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ASASSN-18am/SN 2018...
ASASSN-18am/SN 2018gk : an overluminous Type IIb supernova from a massive progenitor
- Article/chapterEnglish2021
Publisher, publication year, extent ...
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2021-03-04
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Oxford University Press (OUP),2021
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printrdacarrier
Numbers
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LIBRIS-ID:oai:DiVA.org:su-195256
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https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-195256URI
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https://doi.org/10.1093/mnras/stab629DOI
Supplementary language notes
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Language:English
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Summary in:English
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Subject category:ref swepub-contenttype
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Subject category:art swepub-publicationtype
Notes
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ASASSN-18am/SN 2018gk is a newly discovered member of the rare group of luminous, hydrogen-rich supernovae (SNe) with a peak absolute magnitude of M-V approximate to -20 mag that is in between normal core-collapse SNe and superluminous SNe. These SNe show no prominent spectroscopic signatures of ejecta interacting with circumstellar material (CSM), and their powering mechanism is debated. ASASSN-18am declines extremely rapidly for a Type II SN, with a photospheric-phase decline rate of similar to 6.0 mag (100 d)(-1). Owing to the weakening of H I and the appearance of He I in its later phases, ASASSN-18am is spectroscopically a Type IIb SN with a partially stripped envelope. However, its photometric and spectroscopic evolution shows significant differences from typical SNe IIb. Using a radiative diffusion model, we find that the light curve requires a high synthesized Ni-56 mass M-Ni similar to 0.4 M-circle dot and ejecta with high kinetic energy E-kin = (7-10) x 10(51) erg. Introducing a magnetar central engine still requires M-Ni similar to 0.3 M-circle dot and E-kin = 3 x 10(51) erg. The high Ni-56 mass is consistent with strong iron-group nebular lines in its spectra, which are also similar to several SNe Ic-BL with high Ni-56 yields. The earliest spectrum shows 'flash ionization' features, from which we estimate a mass-loss rate of (M) over dot approximate to 2 x 10(-4 )M(circle dot) yr(-1). This wind density is too low to power the luminous light curve by ejecta-CSM interaction. We measure expansion velocities as high as 17 000 km s(-1) for H alpha, which is remarkably high compared to other SNe II. We estimate an oxygen core mass of 1.8-3.4 M-circle dot using the [O I] luminosity measured from a nebular-phase spectrum, implying a progenitor with a zero-age main-sequence mass of 19-26 M-circle dot.
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Dong, Subo
(author)
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Kochanek, C. S.
(author)
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Stritzinger, M. D.
(author)
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Ashall, Chris
(author)
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Benetti, Stefano
(author)
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Falco, E.
(author)
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Filippenko, Alexei
(author)
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Pastorello, Andrea
(author)
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Prieto, Jose L.
(author)
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Somero, Auni
(author)
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Sukhbold, Tuguldur
(author)
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Zhang, Junbo
(author)
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Auchettl, Katie
(author)
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Brink, Thomas G.
(author)
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Brown, J. S.
(author)
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Chen, Ping
(author)
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Fiore, A.
(author)
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Grupe, Dirk
(author)
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Holoien, T. W. S.
(author)
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Lundqvist, PeterStockholms universitet,Institutionen för astronomi,Oskar Klein-centrum för kosmopartikelfysik (OKC)(Swepub:su)lundq
(author)
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Mattila, Seppo
(author)
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Mutel, Robert
(author)
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Pooley, David
(author)
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Post, R. S.
(author)
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Reddy, Naveen
(author)
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Reynolds, Thomas M.
(author)
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Shappee, Benjamin J.
(author)
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Stanek, K. Z.
(author)
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Thompson, Todd A.
(author)
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Villanueva Jr., S.
(author)
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Zheng, Weikang
(author)
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Stockholms universitetInstitutionen för astronomi
(creator_code:org_t)
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In:Monthly notices of the Royal Astronomical Society: Oxford University Press (OUP)503:3, s. 3472-34910035-87111365-2966
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Bose, Subhash
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Dong, Subo
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Kochanek, C. S.
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Stritzinger, M. ...
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Ashall, Chris
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Benetti, Stefano
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Falco, E.
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Filippenko, Alex ...
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Pastorello, Andr ...
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Prieto, Jose L.
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Somero, Auni
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Sukhbold, Tuguld ...
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Zhang, Junbo
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Auchettl, Katie
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Brink, Thomas G.
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Brown, J. S.
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Chen, Ping
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Fiore, A.
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Grupe, Dirk
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Holoien, T. W. S ...
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Lundqvist, Peter
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Mattila, Seppo
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Mutel, Robert
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Pooley, David
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Post, R. S.
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Reddy, Naveen
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Reynolds, Thomas ...
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Shappee, Benjami ...
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Stanek, K. Z.
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Thompson, Todd A ...
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Villanueva Jr., ...
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Zheng, Weikang
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