SN 2016hil– a Type II supernova in the remote outskirts of an elliptical host and its origin. (arXiv:1904.01425v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Irani_I/0/1/0/all/0/1">Ido Irani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schulze_S/0/1/0/all/0/1">Steve Schulze</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:+Lunnan_R/0/1/0/all/0/1">Ragnhild Lunnan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Filippenko_A/0/1/0/all/0/1">Alexei V. Filippenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sollerman_J/0/1/0/all/0/1">Jesper Sollerman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_Y/0/1/0/all/0/1">Yi Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brink_T/0/1/0/all/0/1">Thomas G. Brink</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_W/0/1/0/all/0/1">WeiKang Zheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jaeger_T/0/1/0/all/0/1">Thomas de Jaeger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nugent_P/0/1/0/all/0/1">Peter E. Nugent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasliwal_M/0/1/0/all/0/1">Mansi M. Kasliwal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fremling_C/0/1/0/all/0/1">Christoffer Fremling</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neill_J/0/1/0/all/0/1">James Don Neill</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rebbapragada_U/0/1/0/all/0/1">Umaa Rebbapragada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masci_F/0/1/0/all/0/1">Frank J. Masci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yaron_O/0/1/0/all/0/1">Ofer Yaron</a>

Type II supernovae (SNe) stem from the core collapse of massive ($>8
M_{odot}$) stars. Owing to their short lifespan, we expect a very low rate of
such events in elliptical host galaxies, where the star-formation rate is low,
and which mostly consist of an old stellar population. SN 2016hil (iPTF16hil)
is a Type II supernova located in the extreme outskirts of an elliptical galaxy
at redshift $z=0.0608$ (projected distance $27.2$ kpc). It was detected near
peak brightness ($M_{r} approx -17$ mag) 9 days after the last nondetection.
SN 2016hil has some potentially peculiar properties: while presenting a
characteristic spectrum, the event was unusually short lived and declined by
$sim 1.5$ mag in $< 40$ days, following an apparently double-peaked light curve. Its spectra suggest a low metallicity ($Z<0.4 Z_{odot}$). We place a tentative upper limit on the mass of a potential faint host at $log(M/M_{odot}) =7.27^{+0.43}_{-0.24}$ using deep Keck optical imaging. In light of this, we discuss the possibility of the progenitor forming locally, and other more exotic formation scenarios such as a merger or common-envelope evolution causing a time-delayed explosion. Further observations of the explosion site in the ultraviolet are needed in order to distinguish between the cases. Regardless of the origin of the transient, observing a population of such seemingly hostless Type II SNe could have many uses, including an estimate the number of faint galaxies in a given volume, and tests of the prediction of a time-delayed population of core-collapse SNe in locations otherwise unfavorable for the detection of such events.

Type II supernovae (SNe) stem from the core collapse of massive ($>8
M_{odot}$) stars. Owing to their short lifespan, we expect a very low rate of
such events in elliptical host galaxies, where the star-formation rate is low,
and which mostly consist of an old stellar population. SN 2016hil (iPTF16hil)
is a Type II supernova located in the extreme outskirts of an elliptical galaxy
at redshift $z=0.0608$ (projected distance $27.2$ kpc). It was detected near
peak brightness ($M_{r} approx -17$ mag) 9 days after the last nondetection.
SN 2016hil has some potentially peculiar properties: while presenting a
characteristic spectrum, the event was unusually short lived and declined by
$sim 1.5$ mag in $< 40$ days, following an apparently double-peaked light
curve. Its spectra suggest a low metallicity ($Z<0.4 Z_{odot}$). We place a
tentative upper limit on the mass of a potential faint host at
$log(M/M_{odot}) =7.27^{+0.43}_{-0.24}$ using deep Keck optical imaging. In
light of this, we discuss the possibility of the progenitor forming locally,
and other more exotic formation scenarios such as a merger or common-envelope
evolution causing a time-delayed explosion. Further observations of the
explosion site in the ultraviolet are needed in order to distinguish between
the cases. Regardless of the origin of the transient, observing a population of
such seemingly hostless Type II SNe could have many uses, including an estimate
the number of faint galaxies in a given volume, and tests of the prediction of
a time-delayed population of core-collapse SNe in locations otherwise
unfavorable for the detection of such events.

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