Observations of SN 2017ein Reveal Shock Breakout Emission and A Massive Progenitor Star for a Type Ic Supernova. (arXiv:1812.03076v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Xiang_D/0/1/0/all/0/1">Danfeng Xiang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_X/0/1/0/all/0/1">Xiaofeng Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mo_J/0/1/0/all/0/1">Jun Mo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_L/0/1/0/all/0/1">Lingjun Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Smartt_S/0/1/0/all/0/1">Stephen Smartt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fraser_M/0/1/0/all/0/1">Morgan Fraser</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ehgamberdiev_S/0/1/0/all/0/1">Shuhrat A. Ehgamberdiev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mirzaqulov_D/0/1/0/all/0/1">Davron Mirzaqulov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_J/0/1/0/all/0/1">Jujia Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_T/0/1/0/all/0/1">Tianmeng Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vinko_J/0/1/0/all/0/1">Jozsef Vinko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wheeler_J/0/1/0/all/0/1">J. Craig Wheeler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hosseinzadeh_G/0/1/0/all/0/1">Griffin Hosseinzadeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howell_D/0/1/0/all/0/1">D. Andrew Howell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McCully_C/0/1/0/all/0/1">Curtis McCully</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DerKacy_J/0/1/0/all/0/1">James M DerKacy</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:+Brown_P/0/1/0/all/0/1">Peter Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">Xianfei Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bi_S/0/1/0/all/0/1">Shaolan Bi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Song_H/0/1/0/all/0/1">Hao Song</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_K/0/1/0/all/0/1">Kaicheng Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rest_A/0/1/0/all/0/1">A. Rest</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nomoto_K/0/1/0/all/0/1">Ken&#x27;ichi Nomoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tolstov_A/0/1/0/all/0/1">Alexey Tolstov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blinnikov_S/0/1/0/all/0/1">Sergei Blinnikov</a>

We present optical and ultraviolet observations of nearby type Ic supernova
SN 2017ein as well as detailed analysis of its progenitor properties from both
the early-time observations and the prediscovery Hubble Space Telescope (HST)
images. The optical light curves started from within one day to $sim$275 days
after explosion, and optical spectra range from $sim$2 days to $sim$90 days
after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge,
mbox{SN 2017ein} seems to have more prominent C{footnotesize II} absorption
and higher expansion velocities in early phases, suggestive of relatively lower
ejecta mass. The earliest photometry obtained for mbox{SN 2017ein} show
indications of shock cooling. The best-fit obtained by including a shock
cooling component gives an estimate of the envelope mass as $sim$0.02
M$_{odot}$ and stellar radius as 8$pm$4 R$_{odot}$. Examining the
pre-explosion images taken with the HST WFPC2, we find that the SN position
coincides with a luminous and blue point-like source, with an
extinction-corrected absolute magnitude of M$_V$$sim$$-$8.2 mag and
M$_I$$sim$$-$7.7 mag.Comparisons of the observations to the theoretical models
indicate that the counterpart source was either a single WR star or a binary
with whose members had high initial masses, or a young compact star cluster. To
further distinguish between different scenarios requires revisiting the site of
the progenitor with HST after the SN fades away.

We present optical and ultraviolet observations of nearby type Ic supernova
SN 2017ein as well as detailed analysis of its progenitor properties from both
the early-time observations and the prediscovery Hubble Space Telescope (HST)
images. The optical light curves started from within one day to $sim$275 days
after explosion, and optical spectra range from $sim$2 days to $sim$90 days
after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge,
mbox{SN 2017ein} seems to have more prominent C{footnotesize II} absorption
and higher expansion velocities in early phases, suggestive of relatively lower
ejecta mass. The earliest photometry obtained for mbox{SN 2017ein} show
indications of shock cooling. The best-fit obtained by including a shock
cooling component gives an estimate of the envelope mass as $sim$0.02
M$_{odot}$ and stellar radius as 8$pm$4 R$_{odot}$. Examining the
pre-explosion images taken with the HST WFPC2, we find that the SN position
coincides with a luminous and blue point-like source, with an
extinction-corrected absolute magnitude of M$_V$$sim$$-$8.2 mag and
M$_I$$sim$$-$7.7 mag.Comparisons of the observations to the theoretical models
indicate that the counterpart source was either a single WR star or a binary
with whose members had high initial masses, or a young compact star cluster. To
further distinguish between different scenarios requires revisiting the site of
the progenitor with HST after the SN fades away.

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