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The Peculiar Transient AT2018cow: A Possible Origin of A Type Ibn/IIn Supernova

Xiang, Danfeng and Wang, Xiaofeng and Lin, Weili and Mo, Jun and Lin, Han and Burke, Jamison and Hiramatsu, Daichi and Hosseinzadeh, Griffin and McCully, Curtis and Valenti, Stefan and Vinkó, József and Wheeler, J. Craig and Mirzaqulov, Davron and Bódi, Attila and Bognár, Zsófia and Cseh, Borbála and Hanyecz, Ottó and Ignácz, Bernadett and Kalup, Csilla and Könyves-Tóth, Réka and Kriskovics, Levente and Ordasi, András and Pál, András and Sárneczky, Krisztián and Seli, Bálint and Szakáts, Róbert and Zhang, Tianmeng and Zhang, Jujia (2021) The Peculiar Transient AT2018cow: A Possible Origin of A Type Ibn/IIn Supernova. ASTROPHYSICAL JOURNAL, 910 (1). pp. 1-12. ISSN 0004-637X (print); 1538-4357 (online)

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Abstract

We present our photometric and spectroscopic observations on the peculiar transient AT2018cow. The multi-band photometry covers from peak to $\\sim$70 days and the spectroscopy ranges from 5 to $\\sim$50 days. The rapid rise ($t_{\\mathrm{r}}$$\\lesssim$2.9 days), high luminosity ($M_{V,\\mathrm{peak}}\\sim-$20.8 mag) and fast decline after peak make AT2018cow stand out of any other optical transients. While we find that its light curves show high resemblance to those of type Ibn supernovae. Moreover, the spectral energy distribution remains high temperature of $\\sim$14,000 K after $\\sim$15 days since discovery. The spectra are featureless in the first 10 days, while some broad emission lines due to H, He, C and O emerge later, with velocity declining from $\\sim$14,000 km s$^{-1}$ to $\\sim$3000 km s$^{-1}$ at the end of our observations. Narrow and weak He I emission lines emerge in the spectra at $t>$20 days since discovery. These emission lines are reminiscent of the features seen in interacting supernovae like type Ibn and IIn subclasses. We fit the bolometric light curves with a model of circumstellar interaction (CSI) and radioactive decay (RD) of \\Ni and find a good fit with ejecta mass $M_{\\mathrm{ej}}\\sim$3.16 M$_{\\odot}$, circumstellar material mass $M_{\\mathrm{CSM}}\\sim$0.04 M$_{\\odot}$, and ejected \\Ni mass $M_{^{56}\\mathrm{Ni}}\\sim$0.23 M$_{\\odot}$. The CSM shell might be formed in an eruptive mass ejection of the progenitor star. Furthermore, host environment of AT2018cow implies connection of AT2018cow with massive stars. Combining observational properties and the light curve fitting results, we conclude that AT2018cow might be a peculiar interacting supernova originated from a massive star.

Item Type: Article
Uncontrolled Keywords: Supernovae; Circumstellar matter; Massive stars; Binary stars; Magnetars; Time domain astronomy; Optical observation
Subjects: Q Science / természettudomány > QB Astronomy, Astrophysics / csillagászat, asztrofizika
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 22 Sep 2021 10:07
Last Modified: 22 Sep 2021 10:40
URI: http://real.mtak.hu/id/eprint/130106

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