A hot and luminous source at the site of the fast transient AT2018cow at 2–3 yr after its explosion. Issue 1 (8th March 2022)

• Record Type: Journal Article
• Authors: Sun, Ning-Chen; Maund, Justyn R; Crowther, Paul A; Liu, Liang-Duan
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 512:Issue 1(2022)
• Page Start: L66
• Page End: L70
• Publication Date: 2022-03-08
• Subjects: stars: massive -- supernovae: general -- supernovae: individual: AT2018cow; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slac023
• Languages: English
• ISSNs: 1745-3933

Abstract

ABSTRACT: We report the discovery of a luminous late-time source at the position of the fast blue optical transient AT2018cow on images taken by the Hubble Space Telescope at 714 d and 1136 d after its explosion. This source is detected at both UV and optical wavelengths and has prominent Hα emission. It has a very stable brightness between the two epochs and a very blue spectral energy distribution consistent with f λ $\propto \, \lambda ^{-4.1 \pm 0.1}$, i.e. the Rayleigh–Jeans tail of a hot blackbody with a very high temperature of log( T /K) > 4.7 and luminosity of log( L / L ⊙ ) > 7.0. This late-time source is unlikely to be an unrelated object in chance alignment, or due to a light echo of AT2018cow. Other possible scenarios also have some difficulties in explaining this late-time source, including companion star(s), star cluster, the survived progenitor star, interaction with circumstellar medium, magnetar, or delayed accretion in a tidal disruption event. Long-term and multi-wavelength monitoring will help to resolve its nature and finally reveal the origin of the 'Cow'.