DOI

https://doi.org/10.48717/7exs-4997

Project

EM137

Title

Revealing the radio structure in AT2018cow

Abstract

The transient AT2018cow was discovered on 16th June 2018, offset by 1.7 kpc from the core of galaxy CGCG 137-068 (distance ~ 60 Mpc). Multi-wavelength observations suggest a variety of progenitors (e.g. peculiar supernovae, gamma-ray burst, tidal disruption event), and indicate the prominent influence of a central engine, thus offering an inconclusive picture but a promising opportunity for continued high-resolution VLBI monitoring observations. The source is detected (unresolved) in our recent L-band e-EVN (October 2018) and C-band EVN (November 2018) observations with increasing astrometric accuracy, enabling the characterization of the source morphology and its evolution. Another deep C-band EVN observation currently scheduled for the 1/2019 session can potentially detect a discernable shift in the emission peak and hence constrain proper motion. As the source continues to brighten in the GHz frequencies, we propose another epoch of C-band EVN observations (12-hour; 2/2019 session) to better understand the afterglow and provide strict constraints on the proper motion (> 0.15 mas/yr can be detected with three continuous EVN sessions epochs). The emission structure (jetted or expanding source) and progenitor nature can thus be clarified.