SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy. (arXiv:2006.16443v2 [astro-ph.HE] UPDATED)

SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy. (arXiv:2006.16443v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Lin_W/0/1/0/all/0/1">W. L. Lin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_X/0/1/0/all/0/1">X. F. Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_W/0/1/0/all/0/1">W. X. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_J/0/1/0/all/0/1">J. J. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mo_J/0/1/0/all/0/1">J. Mo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sai_H/0/1/0/all/0/1">H. N. Sai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">X. H. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Filippenko_A/0/1/0/all/0/1">A. V. Filippenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_W/0/1/0/all/0/1">W. K. Zheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brink_T/0/1/0/all/0/1">T. G. Brink</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baron_E/0/1/0/all/0/1">E. Baron</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DerKacy_J/0/1/0/all/0/1">J. M. DerKacy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ehgamberdiev_S/0/1/0/all/0/1">S. A. Ehgamberdiev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mirzaqulov_D/0/1/0/all/0/1">D. Mirzaqulov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_X/0/1/0/all/0/1">X. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_J/0/1/0/all/0/1">J. C. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yan_S/0/1/0/all/0/1">S. Y. Yan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xi_G/0/1/0/all/0/1">G. B. Xi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hsiao_Y/0/1/0/all/0/1">Y. Hsiao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_T/0/1/0/all/0/1">T. M. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_L/0/1/0/all/0/1">L. J. Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_L/0/1/0/all/0/1">L. D. Liu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xiang_D/0/1/0/all/0/1">D. F. Xiang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_C/0/1/0/all/0/1">C. Y. Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rui_L/0/1/0/all/0/1">L. M. Rui</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Z/0/1/0/all/0/1">Z. H. Chen</a>

SN 2018hti is a Type I superluminous supernova (SLSN~I) with an absolute
$g$-band magnitude of $-22.2$ at maximum brightness, discovered in a metal-poor
galaxy at a redshift of 0.0612. We present extensive photometric and
spectroscopic observations of this supernova, covering the phases from $sim
-35$ days to more than +340 days from the $r$-band maximum. Combining our
$BVgri$-band photometry with {it Swift} UVOT optical/ultraviolet photometry,
we calculated the peak luminosity as $sim 3.5times10^{44}$ erg s$^{-1}$.
Modeling the observed light curve reveals that the luminosity evolution of SN
2018hti can be produced by an ejecta mass of 5.8 $M_odot$ and a magnetar with
a magnetic field of $B=1.8times10^{13}$~G having an initial spin period of
$P_0=1.8$ ms. Based on such a magnetar-powered scenario and a larger sample, a
correlation between the spin of the magnetar and the kinetic energy of the
ejecta can be inferred for most SLSNe~I, suggesting a self-consistent scenario.
Like for other SLSNe~I, the host galaxy of SN 2018hti is found to be relatively
faint ($M_{g} = -17.75$ mag) and of low metallicity ($Z=0.3~Z_odot$), with a
star-formation rate of 0.3 $M_odot$ yr$^{-1}$. According to simulation results
of single-star evolution, SN 2018hti could originate from a massive, metal-poor
star with a zero-age main sequence (ZAMS) mass of 25–40 $M_odot$, or from a
less massive rotating star with $M_mathrm{ZAMS} approx 16$–25 $M_odot$. For
the case of a binary system, its progenitor could also be a star with
$M_mathrm{ZAMS} gtrsim 25$ $M_odot$.

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