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SN2017jgh - A high-cadence complete shock cooling lightcurve of a SN IIb with the Kepler telescope

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 Publication date 2021
  fields Physics
and research's language is English




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SN 2017jgh is a type IIb supernova discovered by Pan-STARRS during the C16/C17 campaigns of the Kepler/K2 mission. Here we present the Kepler/K2 and ground based observations of SN 2017jgh, which captured the shock cooling of the progenitor shock breakout with an unprecedented cadence. This event presents a unique opportunity to investigate the progenitors of stripped envelope supernovae. By fitting analytical models to the SN 2017jgh lightcurve, we find that the progenitor of SN 2017jgh was likely a yellow supergiant with an envelope radius of $sim50-290~R_{odot}$, and an envelope mass of $sim0-1.7~M_{odot}$. SN 2017jgh likely had a shock velocity of $sim7500-10300$ km s$^{-1}$. Additionally, we use the lightcurve of SN 2017jgh to investigate how early observations of the rise contribute to constraints on progenitor models. Fitting just the ground based observations, we find an envelope radius of $sim50-330~R_{odot}$, an envelope mass of $sim0.3-1.7~M_{odot}$ and a shock velocity of $sim9,000-15,000$ km s$^{-1}$. Without the rise, the explosion time can not be well constrained which leads to a systematic offset in the velocity parameter and larger uncertainties in the mass and radius. Therefore, it is likely that progenitor property estimates through these models may have larger systematic uncertainties than previously calculated.



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High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $sim$,88 days in the V-band, similar to SN 1987A. A $rm^{56}Ni$ mass of ~0.087$pm$0.004 $rm M_{odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radius ~50 $rm R_{odot}$, a mass of ~14-20 $rm M_{odot}$ and explosion energy of ~1.7-2.9$rm times$ $rm 10^{51} erg$. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A sub-solar metallicity (~0.3 $rm Z_{odot}$) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events.
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