ASASSN-18am/SN 2018gk: an overluminous Type IIb supernova from a massive progenitor
Research output: Contribution to journal › Journal article › Research › peer-review
Standard
ASASSN-18am/SN 2018gk : an overluminous Type IIb supernova from a massive progenitor. / Bose, Subhash; Dong, Subo; Kochanek, C. S.; Stritzinger, M. D.; Ashall, Chris; Benetti, Stefano; Falco, E.; Filippenko, Alexei; Pastorello, Andrea; Prieto, Jose L.; Somero, Auni; Sukhbold, Tuguldur; Zhang, Junbo; Auchettl, Katie; Brink, Thomas G.; Brown, J. S.; Chen, Ping; Fiore, A.; Grupe, Dirk; Holoien, T. W. S.; Lundqvist, Peter; Mattila, Seppo; Mutel, Robert; Pooley, David; Post, R. S.; Reddy, Naveen; Reynolds, Thomas M.; Shappee, Benjamin J.; Stanek, K. Z.; Thompson, Todd A.; Villanueva, S. jR; Zheng, Weikang.
In: Monthly Notices of the Royal Astronomical Society, Vol. 503, No. 3, 05.2021, p. 3472-3491.Research output: Contribution to journal › Journal article › Research › peer-review
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - ASASSN-18am/SN 2018gk
T2 - an overluminous Type IIb supernova from a massive progenitor
AU - Bose, Subhash
AU - Dong, Subo
AU - Kochanek, C. S.
AU - Stritzinger, M. D.
AU - Ashall, Chris
AU - Benetti, Stefano
AU - Falco, E.
AU - Filippenko, Alexei
AU - Pastorello, Andrea
AU - Prieto, Jose L.
AU - Somero, Auni
AU - Sukhbold, Tuguldur
AU - Zhang, Junbo
AU - Auchettl, Katie
AU - Brink, Thomas G.
AU - Brown, J. S.
AU - Chen, Ping
AU - Fiore, A.
AU - Grupe, Dirk
AU - Holoien, T. W. S.
AU - Lundqvist, Peter
AU - Mattila, Seppo
AU - Mutel, Robert
AU - Pooley, David
AU - Post, R. S.
AU - Reddy, Naveen
AU - Reynolds, Thomas M.
AU - Shappee, Benjamin J.
AU - Stanek, K. Z.
AU - Thompson, Todd A.
AU - Villanueva, S. jR
AU - Zheng, Weikang
PY - 2021/5
Y1 - 2021/5
N2 - 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.
AB - 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.
KW - supernovae: general
KW - supernovae: individual: (ASASSN-18am/SN 2018gk)
KW - galaxies: individual: WISE J163554.27+400151.8
KW - CORE-COLLAPSE SUPERNOVAE
KW - NEUTRINO-DRIVEN EXPLOSION
KW - LIGHT-CURVES
KW - SN 2013EJ
KW - EVOLUTION
KW - EMISSION
KW - SPECTRA
KW - SAMPLE
KW - GALAXY
KW - DUST
U2 - 10.1093/mnras/stab629
DO - 10.1093/mnras/stab629
M3 - Journal article
VL - 503
SP - 3472
EP - 3491
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
SN - 0035-8711
IS - 3
ER -
ID: 271822207