), CONICET, Argentina; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
3 Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
4 School of Physics and Astronomy, University of Southampton, Southampton, UK
5 Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
6 Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
7 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
8 Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK
9 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen, Denmark
10 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
11 Research School of Astronomy and Astrophysics, Australian National University, Canberra ACT 2611, Australia
12 ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia
13 Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune 411007, Maharashtra, India
14 Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001, Israel
15 Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Goleta, CA 93117-5575, USA
16 University of California, Santa Barbara, Department of Physics, Santa Barbara, CA 93106-9530, USA
17 Department of Physics, Florida State University, Tallahassee 32306, USA
18 Oskar Klein Centre, Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
19 School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield Dublin 4, Ireland
20 Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603 La Serena, Chile
21 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
22 Institut d’Astrophysique de Paris, CNRS, and Universite Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
23 PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
24 Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
25 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
26 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
27 Las Campanas Observatory, Carnegie Observatories, Casilla 601 La Serena, Chile
28 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
29 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
30 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
31 ARC Future Fellow, School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra ACT 2600, Australia
32 Research School of Astronomy and Astrophysics, Mt Stromlo Observatory, Australian National University, Canberra ACT 2611, Australia
33 Department of Astronomy/Steward Observatory, 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721-0065, USA
34 LSST, 950 N Cherry Ave, Tucson, AZ 85719, USA
35 Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
36 The National Centre for the Public Awareness of Science, Australian National University, Canberra ACT 2611, Australia
37 ARC Centre of Excellence for All-sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
38 Department of Physics, University of California, Davis, CA 95616, USA
Accepted: 16 September 2018
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 a long, 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 × 109 M⊙, and a star formation rate of = 0.50−0.19+2.22 M⊙ yr −1. A nearby H II region has an oxygen abundance (O3N2) of 8.31 ± 0.01 dex.
Key words: supernovae: general / supernovae: individual: SN 2018bsz / supernovae: individual: ASASSN-18km
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.