KSP-SN-2016kf: a long-rising H-rich Type II Supernova with unusually high $^{56}$Ni mass discovered in the KMTNet Supernova Program. (arXiv:1906.09271v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Afsariardchi_N/0/1/0/all/0/1">Niloufar Afsariardchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moon_D/0/1/0/all/0/1">Dae-Sik Moon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Drout_M/0/1/0/all/0/1">Maria R. Drout</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzalez_Gaitan_S/0/1/0/all/0/1">Santiago González-Gaitán</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ni_Y/0/1/0/all/0/1">Yuan Qi Ni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matzner_C/0/1/0/all/0/1">Christopher D. Matzner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_S/0/1/0/all/0/1">Sang Chul Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_Y/0/1/0/all/0/1">Youngdae Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Park_H/0/1/0/all/0/1">Hong Soo Park</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gal_Yam_A/0/1/0/all/0/1">Avishay Gal-Yam</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pignata_G/0/1/0/all/0/1">Giuliano Pignata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koo_B/0/1/0/all/0/1">Bon-Chul Koo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ryder_S/0/1/0/all/0/1">Stuart Ryder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cha_S/0/1/0/all/0/1">Sang-Mok Cha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_Y/0/1/0/all/0/1">Yongseok Lee</a>
We present the discovery and the photometric and spectroscopic study of
H-rich Type II supernova (SN) KSP-SN-2016kf (SN2017it) observed in the KMTNet
Supernova Program in the outskirts of a small irregular galaxy at
$zsimeq0.043$ within a day from the explosion. Our high-cadence, multi-color
($BVI$) light curves of the SN show that it has a very long rise time
($t_text{rise}simeq 20$ days in $V$ band), a moderately luminous peak
($M_Vsimeq -$17.6 mag), a notably luminous and flat plateau ($M_Vsimeq -$17.4
mag and decay slope $ssimeq0.53$ mag per 100 days), and an exceptionally
bright radioactive tail. Using the color-dependent bolometric correction to the
light curves, we estimate the $^{56}$Ni mass powering the observed radioactive
tail to be $0.10pm0.01$ M$_odot$, making it a H-rich Type II SN with one of
the largest $^{56}$Ni masses observed to date. The results of our hydrodynamic
simulations of the light curves constrain the mass and radius of the progenitor
at the explosion to be $sim$15 M$_odot$ (evolved from a star with an initial
mass of $sim$ 18.8 M$_odot$) and $sim1040$ R$_odot$, respectively, with the
SN explosion energy of $sim 1.3times 10^{51}$ erg s$^{-1}$. The above-average
mass of the KSP-SN-2016kf progenitor, together with its low metallicity $
Z/Z_odot simeq0.1-0.4$ obtained from spectroscopic analysis, is indicative of
a link between the explosion of high-mass red supergiants and their
low-metallicity environment. The early part of the observed light curves shows
the presence of excess emission above what is predicted in model calculations,
suggesting there is interaction between the ejecta and circumstellar material.
We further discuss the implications of the high progenitor initial mass and
low-metallicity environment of KSP-SN-2016kf on our understanding of the origin
of Type II SNe.
We present the discovery and the photometric and spectroscopic study of
H-rich Type II supernova (SN) KSP-SN-2016kf (SN2017it) observed in the KMTNet
Supernova Program in the outskirts of a small irregular galaxy at
$zsimeq0.043$ within a day from the explosion. Our high-cadence, multi-color
($BVI$) light curves of the SN show that it has a very long rise time
($t_text{rise}simeq 20$ days in $V$ band), a moderately luminous peak
($M_Vsimeq -$17.6 mag), a notably luminous and flat plateau ($M_Vsimeq -$17.4
mag and decay slope $ssimeq0.53$ mag per 100 days), and an exceptionally
bright radioactive tail. Using the color-dependent bolometric correction to the
light curves, we estimate the $^{56}$Ni mass powering the observed radioactive
tail to be $0.10pm0.01$ M$_odot$, making it a H-rich Type II SN with one of
the largest $^{56}$Ni masses observed to date. The results of our hydrodynamic
simulations of the light curves constrain the mass and radius of the progenitor
at the explosion to be $sim$15 M$_odot$ (evolved from a star with an initial
mass of $sim$ 18.8 M$_odot$) and $sim1040$ R$_odot$, respectively, with the
SN explosion energy of $sim 1.3times 10^{51}$ erg s$^{-1}$. The above-average
mass of the KSP-SN-2016kf progenitor, together with its low metallicity $
Z/Z_odot simeq0.1-0.4$ obtained from spectroscopic analysis, is indicative of
a link between the explosion of high-mass red supergiants and their
low-metallicity environment. The early part of the observed light curves shows
the presence of excess emission above what is predicted in model calculations,
suggesting there is interaction between the ejecta and circumstellar material.
We further discuss the implications of the high progenitor initial mass and
low-metallicity environment of KSP-SN-2016kf on our understanding of the origin
of Type II SNe.
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