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

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.

Accepted for publication in ApJ

References in corpus (26)

• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• A giant outburst two years before the core-collapse of a massive star
• Rapidly-Evolving and Luminous Transients from Pan-STARRS1
• PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
• SN 2006jc: A Wolf-Rayet Star Exploding in a Dense He-Rich Circumstellar Medium
• From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• The magnetar model for Type I superluminous supernovae I: Bayesian analysis of the full multicolour light curve sample with MOSFiT
• The metamorphosis of Supernova SN2008D/XRF080109: a link between Supernovae and GRBs/Hypernovae
• SOUSA: the Swift Optical/Ultraviolet Supernova Archive
• Massive stars exploding in a He-rich circumstellar medium. I. Type Ibn (SN 2006jc-like) events
• SN 2004aw: Confirming Diversity of Type Ic Supernovae
• Firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code
• Massive stars exploding in a He-rich circumstellar medium. II. The transitional case of SN 2005la
• Massive stars exploding in a He-rich circumstellar medium. IV. Transitional Type Ibn Supernovae
• Electron-capture supernovae exploding within their progenitor wind
• iPTF16asu: A Luminous, Rapidly-Evolving, and High-Velocity Supernova
• A Model for Fast Blue Optical Transient AT2018Cow: Circumstellar Interaction of a Pulsational Pair-instability Supernova
• The Peculiar Type Ib Supernova 2006jc: A WCO Wolf-Rayet Star Explosion
• The possible detection of a binary companion to a Type Ibn supernova progenitor
• Type II Supernova Light Curves and Spectra From the CfA
• A Blast from the Pasture: Studying the environment of AT 2018cow with MUSE
• The nearby luminous transient AT2018cow: a magnetar formed in a sub-relativistically expanding non-jetted explosion
• Optical Observations of the Type Ic Supernova 2007gr in NGC 1058 and Implications for the Properties of its Progenitor
• ALMA Polarimetry of AT2018cow
• A unified accreting magnetar model for long-duration gamma-ray bursts and some stripped-envelope supernovae

Cited by in corpus (27)

• A Search for Extragalactic Fast Blue Optical Transients in ZTF and the Rate of AT2018cow-like Transients
• Circumstellar Interaction Powers the Light Curves of Luminous Rapidly Evolving Optical Transients
• The Diverse Properties of Type Icn Supernovae Point to Multiple Progenitor Channels
• Magnetar Engines in Fast Blue Optical Transients and Their Connections with SLSNe, SNe Ic-BL, and lGRBs
• A common envelope jets supernova (CEJSN) impostor scenario for fast blue optical transients
• A hot and luminous source at the site of the fast transient AT2018cow at 2-3 years after its explosion
• An environmental analysis of the fast transient AT2018cow and implications for its progenitor and late-time brightness
• Dust Echoes from Luminous Fast Blue Optical Transients
• Gap Transients Interacting with Circumstellar Medium
• Late-time Hubble Space Telescope Observations of AT 2018cow. II. Evolution of a UV bright Underlying Source 2--4 Yr Post-discovery
• Neutrino Emission from Luminous Fast Blue Optical Transients
• iPTF14hls in the circumstellar medium interaction model: A promising candidate for a pulsational pair-instability supernova
• Evolution of A Peculiar Type Ibn Supernova SN 2019wep
• Multi-wavelength observations of the Luminous Fast Blue Optical Transient AT2023fhn
• New JWST redshifts for the host galaxies of CDF-S XT1 and XT2: understanding their nature
• A Snapshot Survey of Nearby Supernovae with the Hubble Space Telescope
• Late-time Hubble Space Telescope Observations of AT 2018cow. I. Further Constraints on the Fading Prompt Emission and Thermal Properties 50--60 Days Post-discovery
• Real-time Discovery of AT2020xnd: A Fast, Luminous Ultraviolet Transient with Minimal Radioactive Ejecta
• ASASSN-14ms:the Most Energetic Known Explosion of a Type Ibn Supernova and its Physical Origin
• A Population Study on the Radio Emission of Fast Blue Optical Transients
• Terminating a common envelope jets supernova impostor event with a super-Eddington blue supergiant
• Unveiling the nature of the Einstein Probe transient EP 241021a
• The spectra of a radiative reprocessing outflow model for fast blue optical transients
• Luminous Fast Blue Optical Transients as "Failed" Gravitational-wave Sources: Helium Core$-$Black Hole Mergers Following Delayed Dynamical Instability
• The X-ray and Radio Loud Fast Blue Optical Transient AT2020mrf: Implications for an Emerging Class of Engine-Driven Massive Star Explosions
• A study on late time UV-emission in core collapse supernovae and the implications for the peculiar transient AT2018cow
• Luminous Fast Blue Optical Transients and Type Ibn/Icn SNe from Wolf-Rayet/Black Hole Mergers