The Nearby Luminous Transient AT2018cow: A Magnetar Formed in a Subrelativistically Expanding Nonjetted Explosion
Journal article, 2020

The fast-rising blue optical transient AT2018cow indicated unusual early-phase characteristics unlike relatively better studied explosive transients. Its afterglow may be produced by either a relativistically beamed (jetted) or intrinsically luminous (nonjetted) ejecta and carries observational signatures of the progenitor and environment. High-resolution monitoring can distinguish between these scenarios and clarify the progenitor nature. We present very long baseline interferometry (VLBI) observations of AT2018cow at 5 GHz involving 21 radio telescopes from the European VLBI Network with five sessions spanning ≈1 yr. With an astrometric precision up to 25 μas per epoch, the rapidly fading compact mas-scale source is found to be nonjetted with a proper motion of ≤0.15 mas yr-1 (0.14 c). This and a dense (number density ≈104-105 cm-3) magnetized environment (magnetic field strength ≥0.84 G) are characteristic of a newly formed magnetar driven central engine, originating in the successful explosion of a low-mass star.


P. Mohan

Shanghai Astronomical Observatory

T. An

Shanghai Astronomical Observatory

Chinese Academy of Sciences

Jun Yang

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Shanghai Astronomical Observatory

Astrophysical Journal Letters

2041-8205 (ISSN) 2041-8213 (eISSN)

Vol. 888 2 L24

Subject Categories

Astronomy, Astrophysics and Cosmology

Fusion, Plasma and Space Physics



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