期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 503, 期 3, 页码 3472-3491出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab629
关键词
supernovae: general; supernovae: individual: (ASASSN-18am/SN 2018gk); galaxies: individual: WISE J163554.27+400151.8
资金
- NSF [AST-1515927, AST-1814440, AST-1908570, AST-1907570, AST-1908952, AST1920392, AST-1911074, AST-0908816]
- Independent Research Fund Denmark (IRFD) [802100170B]
- VILLUM FONDEN [13261, 28021]
- FONDECYT [1191038]
- Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]
- NASA [80NSSC20K0531]
- Danish National Research Foundation [DNRF132]
- Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) [CE170100013]
- National Natural Science Foundation of China [11803049, 41727803]
- Christopher R. Redlich Fund
- TABASGO Foundation
- Miller Institute for Basic Research in Science (U.C. Berkeley)
- Gordon and Betty Moore Foundation [GBMF5490]
- Mt. Cuba Astronomical Foundation
- Center for Cosmology and AstroParticle Physics, at the Ohio State University
- Chinese Academy of Sciences South America Center for Astronomy (CASSACA)
- Villum Foundation
- George Skestos
- W. M. Keck Foundation
- Open Project Program of the CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences
- NAOC
- CAS
- Special Fund for Astronomy from the Ministry of Finance
- Instrument Center for Danish Astrophysics (IDA)
ASASSN-18am / SN 2018gk is a newly discovered member of rare, luminous, hydrogen-rich supernovae with significant differences in spectrum and luminosity compared to typical IIb supernovae, requiring a high mass of Ni-56 and high kinetic energy for powering.
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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